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Development of Integrated Pest Management (IPM) Strategies for Whitefly (Bemisia tabaci)-Transmissible Geminiviruses
Abstract
Worldwide outbreaks of Bemisia tabaci whiteflies, especially biotype B, have facilitated the emergence of whitefly-transmitted geminiviruses (WTG). These viruses
cause economically important diseases of vegetable and fiber crops, especially in tropical and subtropical regions of the
world. Because small populations of whiteflies can efficiently spread WTGs, management of these diseases is more challenging
than for whiteflies alone. In this chapter, we discuss (1) why WTGs have emerged worldwide, (2) key aspects of the biology
of WTGs and B. tabaci, and (3) how these aspects shape the development of an integrated pest management (IPM) approach for these diseases. The
generalized IPM package involves strategies for (1) before the growing season, such as the use of virus- and whitefly-free
transplants and propagative stock, and resistant varieties; (2) during the growing season, such as whitefly population suppression,
roguing virus-infected plants, floating row covers and reflective mulches; and (3) after the growing season, such as region-wide
sanitation, weed management and implementation of a host-free period. Different combinations of strategies will be used depending
on the crop, cropping system, and properties of the virus and the whitefly vector. This is illustrated with two case studies:
IPM for WTGs in an annual (tomato) and a perennial (cassava) crop.
... Geminiviruses (family Geminiviridae) are a large group of plant viruses that possess small circular single-stranded (ss) DNA genomes that are encapsidated in twinned or geminate virions (194). These viruses cause economically important diseases of food, feed, and fiber crops worldwide (59,84,182). These diseases have resulted in substantial losses to agricultural production, especially in tropical and subtropical regions, and a heavy reliance on insecticides for management (i.e., the pesticide treadmill). ...
... This information is used to make decisions about when to apply insecticides (Figure 1f ). Whitefly populations can also be estimated from the abaxial side of leaves using the leaf-turn method (59). Leafhoppers and treehoppers can be monitored with yellow sticky cards or collected with sweep nets. ...
... For pepper, resistant cultivars are not commercially available; however, pepper germplasm with promising levels of resistance to NW begomoviruses has been identified and is being used in breeding programs (53). In contrast, there are many tomato cultivars with begomovirus resistance and most of these have been generated by introgressing genes from wild tomato species (e.g., the Ty-1 to Ty-6 genes) with conventional breeding methods (34,59,84,96,97). Some of these cultivars have high levels of resistance to begomoviruses, including TYLCV and Tomato severe rugose virus and Tomato mottle leaf curl virus from Brazil (59). ...
Management of geminiviruses is a worldwide challenge because of the widespread distribution of economically important diseases caused by these viruses. Regardless of the type of agriculture, management is most effective with an integrated pest management (IPM) approach that involves measures before, during, and after the growing season. This includes starting with resistant cultivars and virus- and vector-free transplants and propagative plants. For high value vegetables, protected culture (e.g., greenhouses and screenhouses) allows for effective management but is limited owing to high cost. Protection of young plants in open fields is provided by row covers, but other measures are typically required. Measures that are used for crops in open fields include roguing infected plants and insect vector management. Application of insecticide to manage vectors (whiteflies and leafhoppers) is the most widely used measure but can cause undesirable environmental and human health issues. For annual crops, these measures can be more effective when combined with host-free periods of two to three months. Finally, given the great diversity of the viruses, their insect vectors, and the crops affected, IPM approaches need to be based on the biology and ecology of the virus and vector and the crop production system. Here, we present the general measures that can be used in an IPM program for geminivirus diseases, specific case studies, and future challenges.
... No obstante, es común observar en sembradíos de tomate con plantas propagadas bajo umbráculos, algunas sintomáticas de posibles begomovirus, las cuales por mostrar síntomas tempranos en su desarrollo denotan haber sido infectadas en el sitio de propagación. Estas plantas constituyen fuentes de virus (Gilbertson et al., 2011), en especial si se siembran lotes adyacentes en secuencia escalonada, a favor de vientos dominantes, aunado a altas poblaciones de B. tabaci, incentivadas por aplicaciones irracionales de plaguicidas. Esto último es común en Venezuela en cultivos afectados por begomovirus (Chirinos y Geraud-Pouey, 2011). ...
... plantas infectadas con begomovirus, portando insectos vectores (Gilbertson et al., 2011), en especial si son criados sobre ellas, pues como fue señalado, la eficiencia de transmisión aumenta en estos casos (Romay et al., 2010). En la misma sexta semana, siguieron en orden decreciente, las plantas propagadas en el semillero sin protección de la UTF (T3) con cerca de 45 %, mientras que el incremento de plantas sintomáticas cuando el semillero estuvo físicamente protegido (T1), resultó el más lento, con 30 %. ...
... Así, surgieron empresas de propagación de hortalizas bajo umbráculos, las cuales utilizaban en algunos casos mallas de trama gruesa que no impedían la entrada de adultos de B. tabaci, con espacios ocupados por lotes de plantas de diferentes edades, lo cual mantenía la continuidad vegetacional y hacía difícil evitar la presencia del vector y algunas plantas con begomovirus, que aunque asintomáticas, podrían servir de fuente de virus. Muy probablemente es de esas condiciones de propagación en umbráculo, donde salen las pocas plantas infectadas, que luego servirán en el campo como fuente para inicio de epifitias, tal como lo señalan Gilbertson et al. (2011). Dado que muchos productores de tomate de la Planicie de Maracaibo, entre otras regiones del país, utilizan material de propagación proveniente de algunos viveros no protegidos del estado Lara podrían estar expuestos a este problema, pasando desapercibida una de las causas importantes de las infecciones en los campos de producción. ...
The begomovirus-Bemisia tabaci complex is the main limitation for tomato production in Venezuela, and its management begins with the production of healthy seedlings. Starting from seedbeds grown under different physical protection conditions, the spread of begomoviruses was studied in a farm in the north western zone of Zulia State. The treatments were: T1, seedbed protected (SP) with fine screen; T2, SP transplanted together with some seedlings infected with Tomato yellow leaf curl virus; T3, seedbed without protection (SSP), these three in the Phytosanitary Technical Unit of the Universidad del Zulia; T4. SSP in the own farm; T5, SSP grown in a commercial nursery in Lara State. Following transplanting, plants with apparent viral symptoms were weekly counted and in the last three weeks nymph of B. tabaci were also counted. At the end of the experiment, samples of symptomatic plants were taken and presence of begomovirus was detected, by PCR, in all of them. Although all the plants ended symptomatic, symptoms appeared sooner in T5 compared to the rest, especially with T1, where the vector infestation was lower than under T2, T4 and T5 (P≤0.05). Protected seedbeds along with other agronomic practices may represent an alternative to retard begomovirus transmission by B. tabaci.
... The genus begomovirus is the largest group of plantpathogenic viruses that infect dicotyledonous plants in different world regions [24]. This highlights the remarkable success of begomoviruses as emerging plant viruses [7,13], often attributed to factors like the widespread presence of indigenous begomoviruses in non-cultivated plants (such as weeds), which act as precursors for viruses that infect crops. The invasive polyphagous B. tabaci cryptic species complexes have facilitated the introduction of indigenous begomoviruses into different crop plants. ...
... The begomovirus genome has evolved rapidly through other mechanisms via mutation, pseudorecombination, recombination, and acquisition of new DNA components and satellites [23]. Finally, the worldwide cultivation of susceptible crop plants belonging to the family Cucurbitaceae, Euphorbiaceae, Solanaceae, Malvaceae and Fabaceae, often in monocrop and overlapping plantings, has resulted in the exposure of potential host plants to high populations of whitefly cryptic species complexes and diversity of begomoviruses [13,34]. ...
The numerous plants of Solanum nigrum L, and Physalis minima L, well-known weeds with medicinal properties in agriculture and horticulture crops exhibiting severe mosaic, enation and leaf curl symptoms, were collected from the Varanasi and Mirzapur districts of Uttar Pradesh, India. The begomovirus infection in S. nigrum and P. minima was validated by PCR using virus-specific primers. The whole genome of the represented isolate of S. nigrum (SN1), P. minima (PM1), and beta satellite was amplified, cloned and sequenced. The SDT analysis showed that the DNA-A of PM1 and SN1 isolate showed the highest nt identity of 87.4 to 99.1%, with several chilli leaf curl virus (ChiLCuV) isolates from India and Oman, respectively. The betasatellite sequence (PM1β) obtained from the PM1 isolate showed a very low identity of 83.1–84.5%. A demarcation threshold of 91% for betasatellite species delineation has led to identifying a new betasatellite in the PM1 sample. This unique betasatellite has been named "physalis minima leaf curl betasatellite," indicating its novelty with the plant. Whereas, betasatellite sequence (SN1β) obtained from the SN1 sample showed 86.8–91.2% nucleotide identity with ChiLCB isolates infecting several crops in Indian subcontinents. The RDP analysis of the viral genome and betasatellite of SN1 and PM1 isolates revealed recombination in substantial portions of their genetic makeup, which appeared to have originated from pre-existing begomoviruses known to infect diverse host species. The present research also highlights the potential role of these plants as significant reservoir hosts for ChiLCuV in chili plants.
... Row covers combined with insect growth regulators reduced fruit damage and increased fruit size, weight, and quality in zucchini plants due to the reductions in adults, eggs, and pupae/nymphs per leaf compared with those in no-cover treatments [9]. The temporary pest exclusion systems that separate insects from host plants provide short-term solutions to insect damage and avoid an infestation in the critical stages of crop development [22]. ...
... Daily average air temperatures were similar across the three locations and decreased with plant development (Figure 1). Average air temperatures during the study period were 23.6 °C in Georgia 2020, 22 ...
Simple Summary
Sweet potato whitefly is a major pest in zucchini production due to the direct and indirect damage it causes to this crop. The present study evaluated reflective silver plastic mulch and an insect row cover as alternative methods to manage whiteflies in zucchini production in the southeastern U.S. Field experiments indicated reduced whitefly numbers under reflective silver plastic mulching and insect row cover treatments. These methods also improved plant growth and yield compared to conventional white plastic mulch and no-cover treatments. In conclusion, these alternative methods can be considered ready-to-use integrated pest management practices for growers.
Abstract
The challenges that sweet potato whitefly (Bemisia tabaci) creates for vegetable production have increased in the southeastern U.S. Growers must use intensive insecticide spray programs to suppress extremely high populations during the fall growing season. Thus, the objective of this study was to evaluate the use of a reflective plastic mulch and an insect row cover as alternative methods to the current grower practices to manage whiteflies in zucchini (Cucurbita pepo) production. Field experiments were conducted with a two-level factorial experimental design of cover and plastic mulch treatments arranged in a randomized complete block design, with four replications in Georgia in 2020 and 2021, and in Alabama in 2021. Cover treatments consisted of an insect row cover installed on zucchini beds at transplanting and removed at flowering and a no-cover treatment, while plastic mulch treatments consisted of reflective silver plastic mulching and white plastic mulching. During all growing seasons, weather conditions were monitored, whitefly populations were sampled weekly, zucchini biomass accumulation was measured at five stages of crop development, and fruit yield was determined at harvesting. Warm and dry weather conditions early in the growing season resulted in increased whitefly populations, regardless of location and year. In general, the reflective silver plastic mulching reduced whitefly populations compared to the conventional white plastic by 87% in Georgia in 2020, 33% in Georgia in 2021, and 30% in Alabama in 2021. The insect row cover treatment reduced whitefly populations to zero until its removal. Consequently, zucchini plants grown with the insect row cover and reflective silver plastic mulching had an increased rate of biomass accumulation due to the lower insect pressure in all locations. Zucchini grown using silver reflective plastic mulch and row covers had an overall increase of 17% and 14% in total yield compared to white plastic mulch and no-cover treatments, respectively. Significant differences in yield among locations were likely due to severe whitefly pressure early in the fall season, and total yields in Georgia in 2020 (11,451 kg ha⁻¹) were 25% lower than in Georgia in 2021 (15,177 kg ha⁻¹) and in Alabama in 2021 (15,248 kg ha⁻¹). In conclusion, silver plastic mulching and row covers reduced the whitefly population and increased biomass accumulation and total yield. These treatments can be considered ready-to-use integrated pest management practices for growers.
... Control of whitefly vectors with insecticides has met with limited success in preventing the spread of virus diseases (Perring et al. 1999, Gilbertson et al. 2011. The development of resistance by B. tabaci to many classes of insecticides (Palumbo et al. 2001, Dennehy et al. 2010) makes vector control even more difficult. ...
... Unfortunately, due to extensive exposure, resistance to neonicotinoids is now spread worldwide, and several examples of cross resistance with other insecticide classes have been reported for neonicotinoids (e.g., cross resistance between imidacloprid and pymetrozine) (Nauen & Denholm 2005, Gorman et al. 2010. To help overcome insecticide resistance, the chitin synthesis inhibitor, buprofezin, and the juvenile hormone analog, pyriproxyfen, have been used successfully in rotation with neonicotinoids for management of B. tabaci (Stansly & Natwick 2010, Gilbertson et al. 2011. ...
Sweet potato leaf curl virus (SPLCV), which is transmitted by the sweetpotato whitefly, Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae), species complex, can severely affect yields of sweetpotatoes, Ipomoea batatas (L.) Lam. (Convolvulaceae). This virus is endemic in sweetpotato fields at the U.S. Vegetable Laboratory (USVL), Charleston, S.C. In 2010 and 2011, experiments were conducted to determine if repeated insecticide applications were useful for protecting ‘Beauregard’ sweetpotato from SPLCV infection. In 2010, plots were untreated or treated twice weekly with imidacloprid. A row of SPLCV-infected sweetpotato genotype ‘W-258’ was planted between ‘Beauregard’ plots to serve as a source of whiteflies and SPLCV. A similar test was performed in 2011, except that the plots were sprayed only once a week, and a rotation of four insecticides (in the order of imidacloprid, pyriproxyfen, acetamiprid, and pymetrozine) was used. Yellow sticky traps were placed horizontally in the center of each plot at canopy height to monitor whitefly abundance. Leaf samples were taken every other week to test for SPLCV infection using real-time polymerase chain reaction (PCR) techniques. Over the two-year period, there were significantly fewer whiteflies on sticky cards in the sprayed treatment for only two of the 36 weekly samples, indicating that insecticides were largely ineffective in reducing whitefly populations moving into these plots. By the end of the growing season each year, all of the unsprayed plots were infected with SPLCV as determined by real-time PCR. However only about one-half of the sprayed plots were infected with SPLCV. This indicates that insecticides could be useful in protecting sweetpotatoes from SPLCV. The insecticide sprays would likely be more effective under normal production practices where sources of the virus are not in such close proximity to the uninfected crop.
... Conversely, aluminum reflective mulch was ineffective against B. tabaci on squash or tomato (Powell & Stoffella 1993). Floating or supported row covers of spun-bonded polyester, commercially known as Agribon ® or Agril, are commonly employed to exclude B. tabaci from newly transplanted tomato or cucurbits, thereby preventing leaf curl virus infection (Gilbertson et al. 2011). ...
... Vector whitefly Bemisia tabaci L. usually spread CLCuD [31]. Through application of pesticide whitefly population can be controlled and ultimately the disease incidence [33]. ...
Background
Cotton leaf curl virus disease (CLCuD) is one of the major concerns for cotton growers. The traditional approach to managing CLCuD involves the control of the vector (whitefly) population through the use of pesticides. This study compares the efficacy of zinc oxide, iron oxide, copper and silver nanoparticles with conventional pesticides. Nanoparticles dose was optimized by evaluating their phytotoxic threshold in our previous study. In this study, optimized doses of nanoparticles such as zinc oxide (100 ppm), iron oxide (50 ppm), copper (50 ppm) and silver nanoparticles (25 ppm) were applied in a field trial of cotton against cotton leaf curl virus disease (CLCuD). Morphological parameters (height of stem, monopodial branches, sympodial branches, staple length, boll weight and number of bolls), yield parameters (seed cotton yield and ginning outturn), chlorophyll content (chlorophyll a, chlorophyll b, carotenoids and total chlorophyll), biochemical parameters (superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), hydrogen peroxide (H2O2) and electrolyte leakage) and disease parameters (reduction infection, disease severity and disease incidence) were determined in this study.
Results
The incidence of cotton leaf curl virus was confirmed by triple antibody sandwich–enzyme-linked immunosorbent assay (TAS-ELISA). The pesticide Imidacloprid significantly reduced the infection by 79.3%. However, in comparison to pesticide, application of nanoparticles also reduced the infection. ZnO NPs reduced the infection by 42.33%, FeO NPs by 41%, Cu NPs by 34.7%, and Ag NPs by 44.8%. Moreover, these nanoparticles also improved the plant growth parameters as compared to control treatment. ZnO NPs enhanced morphological, yield parameters, and chlorophyll content by 36%, 22%, and 29%, respectively. FeO NPs showed improvements by 38%, 21%, and 29%; Cu NPs 39%, 25%, and 29%; and Ag NPs 31%, 19%, and 18%, respectively.
Conclusion
Although treatment pesticide showed the least disease incidence compared to nanoparticles, nanoparticles are eco-friendly and safe as compared to pesticides. Farmers can apply these nanoparticles at their optimal thresholds through foliar application as an alternative to traditional pesticides. It is concluded that nanocomposites and hybrid modes may be used for managing CLCuD efficiently in the future.
Graphical abstract
... [31]. Through application of pesticide white y population can be controlled and ultimately the disease incidence [33]. ...
Background
Cotton Leaf Curl Virus Disease (CLCuD) is one of the major concerns for cotton growers. The traditional approach to managing CLCuD involves the control of the vector (whitefly) population through the use of pesticides. In this study, the efficacy of nanoparticles was compared with pesticides. The present study was conducted to evaluate the comparative efficacy of zinc oxide nanoparticles (ZnO nanoparticles), iron oxide nanoparticles (FeO nanoparticles), copper nanoparticles (Cu nanoparticles) and silver nanoparticles (Ag nanoparticles). Optimized doses of zinc oxide nanoparticles (ZnO nanoparticles), iron oxide nanoparticles (FeO nanoparticles), copper nanoparticles (Cu nanoparticles) and silver nanoparticles (Ag nanoparticles) were applied in a field trial of cotton against Cotton Leaf Curl Virus Disease (CLCuD) in cotton. The study consisted of morphological parameters (height of stem, monopodial branches, sympodial branches, staple length, boll weight and number of bolls), yield parameters (seed cotton yield and ginning outturn), chlorophyll content (chlorophyll a, chlorophyll b, carotenoids and total chlorophyll), biochemical parameters (superoxide dismutase (SOD), peroxidase (POD), ascorbate peroxidase (APX), catalase (CAT), hydrogen peroxide (H2O2) and electrolyte leakage) and disease parameters (reduction infection, disease severity and disease incidence).
Results
Cotton Leaf Curl Virus (CLCuV) was detected by TAS-ELISA (Triple Antibody Sandwich-Enzyme-linked immunosorbent assay). Pesticide reduced the infection as 79.3%. Zinc oxide nanoparticles (ZnO nanoparticles), iron oxide nanoparticles (FeO nanoparticles), copper nanoparticles (Cu nanoparticles) and silver nanoparticles (Ag nanoparticles) reduced the infection as 42.33%, 41%, 34.7% and 44.8% respectively. The statistical design for field trial was randomized complete block design (RCBD). One-way ANOVA was performed.
Conclusion
Although treatment pesticide showed the least disease incidence compared to nanoparticles. Nanoparticles are eco-friendly and safe as compared to pesticides. It is concluded that nanocomposites and hybrid modes may be used for managing CLCuD efficiently in the future.
... Agrotechnological methods, including site selection, crop rotation, choice of variety (hybrid) and seed material, timing and method of sowing, can to some extent reduce the number of some insect pests. For example, [4] reported a decrease in the number of aphids on wheat during early sowing. Aheer G.M. etc. [16] showed that the timing of sowing affects the population of aphids and other pests of leguminous crops. ...
The aim of the study was to study the effectiveness and provide an economic assessment of the use of various
insecticides against pests on alfalfa seed crops in the second year of the grass stand. The research was conducted
during 2019–2021 at the experimental field of the Institute of Irrigated Agriculture of the NAAS. Treatment with
insecticides was carried out: the first – in the phase of the beginning of budding, the second - before the beginning
of flowering. The use of insecticides reduced the number of pests on the grass stand. The most effective in the fight
against pests (with the exception of Aphis craccivora Koch) was the preparation with the active substances
Chlorpyrifos, 500 g/l and Cypermethrin, 50 g/l and the consumption rate of 1.00 l/ha. The highest seed yield was
obtained in the first treatment with an insecticide preparation with the active substances Chlorpyrifos, 500 g/l and
Cypermethrin, 50 g/l and the consumption rate of 1.00 l/ha, and in the second treatment with preparations with the
active substances Chlorantraniliprole, 200 g/l and Lambda-cyhalothrin, 50 g/l at a rate of 0.17 and 0.15 l/ha,
respectively. When irrigated with this variant, the seed productivity was 635.2 kg/ha, which was higher than the
control variant by 115.3 kg/ha. Under conditions of natural moisture, the seed yield was 452.5 kg/ha, and was
higher than the control by 74.3 kg/ha. The lowest cost price of 0.66 €/ha and the highest conditional net profit of
1702.87 €/ha was obtained on the option: the first treatment - Chlorpyrifos, 500 g/l and Cypermethrin, 50 g/l, the
second – Chlorantraniliprole, 200 g/l and Lambda-cyhalothrin, 50 g/l.
Key words: alfalfa, seeds, insect, irrigation, economic efficiency
... Merely ten whiteflies per plant are sufficient to induce 100% infection, although even a single whitefly can effectively transmit the virus (Venkataravanappa et al. 2014). Managing this disease primarily revolves around controlling the vector through integrated pest management strategies such as barrier crops, sticky traps, roguing, chemical sprays, and field sanitation (Gilbertson et al. 2011;Kumar et al. 2017). Excessive pesticide use not only increases production costs but also poses environmental risks while offering limited effectiveness in controlling the vectors, especially in high humidity areas. ...
Yellow vein mosaic virus (YVMV) poses a significant threat to okra production. Breeding for genetic resistance is a promising approach for YVMV management. This study aimed to investigate the inheritance of YVMV resistance and identify molecular markers associated with resistance in okra. Recombinant inbred lines (RILs) were developed from a cross between a YVMV-resistant breeding line (NS25581) and a susceptible line (NS17556). Phenotypic data from the RIL population exhibited a segregation ratio of 1:3 for resistant and susceptible plants, suggesting the involvement of a single recessive gene in controlling YVMV resistance over two consecutive years (Summer 2020 and 2021). A parental polymorphism survey using 212 markers identified six polymorphic markers. Genotyping of RILs with these markers, followed by single marker analysis, revealed a significant association between YVMV resistance and the SSR54 marker. SSR54 accounted for 4.42% and 5.05% of the phenotypic variance (R²) during Summer 2020 and Summer 2021, respectively. Notably, this study marks the first identification of a marker associated with YVMV resistance in okra. These findings provide valuable insights into the genetic basis of YVMV resistance and pave the way for marker-assisted breeding programs targeting enhanced resistance in okra cultivars.
... This increases its importance, especially in areas destined for tomato cultivation, since the begomovirus is predominant in tomato-growing regions of south-central Brazil (Federal District, Minas Gerais, São Paulo and Goiás) (Inoue-Nagata et al. 2016). Eradication programs and periods without the presence of hosts can play an important role in the integrated management of whitefly and insect-transmitted viruses, reducing inoculum sources within and adjacent to the crop (Gilbertson et al. 2011). In this sense, the monitoring and control of these species can contribute to management strategies aimed at controlling populations of B. tabaci MEAM1 and its associated diseases under field conditions. ...
The whitefly, Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae), is considered one of the most invasive and destructive pests for agriculture worldwide. Whitefly populations are maintained throughout the year by continuous exploitation of different plant species and, in this context, weeds can serve as alternative hosts, making permanent populations possible in the field with the migration of individuals to cultivated plant species. Invasive plant species can also serve as inoculum sources of whitefly-transmitted viruses, being more favorable to disease dissemination in agricultural fields. Thus, studies investigating B. tabaci performance on different hosts are highly relevant for a better understanding of the insect’s population dynamics. Further study may assist in directing management actions and eradication of the most suitable plants for the whitefly development. With these goals in mind, the present study assessed biological aspects of B. tabaci MEAM1 on 14 weed species commonly found in Brazilian agricultural fields, in addition to five cultivated plant species. It was verified that the species Ipomoea grandifolia, Solanum lycopersicum and Emilia sonchifolia required the shortest development periods (egg-adult) (23.90 to 24.67 days), indicating high susceptibility. High nymphal viability rates (98.33 to 80.83%) were observed in S. lycopersicum, Gossypium hirsutum, Raphanus raphanistrum, Glycine max, Amaranthus viridis, Euphorbia heterophylla, Commelina benghalensis, Galinsoga parviflora, Sida rhombifolia, E. sonchifolia, Merremia aegyptia and I. grandifolia, also indicating susceptibility. These plant species were revealed to be suitable hosts for whitefly development and, with the exception of the cultivated species, should be monitored and eradicated, expanding the management strategies for B. tabaci MEAM1 populations in agricultural scenarios.
... Crop yield losses can be very high based on the time of disease incidence and its quick spread (Varma and Malathi 2003;Obaiah et al. 2013;Gupta et al. 2015). Managing the disease through vector control using insecticides is ineffective since even a very small population of whiteflies can also cause severe disease outbreak (Gilbertson et al. 2011). Cultural management through the selection of an appropriate time and season of sowing that would avoid disease build-up is effective but not totally reliable. ...
Yellow mosaic disease (YMD) is a major problem in Urd bean (Vigna mungo L.) in India, which causes huge yield losses. Breeding for wide spectrum and durable Mungbean yellow mosaic virus (MYMV) resistance and cultivating resistant cultivars is the most appropriate and effective approach. However, the task has become challenging with the report of at least two species of the virus, viz., Mungbean yellow mosaic virus (MYMV) and Mungbean yellow mosaic India virus (MYMIV) and their recombinants; the existence of various isolates of these species with varied virulence and rapid mutations noted in the virus as well as in the whitefly vector population. Thus the present study was carried out to identify and characterize novel and diverse sources of YMV resistance and develop linked molecular markers for breeding durable and broadspectrum resistant urdbean cultivars against YMV. Towards this goal, we have screened 998 accessions of urdbean national collection of germplasm against YMD Hyderabad isolate both in a field under the natural level of disease incidence and through agro inoculation in the laboratory using viruliferous clones of the same isolate. Ten highly resistant accessions identified through repeated testing have been characterized in terms of reported linked markers. We attempted to see diversity among the ten resistant accessions reported here using earlier reported resistance-linked SCAR marker YMV1 and SSR CEDG180 marker. SCAR marker YMV1 did not amplify with any of the 10 accessions. But with CEDG180, results suggested that 10 accessions shortlisted through field and laboratory tests do not carry PU31 allele and this shows that it may be likely to carry novel gene(s). Further studies are needed to genetically characterize these new sources.
... This information can be used to guide phytosanitary practices and eradication programs on farms. At a regional scale, scenario analysis can evaluate how virome traits, management options, and growers' decision-making processes combine to influence whether policies are successful for reducing the socioeconomic impacts of crop epidemics (Gilbertson et al., 2011;Garcia-Figuera et al., 2021;Etherton et al., 2023). ...
Virome analysis via high-throughput sequencing (HTS) allows rapid and massive virus identification and diagnoses, expanding our focus from individual samples to the ecological distribution of viruses in agroecological landscapes. Decreases in sequencing costs combined with technological advances, such as automation and robotics, allow for efficient processing and analysis of numerous samples in plant disease clinics, tissue culture laboratories, and breeding programs. There are many opportunities for translating virome analysis to support plant health. For example, virome analysis can be employed in the development of biosecurity strategies and policies, including the implementation of virome risk assessments to support regulation and reduce the movement of infected plant material. A challenge is to identify which new viruses discovered through HTS require regulation and which can be allowed to move in germplasm and trade. On-farm management strategies can incorporate information from high-throughput surveillance, monitoring for new and known viruses across scales, to rapidly identify important agricultural viruses and understand their abundance and spread. Virome indexing programs can be used to generate clean germplasm and seed, crucial for the maintenance of seed system production and health, particularly in vegetatively propagated crops such as roots, tubers, and bananas. Virome analysis in breeding programs can provide insight into virus expression levels by generating relative abundance data, aiding in breeding cultivars resistant, or at least tolerant, to viruses. The integration of network analysis and machine learning techniques can facilitate designing and implementing management strategies, using novel forms of information to provide a scalable, replicable, and practical approach to developing management strategies for viromes. In the long run, these management strategies will be designed by generating sequence databases and building on the foundation of pre-existing knowledge about virus taxonomy, distribution, and host range. In conclusion, virome analysis will support the early adoption and implementation of integrated control strategies, impacting global markets, reducing the risk of introducing novel viruses, and limiting virus spread. The effective translation of virome analysis depends on capacity building to make benefits available globally.
... A wide array of tactics including chemical, biological, physical and cultural control strategies as well as crop plant resistance has been utilized to manage B. tabaci populations. In the majority of cases, chemical control of B. tabaci predominate, however, incorporation of several strategies in the form of an Integrated Pest Management (IPM) programme provides substantially better control than any single control tactic (Horowitz et al., 2011;Gilbertson et al., 2011;Guo et al., 2021). In a comparative study of biological, chemical and integrated control (IPM) of B. tabaci, it was concluded that the best strategy for B. tabaci management was IPM which provided 73% control followed by biological control (58%), then chemical control (44%) (Rodriguez et al., 2019). ...
Bemisia tabaci is among the top ten most important plant pests worldwide. It is highly invasive and causes immense economic losses globally, both directly by feeding and indirectly via transmission of various plant viruses. As a result of its worldwide agricultural and horticultural importance, a substantial amount of research has been conducted on its biology and management. However, substantially fewer studies have been done on the behavioural aspects of this pest, particularly with reference to its interactions with various chemical (insecticides, essential oils) and biological (entomopathogens) agents. The current chapter reviews the available literature on this aspect of B. tabaci and makes recommendations for future research.
... In regions with high population densities of white y year around, it is important to focus on the presence of the weed species highlighted above. In addition to acting as attractive hosts for the white y, some invasive species play an important role in the dissemination of viruses transmitted by the insect, making it appropriate to adopt strategies aimed at eradicating and eliminating such plants (Gilbertson et al., 2011). Monitoring and control of these species can be recommended in order to reduce favorable conditions for the insect and possible sources of inoculum, thus contributing to the management of B. tabaci MEAM1 populations and its associated diseases in the eld. ...
Being capable of infesting a wide variety of plant species, the whitefly Bemisia tabaci MEAM1 (Hemiptera: Aleyrodidae) is responsible for severe losses in numerous agricultural crops. In order to increase knowledge regarding interactions involving B. tabaci MEAM1 and plants associated with agricultural landscapes, the present study sought to identify preferential hosts by comparing 15 different common weed species and five cultivated plants (tomato, bell pepper, soybean, maize and cotton) through free and no-choice tests. Additionally, a possible correlation between physical-morphological plant aspects and insect’s colonization behavior was assessed. Positive correlations were verified between the oviposition index and trichome density, and between the number of adults and b* (yellow intensity) index. Negative correlations were observed between the number of adults and L* and a* (luminosity and green intensity, respectively) indexes. In the free choice test, the species Solanum lycopersicum , Senna obtusifolia , Glycine max , Emilia sonchifolia and Euphorbia heterophylla were the most infested during the mean of the evaluation periods, differing from Spermacoce latifolia , Amaranthus viridis and Richardia brasiliensis , which presented the lowest means of insect infestation. In this same test, S. lycopersicum and E. sonchifolia had the greatest oviposition, differing from most of the species. In the no-choice test, E. heterophylla , Galinsoga parviflora and S. latifolia had the highest means of eggs and nymphs per cm². Our results show evidence of the expressive potential of weed species frequently found in Brazilian agricultural fields, such as E. sonchifolia , S. obtusifolia, and E. heterophylla , as alternative hosts of B. tabaci MEAM1.
... The aggregation of WTVC infection occurring in both experimental and commercial fields (Table 7) suggests that the spatial patterns observed in fields where whiteflies were not managed (experimental) could also occur in commercial fields where management tactics against whiteflies were applied. The higher WTVC incidence and aggregation of infected plants in some commercial fields could also indicate an inadequate management of whiteflies, as was reported in other papers (Hilje et al., 2001;Gilbertson et al., 2011;Ally et al., 2019). One example of a management tactic used for managing insecttransmitted viruses that have an aggregated distribution is the removal of all PPV hosts (Prunus spp.) within 500m of PPVinfected trees, which contributed to the overall eradication of PPV in Pennsylvania, USA (Gottwald et al., 2013). ...
A two-year study was conducted in 2019 and 2020 to characterize the spatial distribution of whitefly-transmitted virus complex (WTVC) in experimental and commercial yellow squash ( Cucurbita pepo ) fields in southern Georgia, USA. Field trials planted in Tifton, Georgia, USA were comprised of 30 rows of squash (variety: Gentry) divided into 300 quadrats. Six commercial fields in Tift, Worth, and Colquitt Counties in Georgia, USA were surveyed. In each field, 10 rows of plants per field were partitioned into 70 quadrats so that their approximate location could be mapped and disease incidence tracked in space over time. Plants in each quadrat were visually assessed for TVC symptoms at seven-day intervals (experimental fields) or at fourteen-day intervals (commercial fields). The spatial distribution of WTVC in a one-dimensional space was determined through ordinary runs analysis and in two-dimensional space through spatial autocorrelation analysis and spatial analysis by distance indices (SADIE). Ordinary runs analysis down and between rows suggested that disease was more likely to be transmitted from infected plants within rows than across rows. WTVC incidence in space was positively correlated with adult whiteflies on squash leaves taken one or two weeks prior to the assessment of virus incidence coinciding with latent period of Geminiviruses. SADIE generated disease severity maps indicated a shift from sparse and randomly distributed disease early in the infection cycle to denser, more aggregated patterns later in time in both experimental and commercial fields. Contour plots of interpolated indices from SADIE analysis suggested an edge effect on the spatial distribution of WTVC in experimental fields as well as in two of the commercial fields. An understanding of the shift from random to aggregated distribution and the edge effect on WTVC incidence are considerations for refining current management strategies.
... This insect causes direct and indirect damage through the feeding and transmissions of plant viruses, respectively (Jones 2003;Palaniswami 2020). The economical relevance of B. tabaci reside on the fact that plant viruses have no known cure (Gilbertson et al. 2011). Therefore, growers emphasize the management of these diseases in the reduction of vectors (Castle et al. 2009). ...
Management of Bemisia tabaci (Gennadius) (Hemiptera: Aleyrodidae) populations is a key strategy to reduce the transmission of viruses to crops. Yellow sticky traps are widely used tools to monitor and/or reduce B. tabaci populations. Nevertheless, these traps also allow the collection of debris and nontarget organisms including B. tabaci natural enemies. Covering the surface of the traps with a mesh is an alternative to mitigate those unwanted effects. Two field experiments were carried out to determine the color and size effect of the mesh on the capture of B. tabaci and nontarget organisms. The color experiment showed that among the 13 colors evaluated, only the yellow mesh did not reduce statically the number of B. tabaci captured compared with the uncovered traps. On the size experiment, among the three sizes evaluated, no statistical effect on the number of B. tabaci captured was exhibited. For the capture of nontarget organisms, the significative lowest values were showed in the small diamond and hexagon grooves. Those mesh traits were validated with two additional field experiments. The results of this study indicate that yellow sticky traps covered with a yellow mesh reduce the collection of nontarget organisms without affecting the capture of B. tabaci.
... Together with an infectious clone of the genomic DNA of TYLCV, we next investigated virus-tomato interactions in single and mixed infections based on symptom development and viral DNA accumulation. This information can help (i) predict the future impact of these begomoviruses on tomato production in Costa Rica and (ii) guide the development of integrative pest management (IPM) approaches (Gilbertson et al., 2011;Rojas et al., 2018). ...
Since the late 1980s, tomato production in Costa Rica has been affected by diseases caused by whitefly-transmitted begomoviruses. The first was tomato yellow mottle virus (ToYMoV), a locally evolved New World (NW) bipartite begomovirus associated with the tomato yellow mottle disease (ToYMoD). In the late 1990s, the invasive NW bipartite tomato leaf curl Sinaloa virus (ToLCSiV) was detected in Costa Rica and has become established and associated with ToYMoD. Finally, the invasive Old World (OW) monopartite tomato yellow leaf curl virus (TYLCV) was detected in Costa Rica in 2012 and has also become established and is causing tomato yellow leaf curl disease (TYLCD). In the present study, we investigated the invasion biology of these tomato-infecting begomoviruses in Costa Rica in terms of (i) their biological and genetic properties and (ii) disease symptoms and viral DNA accumulation in tomato plants having single and mixed infections. We first generated infectious DNA-A and DNA-B clones and agroinoculation systems for ToYMoV and ToLCSiV isolates recovered from archival ToYMoD samples collected in Costa Rica in 1990 and 2002, respectively. Tomato plants agroinoculated with the infectious clones of both viruses developed ToYMoD symptoms, completing Koch's postulates for ToYMoV, and showing that ToLCSiV also causes this disease. However, pseudorecombinants formed between the DNA components of these viruses were not infectious, which is consistent with independent evolution in different lineages and limits genetic interactions. Furthermore, ToYMoV is well-adapted to tomato, has a narrow host range and is mechanically transmissible. The DNA-A component has a recombination event in the hot spot area and induced a symptomless infection in agroinoculated N. benthamiana and tomato plants. Tomato plants co-infected with two or all three viruses developed more severe symptoms compared with plants infected with each virus alone. Symptoms induced by the NW bipartite ToYMoV and ToLCSiV appeared earlier (∼7 d post-inoculation [dpi]) than those induced by TYLCV (∼10 dpi), but TYLCD symptoms became predominant in single and mixed infections by 14 dpi. Viral DNA accumulation was quantified by qPCR and generally revealed a neutral synergistic interaction in which the viruses co-existed in mixed infections. A transient reduction in accumulation of ToYMoV and ToLCSiV was detected in mixed infections at 7 dpi, whereas TYLCV accumulation was not affected in mixed infections and was uniform among treatments and time points. Together our results suggest that this neutral synergistic interaction will lead to increased begomovirus disease severity in Costa Rica. We discuss this in terms of begomovirus invasion biology and disease management.
11. INTRODUCTION
... Yellow and zucchini squash varieties with resistance or tolerance to whiteflies and/or whitefly-transmitted viruses are not commercially available [34,35]. Current management programs for whiteflies and whitefly-transmitted viruses rely heavily on insecticides [37,42,57]. There is not a single management tactic available that can effectively reduce whitefly-mediated transmission of viruses to desirable levels. ...
The sweet potato whitefly, Bemisia tabaci MEAM1 Gennadius (Hemiptera: Aleyrodidae), and the complex of viruses it transmits are major limiting factors to squash production in the southeastern United States. At this time, insecticides are extensively relied upon for the management of whiteflies and, indirectly, whitefly-transmitted viruses. The development of a multi-faceted, integrated pest management (IPM) program is needed to increase the sustainability and profitability of squash production. Experiments in 2018 and 2019 evaluated the effects of insect exclusion netting (IEN) in combination with selected pesticides on whitefly population dynamics and virus incidence in greenhouse-grown squash seedlings. Field experiments from 2018 to 2021 evaluated the effects of mulch type (UV-reflective mulch, live mulch, and white plastic mulch), row covers, and insecticides on whitefly population dynamics, silver leaf disorder (SSL) intensity, virus symptom severity, and marketable yield. IEN significantly reduced whiteflies and virus incidence on squash seedlings in the greenhouse study. In the field mulch study, lower whitefly abundance and SSL intensity, as well as reduced virus symptom severity, were observed in plots with reflective mulch compared with white plastic or live mulch. In the insecticide/row cover study, whitefly abundance, SSL intensity, and virus symptom severity were lowest in the row cover and cyantraniliprole- and flupyradifurone-treated plots. Field plots with row covers and those with UV-reflective mulch consistently produced the greatest marketable yields. These findings demonstrate that growers can reduce whitefly and virus pressure and preserve yields in squash production in the southeastern United States by combining cultural and chemical tactics, including row covers, UV-reflective mulch, and select insecticides.
... Farmers rely heavily on synthetic pesticides to control whiteflies (Nderitu et al., 1997) and this has been the basis to suppress the pest populations (Kim et al., 2014;Lapidot et al., 2014). However, factors such as high fecundity rates, a short life cycle which enables quick population build-up within a short time, a waxy cuticle layer that limits penetration by contact pesticides, and polyphagy which ensures abundant alternative hosts have led to the low success of the chemical control (Hirano et al., 1993;Gilbertson et al., 2011;Abd-Rabou and Simmons, 2012). This has thus placed them among the few pest species that have driven intensive pesticide use. ...
In the scope of mitigating the negative impacts of pesticide use and managing greenhouse whiteflies, Trialeurodes vaporariorum sustainably, 16 endophytic fungal isolates from five different genera (Beauveria, Trichoderma, Hypocrea, Bionectria, and Fusarium) were screened for their ability to colonise two preferred host plant species, namely, tomato (Solanum lycopersicum L.) and French bean (Phaseolus vulgaris L.), through seed inoculation. Seven and nine isolates were endophytic to P. vulgaris and S. lycopersicum, respectively, where significant differences in the endophytic colonisation rates were observed among the fungal isolates in P. vulgaris and its plant parts, with a significant interaction between the isolates and plant parts in S. lycopersicum. Hypocrea lixii F3ST1, Trichoderma asperellum M2RT4, Trichoderma atroviride F5S21, and T. harzianum KF2R41 successfully colonised all the plant parts of both hosts and therefore were selected and further evaluated for their endophytic persistence, effect on plant growth, and pathogenicity to T. vaporariorum adults and F1 progeny. The four endophytes remained in both host plants for the 5-week assessment with varied colonisation rates related to the strong interaction with the time, isolates, and plant parts in both hosts. The effect of the same endophytes on the different host growth parameters varied in P. vulgaris and S. lycopersicum, with T. asperellum M2RT4 not boosting the growth in both host plants while T. atroviride F5S21 resulted in enhanced shoot biomass in S. lycopersicum. T. atroviride F5S21 and T. harzianum KF2R41 inoculated S. lycopersicum plants and H. lixii F3ST1, T. asperellum M2RT4, and T. harzianum KF2R41 inoculated P. vulgaris plants had significantly lower oviposition, while nymph development in both hosts was significantly prolonged in all the endophytically–colonised plants. The endophytes H. lixii F3ST1 and T. asperellum M2RT4 significantly reduced the longevity/survival of the exposed T. vaporariorum adults and the progeny in both S. lycopersicum and P. vulgaris. The findings demonstrate the attributes of the various endophytes in host plant growth promotion as well as their effects on the life-history parameters of T. vaporariorum and could consequently be developed as potential endophytic fungal-based biopesticides for the sustainable management of the pest in S. lycopersicum and P. vulgaris cropping systems.
... In addition, the excessive and constant use of these products compromises their performance along time, as more pests become resistant to them. The availability of alternative practices, such as resistant varieties use, are essential to provide integrated pest control (Gilbertson et al. 2011(Gilbertson et al. ). https://doi.org/10.1590(Gilbertson ...
Whiteflies (Bemisia tabaci) are a serious threat to tomato (Solanum lycopersicum) yield and production since all varieties are highly susceptible to this insect. The wild tomato Solanum pennellii shows resistance towards whiteflies infestation due the high contents of acylsugars presents in its leaflets, which is not observed in S. lycopersicum. Thus, plants from the F2BC2 population derived from the cross between the cultivar S. lycopersicum ‘Redenção’ and S. pennellii (accession LA-716) were selected for acylsugars levels and evaluated for resistance to whitefly and fumagine, a saprophyte fungus from genus Capnodium (sooty mold) that grows on leaves using whiteflies excretion. Biological behavior of B. tabaci was significantly influenced by the levels of acylsugars on the leaflets of the different genotypes. Solanum pennellii and the genotypes with higher acylsugars contents exhibited the lowest whitefly oviposition preference, number of nymphs, exuviae and adult survival. Also, the percentage of leaf coverage with fumagine was significantly reduced on leaves of the S. pennellii and the genotypes with higher acylsugars. Thus, it confirms that the use of S. pennellii LA-716 enabled the introgression of genes to increase the degrees of resistance in the F2BC2 genotypes. Finally, the results presented suggest that the genotypes RVTA-2010-31-177pl#39, RVTA-2010-31-319pl#214 and RVTA-2010-83-347pl#257 can be used as potential sources of genes for resistance to B. tabaci in tomato breeding programs.
Key words:
Solanum lycopersicum ; Solanum pennellii ; Bemisia tabaci ; Capnodium
... While, the modern methods include pathogen-derived resistance, RNAi-mediated resistance, ribozymemediated resistance, and genome editing. It should also be clear that management of whiteflies and begomovirus diseases cannot be accomplished by any single control measure, especially reliance on insecticides and that an IPM approach is needed (Gilbertson et al. 2011). ...
Plant virus diseases result from a complex interplay of virus, vector, and host over time under environmental conditions that allow efficient spread and survival of the virus, its host, and its vector. This chapter relates to the ecology of plant infecting viruses with emphasis on geminiviruses and their satellites. The ability of the virus to spread and reach epidemic proportions depends on several ecological factors that directly or indirectly influence the population dynamics of the aerial vectors, their feeding behavior, their movement over long distances, and certainly the availability of susceptible cultivated or wild hosts. In light of these ecological factors, management strategies to prevent virus infections are highlighted in this chapter. Finally, the role of humans is discussed as their impact on the agro‐climatic environment and their movement of plant material has led, in some instances, to the emergence of new recombinant geminiviruses and to epidemics of viral disease in plant hosts.
... Chemical control plays an important role in the management of insect-vector populations [17], reducing the number of individuals that can transmit plant pathogens in the field. However, successful chemical control requires extensive knowledge of the effects of insecticides, not only on the mortality and oviposition of the vector insect, but also on the feeding behavior associated with the acquisition and inoculation of viruses and other pathogens. ...
Tomato chlorosis virus (ToCV) is a phloem-limited crinivirus transmitted by whiteflies and seriously affects tomato crops worldwide. As with most vector-borne viral diseases, no cure is available, and the virus is managed primarily by the control of the vector. This study determined the effects of the foliar spraying with the insecticides, acetamiprid, flupyradifurone and cyantraniliprole, on the feeding behavior, mortality, oviposition and transmission efficiency of ToCV by B. tabaci MEAM1 in tomato plants. To evaluate mortality, oviposition and ToCV transmission in greenhouse conditions, viruliferous whiteflies were released on insecticide-treated plants at different time points (3, 24 and 72 h; 7 and 14 days) after spraying. Insect mortality was higher on plants treated with insecticides; however, only cyantraniliprole and flupyradifurone differed from them in all time points. The electrical penetration graph (DC-EPG) technique was used to monitor stylet activities of viruliferous B. tabaci in tomato plants 72 h after insecticide application. Only flupyradifurone affected the stylet activities of B. tabaci, reducing the number and duration of intracellular punctures (pd) and ingestion of phloem sap (E2), a behavior that possibly resulted in the lower percentage of ToCV transmission in this treatment (0–60%) in relation to the control treatment (60–90%) over the periods evaluated. Our results indicate that flupyradifurone may contribute to management of this pest and ToCV in tomato crops.
... The management of ToSRV is based on several cultural practices, such as crop rotation, crop-free periods, and weed management. However, the main strategy used today is based on vector control with insecticides (Gilbertson et al., 2011;Lapidot et al., 2014). The Brazilian state of Goiás has implemented a tomato-free period for managing B. tabaci and ToSRV spread, but this policy has not been efficient due to the capacity of ToSRV to infect other vegetable and weed species (Inoue-Nagata et al., 2016b;Macedo et al., 2017aMacedo et al., , 2017b. ...
Tomato severe rugose virus (ToSRV) is the most important begomovirus transmitted and spread by Bemisia tabaci in tomato crops in Brazil. Cultural practices are being adopted, along with insecticides, for controlling this virus. However, little is known about the importance of weeds in the pathosystem, which can contribute to the failure of these practices. This work aimed to evaluate the role of Datura stramonium and Nicandra physaloides as alternative hosts of ToSRV and verify the viral influence in biological performance of Bemisia tabaci Middle East‐Asia Minor 1 (MEAM1) and Mediterranean (MED) cryptic species. Nicandra physaloides was a better alternative host for ToSRV when combined with MEAM1 whiteflies, while D. stramonium was mostly a good host for whitefly reproduction. Viral infection improved MEAM1 performance on both host plants but affected MED performance negatively. These data suggest that both weeds can have some importance for the pathosystem, and their control should be included in management programs.
... Management for virus infecting crop plants is attaining magnitude with the increased spread of viruses and threats of their epidemics (Gilbertson et al. 2011;Khurana and Marwal 2016). The extent of evolution of Mastreviruses is predominantly quite rapid due to highest rate of recombination in this genus, forming newer strains by overpowering the host genes viable for confrontation/resistance. ...
Mastreviruses are the main causal viral agent of a variety of plant diseases in African continent posing a serious threat to economically important plant species, residing/harbouring chiefly in the uncultivated ones. Mastreviruses are known to have numerous diverse carrier vectors infecting either monocotyledons or dicotyledons plants. More than 1950 Mastreviruses sequences are publically available in nucleotide database of NCBI, majority (~850) of them are reported from Africa alone. All the known Mastreviruses encompass a monopartite genomic nature (ranges from 2.5 to 2.7 kb) encoding four genes. Reports and evidences suggest a strong intra- or inter-specific recombination among the identified Mastreviruses, but the extent to which it creates diversity is still a challenging task to understand and get a clear insight. Such diversity is also supported by gene acquisition and mutations (especially point mutations and small insertions or deletions). Current study focuses on the molecular diversity analysis and genomic characterization of the reported Mastreviruses from the African continent.
... The tissue culture technique engages meristem tip excision, thermotherapy, and virus indexing for producing virus-free plants (Legg et al. 2006). Row covers in Israel and Guatemala have been used to protect plants from whiteflies in crops such as cucurbits, pepper, and tomato (Natwick and Durazo 1985;Gilbertson et al. 2011). Another interesting approach that has been applied in Israel is to grow vegetables (like tomatoes) in greenhouses (glass, plastic, and double doors with positive pressure), protecting from whitefly damage and virus infection by physical means. ...
There are a large number of threats to the agricultural crops across the world. Many insect pests harmthe crops and reduce the yield, but apart from these there are other microscopic pathogens that causea great annual loss to the agriculture sector and the livelihood of Indian farmers and world agriculturaleconomy. Worldwide expansion of agriculture has also resulted in the emergence and spread ofnumerous diseases and insect pests. Of particular importance are insect-transmitted viruses, especiallyin tropical and subtropical regions. Geminiviruses are insect-transmitted viruses that have emergedover the past 20 years as the largest group of plant viruses (322 species) and one of the most eco-nomically important
... In this study, they employed intercropping with cucumber and tomato (both T. vaporariorum hosts), organic and inorganic fertilizers, release of predators and entomopathogenic fungi, and trapping to manage B. tabaci, leaf miners, and lepidopteran pests. In addition to integrated management programs for direct whitefly damage, Gilbertson et al. (2011) andPratissoli et al. (2015) present IPM programs to reduce whitefly-vectored plant viruses. ...
... La aplicación de insecticidas sigue siendo una herramienta muy utilizada (Perring et al., 1999) y en algunos casos la única forma de manejo. La literatura señala que las aplicaciones frecuentes y prolongadas de imidacloprid promueven la aparición de individuos resistentes tanto de B. tabaci y B. argentifolii (Elbert y Nauen, 2000;Li et al., 2001, Nauen et al., 2002, como de T. vaporariorum (Gorman et al., 2007), lo que prueba que un único método de control puede ser evadido de muchas maneras, por lo que para un manejo eficaz puede ser necesario implementar varias estrategias a la vez (Gilbertson et al., 2011). ...
... La aplicación de insecticidas sigue siendo una herramienta muy utilizada (Perring et al., 1999) y en algunos casos la única forma de manejo. La literatura señala que las aplicaciones frecuentes y prolongadas de imidacloprid promueven la aparición de individuos resistentes tanto de B. tabaci y B. argentifolii (Elbert y Nauen, 2000;Li et al., 2001, Nauen et al., 2002, como de T. vaporariorum (Gorman et al., 2007), lo que prueba que un único método de control puede ser evadido de muchas maneras, por lo que para un manejo eficaz puede ser necesario implementar varias estrategias a la vez (Gilbertson et al., 2011). ...
The aim of this work was to detect plant infections caused by Tomato chlorosis virus (ToCV) and begomovirus in tomato plantlets, and in growing weeds around nursery greenhouses. During one year, starting in April 2008, 168 leaf tissue samples were collected, 90 tomato plantlets and 78 weeds from three different nurseries in Cartago province, Costa Rica. Reverse transcription and real time polymerase chain reaction (qRT-PCR) was used to determine that 18,9% of tomato plantlets and 7,7% of weeds were infected with ToCV virus. Begomoviruses were detected using Dot Blot hybridization and non-radioactive probe. Next, hybridization results were confirmed using Rolling Circle Amplification (RCA) followed by PCR, using universal primers. None tomato plantlet resulted positive when tested, but there were six weeds infected; in fact, Phytolacca icosandra and Brassica sp. were both coinfected with ToCV virus. These results suggest that ToCV infected tomato plantlets when commercialized, could serve as way of virus introduction to other country regions. Finally, weeds growing around greenhouses have shown to be potential viral sources of ToCV and begomovirus.
... Synthetic pesticides have largely failed to address the problem of whitefly population in field. Management of whiteflies and begomovirus diseases, IPM approach is needed [52]. Biological and ecofriendly management alternatives could be the answer as in the case of heavy population of biotype B of whitefly, which was successfully, controlled using its natural enemies [75]. ...
Begomoviruses (family Geminiviridae) are responsible for extreme yield reduction in a number of economically important crops including medicinal and aromatic plants (MAPs). Emergence of new variants of viruses due to recombination and mutations in the genomes, modern cropping systems, introduction of susceptible plant varieties, global trade in agricultural products, and changes in climatic conditions are responsible for aggravating the begomovirus problems during the last two decades. This review summaries the current research work on begomoviruses affecting MAPs and provides various traditional and advanced strategies for the management of begomoviruses and vector in MAPs.
... Cultivation of susceptible tomato germplasm leads to high whitefly population infestation and virus incidence on host plants (Gilbertson et al., 2011). Several pesticides/chemicals applied against the insects failed to control the B. tabaci and attributed to the emergence of insecticidal resistance (Hameed et al., 2010). ...
Tomato leaf curl virus (TLCV) is the most devastating virus of tomato crop. TLCV is transmitted by whitefly (Bemisia tabaci) in a persistent and circulative manner. For the management of this problem, twenty seven tomato varieties/lines were screened for the source of resistance against tomato leaf curl virus disease (TLCVD) in field trial because no viricide was available to combat the viral diseases and insect vectors had developed resistance against the insecticides. The observations of TLCVD incidence were recorded on weekly basis. Varieties/lines were evaluated on the basis of symptomology. Grafting and whitefly mediated inoculation techniques were adopted to confirm the virus. Out of twenty seven varieties/lines, three were highly susceptible, six were susceptible, four were moderately susceptible, six were moderately resistant and eight cultivars were resistant. No variety/line was highly resistant or immune against TLCVD. Resistant genotypes (varieties/lines) can be used in breeding programs as an eco-friendly management approach. © 2016, Pakistan Agricultural Scientists Forum. All rights reserved.
... Most of these insects are disease non-transmitters. However, an IPM strategy incorporating all crops is necessary in order to reduce the insect Fig. 12 Schematic view of host-free periods of pathogens of tomato and other crops implemented in Brazil population size, and ultimately virus incidence (Gilbertson et al. 2011). Tomato crops are a primary target for management, especially when plants are old and host large insect populations. ...
... Most of these insects are disease non-transmitters. However, an IPM strategy incorporating all crops is necessary in order to reduce the insect Fig. 12 Schematic view of host-free periods of pathogens of tomato and other crops implemented in Brazil population size, and ultimately virus incidence (Gilbertson et al. 2011). Tomato crops are a primary target for management, especially when plants are old and host large insect populations. ...
In some epidemics that have devastating consequences, the primary inoculum plays an important role in both epidemic onset and intensification. This article documents the dynamics of such epidemics, and illustrates their importance using two examples: Huanglongbing of citrus and begomoviruses of tomato. The latter disease is a major constraint to tomato production in Brazil, while the former has become a threat to global citrus production and farmers’ livelihoods. In spite of their importance little is known of the characteristics of these diseases and their management. This is because classical botanical epidemiology considers two types of diseases: polycyclic diseases, where the inoculum that causes infections is produced during the epidemic in or on individual plants that had been previously infected in the course of that epidemic; or monocyclic diseases, where inoculum that causes infection is not produced in or on individual plants that had been infected in the course of the epidemic, but in the soil, on secondary hosts, or in infected crop plants of the same host in other fields. Diseases of the first type typically present a logistic disease progress curve and management is based on reducing the rate of infection, whereas diseases of the second type present a monomolecular disease progress curve and management is based on reducing the initial inoculum. This article deals with plant diseases that depart in their structure and behaviour from these two archetypes, because they borrow elements from both. We address polycyclic diseases in which the primary inoculum has a continuous and dynamic role, and in which the secondary inoculum contributes to epidemic build-up, i.e., polycyclic diseases with continuous primary spread. This epidemiological structure generates less clear-cut disease progress curves, but usually follows a monomolecular dynamic. Our focus on this type of disease is multifold because (1) this more complex, combined, pattern is actually quite common, often leading to grave plant diseases epidemics, with impacts at the farm, community, and country scales, and (2) such epidemics are among the most difficult to manage. Our analysis leads us to assess past errors and current courses of action. It allows us to recognize, in addition to the conventional tools for management with local effects, the critical importance of collective action. Collective management action – at the farm, community, or national scales – is congruent with the characteristics of many epidemics, because they also entail properties at successive and nested scales. The management of such epidemics needs to address both the primary and secondary inoculum. More importantly, these actions have to be performed in an area-wide, regional basis in order to be effective.
... We define an emerging virus as a previously unknown virus or a known virus that has expanded its geographical range, incidence, and importance because of an arthropod vector. The reasons for virus emergence include evolution of new viruses or new strains of existing viruses; changes in the geographical range, properties, and populations of insect vectors; changes in agricultural practices; and climate change (8)(9)(10)(11). One of the most notable trends has been the emergence of two insect vectors, Bemisia tabaci (sweet potato, tobacco, or silverleaf whitefly) and Frankliniella occidentalis (Western flower thrips), as driving forces in the emergence of plant viruses in agricultural ecosystems (Figure 1). These two vectors alone transmit >300 viruses representing 10 genera ( Table 1) (12)(13)(14). ...
Emergence of insect-transmitted plant viruses over the past 10-20 years has been disproportionately driven by two so-called supervectors: the white-fly, Bemisia tabaci, and the Western flower thrips, Frankliniella occidentalis. High rates of reproduction and dispersal, extreme polyphagy, and development of insecticide resistance, together with human activities, have made these insects global pests. These supervectors transmit a diversity of plant viruses by different mechanisms and mediate virus emergence through local evolution, host shifts, mixed infections, and global spread. Associated virus evolution involves reassortment, recombination, and component capture. Emergence of B. tabaci-transmitted geminiviruses (begomoviruses), ipomoviruses, and torradoviruses has led to global disease outbreaks as well as multiple paradigm shifts. Similarly, F. occidentalis has mediated tospovirus host shifts and global dissemination and the emergence of pollen-transmitted ilarviruses. The plant virus-supervector interaction offers exciting opportunities for basic research and global implementation of generalized disease management strategies to reduce economic and environmental impacts.
... B. tabaci is a pest of great economic importance, attacking crops in the field as well as in greenhouses, and its host plant list includes hundreds of species, with the number increasing as the pest invades new countries (Mound and Halsey 1978;Li et al. 2011). B. tabaci can cause significant damage to crops due to the feeding activity, honeydew production and physiological disorders induction; moreover, in many cases, it can transmit serious plant pathogenic viruses (Schuster et al. 1995;Gilbertson et al. 2011). Furthermore, in B. tabaci populations, the problem of insecticide resistance is widely diffused so that conventional chemical control often fails (Castle et al. 2010). ...
The behavioural response of the sweet potato whitefly, Bemisia tabaci biotype B, to the volatiles emitted by three different species of Callistemon (C. laevis, C. pallidus and C. phoeniceus) was assayed in still-air, and Y-tube olfactometers. B. tabaci adults showed a preference for C. pallidus, while C. laevis and C. phoeniceus were less attractive to the insects when compared to a blank control or to C. pallidus. Volatile organic compounds emitted by the leaves of the three Callistemon species were analysed by solid phase microextraction coupled with GC-MS. 1,8-Cineole was detected in high percentages in C. phoeniceus and C. laevis headspaces, while linalool was abundant in the headspace of C. pallidus. Because of this difference, behavioural tests in the Y-tube olfactometer were carried out also with 1,8-cineole and linalool. Adults of B. tabaci were attracted by linalool, while they were repelled by 1,8-cineole compared with pure air or linalool. These results support the role of these volatiles in the host plant selection process by a herbivorous insect and lay the foundations for the development of sustainable control strategies based on the manipulation of insect pest behaviour.
... Protecting the tomato crop from viral infection during the first 6 weeks after transplanting is crucial to mitigate yield loss (Lapidot & Levy 2010). At-plant and early season applications of insecticides have been key components to managing TYLCV and B. tabaci in Florida tomato and elsewhere (Gilbertson et al. 2011;Schuster et al. 2008). However populations of B. tabaci biotype B have developed resistance to several modes of action globally (Castle et al. 2010;Ma et al. 2010;Rao et al. 2012), and resistance to neonicotinoids, one of the most useful insecticide groups for managing B. tabaci, has been documented in Florida (Schuster et al. 2010). ...
Management of Tomato yellow leaf curl virus (TYLCV) in Florida tomato involves destroying inoculum sources, using reflective mulches to repel the vector, growing TYLCV-tolerant varieties, and using insecticidal control. Three new insecticides with distinct modes of action were evaluated for management of Bemisia tabaci (Gennadius) and the whitefly-transmitted TYLCV. Chemicals were applied in paired combinations during the first 5 weeks after transplanting. Flupyradifurone (Sivanto) and cyantraniliprole (Cyazypyr (TM)) are systemic insecticides that can be applied to soil or foliage and pyrifluquinazon is a translaminar material for foliar application. In order to determine optimal combination of chemicals with different modes of action for early-season whitefly control and virus suppression, systemic materials were soil-applied at-plant followed by foliar applications of a material with a distinct mode of action. Dinotefuran (Venom) was included as a standard at-plant material for comparison. Field trials were carried out using a split plot design with insecticide programs as main plot treatments which were split into plots covered under a floating row cover for the first 2 weeks after planting or left uncovered. The intention of the row cover treatment was to compare the degree of protection offered by at-plant treatments when the crop was exposed to virus immediately after transplanting to exposure two weeks after transplanting, and to determine if any at-plant treatment were comparable to mechanical exclusion of the vector. In fall 2012, when virus pressure was moderate, end of season virus incidence was lower than the untreated control in all chemical treatments except dinotefuran drench alone or followed by cyantraniliprole. Percentage virus in these 2 treatments were not significantly different from the untreated plots as of 5 weeks after transplanting in both fall trials (2012 and 2013). During both fall trials, percent virus was numerically lowest each week in either the flupyradifurone or flupyradifurone followed by pyrifluquinazon treatments, although the differences from other treatments were not always statistically significant. In spring 2013, when virus pressure was negligible, yield was higher in plots treated with dinotefuran followed by cyantraniliprole than in other treated plots, with the exception of flupyradifurone followed by cyantraniliprole. Row cover treatments were only partially successful, and did not indicate that any at-plant treatment was comparable to mechanical exclusion of the vector. Integration of new materials into insecticide recommendations and resistance management plans for Florida tomato (Solanum lycopersicum L.) production are discussed.
... In this study, they employed intercropping with cucumber and tomato (both T. vaporariorum hosts), organic and inorganic fertilizers, release of predators and entomopathogenic fungi, and trapping to manage B. tabaci, leaf miners, and lepidopteran pests. In addition to integrated management programs for direct whitefly damage, Gilbertson et al. (2011) and Pratissoli et al. (2015) present IPM programs to reduce whitefly-vectored plant viruses. ...
Plants are efficient producers of chemical compounds that are used in defense against herbivore attack. Botanical compounds have been used in several parts of the world long before the arrival of synthetic pesticides. Plant-derived pesticides or extracts containing active compounds can be used directly and can also form the basis for synthesizing products with similar or even better insecticidal properties. For example, pyrethrum has been used as the basis for the synthesis of the synthetic pyrethroids, which are important in modern chemical crop protection. Most widespread among the synergists are the inhibitors of different insect enzymes, including mixed-function oxidases and esterases. This chapter focuses on the effects of some crude extracts from plants and some commercially available botanical insecticides on important insect pests of cruciferous vegetables. The botanical materials include crude extracts and isolated or purified compounds from various plants species and commercial products. The insect pests tested include Trichoplusia ni, Spodoptera exigua, S. litura, Pieris rapae, Helicoverpa spp., Evergestis rimosalis, and Mythimna separate in Lepidoptera, Aphis gossypii, Lipaphis erysimi, Myzus persicae, Brevicoryne brassicae, and Bemisia spp. in Hompotera, Phyllotreta vittata in Coleoptera, and L. sativae in Diptera. The advantages and disadvantages of using those materials and the potential of these botanical materials in the integrated pest management of cruciferous vegetables are discussed in the chapter.
Tomato (Solanum lycopersicum L.) is important vegetable crop in India. Tomato leaf curl viral disease caused by tomato leaf curl virus (ToLCV) (genus: Begomovirus, family: Geminiviridae) and transmitted by whitefly (Bemisiatabaci) is considered as the most devastating one. Recently, available tomato varieties are not screened against this disease in the agro ecosystem of India. Therefore, in this study commercial varieties of tomato genotypes including 32 lines including1 resistant and
1 susceptible check were screened against ToLCV in open field condition at Vegetable Research Farm, Department of Horticulture, Institute of Agricultural Sciences, Banaras Hindu University, Varanasi during 2019-20. Among the screened genotypes, H-24, H- 88-78-1, Arka Alok and ArkaVardan showed highly resistant reaction to (ToLCV). The Per cent Disease Incidence (PDI) of ToLCV were significantly lower for all these of genotypes. Hence, these resistant sources can be used in resistant breeding programme for further development of varieties/hybrids against ToLCV virus.
Cassava is the second most important source of calories in Sub-Saharan Africa. It is subject to economically important yield losses from viral diseases, including cassava brown streak disease and cassava mosaic disease. These diseases are vectored by cassava whitefly, so improved approaches for whitefly and disease control are needed to enable smallholder farmers to protect their cassava crops. To investigate the economic viability of insecticide applications against whitefly, the effect of four insecticide application regimes on three cassava genotypes (NASE 3, NASE 12, MKUMBA) and a local landrace were evaluated, for different farmer groups. Data were collected from researcher–farmer managed fields and descriptive statistics were analyzed. Insecticide and personal protective equipment were the major costs for those farmers that applied insecticide and the dipping treatment had a marginal rate of return of 1.66 (166%), demonstrating that this option was the most profitable and effective. While insecticide users incurred more production costs, they also accrued more profit than non-insecticide users, especially if insecticide was applied at early stages of cassava growth. There is a clear need, therefore, to strengthen the commercialization of cassava crop through plant protection measures such as judicious insecticide application on susceptible varieties, so as to increase yield and crop quality.
Geminiviruses are a family of phytopathogens that measure around 30 nm and their virion is made up of two geminated particles. Their genome is made up of 2.5–5.2 kb ssDNAs. Geminiviruses conserve the nucleotide segment TAATATTAC that forms a stem-loop-like structure, involved in the initiation of viral replication. Some species have single-stranded DNA molecules, called α- or β-satellites. Geminiviruses infect almost all known crops and weeds. Includes crops such as wheat, corn, tomato, and cassava. For the management of the diseases they cause, resistant varieties have been generated by conventional genetics and by genetic manipulation in laboratories. Likewise, practices have been designed that include chemical, biological, and physical management.
An evaluation of the different management strategies leads to the following: first, although it has been successful for some time, the evolutionary complexity of geminiviruses will continue to demand practices and strategies for their management. Second, the most relevant objective should be vector management, since the same vector species transmits several species of geminivirus in different plant species; third, practices directed against the pathogen should target the universally conserved geminivirus sequence: TAATATTAC. Finally, promising results have now been found in the use of compounds such as nanoparticles or biotic inducers for direct control of geminivirus.
Purpose. To evaluate the effectiveness of different insecticides against pests on two-year old alfalfa grown for seeds. Materials and methods. The study was conducted in the experimental field of the Institute of Irrigated Agriculture of NAAS in 2017–2019. The filed experiments were laid out in split plots. The main plots (factor A) were for water supply conditions (no irrigation vs. irrigation); sub-plots (factors B and C) were for application of insecticides. Seeds were sown in wide rows with interrows of 70 cm. Results and discussion. When the two-year old alfalfa canopy (budding onset) was inspected before insecticide treatment, the average numbers of pests were as follows: alfalfa plant bug – 3.0 specimens/10 sweeps, alfalfa aphid – 20.0 specimens/10 sweeps, beet webworm – 3.0 specimens/10 sweeps, alfalfa weevil (imagoes/grubs) – 1.0/3.0 specimens/10 sweeps, and alfalfa seed weevil – 1.0 specimens/10 sweeps. Treatment 1 reduced the pest numbers in the canopy: alfalfa plant bug – by 70.0–93.3%, alfalfa aphid – by 93.0–97.5%, beet webworm – by 80.0–96.7, alfalfa weevil (imagoes/grubs) – by 60.0–90.0%/73.3–93.3%, and alfalfa seed weevil – by 76.0–94.0%, depending on the insecticide. Treatment 2 helped to reduce the pest numbers in the canopy. Insecticide containing active substances chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha was the most effective. The highest seed yield was achieved after treatment 1 with insecticide containing active ingredients chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha and treatment 2 with insecticide containing active ingredients chlorantraniliprole 200 g/L and lambda-cyhalothrin 50 g/L applied at a dose of 0.17 L/ha and 0.15 L/ha, respectively. Conclusions. The highest seed yield was achieved after treatment 1 with insecticide containing active ingredients chlorpyrifos 500 g/L and cypermethrin 50 g/L applied at a dose of 1.00 L/ha and treatment 2 with insecticide containing active ingredients chlorantraniliprole 200 g/L and lambda-cyhalothrin 50 g/L applied at a dose of 0.17 L/ha and 0.15 L/ha, respectively
Метою дослідження було виявити ефективність різ- них інсектицидів проти шкідників на насінницьких посівах люцерни першого року життя травостою. Методи дослі- джень. Дослідження проводили протягом 2016–2018 рр. на дослідному полі Інституту зрошуваного землеробства НААН. У ґрунтово-кліматичному відношенні розташоване в степовій зоні, на Інгулецькому зрошуваному масиві. Метод закладки польового досліду – розщеплені ділянки. Видовий склад шкідливих комах виявляли за проведення обстежень, чисельність їх і співвідношення різних стадій пов’язували з фазами розвитку рослин і погодними умо- вами (температура, вологість повітря та опадами) за допо- могою ентомологічного сачка (10 помахів). Оцінку ефек- тивності термінів та кратності хімічних обробок визначали за методикою С.О. Трибеля та з врахуванням економічних порогів шкідливості. Статистичну обробку експерименталь- них даних проводили AgroSTAT, XLSTAT, Statistica (v. 13). Результати досліджень. Найефективнішим у боротьбі зі шкідниками (за винятком люцернової попелиці) виявився препарат з діючими речовинами Хлорпірифос, 500 г/л й Циперметрин, 50 г/л та нормою витрати 1,00 л/га. Він знижував чисельність шкідників: люцернового клопа – на 85,5%, люцернової попелиці – 92,7, гусениці лучного мете- лика – 93,0, люцернового насіннєїду – 85,7 та люцерно- вої товстоніжки – на 94,0%, відповідно й зменшувалося пошкодження генеративних органів та насіння. Висновки. Найефективнішим у боротьбі зі шкідниками (за винятком люцернової попелиці) виявився препарат з діючими речо- винами Хлорпірифос, 500 г/л й Циперметрин, 50 г/л та нор- мою витрати 1,00 л/га). Але наявність у даного препарату фумігаційної дії негативно позначилась на чисельності комах-запилювачів, що зменшило утворення бобів і насіння в них та в подальшому вплинуло на продуктивність рослин. Найбільшу врожайність насіння отримали на варіанті при застосуванні суміші інсектицидів з діючими речовинами Хлорантраніліпрол, 200 г/л й Лямбда-цигалотрин, 50 г/л.
Papaya leaf curl disease is caused by Papaya leaf curl virus (PaLCuV), a begomovirus naturally transmitted through whitefly (Bemisia tabaci). Main symptoms of papaya leaf curl disease are inward/outward curling of plant leaves, vein thickening, and stunted plant growth with small distorted fruits or no fruits. Papaya leaf curl virus is a major threat for the crop production, and the virus has the capability to adapt new plant hosts very rapidly which helps in their host range extension that also has emerged as an evolving risk in papaya production. Whitefly management is the main method to control the spread of this virus so far. Several diagnostic techniques especially molecular techniques have been developed to detect the begomoviruses at early stages of infection to control the further spread of the begomovirus, but so far not much reports are available to control the begomoviral infection at later stage. This chapter provides the information about many aspects like causal pathogen, vector responsible for disease spread/transmission, host range and phylogenetic analysis of virus associated with the papaya leaf curl disease, and different resistance approaches for possible management of the disease.
The horticultural crops are severely threatened by many insects, pests and diseases. In this backdrop, viral diseases assume much greater significance as most of these viral diseases are transmitted through insects. The source of resistance for these viral diseases is scanty. Begomoviruses affect a large number of vegetables and few fruit crops. Begomoviruses cause significant crop losses in horticultural crops like tomato, okra, chilli, papaya, brinjal, cassava, squash, sweet potato, potato, etc. Despite the amount of efforts that has gone into the control of begomoviruses, sustained resistance has not been acquired in many crops. Obtaining crops resistant to begomoviruses is very difficult because the insect vector is whitefly (Bemisia tabaci) which develops resistance against insecticides, and it is increasingly spreading over large parts of the world. Molecular markers and other genomic information are allowing more precision breeding for greater tolerance to viral diseases in general and begomoviruses in particular. This chapter highlights many fruit and vegetable crops which are affected by begomoviruses.
Viruses have long been known to be prevalent in plants in tropical and sub-tropical developing countries, particularly in staple crops such as cassava, rice, coconut and pulses. The need to address a wider range of vegetable crops was identified by the IPM-Innovation Lab. To meet these needs, a team of virologists was organized to work across countries and regions with IPM specialists to document virus disease problems in priority crops; mainly tomato and peppers, melons and various gourds and cucurbits, locally preferred vegetables such as eggplant (brinjal), okra (bhendi) and yardlong bean, and fruits (passion fruit, tree tomato). These crops constitute important sources of income and food sources, for many farmers, and were observed to be infected by a wide diversity of viruses. Demands for increased production, increased uniformity of vegetables grown for domestic and export markets, changes in production practices leading to scale up of production of seeds and seedlings, changes related to intensification and global climate change, and greater crop uniformity across regions, appear to be associated with crop losses due to viruses. This chapter summarizes more than two decades of research results to identify problems, and describes progress to enhance local capacity for in-country diagnosis and implementation of integrated disease management practices.
The CRISPR/Cas9 system has recently been used to confer molecular immunity against several eukaryotic viruses, including plant DNA geminiviruses. Here, we provide a detailed analysis of the efficiencies of targeting different coding and non-coding sequences in the genomes of multiple geminiviruses. Moreover, we analyze the ability of geminiviruses to evade the CRISPR/Cas9 machinery. Our results demonstrate that the CRISPR/Cas9 machinery can efficiently target coding and non-coding sequences and interfere with various geminiviruses. Furthermore, targeting the coding sequences of different geminiviruses resulted in the generation of viral variants capable of replication and systemic movement. By contrast, targeting the noncoding intergenic region sequences of geminiviruses resulted in interference, but with inefficient recovery of mutated viral variants, which thus limited the generation of variants capable of replication and movement. Taken together, our results indicate that targeting noncoding, intergenic sequences provides viral interference activity and significantly limits the generation of viral variants capable of replication and systemic infection, which is essential for developing durable resistance strategies for long-term virus control.
The begomovirus-Bemisia tabaci (Gennadius) complex is the main sanitary problem of tomatoes in Venezuela. Genotypes resistant to begomoviruses are a valuable alternative for integrated management of this problem. Consequently, it was assessed the performance of the cultivars Rio Grande (CRG), Alba El cid and Shan TY, the first one susceptible and the other three promoted as resistant to TYLCV. This virus, along with ToVEV, are two common tomato begomoviruses in Venezuela. Transmission assays mediated by B. tabaci were conducted to assess time for symptoms appearance and transmission efficiency. CRG showed TYLCV symptoms after 12.6 ± 1.2 days post inoculation (DPI) in 100 % of the plants, while for the remaining cultivars it ranged from 14.1 ± 1.3 to 16 ± 1.5 DPI with 18.5-33.3 % of symptomatic plants, generally with mild symptoms. With ToVEV for CRG, symptoms appeared at 12.4 ± 1.2 DPI with 100 % of affected plants, and for the other cultivars more than half of the plants (ranging 66.7 to 81.5 %) showed symptoms at 12 ± 1.1 to 14.9 ± 1.4 DPI. El Cid showed the most severe symptoms. In all plants exposed to begomovirus, viral DNA was detected by PCR. The resistance to a begomovirus can provide some resistance to another but not to all of them. However, those that showed tolerance could be utilized to reduce the effect of these begomoviruses on tomato crops in Venezuela. © 2015, Universidad Centroccidental Lisandro Alvarado (UCLA). All rights reserved.
All characterized whitefly-transmitted geminiviruses (begomoviruses) with origins in the New World (NW) have bipartite genomes composed of a DNA-A and DNA-B component. Recently, a NW begomovirus lacking a DNA-B component was associated with tomato leaf curl disease (ToLCD) in Peru and named Tomato leaf deformation virus (ToLDeV). Here, we show that isolates of ToLDeV associated with ToLCD in Ecuador and Peru have a single, genetically diverse, genomic DNA that is most closely related to DNA-A components of NW bipartite begomoviruses. Agroinoculation of multimeric clones of the genomic DNA of three ToLDeV genotypes (two variants and a strain) resulted in the development of tomato leaf curl symptoms indistinguishable from those of ToLCD in Ecuador and Peru. Biological properties of these ToLDeV genotypes were similar to those of Old World (OW) monopartite tomato-infecting begomoviruses, including lack of sap-transmissibility, phloem limitation, a resistance phenotype in tomato germplasm with the Ty-1 gene and functional properties of the V1 (capsid protein) and C4 genes. Differences in symptom phenotypes induced by the ToLDeV genotypes in tomato and Nicotiana benthamiana plants were associated with a highly divergent left intergenic region and C4 gene. Together, these results establish that ToLDeV is an emergent NW monopartite begomovirus, which is causing ToLCD in Ecuador and Peru. This is the first report of an indigenous NW monopartite begomovirus, and evidence is presented that it emerged from the DNA-A component of a NW bipartite progenitor via convergent evolution and recombination.
Geminiviruses are widely recognised as a serious threat to vegetable production in many tropical and subtropical regions. This has increased the need for accurate identification of these viruses. Geminiviruses are well suited to polymerase chain reaction (PCR) methods because they replicate via a double-stranded, circular DNA form. Degenerate PCR primers were designed to anneal to highly conserved nucleotide sequences identified in the genomes of 10 whitefly-transmitted geminiviruses. The PCR primers were tested for their effectiveness in the amplification of viral DNA fragments from the DNA-A and/or DNA-B components of 15 previously uncharacterized geminiviruses from the Americas, the Caribbean Basin, and Africa (.)
The influence of floating row cover on cantaloupe, alone or combined with transparent polyethylene mulch, was evaluated to determine its effect on population densities of aphids, sweetpotato whitefly, Bemisia tabaci (Gennadius), and the vegetable leafminer, Lyriomyza sativae Blanchard, as well as virus incidence and yield of cantaloupe, Cucumis melo L. Cv. Durango. The study was carried out in a dry tropic region of Colima, Mexico. Aphids, sweetpotato whitefly and vegetable leafminer were completely excluded by floating row cover while the plots were covered. Transparent polyethylene mulch reduced aphids and whitefly populations, but did not affect infestation by L. sativae. Floating row cover delayed the appearance of virus-diseased plants for two weeks with respect to control (bare soil). Furthermore, the transparent mulch reduced virus incidence. The yield (weight) and number of cantaloupe melons harvested were nearly four-fold higher in mulch plus row cover plots (when the cover was removed during perfect flowering) compared with the control plots, while the yield with floating row cover alone was tripled. The yield from mulched plants alone and covered plants (the cover removed during vegetative growth) was higher than that from plants grown on bare soil. /// Se evaluó la influencia de las cubiertas flotantes, solas o combinadas con una cobertura de plástico transparente, sobre la densidad de población de áfidos y de mosca blanca de la batata, Bemisia tabaci (Gennadius), y sobre la infestación del minador de la hoja Lyriomyza sativae Blanchard, así como sobre la incidencia de virus y la producción de melón "Cantaloupe", Cucumis melo L. Cv. Durango. La investigación se realizó en la región tropical seca del estado de Colima, México. Los áfidos, la mosca blanca de la batata y el minador de la hoja fueron completamente excluídos por las cubiertas flotantes, mientras las plantas estuvieron protegidas con la tela de polipropileno. El acolchado con plástico transparente redujo la población de áfidos y mosca blanca, pero no tuvo efectos sobre la infestación por L. sativae. La cubierta flotante retrasó durante dos semanas la presencia de plantas afectadas por virus con respecto al testigo (suelo desnudo). El plástico transparente también redujo la incidencia de virus. El número de frutos y el rendimiento del melón en las parcelas con cubierta de plástico + cubierta flotante (la cubierta fue retirada durante la floración perfecta) fue casi cuatro veces más alto en comparación a las parcelas con suelo desnudo, mientras que en aquellas con cubierta flotante sola, el rendimiento se triplicó. La producción de las plantas con cubierta plástica sola o de las plantas con cubierta flotante (retirada durante el crecimiento vegetativo) fue más alta que la de las plantas cutivadas sobre suelo desnudo.
Tomato genotypes with resistance to begomoviruses derived from different wild species were evaluated in Guatemala. Selection of individual plants for several generations resulted in breeding lines with high levels of resistance. Resistance derived from L. hirsutum was dominant, while resistance from the other sources was more recessive in nature. Crosses among resistant lines resulted in higher levels of resistance for F1 populations than crosses between resistant and susceptible lines. Resistant lines were crossed to susceptible lines with other traits of interest, namely resistance to other pathogens and desirable fruit characters. Improved breeding lines with begomovirus resistance have been selected from these hybrids. These breeding lines are currently being used in the production of begomovirus-resistant hybrids with acceptable market quality and yields.
Begomoviruses (Family Geminiviridae, Genus Begomovirus) have become the most destructive group of plant viruses in tropical and subtropical regions of the world. The recent emergence of begomoviruses is notable, as these viruses have been co-evolving with their dicotyledonous plant hosts for millennia. Agricultural intensification has been proposed as one of the main causes, together with increases in populations of their vector Bemisia tabaci, partly due to the worldwide spread of the more fecund B-biotype. Reports of new diseases and associated epidemics are frequent. Many such reports describe the evolution of more aggressive virus variants through recombination. Little is known about the selection pressures that seem to operate and drive begomovirus evolution towards increased virulence and an extended host range. It is apparent, however, that the genomes of begomoviruses show extreme plasticity leading to an ability to evolve very rapidly in response to changing cropping systems. Genetic diversity is created not only by recombination between genomic components, but also by exchange (pseudorecombination) of their genomic components, and even by acquiring DNA sequences from viruses of other genera. Recently, associations with some satellite molecules, termed DNA-β and DNA1, have also been shown to be widespread in the Old World. Functional DNA-β molecules encode pathogenicity determinants and are often critical for disease symptom development. They appear to act by suppressing host plant defense mechanism(s), such as post-transcriptional gene silencing (PTGS), enabling a diverse range of begomoviruses to infect particular hosts. In this review, suppression of PTGS is one of the driving forces discussed as a likely and important influence on the evolution of begomoviruses. The known sources of genetic variation in begomoviruses are also considered together with the factors driving evolutionary change, the potential for limiting the extent and rate of adverse change, and therefore the potential for achieving more sustainable control of crop disease epidemics.Referee: Professor J.O. Strandberg, Mid-Florida Research and Education Center, University of Florida/IFAS, 2725 Binion Road, Apopka, FL 32704 USA
Resistance to begomoviruses including bipartite Tomato mottle virus (ToMoV) and monopartite Tomato yellow leaf curl virus (TYLCV) has been introgressed to cultivated tomato (Solanum lycopersicum) from S. chilense accessions LA1932, LA2779, and LA1938. Previous research demonstrated that three regions on chromosome 6 were associated
with the resistance, two of which were required for a line to provide a high level of resistance. In the present study, we
identified a large S. chilense introgression spanning markers from C2_At2g39690 to T0834 in LA2779-derived advanced breeding lines resistant to both TYLCV
and ToMoV. A begomovirus resistance locus, Ty-3, was mapped to the marker interval between cLEG-31-P16 and T1079 on the long arm of chromosome 6. In addition to the Ty-3 locus, the large introgression also spans the Ty-1 region near the Mi gene, suggesting the possible coexistence and linkage of resistance alleles at both Ty-1 and Ty-3 loci in these lines. In contrast, LA1932-derived advanced breeding lines possess a much shorter introgression from cLEG-31-P16
to C2_At5g41480, which also carries a begomovirus resistance locus that is probably allelic at the Ty-3 locus. The PCR-based markers tightly linked to the Ty-3 locus as well as the markers near the Ty-1 region have been used in our breeding program for efficient selection of begomovirus resistance in the past three growing
seasons and will be useful resources for tomato breeders around the world.
Continuing outbreaks of Tomato yellow leaf curl virus (TYLCV) in southern Florida emphasize that the vector of the virus, biotype B of the sweetpotato whitefly (SPWF), Bemisia tabaci (Gennadius) (also known as the silverleaf whitefly, B. argentifolii Bellows & Perring), remains the key insect pest of tomatoes in Southern Florida. Growers rely heavily on insecticidal programs to combat the whiteflies and subsequent virus outbreaks. Transplants in the production house are drenched with the neonicotinoid
Pymetrozine, a novel compound belonging to the class pyridine-azomethines, is a feeding inhibitor labeled for use against
plant pests in the order Hemiptera. Pymetrozine was evaluated for its ability to interfere with whitefly transmission of the
begomovirusTomato yellow leaf curl virus (TYLCV). Pymetrozine was applied as Fulfill
TM
50 WG at two rates (0.291 and 0.582 g formulationl
−1) to tomato seedlings with four to six true leaves. Viruliferous whiteflies (three to five per plant) were added 1, 4, 7 and
11 d after a single application of pymetrozine, and transmission rates were determined 4 wk after the addition of whiteflies.
Pymetrozine provided protection against transmission of TYLCV by viruliferous whiteflies for up to 1 wk after a single apliation.
No phytotoxicity was observed on tomato transplants. These results indicate that pymetrozine could be an effective tool for
tomato transplant producers to protect susceptible transplants from infection by begomoviruses, such as TYLCV. Pymetrozine
might also work well as part of an integrated approach to begomovirus management in greenhouse tomato fruit production.
A 2-yr, multistate project was initiated in 1994 to determine action thresholds for management of Bemisia tabaci (Gennadius) Biotype B (= B. argentifolii Bellows & Perring) in cotton using chemical insecticides. Identical experimental designs and data collection protocols were used at sites in Brawley, CA, Yuma and Maricopa, AZ, and Weslaco, TX. The prescriptive application of insecticides based on 4 candidate action threshold levels (2.5,5, 10, or 20 adult B. tabaci per leaf) were compared with one another and an untreated control. In general, there were few differences in whitefly populations among action thresholds of 2.5, 5, and 10 adults per leaf at sites in Arizona and California. All insecticide treatments typically reduced population densities below those in untreated control plots. Insecticide applications were generally ineffective in Weslaco, possibly due to reduced insecticide susceptibility or the late onset of pest infestation, and there were few differences in population density among treatments. Yields were higher in sprayed treatments, but there was little difference among threshold levels. Yield differences were not detected among any treatments for Yuma and Weslaco in 1994 and for Maricopa in 1995. The levels of lint stickiness due to honeydew deposition, as measured by thermodetector, were not consistent among sites and were not generally related to pest densities in the different threshold treatments. Levels of stickiness tended to be higher in 1994. There were no treatment effects on other standard measures of lint quality. A simple budgeting analysis assuming 43.24/ha per application for insecticides and 1.59/ kg for lint suggested that action thresholds of 5-10 adults per leaf provided the highest net return at most sites.
Bemisia tabaci biotipo B (Gennadius) (Homoptera: Aleyrodidae) también conocida como Bemisia argentifolii (Bellows and Perring) es una plaga principal del cultivo de calabacín (Cucurbita pepo L.) causando daños directos e indirectos. En un experimento llevado a cabo en el otoño del 2005 y repetido en la misma época en el 2006 investigo el efecto de coberturas solas o en combinación con el insecticida de riesgo reducido imidacloprid (Admire® 2F) para el control de mosca blanca y otros problemas relacionados en calabacín. Coberturas UV-reflectivas, y coberturas naturales (Fagopyrum esculentum Moench), solas o en combinación con imidacloprid fueron evaluadas usando el diseño de bloques completos al azar con cuatro repeticiones. También una cobertura blanca fue incluida como control del experimento. Coberturas combinadas con imidacloprid en el 2005 y 2006 tuvieron significativamente menos mosca blanca. La cobertura de plástico blanco mostro el mayor número de mosca blanca en ambos años. En la temporada del 2006, las plantas mostraron los primeros síntomas de infecciones virales causadas por el virus del plegamiento de las hojas de calabazas (CuLCrV), el cual es un geminivirus transmitido por la mosca blanca. Coberturas vivas y reflectivas fueron más efectivas que las coberturas blancas en la reducción del número de mosca blanca y la incidencia de CuLCrV en las plantas de calabacín. Translation provided by the authors.
Bemisia tabaci (Gennadius) currently is believed to be a species complex, with many biotypes and two described extant cryptic species, B. tabaci and Bemisia argentifolii Bellows and Perring. This paper examines the historical record of B. tabaci and its synonyms, and discusses research that has resulted in the species complex hypothesis. It also reviews work that has been done comparing populations from various geographic locations. This comparative research, using a variety of techniques, forms the basis from which similarities and differences between populations can be inferred. Based on these studies, seven groups within the species complex are proposed.
A model of whitefly integrated pest management (IPM) has been proposed that conveniently organizes all Bemisia tabaci control tactics into a multi-level, multi-component pyramid and defines three major keys as “sampling”, “effective chemical use”, and “avoidance”. Each component is described along with information about its implementation, adoption, and importance in the low (<700 m) desert agroecosystem of North America, which recently sustained the introduction and expansion of the B biotype during the 1990s. Insect growth regulators (buprofezin and pyriproxyfen; insect growth regulator (IGR)) in cotton and imidacloprid use in vegetables and melons were key chemical tactics, especially in the US, that were fully integrated with formal sampling plans and action thresholds, and resistance management guidelines. In Mexico, tactics of avoidance such as mandatory planting and harvest dates, post-harvest sanitation, and host-free periods along with strategic use of insecticides implemented cooperatively were key to the recovery of this agroecosystem. A concept, “bioresidual”, was developed to explain the extended period of suppression possible through the proper use of IGRs. Organized and sustained grower education was key to the areawide adoption and deployment of this successful IPM plan, which has drastically lowered whitefly targeted insecticide use and whitefly related problems since 1996.
Tomato yellow leaf curl virus (TYLCV) and tomato mottle virus (ToMoV) are two of the most destructive whitefly-transmitted begomoviruses of tomato (Lycopersicon esculentum). Resistance to these viruses has been found in several accessions of the wild species L. chilense. Three different regions in chromosome 6 of L. chilense have been shown to be associated with the resistance, indicating that at least three genetic loci contribute to the resistance. In the present study, we aim to identify molecular markers tightly linked to the resistant loci, by using L. chilense (accessions LA2779, LA1932, and LA1938) derived breeding lines that have been phenotypically selected for TYLCV and ToMoV resistance. Three plants from each line displaying resistance to both viruses were selected to screen against previously mapped RAPD (randomly amplified polymorphic DNA) markers. We also employed L. chilense derived F3 and segregating lines in our study. Markers displaying high reproducibility of the polymorphism between the susceptible control 'Horizon' and the L. chilense derived lines were identified. These include UBC697 and UBC621 from region 1 (Ty-1 gene in this region); UBC264, UBC169, UBC197, and UBC365 from region 2; and UBC131, UBC137, UBC236, and UBC389 from region 3. Among these markers, UBC697 from region 1 and UBC264 from region 2 showed tight linkage to the resistant genes, while markers from region 3 showed varied degrees of segregation from the resistant gene. We have cloned the polymorphic bands from all these markers. The conversion of these linked RAPD markers to co-dominant sequence characterized amplified region (SCAR) markers is in progress.
The whitefly, Bemisia tabaci (Gennadius), is one of the most devastating pests in modern agriculture today. The whitefly feeds on plants by inserting the stylets into the leaf and withdrawing sap from the phloem. Feeding by whiteflies causes extensive direct damage to crops through excessive sap removal, excretion of honeydew that promotes growth of sooty mold fungi, and by inducing systemic disorders such as leaf silvering in squash and irregular ripening in tomato. However, the most devastating damage induced by whiteflies is due to virus transmission. During feeding whiteflies acquire plant viruses that are in the phloem. After moving to and feeding on another plant, the whiteflies may transmit the acquired viruses. Despite the large number of whitefly species, only three, B. tabaci, Trialeurodes vaporariorum and T. abutiloneus are known as vectors of plant viruses. B. tabaci is the most important of these three and has been demonstrated to vector over 150 different viruses in the tropics and subtropics, most of which belong to the Begomovirus genus.
Field studies were conducted for three seasons, Fall 1988 and Spring and Fall 1989, on the effect of six mulch colors: blue, orange, red, aluminum, yellow, and white (fall) or black (spring), on fruit yields and on insect vectors of Sunny' tomato (Lycopersicon esculentum Mill.). Plant growth and yields were inconsistent with mulch colors during the three seasons. In Fall 1988, in a once-over harvest, extra-large (≥ 70 mm diameter) and marketable fruit yields were higher (P ≤ 0.05) on blue than on the conventional white mulch. In Spring 1989, early marketable yields on red mulch were higher than on black mulch, and in Fall 1989, under high stress from tomato mottle virus (TMoV) transmitted by silverleaf whitefly [Bemisia argentifolii (Bellows and Perring)], seasonal yield of extra-large fruit was better on orange than white mulch. In Fall 1988 and 1989, fruit size and marketable yields were reduced on yellow mulch. Aphids (Aphididae), thrips (Thripidae), and whiteflies were counted monthly in traps placed on the mulched beds. Aphids were least numerous on the aluminum and yellow and most numerous on the blue mulch. Where differences occurred, the fewest thrips were captured on aluminum and the fewest whiteflies were captured on the yellow, aluminum and orange mulches. Although differences were not always significant, the fewest adult whiteflies also were observed on foliage of tomato plants grown on these latter three mulches. Later in the seasons, as plant foliage covered the mulch, differences in the number of insects captured were similar for all mulch colors. Low numbers of whiteflies on the orange and aluminum mulches early in Fall 1989 delayed virus symptom development and increased yields. Virus symptom development was not delayed and yields were low on the yellow mulch, in spite of the low number of whiteflies. When averaged over all mulch colors, extra-large and marketable fruit yields increased linearly with delayed symptom development. It is proposed that, under high insect stress, mulches should be selected for their effects on insects in addition to their effects on soil temperature and plant morphology.
Protection of Honeydew melons, Cucumis melo, from infestation by the sweetpotato whitefly, Bemisia tabaci, (Gennadius) and the vegetable leafminer, Liriomyza sativae Blanchard, varied relative to the row cover product used. Melon plants were also protected in varying degrees from squash leafcurl virus and lettuce infectious yellows virus. Exclusion of sweetpotato whitefly was best achieved by Kimberly Farms row cover followed by Reemay, LF0125, Tufbel 900N, Tufbel 4000N, and Agronet. All row cover treatments had fewer insect pests and were lower in disease incidence than the untreated control. Vegetable leafminer was completely excluded by all row cover products. The number of honeydew melons harvested from Kimberly Farms treated plots was greatest followed by Tufbel 900N, Agronet, LF0125, Reemay, Tufbel 4000N and the untreated control. /// La proteccion de los melones "rocio de miel", Cucumis melo, contra la infestacion de la mosca de la batata, Bemisia tabaci (Gennadius) y del minador Liriomyza sativae Blanchard, varia con relacion al tipo de cobertura usada. Las plantas de melon fueron protejidas de los virus de hoja arrugada de la cucurbitaceas y del virus infeccioso de la lechuga. La mejor forma de exclusion de la mosca de la batata fue a traves del uso de la cobertura Kimberly Farms, seguida por Reemay, LF0125, Tufbel 900N, Tufbel 4000N, y Agronet. Todos los tratamientos de coberturas tuvieron menos insectos plaga y tuvieron una menor incidencia de enfermedades que el testigo. El uso de cualquier tipo de cobertura excluyo completamente a el minador. El mayor numero de melones cosechados fue de aquellas parcelas con cobertura Kimberly Farms, seguido de Tufbel 900N, Agronet, LF0125, Reemay, Tufbel 4000N y el testigo.
The island country of the Dominican Republic (DO, Republica Dominicana) is located in the Caribbean Ocean, where it shares
the island of Hispaniola with Haiti. The island lies to the West of Puerto Rico and to the East of Cuba and Jamaica. The DO
is perhaps best known for producing some of the world’s greatest baseball players, and agricultural products such as sugar
and tobacco. The DO also had established a flourishing processing tomato industry, which was able to provide tomato paste
to satisfy the needs of the ~7–8 million inhabitants of the country. This production was concentrated in two areas, Northern
production area (around Santiago) and Southern production area (centered on the Azua Valley). The total area under production
was ~8000 ha.
Confidor, an imidacloprid insecticide, was used in two applications at four rates (47.6, 71.4, 95.2, and 119 g a.i./ha) for indirectly controlling Tomato yellow leaf curl virus (TYLCV) in field plantings of tomato. This spray regimen was compared with standard applications of cypermethrins at 10- to 15-day intervals throughout the growing season. In three field trials, a combination of integrated pest management (IPM) practices and two applications of Confider at the two highest rates immediately after planting and 6 weeks later, protected tomato plants against the disease until 12 weeks after sowing. All rates of Confider reduced disease incidence compared with standard chemical control applied in an integrated strategy, and quantitative efficacy increased with increase of insecticide rate. In the three seasons, the mean incidence of TYLCV 12 weeks after sowing was 42.7% in plots not adopting IPM compared with 15.7% in those that did. Disease incidence was reduced by Confider treatments to 2.2 to 17%. Confider-treated plots consistently had higher yields than control plots. and the yields decreased with the decrease in the rate of Confider application. Confider offers several advantages over standard applications of cypermethrins to control TYLCV. When applied immediately after planting, its long-lasting systemic activity protected the crop against the disease during early stages of growth. In addition, it reduced the number of sprays and increased tomato yield.
Ralf Nauen, Thomas Bretschneider, Alfred Elbert, Reiner Fischer and Ralf Tiemann from Bayer CropScience describe these new spirocyclic tetronic acid derivatives for spider mite and whitefly control.
Five mulch types, i.e. silver plastic, black plastic, paper, white/black plastic and black/white plastic, were evaluated in terms of their effect on tomato growth, yield, fruit quality and incidence of tomato yellow leaf curl (TYLC) virus.Highest early marketable yields were obtained from the silver, white/black and black/white plastic mulches. Total marketable yields were significantly increased by all the mulch treatments.Both the silver and white/black plastic mulches were superior to other treatments in early and total fruit counts. Average weight per fruit was similar for all treatments and was acceptable in the Jordanian market.While incidence of sunscald increased significantly, blossom end rot (BER) incidence, seasonal cracking and shoot dry weight were not affected by the mulch treatments.Incidence of TYLC virus was reduced by the silver plastic mulch.
Tomato yellow leaf curl disease caused by the whitefly-transmitted begomovirus (genus Begomovirus, family Geminiviridae) Tomato yellow leaf curl virus (TYLCV) is one of the most damaging diseases of tomato. TYLCV was introduced into the New World in the early 1990s and by the late 1990s, it was found in Florida (2). In 2005 and 2006, the virus was reported from northern Mexico (states of Sinaloa and Tamaulipas) (1) and subsequently from Texas and Arizona. In March 2007, tomato (Lycopersicon esculentum) plants growing in a greenhouse in Brawley, CA showed TYLCV-like symptoms including stunted upright growth, shortened internodes, and small upcurled leaves with crumpling and strong interveinal and marginal chlorosis. These plants also sustained high populations of whiteflies. Symptomatic tomato leaves and associated whiteflies were collected from inside the greenhouse. Leaf samples also were collected from symptomless weeds (cheeseweed [Malva parviflora] and dandelion [Taraxacum officinale]) outside of the greenhouse. Total nucleic acids were extracted from 41 symptomatic tomato leaf samples, seven samples of adult whiteflies (approximately 50 per sample), and six leaf samples each from cheeseweed and dandelion. PCR analyses were performed with the degenerate begomovirus primers PAL1v1978 and PAR1c496 (3) and a TYLCV capsid protein (CP) primer pair (4). The expected size of approximately 1.4-kbp and 300-bp DNA fragments, respectively, were amplified from extracts of all 41 symptomatic tomato leaves and adult whitefly samples; whereas the 300-bp DNA fragment was amplified from all six cheeseweed samples and four of the six dandelion samples. Sequence analysis of a portion of the AC1/C1 gene from the approximately 1.4-kbp fragment amplified from 12 tomato leaf samples and four whiteflies samples revealed 99 to 100% identity with the homologous sequence of TYLCV from Israel (GenBank Accession No. X15656). The putative genome of the California TYLCV isolate was amplified using PCR and an overlapping primer pair (TYBamHIv: 5′-GGATCCACTTCTAAATGAATTTCCTG-3′ and TYBamHI2c: 5′-GGATCCCACATAGTGCAAGACAAAC-3′), cloned and sequenced. The viral genome was 2,781 nt (GenBank Accession No. EF539831), and sequence analysis confirmed it was a bona fide isolate of TYLCV. The California TYLCV sequence is virtually identical (99.7% total nucleotide and 100% CP amino acid sequence identity) to a TYLCV isolate from Sinaloa, Mexico (GenBank Accession No. EF523478) and closely related to isolates from China (AM282874), Cuba (AJ223505), Dominican Republic (AF024715), Egypt (AY594174), Florida (AY530931), Japan (AB192966), and Mexico (DQ631892) (sequence identities of 98.2 to 99.7%). Together, these results establish that TYLCV was introduced to California, probably from Mexico. Because the tomatoes in this greenhouse were grown from seed, and symptoms did not appear until after initial fruit set, the virus was probably introduced via viruliferous whiteflies. To our knowledge, this is the first report of TYLCV infecting tomato plants in California.
References: (1) J. K. Brown and A. M. Idris. Plant Dis. 90:1360, 2006. (2) J. E. Polston et al. Plant Dis. 83:984, 1999. (3) M. R. Rojas et al. Plant Dis. 77:340, 1993. (4) R. Salati et al. Phytopathology 92:487, 2002.
The DNA of several monopartite and bipartite whitefly-transmitted (WFT) geminiviruses was amplified from a viral template present in infected leaves after either direct addition of clarified plant extracts to an otherwise complete polymerase chain reaction (PCR) mix or after immobilization of template to microfuge tubes. A degenerate primer pair was designed to specifically target the middle or 'core' region of the capsid protein gene of subgroup III geminivirus isolates and amplify a viral DNA fragment of approximately 550 bp. Using this method, a single PCR product of the expected size (550 bp), as estimated by agarose gel electrophoresis, was amplifiable from plants infected with a representative set of subgroup III geminivirus isolates with a broad biogeographic base. That the 550-bp PCR product had a geminiviral gene origin was demonstrated by direct sequencing of the 550-bp fragments (yielding approximately 470 to 490 bases of informative sequence) and was validated through comparison (alignment) of the sequences with the published DNA sequences of several well-characterized WFT geminiviruses. Analogous viral fragments were not detectable by PCR with the subgroup III core coat protein primers and extracts of plants infected with either subgroup I or II geminivirus isolates. The demonstrated exclusive specificity of the assay for subgroup III geminiviruses offers a highly simplified PCR- based assay that permits the detection of a geographically diverse collection of WFT geminiviruses infecting cultivated crops, ornamentals, and weed hosts with minimal sample preparation. This approach is highly useful for the amplification of subgroup III geminiviral DNA templates from total nucleic acid extracts from infected plants and partially purified virion preparations.
Two morphological classes have been demonstrated among the whitefly-viruses: the Gemini viruses and the flexuous rod group. Most of the viruses are of the persistent-circulative type. There is no direct evidence for the multiplication of these types of viruses in the whitefly bodies. However, there are some indications that the pathway of these viruses is not a passive one. In a few cases, and these only in the group of elongated viruses, semi-persistent or non-persistent relationships were described. Control by cultural practices includes yellow mulching, mixed cropping, physical barriers and the use of resistant cultivars.
Geminiviruses form the second largest family of plant viruses, the Geminiviridae, represented by four genera: Mastrevirus, Curtovirus, Topocuvirus and Begomovirus. During the last two decades these viruses have emerged as devastating pathogens, particularly in the tropics and subtropics, causing huge economic losses and threatening crop production. Epidemics caused by re-emerging and newly emerging geminiviruses are becoming frequent even in regions that were earlier free from these viruses. Compared to mastreviruses and curtoviruses, begomoviruses have emerged as more serious problems in a variety of crops, for example, cassava, cotton, grain legumes and vegetables. Major contributory factors for the emergence and spread of new geminivirus diseases are the evolution of variants of the viruses, the appearance of the whitefly 'B' biotype and the increase in the vector population. Variability in geminiviruses has arisen through mutations, recombination and pseudorecombination. Genomic recombination in geminiviruses, not only between the variants of the same virus but also between species and even between genera, has resulted in rapid diversification. From the disease point of view, most virulent variants have developed through recombination of viral genomes such as those associated with cassava mosaic, cotton leaf curl, and tomato leaf curl diseases. Heterologous recombinants containing parts of the host genome and/or sequences from satellite-like molecules associated with monopartite begomoviruses provide unlimited evolutionary opportunities. Human activity has also played an important role in the emergence of serious geminivirus diseases across the globe, like the changes in cropping systems, the introduction of new crops, the movement of infected planting materials and the introduction of host susceptibility genes through the exchange of germplasm.
Cassava mosaic disease (CMD) is a widespread viral disease that causes high yield losses in susceptible genotypes in Sub-Saharan Africa. Effective control of CMD is beneficial and justifiable since cassava is an important source of carbohydrates for over 200 million people in most African countries where the crop is grown. Despite much research effort, CMD has not been completely brought under control, and this remains a tremendous challenge to scientists and other stakeholders. This paper highlights and discusses some of the challenges in controlling CMD and offers some solutions. The need to diversify cassava utilization as food, feed and industrial raw material is crucial for the commercialization of the crop, and this diversification will eventually lead to farmers making extensive use of improved CMD-resistant genotypes and other inputs.
A lightweight floating row cover, used alone and in combination with a white-on-black polyethylene mulch, was evaluated under the hot, humid conditions of the fall growing season in Florida as a method of controlling aphid-borne mosaic viruses, whitefly-induced leaf silvering, and insects directly damaging zucchini squash. Yields increased dramatically with the use of covers, especially if covers were left in place for at least 1wk after plants began to bloom. Covers excluded pickleworm, Diaphania nitidalis (Stoll); melonworm, Diaphania hyalinata (L.); sweetpotato whitefly, Bemisia tabaci (Gennadius), and several colonizing aphid species. Except for B. tabaci, insects colonized newly uncovered plants slowly, remaining at low densities for up to 2 wk after removal of covers. Few winged aphids landed in water pan traps placed over covers, which may explain why aphids and aphid-vectored viruses remained at low levels even when covers were torn. Incidence of potyviruses and silverleaf was greatly reduced by use of row covers, but symptoms of viral infection developed 1-2 wk after removal. If used over an entire planting, high levels of inoculum presumably would not develop, and viral infection might be delayed even longer.