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Effect of Rainfall on Population Abundance of Aphids (Homoptera: Aphididae) on Pecan

Authors:
  • Global Experts for Environmental and Agricultural Consultancy
... Aphids are very affected by weather parameters such as temperature, relative humidity, rainfall, wind, and sunshine (Piyaratne et al. 2014). Rainfall generally is considered detrimental to aphids (Kaakeh andDutcher 1993, Piyaratne et al. 2014). However, M. sacchari feeds mostly underneath leaves, so might have some protection from rain. ...
... Wind speed accompanying rainfall is perhaps the major cofactor for contributing to aphid mortality (Walker et al. 1984, Bailey et al. 1995. Although rainfall can eliminate significant numbers of aphids, in most cases aphids are able to return to original numbers within a week (Kaakeh et al. 1993). Rainfall also can affect interactions of aphids with parasitoids and predators (Fink and Volkl 1995, Weisser et al. 1997, von Berg et al. 2008. ...
... Aphids were not observed in all the regions sampled and this could be attributed to high amount of rains in most places that were surveyed. Rainfall has previously been shown to be a factor regulating the population of aphids as it can dislodge the pest from their host plants (Kaakeh and Dutcher 1993). ...
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Passion fruit (Passiflora edulis) is an important fruit crop with great commercial potential since the demand for both fresh fruit and processed juice for both local and export is on the increase. Like in other countries, passion fruit productivity in Kenya is low due to both biotic and abiotic constraints. Pest and diseases contribute largely to non-availability of clean planting material. Woodiness disease caused by viral pathogens is one of the most devastating diseases of passion fruit in the world. The disease results from synergistic interactions of potyviruses that are vectored by aphids. However, the distribution of the economically important pests for the crop is not well documented. Surveillance was carried out to establish the distribution of the pests in the major growing areas in Kenya between March and May, 2019. A total of 69 farms were sampled and 142 samples were collected. Most farmers (95%) prepared their own seeds for sowing from previous crops which they also shared amongst the neighbors. Passion fruit woodiness (PWD) was the major disease observed in most farms in Uasin Gishu, Marakwet, Nyamira and Kisii Counties. Majority of the farmers (75%) rated PWD as the major constraint to passion fruit production followed by Fusarium wilt. However, in Nyeri, Embu and Meru counties, farmers rated fusarium wilt as the major constraint followed by PWD. There was decrease in passion fruit production in all areas surveyed whereas in some Counties like Baringo, Nakuru and Migori had totally abandoned the production of this crop, mainly due to the devastation of PWD. Upto 46% of the samples tested positive for potyviruses. Elgeyo Markwet recorded the highest incidence potyviruses at 69% followed by UasinGishu at 68%. Bungoma County had the least potyviruses incidence at 17%. Fusarium sp and Colletotrichum spp were detected in 4 samples. Passion fruit farming has reduced due to biotic constraints mainly PWD and Fusarium sp. There is need for farmers to access and adopt use of certified seedlings in order increase productivity.
... It causes crop loss directly as a plant sap feeder and indirectly as a vector of many plant diseases (Blackman and Eastop 2007). Aphid survival and reproduction are greatly affected by different abiotic stresses such as temperature (Ma et al. 2004;Hulle et al. 2010), rainfall (Kaakeh and Dutcher 1993) and humidity (Leather 1985). Interestingly, several studies have shown the role of microbial symbionts in aphids in overcoming these abiotic stresses (Montllor et al. 2002;Guay et al. 2009). ...
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Aphid populations were collected on cowpea, dolichos, redgram and black gram from Belagavi and Udupi locations. The samples were shotgun sequenced using the Illumina NovaSeq 6000 system to understand the spatial distribution and community structure of microbiota (especially bacteria) associated with aphids. In the present study, we identified obligatory nutritional symbiont Buchnera aphidicola and facultative symbionts Rickettsia sp. and Bacteroidetes endosymbiont of Geopemphigus sp. in all the aphid samples studied, although in varied abundance. On the other hand, Serratia symbiotica, Arsenophonus sp. and Acinetobacter sp. were only found in aphids on specific host plants, suggesting that host plants might influence the bacterial community structure. Furthermore, our study revealed that microbiota other than bacteria were highly insignificant in the aphid populations. Additionally, functional annotation of aphid metagenomes identified several pathways and enzymes involved in various physiological and ecological functions. Amino acid and vitamin biosynthesis-related pathways were predominant than carbohydrate metabolism, owing to their feeding habit and nutritional requirement. Chaperones related to stress tolerance such as GroEL and DnaK were identified. Enzymes involved in toxic chemical metabolisms such as glutathione transferase, phosphodiesterases and ABC transferases were observed. These enzymes may confer resistance to pesticides in the aphid populations. Overall, our results support the importance of host plants in structuring bacterial communities in aphids and show the functional roles of symbionts in aphid survival and development. Thus, these findings can be the basis for further detailed investigations and devising better strategies to manage the pests in field conditions. Supplementary information: The online version contains supplementary material available at 10.1007/s13205-022-03142-1.
... Rainfall may have also been a factor in our study. A previous study by Kaakeh and Dutcher found a significant reduction in aphid numbers collected post-rainfall compared to pre-rainfall [34]. This is in accordance with other studies in different systems [35,36]. ...
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Aphids are important pests of pecans. Traditionally, insecticides have been the primary method of management. However, over-reliance and non-judicious use has led to resistance and damage to natural enemy populations. Therefore, frequent assessment of insecticides is necessary in order to monitor resistance development and non-target impacts. Aphicides, flonicamid, sulfoxaflor, and afidopyropen were assessed for their effects on pecan aphids and parasitoid, Aphelinus perpallidus, in a mature pecan orchard in 2019 and 2020. Post-application assessments were performed 7, 14, and 21 days post-application. Leaf samples from non-treated trees had greater aphid numbers than treated trees 7 days post-application with differences diminishing throughout the other two treatment periods in 2019. In 2020, aphid numbers were lower but leaf samples from non-treated trees had more aphids than treated trees 7 days post-application in the lower canopy. These differences again diminished 14 and 21 days post-application. There was no difference among treatments in number of parasitoid adults or mummies. These findings indicate that pecan growers have multiple potential options available for aphid management that do not negatively impact the primary pecan aphid parasitoid. Implications of the results on pecan aphid management are discussed.
... The top of net house was flat and rain penetrated through the mesh. Rainfall is considered to regulate aphid population densities (Kaakeh and Dutcher, 1993). The lower aphid numbers in the net house and net house + push-pull treatments suggest that the microclimate was unsuitable for these pests during the rainy period. ...
Article
Net houses can be used in tropical environments to protect crops such as cowpea against large insect pests, thereby avoiding pesticide treatments while sustainably mitigating the effects of climate change. We investigated a push-pull strategy to prevent small insect pest outbreaks in a net house. The push component consisted of two stimulus plants, i.e. Cymbopogon citratus and Tagetes minuta, and the pull stimuli consisted of visual cues from blue and yellow sticky traps. Field experiments were set up in central Kenya and conducted during a rainy and a dry season, involving an open field control treatment, and three management treatments consisting of (1) an open field push-pull treatment, (2) a net house treatment and (3) a combined net house + push-pull treatment. Trialeurodes vaporariorum infestations were lower in the net house and net house + push-pull treatments than in the two open field treatments during the dry period or in the control treatment during the rainy period. Aphis craccivora infestations were higher in the net house and net house + push-pull treatments than in the control and open field push-pull treatments during the dry period, while no differences were observed among treatments during the rainy period. Megalurothrips sjostedti infestations did not vary among treatments in both periods. Among the larger insect pests, Clavigralla tomentosicollis infestations were lower in the net house and net house + push-pull treatments than in the open field treatments during the dry period, while Maruca vitrata infestations were lower in the net house treatment than in the control. During the rainy period, C. tomentosicollis infestations were higher in the net house + push-pull treatment than in the net house treatment, whereas M. vitrata in- festations did not vary among treatments. Compared to the control, Empoasca sp. infestations were lower in the net house and net house + push-pull treatments in both periods, and in the open field push-pull treatment in the rainy period. Cowpea pod and grain yield and quality were higher in the net house and net house + push-pull treatments than in the control irrespective of the period. Although the treatments 1 reduced some of the pests, the net house and net house + push-pull treatments were effective in protecting cowpeas against most of the pests while improving pod yields in both periods.
... The highest number of the aphid species recorded from Trabzon Province and the lowest rainfall. It has been considered that rainfall might cause differences in determined aphid species among studied provinces and also from the other regions of Turkey as there are some studies indicated how negatively strong rainfall effect aphid biodiversity and seasonal variability (Kaakeh & Dutcher, 1993). In addition to strong rainfall in study area during sampling period and average values compared with other regions of Turkey, it has been considered that there are a lot of underbrush plant species and most of them do not get enough sunshine. ...
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Aphid-host plant relationship has fascinated scientist for a long time as they had some tight interactions. There is considerable amount of mountainous land area in Far Eastern Black Sea Region of Turkey which is almost %27 and about 165 aphid species have been determined. There has been no study conducted either to detect aphid fauna of region or aphid-host plant interaction up to last decades. Compared with determined aphid species diversity with floristic richness of region and each province, number of the aphid species recorded does not reflect real aphid composition of study area. According to proposed model related with aphid-host plant diversity around the world, both heavy rainfall and mix of higher vegetation biodiversity especially underbrush plant richness might explain unexpected lower aphid species diversity compared with higher plant diversity. Recent studies carried out clearly indicated that aphid-host plant relations should be studied in detail as these relations are become much more dynamic as a result of recent climatic changes. ÖZ Kendi aralarında sıkı etkileşime sahip olan afit-konak bitki ilişkileri biliminsanlarını uzun süreden beri etkilemektedir. Türkiye'nin Doğu Karadeniz Bölgesi'nde kayda değer miktarda (%27) dağlık arazi alanı vardır ve bu alandan yaklaşık 165 afit türü tespit edilmiştir. Bölgenin afit faunası veya afit-konak bitki ilişkilerini son yıllarda belirlemek amacıyla herhangi bir çalışma yapılmamıştır. Bölgenin floristik zenginliği ile belirlenen afit tür çeşitliliğini karşılaştırıldığında, kaydedilen afit türü sayısı çalışma alanının gerçek afit sayısını yansıtmamaktadır. Dünyadaki afit-bitki çeşitliliği ile ilgili tahmini modele göre, hem yoğun yağış hem de yüksek vejetasyonlardaki karışık biyoçeşitliliğe sahip olan, özellikle de bitkisel zenginliğe sahip ormanaltı alanlar gibi bölgeler ile karşılaştırıldığında, afit tür çeşitliliği miktarının beklenenin altında bir sayıda olduğunu açıklayabilir. Son zamanlarda yapılan çalışmalarda, afit-konak bitki ilişkilerinin son iklim değişikliklerinin bir sonucu olarak çok daha dinamik hale gelmesi nedeniyle detaylı olarak çalışılması gerektiği açıkça göstermektedir.
... Heavy rain can mechanically disturb aphid colonies. Nevertheless, studies that evaluated the effect of rain on aphid populations in perennial crops did not find important demographic reductions even after torrential downpours (Kaakeh andDutcher 1993, Michaud 1999). Shoots are an ephemeral resource essential to aphid development. ...
Article
The Spirea citrus aphid, Aphis spiraecola Patch, and the cotton aphid, Aphis gossypii Glover (Hemiptera: Aphididae), are key pests of clementine mandarines in the Mediterranean basin. Severity of aphid infestations is determined by environmental variables, host plant phenology patterns, and the biological control exerted by their associated natural enemies. However, there is no information about the role these limiting and regulating factors play. Aphid densities, citrus phenology, and associated predators that overwinter in the crop were monitored weekly throughout two flush growth periods (February to July) in four clementine mandarin groves; relationships between these parameters and environmental variables (temperature and precipitation) were studied. Our results show exponential increase in aphid infestation levels to coincide with citrus phenological stages B3 and B4; shoots offer more space and nutritional resources for colony growth at these stages. Duration of these phenological stages, which was mediated by mean temperature, seems to importantly determine the severity of aphid infestations in the groves. Among those studied, the micro-coccinellids, mostly Scymnus species, were the only group of predators with the ability to efficiently regulate aphid populations. These natural enemies had the highest temporal and spatial demographic stability. Aphid regulation success was only achieved through early presence of natural enemies in the grove, at the aphid colonization phase. Our results suggest that conservation strategies aimed at preserving and enhancing Scymnus sp. populations may make an important contribution to the future success of the biological control of these key citrus pests.
... The coast of Alabama-an area of substantial pecan production-has an ≈11% chance of being hit in any one year, plus there is the potential for recurvature across the Georgia production zone. (Kaakeh and Dutcher, 1992) and also probably by a proliferation of entomophagous fungi due to a relatively wet environment. The pecan leaf scorch mite [Eotetranychus hicoriae McGregor] is also a severe pest that is subject to population suppression for the same reasons as are aphids. ...
Article
Foliage-feeding aphid species infest pecan orchards and damage them by causing early defoliation leading to reductions in staminate and pistillate flowers and nut production. Long-term orchard management practices are effective in pecan orchards to stabilize the abundance of imported and indigenous natural enemies. The producer has a long-term investment in the orchard and can implement conservation techniques over several years. Conservation techniques of intercropping with sesbania alone, the combination of mowed sod and ant exclusion, and the combination of intercropping with hairy indigo and ant exclusion has reduced pecan aphid populations in Georgia. The development and implementation of an alternative to chemical control of pecan aphids require greater monitoring and another level of decision making for producers. Producers of improved cultivars typically apply one spray for pecan nut casebearer, one spray for early season hickory shuckworm, and three sprays for the late season pest complex (that is, pecan weevil, kernel-feeding hemipterans, leafminers, aphids, mites, and late season hickory shuckworm). Chemical control of foliage-feeding insects is achieved by mixing a specific larvicide, aphidicide, or miticide with the principal insecticide for nut pests.
Article
The current state of pecan insect pest management in improved and seedling orchards in the southern U.S. is described by a review of the recent literature generated by research and extension programs. New research results are reported on the damage potential of late season insect pests in pecan orchards from controlled field experiments. Controlling the shuckmining injury caused by hickory shuckworm did not increase pecan yield or kernel quality during the current season on 'Desirable' pecan trees in an infestation that developed between two and four weeks after shell-hardening. The combination of injury by a low population of blackmargined aphids and a late season infestation of hickory shuckworm in 'Desirable' pecan trees caused a significant degradation in kernel color; whereas, trees treated with selective chemical control of either the aphids or the hickory shuckworm or both insects had significantly brighter kernel color. Significant linear regression models were found between abundance of adult pecan weevil emerging from the soil beneath tree crown and number of damaged nuts in the tree. The regression models indicated that trees with higher weevil density emerging beneath the canopy tended to have more damaged pecans than trees with lower weevil density in the soil beneath the canopy.
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