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Evaluation of entomopathogenic fungi for control of Tetranychus urticae Koch (Acari: Tetranychidae)
... These results suggested that the experiments with some EPF require a long incubation time before evaluating their results (Amjad et al., 2012). Tamai et al. (2002) reported that all isolates of M. anisopliae and B. bassiana were pathogenic to T. urticae with increased mortality rates after the 3rd day and peaking on the 4th or 5th day post treatment. Thus, the bioassay of some EPF against mites requires a long period of incubation before evaluating the results. ...
... The efficacy trials carried out in the field are largely supported by laboratory tests. While searching for microbial control agents in laboratory experiments, several workers have found that the mobile stages of T. urticae were sensitive and influenced to a large extent by the Fig. 1 Lethal effect of Metarhizium anisopliae isolate to Tetranychus urticae after treatment with conidial suspensions at concentration 1 × 10 5 , 1 × 10 6 , 1 × 10 7 , 1 × 10 8 conidia ml −1 (control variant, 0 conidia) Error bars: SD (Tamai et al., 2002;Chandler et al., 2005;Draganova and Simova, 2010;Schapovaloff et al., 2014 andZare et al., 2014). It was also found that T. harzianum was the least virulent fungus with LC 50 9.4 × 10 6 conidia/ml. ...
... Investigation of smears of cadaver of mites confirmed mycosis infectivity as cause of death in individuals treated with conidial suspensions of the fungal isolates. Considering the deadly effect of the tested fungi to T. urticae was due to the secondary metabolites toxicity and the dyes they produced (Tamai et al., 2002), a variety of degrading enzymes were produced by EPF worked in a coordinated manner, popularly known as cuticle degrading enzymes, including chitinases, proteases, and lipases, making their entry through the massive barriers of mite cuticle easier (Krieger de Moraes et al., 2003;Zare et al., 2014). ...
Abstract The virulence and proteolytic activity of some entomopathogenic fungi isolates, viz., Metarhizium anisopliae, Beauveria bassiana, Verticillium lecanii, and Trichoderma harzianum , against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae), were evaluated. Common maize plants (Zea mays L.) infested with females of T. urticae were treated in vivo by spraying with suspensions of 1 × 108 conidia ml−1 concentration of selected isolates. Lethal effects of fungal isolates were assessed as percentages of daily mortalities of mites, compared to the mortality in control. Virulence of the fungi isolates was estimated based on the LC50 values calculated by probit analysis for the individuals treated by 1 × 105 conidia ml−1 concentration. Proteolytic activity of isolates was assayed on casein substrate to reflect their virulence towards T. urticae. The mite mortality rates increased with increasing conidial concentrations as well as days after treatment. The mortality rate caused by M. anisopliae isolate varied from 18.75 to 85%, with LC50 value of 4.6 × 105 conidia/ml and LC90 value of 2.4 × 108 conidia/ml during 7 days, respectively. The isolate of B. bassiana caused 15 to 70% mortality, and its LC50 and LC90 values estimated 3.3 × 106 and 7.8 × 109 conidia/ml, respectively. However, V. lecanii isolate caused 11.25 to 72.50% mortality with LC50 of 5.2 × 106 conidia/ml, while T. harzianum was potentially less virulent than other isolates causing 8.75 to 63.75% mortality rate to T. urticae with LC50 of 9.4 × 106 conidia/ml. M. anisopliae showed the highest proteolytic activity at all concentrations, followed by B. bassiana in 3rd, 5th, and 7th day post treatment. These findings recommend the selection of virulent fungal isolates for use as natural and environmentally safe agents in biological control programs to combat mite pests.
... Sorokin, Hirsutella thompsonii Fisher and Lecanicillium lecanii (Zimm.) (Viegas) Zare & Gams have been screened against two-spotted spider mite and hold potential for their development as bioacaricides (Tamai et al., 2002a;Chandler et al., 2005;Gatarayiha et al., 2010). In Korea, it is also necessary to develop biological control mechanisms as a part of integrated pest management programs against the two-spotted spider mite. ...
... Recently, entomopathogenic fungi including B. bassiana, M. anisopliae, P. farinsus (Holmsk) and Hirsutella sp. was considered as promising fungi for two-spotted spider mite control (Tamai et al., 2002a). Paecilomyces lilacinus is a commonly isolated form soil and as one of the effective biological control agents against plant-pathogenic nematodes and pest (Marti et al., 2006;Fiedler and Sosnowska, 2007;Demirci and Denizhan. ...
The virulence against the two-spotted spider mite, Tetranychus urticae Koch, was evaluated with entomopathogenic fungus Paecilomyces lilacinus (Thom) Samson HY-4 which is isolated from coleopteran insect and registered to Korean and US patents. Virulence tests were conducted with conidial suspensions () of P. lilacinus HY-4 against T. urticae adults and positive results were recorded in laboratory conditions. The spraying device was also developed for the efficient and exact evaluation of treatment. The developed spraying device was named as SD-tower sprayer and its efficacy of spraying conidia was evaluated. The accumulated mortality caused by P. lilacinus HY-4 using SD-tower spray was about 73% at 6 days after inoculation. This suggest that the isolate P. lilacinus HY-4 may be considered as promising for a new approach to prevent adult infestations by T. urticae.
... Fries (=Paecilomyces farinosus), Hirsutella thompsonii Fisher, and Neozygites floridana Weiser and Muma often play an important role in decreasing native populations of phytophagous mites (Chandler et al., 2000; Van der Geest et al., 2000 ). Searching for microbial control agents in laboratory experiments it has been shown that some of the tested isolates of B. bassiana and M. anisopliae are highly virulent to the active stages of T. urticae (Alves et al., 2002a; Tamai et al., 2002; Chandler et al., 2005) and T. evansi Baker and Pritchard (Wekesa et al., 2005). According to Shi and Feng (2006, 2009) some of the tested isolates of B. bassiana, Paecilomyces fumosoroseus (Wize) Brown and Smith and M. anisopliae have high lethal effect on eggs and females of T. urti- cae. ...
... Chandler et al. (2005) found in a glasshouse experiment that Beauveria bassiana cultured from Naturalis-L (Troy Biosciences, USA) reduced the numbers of T. urticae adults, nymphs and eggs (98% reduction in all three cases) on glasshouse tomato crops. Opportunities to exploit entomopathogenic fungi for biological control of mites were summarized by Chandler et al. (2000), Alves et al. (2002) and Maniania et al. (2008). Maniania et al. (2008, reviewing the use of fungal pathogens in inundative, conservation and conventional biological control of T. urticae and T. evansi, concluded that there is a great potential for use of entomopathogenic fungi in conservation and conventional biological control programs. ...
Bioassays with five isolates of the entomopathogenic fungus Beauveria bassiana (Bals.- Criv.) Vuillemin were conducted under laboratory conditions with a goal to estimate their virulence to the two-spotted spider mite Tetranychus urticae Koch. (Acari: Tetranychidae). Common bean plants with mites were treated by spraying conidial suspensions of isolates at concentrations of 106, 107 and 108 conidia/ml. Lethal effects of the fungal isolates wereevaluated as percentages of cumulative daily mortality due to mycoses, corrected for mortality in the control variant. Virulence of the isolates was estimated based on values of the median lethal time (LT50) calculated by probit analysis for the variants treated with conidial suspensions at the concentration of 106 conidia/ml.The two-spotted spider mite was found susceptible to the examined isolates of the entomopathogenic fungus B. bassiana. Mycosis caused to T. urticae by the B. bassiana isolates 444 Bb and 445 Bb had fast lethal effect after treatment with conidial suspensions even at the concentration of 106 conidia/ml. The mean mortality values of host individuals were 83.78 ± 3.62% and 68.49 ± 4.28% on the first day, respectively, and up to 100% in both variants on the fourth day.The isolates 426 Bb, 444 Bb and 445 Bb of B. bassiana were highly virulent to two-spotted spider mites with values of the median lethal time varied within overlapped narrow confidence intervals from 0.122 to 1.084 days (average value 0.162 days), from 0.117 to 1.398 days (average value 0.146 days) and from 0.106 to 1.162 days (average value 0.131 days),respectively. Significant differences regarding virulence of the three isolates at p-level < 0.05 could not been proved. The other two examined isolates were distinctly less virulent to T. urticae than these three B. bassiana isolates.
... r (1949) treated T. urticae with a dust formulation of conidia containing 0.5% spores of B. bassiana in the Weld and obtained 71% mortality. In a semi-Weld experiment using B. bassiana against T. urticae infesting chrysanthemum (Dendranthema grandiXora) (Ramat), Alves et al. (1998) obtained results that were better than the chemical pesticide used. Tamai et al. (2002a) reported similar results with B. bassiana against T. urticae on chrysanthemum when the fungus was applied at a concentration of 2 £ 10 8 conidia ml ¡1 . They also observed that with four fungal sprays within 14 days, mite density was reduced from 1.8 to 0.1 mites/leaf. However, the reduction was lower in strawberry (Fragaria sp.) than i ...
... .) than in chrysanthemum, with a mean density of 13 mites/leaXet 21 days after application of 1 £ 10 8 or 5 £ 10 7 conidia ml ¡1 , compared to 43 mites/leaXet in control plots. The authors also observed an eVect of strawberry varieties on the pathogen performance, with the varieties 'Campinas' and 'Princesa Isabel' having the lowest mite densities. Tamai et al. (2002a) concluded that M. anisopliae, B. bassiana and Hirsutella sp. were the promising fungi to be formulated as mycoacaricides for T. urticae control. Chandler et al. (2005) obtained reductions of T. urticae populations in a glasshouse following spray applications of B. bassiana, H. thompsoni, M. anisopliae, L. lecanii and Naturalis-L ® . Nat ...
The spider mites Tetranychus urticae Koch and Tetranychus evansi Baker and Pritchard are important pests of horticultural crops. They are infected by entomopathogenic fungi naturally or experimentally. Fungal pathogens known to cause high infection in spider mite populations belong to the order Entomophthorales and include Neozygites spp. Studies are being carried out to develop some of these fungi as mycoacaricides, as stand-alone control measures in an inundative strategy to replace the synthetic acaricides currently in use or as a component of integrated mite management. Although emphasis has been put on inundative releases, entomopathogenic fungi can also be used in classical, conservation and augmentative biological control. Permanent establishment of an exotic agent in a new area of introduction may be possible in the case of spider mites. Conservation biological control can be achieved by identifying strategies to promote any natural enemies already present within crop ecosystems, based on a thorough understanding of their biology, ecology and behaviour. Further research should focus on development of efficient mass production systems, formulation, and delivery systems of fungal pathogens.
... Similarly, the previous studies demonstrated that B. bassiana was pathogenic against T. urticae, but the levels of mortality were different among the isolates [35,36]. B. bassiana isolate AT076 was found to be highly pathogenic against T. urticae even when it was exposed to low RH with low conidial concentrations. ...
This study was conducted to assess highly pathogenic Beauveria bassiana isolates to be used in biocontrol and to determine their potentials as mycopesticide. For this purpose, two B. bassiana isolates, which were locally isolated from T. urticae , were chosen. Firstly, three suspensions were investigated at the degree of humidity of 65 ± 5% and 100% RH. Secondly, these strains were selected according to their tendency to mass production, tolerance to UV radiation, and capability of producing spore at the different temperatures. Finally, identification of the selected isolate was performed by using ITS rDNA analysis. Both tested fungal isolates were pathogenic to the T. urticae . Mycelial growths of isolate AT076 at 20°C and 30°C were found to be greater than isolate AT007. It was observed that isolate AT076 had more spore production with 1.61 × 10 ⁷ spore/disc at 30°C and 44.33% germination after UV radiation for 15 min. The numbers of spores per 5 mm disk area for isolates AT076 and AT007 were found to be 1.2 × 10 ⁶ and 1.0 × 10 ⁶ . These results show that isolate AT076 was more virulent and more UV-tolerant and had higher tendency to mass production compared to isolate AT007 against T. urticae . As a result of this study, isolate AT076 can be used in the biocontrol as mycopesticide.
... Leger et al., 1996). In the study of Tamai et al., (1998) on the mite T. urticae using Beauveria spp. isolates at a concentration of 5 × 10 8 conidia ml -1 , mortality ranged from 5.5 to 100% in total. ...
Fungi has been tested as one of the potential control agents for insect pests, which raises hopes for developing fungi as good biopesticides. The high variation within fungi species made taxonomic identification procedures more complex, thus molecular identification techniques are needed in addition to traditional morphological characteristics currently used as primary methods to classify fungi species. The objective of this research was to identify the species of the most pathogenic fungi to Tetranychus kanzawai Kishida using RAPD-PCR. The internal transcribed spacer of 5.8s rDNA (ITS-5.8s rDNA) sequence of these fungal isolates were amplified using two sets of universal primers for ITS and then analyzed. Molecular identification showed that these isolates had a higher of similarity to Metarhizium anisopliae than Metarhizium flavoviride. © 2016, Agriculture Faculty Brawijaya University. All rights reserved.
... Leger et al., 1996). In the study of Tamai et al., (1998) on the mite T. urticae using Beauveria spp. isolates at a concentration of 5 × 10 8 conidia ml -1 , mortality ranged from 5.5 to 100% in total. ...
The characteristics of six Beauveria bassiana isolates against Tetranychus kanzawai were investigated. The investigated aspects were B. bassiana isolates': (1) pathogenicity to T. kanzawai, (2) cellular characteristics, (3) infection process (4) phylogeny. The isolates were planted onto potato dextrose agar (PDA) in flat bottle flasks and incubated at certain room condition, i.e. 26±1°C temperature and 12-hour photoperiod, for a maximum of 21 days. The results showed that isolates' phatogenicity level decreased in the following order: Bb6>Bb5>Bb4>Bb3>Bb1>Bb2. The surface of Bb4 and Bb5 isolates were yellowish-white, while Bb6 had a white color. The bottom of Bb4 had brown and white colors while both Bb5 and Bb6, on the other hand, had yellow color. All isolates had round shapes. Bb6 had the fastest sporulation growth of 3 days post inoculation while others grew approximately at 4 days post inoculation. The ITS region examination showed that three B. bassiana isolates were related, in which Bb4 and Bb5 (from Indonesia) were closely related and Bb6 (from Philippines) was distantly related.
... In the study of Tamai et al. (1998) on the mite T. urticae using Beauveria spp. isolates at a concentration of 5 × 10 8 conidia ml -1 , mortality ranged from 5.5 to 100% in total. ...
The importance of fungal attack to acarina has been observed but not yet on Tetraychus kanzawai. When infected mite, either within in a same species or even in a different species of entomopathigenic probably have similar signs and simptoms to mites. Characteristic of entomopathogenic fungus to Tetranychus kanzawai was investigated. Three selected isolates of Metarhizium aniopliae, from Philippines and Indonesia were evaluated. The following aspects were investigated: (1) Bioassay tes of virulence, (2) Koch Postulate and (3) Infection process on each fungus against mite. Virulence of Metarhizium anisopliae was 1.4 × 103, 7.2 × 102, 5 × 102 PIB per ml on Ma4, Ma5 and Ma6, respectively. On Koch Postulates, Reinoculation and reisolation of all seven isolates from infected T. kanzawai showed definite signs of infection. This demonstrated its entomopathogenic capacity. In this experiment, adult mites were sprayed with 108 per ml concentrations of conidia observed under light microscope and Scanning Electron Microscopy (SEM). The result found T. kanzawai was very susceptible to three isolates M. anisopliae. In the end of the trials, fungal growth was detectable as early as 2 until 4 days of observation. Infection process withmicrophotograph and Scanning Electro Microscopy showed attachment, germination and penetration, extrusion and conidiogenesis fungal form.
... For instance, abamectin was highly compatible, while spiromesifen was moderately toxic. Abamectin has also been reported to be compatible with entomopathogenic fungi (Tamai et al. 2002). Imidacloprid and thiamethoxam did not have deleterious effects on VG and conidia production. ...
The compatibility of the Metarhizium anisopliae (Metschnikoff) Sorokin isolate ICIPE 69 which is being developed as a biopesticide for the control of Frankliniella occidentalis Pergande was assessed under laboratory conditions with 12 agrochemicals including 5 insecticides (thiamethoxam, L-cyhalothrin, imidacloprid, chlorpyrifos and diazinon), one botanical insecticide (azadirachtin), 2 acaricides (abamectin and spiromesifen), and 3 fungicides (carbendazim, copper hydroxide and propineb), used in French Bean production. The insecticides abamectin and imidacloprid were highly compatible with M. anisopliae; thiamethoxam was compatible whereas azadirachtin and L-Cyahalothrine were toxic to the fungus, adversely affecting vegetative growth and sporulation. The acaricide spiromesifen was moderately toxic, while the fungicides carbendazim, probineb and copper-hydroxide were very toxic to the fungus. The combination of the M. anisopliae isolate ICIPE 69 with imidacloprid or thiamethoxam did not result in any synergistic or antagonistic effects to larvae of F. occidentalis. However, the combination of lower concentrations of the fungus with thiamethoxam resulted in a shorter lethal time (LT50) compared to individual treatments. Our results suggest that application of the fungus with agrochemicals has to be assessed carefully prior to any field intervention.
... Variation in the pathogenic activity between the 26 fungal isolates against T. evansi was also observed in the present study. Intraspecific differences in the pathogenicity of the mitosporic fungi B. bassiana, M. anisopliae, Hirsutella thompsonii Fisher and Lecanicillium lecanii complex have also been reported in other mite species (Tamai et al. 2002;Barreto et al. 2004;Alves et al. 2005;Brooks and Wall 2005;Chandler et al. 2005). ...
The virulence of three isolates of Beauveria bassiana (Bals.) Vuill. and 23 isolates of Metarhizium anisopliae (Metschnik.) Sorok. (Ascomycota: Hypocreales) against the tomato spider mite, Tetranychus evansi Baker and Pritchard (Acari: Tetranychidae), was assessed in the laboratory. The effect of temperature on germination, radial growth and virulence of selected isolates (two isolates of B. bassiana and nine of M. anisopliae) on T. evansi was also investigated in the laboratory. All the fungal isolates tested were pathogenic to the adult females of T. evansi, and there were significant differences in mortality between fungal isolates. The lethal time to 50% mortality (LT(50)) values ranged from 4.2 to 8.1 days and the LT(90) values from 5.6 to 15.1 days. Temperature had significant effects on germination, radial growth and virulence of the various isolates. The best fungal germination was observed at 25 and 30 degrees C, while for the fungal radial growth it was 30 degrees C. All the isolates germinated and grew at all temperatures, but germination and radial growth varied with isolate and temperature. The selected isolates were all virulent to T. evansi, but virulence varied also with isolate and temperature.
Agriculture is the most important economic activity around the world with its contributions reflected by its share in the gross domestic product of countries. It ensures food security, provides raw materials for many industries and employment opportunities. Today, pest and diseases are among the main challenges plaguing the agricultural sector. More specifically, phytophagous mites are devastating many economically important crops worldwide. Tetranychus urticae Koch (Two-spotted spider mites), Raoiella indica Hirst, (red palm mites), Polyphagotarsonemus latus Banks (broad mites) and Panonychus ulmi Koch (European red mites) are widely known for their extensive damage to crops. To control these mites, farmers have incorporated the use of pesticides into their farming systems. However, chemical control comes with many problems such as insect resistance, detrimental environmental effects and various human health implications. As such biological control is an environmentally friendly alternative that uses bio-control agents such as predators, pathogens and parasitoids to control pests. In this review, it was found that predators and pathogens were the most widely used biocontrol agents, specifically, the Amblyseius spp. Berlese were most effective and widely documented. The available literature also suggests that for successful control of agricultural mites via biological control, there needs to be a clear understanding of the behaviors of these mites and the bio-control agents used.
Tetranychus kanzawai is an economically important polyphagous mite species in East and South Asia. In the Philippines, it commonly infests cassava and papaya plants. The mites attack and severely damage the older leaves of papaya trees as well as seedlings. Its serious damage causes the leaves to dry up, thus, reducing the photosynthetic activity of the plant. Three entomopathogenic fungal isolates were tested on mites under greenhouse conditions using treated papaya seedlings following a completely randomized design. The mites tested were examined under a dissecting scope to determine the causal agent and to confirm mortality. The LT50 of Metarhizium anisopliae, Beauveria bassiana and Paecilomyces lilacinus on T. kanzawai were estimated. Our results indicate that among these entomopathogenic fungi, the Metarhizium anisopliae Ma6 isolate (LT50= 3.00 days) has potentiality for the control of T. kanzawai.
The characteristics of six Beauveria bassiana isolates against Tetranychus kanzawai were investigated. The investigated aspects were B. bassiana isolates': (1) pathogenicity to T. kanzawai, (2) cellular characteristics, (3) infection process (4) phylogeny. The isolates were planted onto potato dextrose agar (PDA) in flat bottle flasks and incubated at certain room condition, i.e. 26±1°C temperature and 12-hour photoperiod, for a maximum of 21 days. The results showed that isolates' phatogenicity level decreased in the following order : Bb6>Bb5>Bb4>Bb3>Bb1>Bb2. The surface of Bb4 and Bb5 isolates were yellowish-white, while Bb6 had a white color. The bottom of Bb4 had brown and white colors while both Bb5 and Bb6, on the other hand, had yellow color. All isolates had round shapes. Bb6 had the fastest sporulation growth of 3 days post inoculation while others grew approximately at 4 days post inoculation. The ITS region examination showed that three B. bassiana isolates were related, in which Bb4 and Bb5 (from Indonesia) were closely related and Bb6 (from Philippines) was distantly related.
In the present study, the susceptibility of different developmental stages (eggs, larvae, protonymphs, deutonymphs and adults) of Tetranychus urticae Koch to the entomopathogenic fungi Beauveria bassiana (Balsamo-Crivelli) Vuillemin and Metarhizium anisopliae (Metchnikoff) Sorokin was evaluated in the laboratory. At each developmental stage, four concentrations (3 × 10 5, 1 × 106, 3 × 106 and 1 × 107 conidia/ml) of both fungi were sprayed. Egg viability and motile-stage mortality varied among the fungal isolates and conidial concentrations. The highest conidial concentration (1 × 107 conidia/ml) significantly reduced the viability of eggs and increased the mortality of motile stages. However, deutonymphs and adults were more susceptible to fungal infection than larvae and protonymphs. The lethal concentration values to 50% (LC50) and 90% mortality (LC90) varied with the fungal isolates and developmental stages. The results show the prospects of B. bassiana and M. anisopliae for the control of T. urticae.
Due to the problems caused by the indiscriminate use of pesticides, biological control has been used to control the population of insects in agriculture and stored beans. Entomopathogenic fungi are among the organisms that are used, specially Beauveria bassiana and Metarhizium anisopliae. Despite their expected safety to non-target organisms, it may be possible that these microbian control agents affect benefi cial invertebrates and even vertebrates. It is certain that they may cause abnormalities in fi sh embryos and infection in other verte-brates, but there are recent studies that testify the safety of M. anisopliae to Astynax scabripinis, and of B. bassiana to Gallus domesticus. Thus, due to the existence of confl icting information, it is evident that more tests are required in order to verify the safety of entomopathogenic fungi to vertebrates.
Phytophagous mites cause biotic stress to its host plant and adversely affect the marketable produce causing losses to growers. Cost effective and energy efficient measures are needed to provide alternative ways to limit chemical treatments which disrupts biotic balance and leads to secondary pest outbreaks, pest resistance and resurgence. Among eco-friendly measures, cultural control, use of mite and insect predators, botanicals/bio-pesticides, fungi, bacteria and virus play an important role in managing mite population in various agricultural crops. The performance of natural enemies is also influenced by host plant characteristics and environmental conditions. Natural enemies efficient on crop may not do well on other crops, e.g., Phytoseiulus persimilis does not do well on tomato because the mites become trapped on glandular hairs on the leaf petioles. Secondly, it performs better under warm, humid conditions whereas; Mesoseiulus longipes is frequently used under hot and dry conditions to control spider mites. Compatibility of Entomopathogenic fungi with other control measures and its safety towards non target organisms makes them good candidates for phytophagous mites' control.
This study aimed to confirm the identity of three strains of the entomopathogenic fungus Beauveria bassiana from South African soils and to investigate their phylogenetic relationship with non-indigenous strains from other geographic regions. Sequences of the rDNA ITS1-5.8S-ITS2 region of 23 strains were compared with the Genbank reference sequences of 20 other cosmopolitan strains. Fitch parsimony and neighbor-joining analyses of the ITS1-5.8S-ITS2 regions resolved the strains into two distinct clades and matched them to four species groups/lineages: Beauveria bassiana, B. cf. bassiana (pseudobassiana), B. brongniartii and B. caledonica. Two of the South African strains initially identified as B. bassiana grouped with B. caledonica, whereas the third strain was confirmed as B. bassiana. Because of the paucity of Genbank references for B. caledonica, we have designated the two South African B. caledonica strains as B. sp. aff. caledonica. Other reassignments included two strains from Norway, originally classified as B. bassiana, being grouped with B. brongniartii, and three of the B. brongniartii reference taxa from Brazil which were clearly placed in the B. bassiana clade. The study provides a first report of the presence of the B. caledonica lineage in Africa and confirms current Beauveria phylogenies inferred from molecular data.
This study was carried out to select isolates of the entomopathogenic fungus Beauveria bassiana with pathogenic potential to control the Rhipicephalus (Boophilus) microplus tick. The effectiveness of thirty isolates was first tested at a concentration of 5 x 108 conidia.mL(-1). Of these, eight were evaluated (IBCB01, IBCB02, IBCB07, IBCB17, IBCB21, IBCB74, IBCB149, IBCB165) and showed an effectiveness between 90 and 99%; thirteen (IBCB03, IBCB14, IBCB16, IBCB24, IBCB95, IBCB97, IBCB102, IBCB141, IBCB146, IBCB147, IBCB150, IBCB154, IBCB157) between 80 and 89,5%; six (IBCB47, IBCB75, IBCB84, IBCB145, IBCB161, IBCB164) between 70 and 79%, and only two (IBCB13 and IBCB143) had lower pathogenicity (70% or below). In the second step of the study, the five more effective strains in the first phase of the experiment (IBCB01, IBCB07, IBCB21, IBCB66, IBCB165) were analyzed comparatively. Based on in vitro results, it can be concluded that IBCB66 and IBCB21 are the isolates with higher potential for field control of R. (B.) microplus. IBCB01, IBCB07, IBCB21, IBCB66 e IBCB165 isolates were submitted to a conidial production test using a rice-based substrate. The best mass production of the entomopathogenic fungus was obtained with the IBCB66 strain.
The activity of Metarhizium anisopliae and Beauveria bassiana towards eggs and larvae of Tuta absoluta (Meyrick) was evaluated. Our data showed that the isolates were pathogenic to both developmental stages tested and the eggs were more susceptible than the 1st instars. The isolates URPE-6 and URPE-19 of M. anisopliae were more pathogenic to eggs and larvae, respectively. The compatibility of these two isolates with the insecticides chlorfenapyr, spinosad, indoxacarb, abamectin, and neem were evaluated. Spinosad and indoxacarb were compatible with the two M. anisopliae isolates in all tested concentrations. At the average recommended concentration, chlorfenapyr was compatible to URPE-6 and abamectin to UFPE-19. The use of entomopathogenic fungi associated with compatible insecticides may be a useful alternative to control T. absoluta.
The fungal pathogen Neozygites floridana Weiser and Muma has been evaluated as a classical biological candidate for introduction into Africa against the invasive tomato red spider mite Tetranychus evansi Baker and Pritchard. In this study, the effect of temperature on sporulation, germination and virulence of three isolates of N. floridana collected from T. evansi in three climatically distinct regions of Brazil and Argentina was determined. Six constant temperatures of 13 degrees C, 17 degrees C, 21 degrees C, 25 degrees C, 29 degrees C and 33 degrees C were tested for their effect on the ability of the three fungal isolates to sporulate, germinate and kill the mites. Six alternating-temperature regimes of 17-13 degrees C, 21-13 degrees C, 29-13 degrees C, 33-13 degrees C, 33-23 degrees C, 33-28 degrees C under a 12h photophase were also tested to estimate virulence of the three isolates against T. evansi. The Vipos isolate discharged more conidia than isolates from Recife or Piracicaba at all temperatures and sporulation was strongly temperature dependent. Optimal sporulation rates were observed at 25 degrees C while optimal germination rates were observed at 25 degrees C and 29 degrees C. At 29 degrees C, the shortest mean survival time of T. evansi (3.16 days, 95% CI of 3.05-3.27) was observed for the isolate from Vipos, while the longest LT(50) (3.47 days, 95% CI 3.34-3.59) was observed for the isolate from Piracicaba. Mortality of mites increased as the differences between alternating day and night temperatures increased from 8 degrees C (21-13 degrees C), to 10 degrees C (33-23 degrees C), to 16 degrees C (29-13 degrees C), with smallest and highest temperature differences of 4 degrees C (17-13 degrees C) and 20 degrees C (33-13 degrees C), both producing low mortalities. The overall results suggest that the Vipos isolate is better adapted to a wider range of temperatures than the other isolates tested.
Twenty-three isolates of Metarhizium anisopliae (Metschnikoff) Sokorin and three isolates of Beauveria bassiana (Balsamo) Vuillemin (Ascomycota: Hypocreales: Clavicipitaceae) were assessed for their virulence against the two-spotted spider mite, Tetranychus urticae Koch (Acari: Tetranychidae). Based on the screening results, nine isolates of M. anisopliae and two isolates of B. bassiana were tested for their virulence against young adult (1- to 2-day-old) female T. urticae at constant temperatures of 20, 25, 30 and 35 degrees C. At all temperatures tested, all the fungal isolates were pathogenic to T. urticae but mortality varied with isolates and temperatures. Fungal isolates were more virulent at 25, 30 and 35 degrees C than at 20 degrees C. The lethal time to 50% mortality (LT(50)) and lethal time to 90% mortality (LT(90)) values decreased with increased temperature. There were no significant differences in virulence between fungal isolates at 30 and 35 degrees C; however, significant differences were observed at 20 and 25 degrees C.
The pathogenicity of Beauveria bassiana to one of the major pests of citrus crops, Phyllocoptruta oleivora, was assessed by inoculating mites with different concentrations of conidia (1 x 10(6), 5 x 10(6), 1 x 10(7), 5 x 10(7) and 1 x 10(8)). Treated mites were kept at controlled conditions (25 +/- 0.5 degrees C, 12 h photoperiod and 98% relative humidity) and mite survivorship was evaluated daily. Mortality was found to increase in time and was dependent on the conidia concentration, with values ranging from 24 to 91% for the lowest and highest conidia concentration, respectively. The calculated LC50 on the fifth day was 4.23 x 10(6) conidia/ml. Mean lethal time was 3.98, 9.79, 3.09 and 2.74 days for 5 x 10(6), 1 x 10(7), 5 x 10(7) and 1 x 10(8) conidia/ml, respectively. Conidia were found to adhere all over the mite body surface, especially at the anal region, where vegetative mycelium was found entering the mite body. We noticed the formation of small crystals inside the mite's body that were produced during colonization of the body cavity by the fungus. This is the first report of B. bassiana pathogenicity for this species.
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