Control Of Cotton Pests Research Articles

Residual swin transformer for classifying the types of cotton pests in complex background.

Cotton pests have a major impact on cotton quality and yield during cotton production and cultivation. With the rapid development of agricultural intelligence, the accurate classification of cotton pests is a key factor in realizing the precise application of medicines by utilize unmanned aerial vehicles (UAVs), large application devices and other equipment. In this study, a cotton insect pest classification model based on improved Swin Transformer is proposed. The model introduces the residual module, skip connection, into Swin Transformer to improve the problem that pest features are easily confused in complex backgrounds leading to poor classification accuracy, and to enhance the recognition of cotton pests. In this study, 2705 leaf images of cotton insect pests (including three insect pests, cotton aphids, cotton mirids and cotton leaf mites) were collected in the field, and after image preprocessing and data augmentation operations, model training was performed. The test results proved that the accuracy of the improved model compared to the original model increased from 94.6% to 97.4%, and the prediction time for a single image was 0.00434s. The improved Swin Transformer model was compared with seven kinds of classification models (VGG11, VGG11-bn, Resnet18, MobilenetV2, VIT, Swin Transformer small, and Swin Transformer base), and the model accuracy was increased respectively by 0.5%, 4.7%, 2.2%, 2.5%, 6.3%, 7.9%, 8.0%. Therefore, this study demonstrates that the improved Swin Transformer model significantly improves the accuracy and efficiency of cotton pest detection compared with other classification models, and can be deployed on edge devices such as utilize unmanned aerial vehicles (UAVs), thus providing an important technological support and theoretical basis for cotton pest control and precision drug application.

Integrated Omics Analysis Reveals Key Pathways in Cotton Defense against Mirid Bug (Adelphocoris suturalis Jakovlev) Feeding.

The recent dominance of Adelphocoris suturalis Jakovlev as the primary cotton field pest in Bt-cotton-cultivated areas has generated significant interest in cotton pest control research. This study addresses the limited understanding of cotton defense mechanisms triggered by A. suturalis feeding. Utilizing LC-QTOF-MS, we analyzed cotton metabolomic changes induced by A. suturalis, and identified 496 differential positive ions (374 upregulated, 122 downregulated) across 11 categories, such as terpenoids, alkaloids, phenylpropanoids, flavonoids, isoflavones, etc. Subsequent iTRAQ-LC-MS/MS analysis of the cotton proteome revealed 1569 differential proteins enriched in 35 metabolic pathways. Integrated metabolome and proteome analysis highlighted significant upregulation of 17 (89%) proteases in the α-linolenic acid (ALA) metabolism pathway, concomitant with a significant increase in 14 (88%) associated metabolites. Conversely, 19 (73%) proteases in the fructose and mannose biosynthesis pathway were downregulated, with 7 (27%) upregulated proteases corresponding to the downregulation of 8 pathway-associated metabolites. Expression analysis of key regulators in the ALA pathway, including allene oxidase synthase (AOS), phospholipase A (PLA), allene oxidative cyclase (AOC), and 12-oxophytodienoate reductase3 (OPR3), demonstrated significant responses to A. suturalis feeding. Finally, this study pioneers the exploration of molecular mechanisms in the plant-insect relationship, thereby offering insights into potential novel control strategies against this cotton pest.

Identification of cotton pest and disease based on CFNet- VoV-GCSP -LSKNet-YOLOv8s: a new era of precision agriculture.

The study addresses challenges in detecting cotton leaf pests and diseases under natural conditions. Traditional methods face difficulties in this context, highlighting the need for improved identification techniques. The proposed method involves a new model named CFNet-VoV-GCSP-LSKNet-YOLOv8s. This model is an enhancement of YOLOv8s and includes several key modifications: (1) CFNet Module. Replaces all C2F modules in the backbone network to improve multi-scale object feature fusion. (2) VoV-GCSP Module. Replaces C2F modules in the YOLOv8s head, balancing model accuracy with reduced computational load. (3) LSKNet Attention Mechanism. Integrated into the small object layers of both the backbone and head to enhance detection of small objects. (4) XIoU Loss Function. Introduced to improve the model's convergence performance. The proposed method achieves high performance metrics: Precision (P), 89.9%. Recall Rate (R), 90.7%. Mean Average Precision (mAP@0.5), 93.7%. The model has a memory footprint of 23.3MB and a detection time of 8.01ms. When compared with other models like YOLO v5s, YOLOX, YOLO v7, Faster R-CNN, YOLOv8n, YOLOv7-tiny, CenterNet, EfficientDet, and YOLOv8s, it shows an average accuracy improvement ranging from 1.2% to 21.8%. The study demonstrates that the CFNet-VoV-GCSP-LSKNet-YOLOv8s model can effectively identify cotton pests and diseases in complex environments. This method provides a valuable technical resource for the identification and control of cotton pests and diseases, indicating significant improvements over existing methods.

Farmers' Production Practices, Incidence and Management of Pests and Diseases, Extension Services, and Factors Limiting Cotton Production and Quality in South Africa

Cotton is one of the essential cash crops; however, several factors, such as low yields and pest and disease infestations, affect the production. In South Africa, cotton production has increased among small-scale farmers since the late 1990s. Although the crop is not new to South African farmers, no recent information reflects the current status of cotton production practices. A study evaluated farmers' production practices, the incidence and management of pests and diseases, extension services, and factors limiting cotton production and quality in South Africa. One hundred and forty farmers, mainly smallholder farmers, were interviewed during the 2017/18 growing season. Most farmers planted genetically modified (GM) cotton on less than 5 ha of cotton, with 96% planting under dryland. Most farmers neither practised conservation agriculture (95%) nor conducted soil analyses (87%). A mean cottonseed yield of 700 kg ha-1 was reported on dryland cotton, and 5 000 kg ha-1 was obtained from irrigated cotton. Most of the farmers (99%) harvested their cotton by handpicking. Farmers' pest knowledge was higher than their knowledge of different diseases. Most participants were unaware of nematodes (88%) or disease-resistant cultivars (74%), while 91% were aware of insect-resistant cultivars. Extension officers only mentored and supported many respondents (82%). Most farmers (93%) relied on pesticides to control cotton pests, and the rest (7%) used biological control. Climatic conditions (98%), labour costs (88%), and insect infestations (42%) were identified as the main constraints in cotton production. Although this study had a limited number of surveyed farmers, it gives some insight into their knowledge and challenges.

Pink bollworm, Pectinophora gossypiella (Saunders) management strategy, dissemination and impact assessment in India

The recent emergence of pink bollworm (PBW), Pectinophora gossypiella (Saunders) has posed serious ecological and economic implications for cotton production in India since 2017. The project “Insecticide Resistance Management (IRM): Dissemination of pink bollworm management strategies in Bt-cotton” was implemented consecutively for four years from 2018 -19, 2019–20, 2020-21 and 2021-22 in 21 districts across three cotton growing zones of the country. In each year, field demonstrations were conducted on 1050 acres of cotton area and mass awareness was created through outreach activities. With concerted and focused efforts, the PBW infestations could be brought down by 42.75% in 2018–19, 43.49% in 2019–20, 35.55% in 2020-21 and 33.77% in 2021-22 in the demonstration plots over the farmer practices. An increased benefit: cost ratios of 2.16:1, 2:1, 1.89:1 and 2.24:1 were realized during 2018–19, 2019–20, 2020-21 and 2021–22, respectively. Similarly, the average number of sprays for the control of cotton pests during the season was reduced to 5.02, 4.94, 5.19 and 5.18 in integrated pest management (IPM) fields as compared to 6.98, 7.66, 8.07 and 8.20 in non-integrated pest management (NIPM) fields in the corresponding years. Reduction in pesticide usage in IPM vs NIPM fields was 46.39% in terms of cost, and 38.96% in terms of volume during 2019-20 while concurrent percent reduction in pesticide usage was 41.03 & 39.33 during 2020-21 and 40.70 & 39.38 in 2021–22. Comparatively more seed cotton was harvested from IPM than NIPM fields i.e. 2190 vs 1820 kg/ha in 2018–19, 2049 vs 1715 kg/ha in 2019–20, 1881 vs 1585 kg/ha in 2020-21 and 1901 vs 1607 kg/ha in 2021–22. Significant success in reducing PBW infestation, pesticide usage and corresponding improvement in yield, economic benefits and environmental quality in terms of reduced EIQFUR has been achieved through IPM demonstrations. This area-wide success was achieved through collective efforts and active involvement of all concerned stakeholders.

Use of different cotton pest control strategies (conventional, organic and transgenic) had no impact on insecticide resistance in Anopheles gambiae s.l. populations in Burkina Faso, West Africa

Resistance to insecticides in the mosquito Anopheles gambiae s.l can jeopardize malaria vector control strategies. Previous studies have shown that the agricultural chemicals, used particularly for cotton protection, selected the insecticide resistant malaria vectors. Our study aimed at assessing the impact of three cotton pest management strategies in different ecological settings (conventional, organic and transgenic cotton growing areas) on the i) susceptibility to insecticides belonging to pyrethroids, DDT, carbamate and organophosphate tested on the main malaria vectors and ii) frequencies of kdr L1014F, during rainy season of 2008, 2009, 2013 and 2014 in Burkina Faso. From 2008 to 2014, most of populations of An. gambiae s.l from the three cotton growing areas exhibited a reduction in susceptibility to almost all insecticide classes. The frequency of kdr L1014F mutations varied depending on both localities and species within the An. gambiae complex, but no relationship was found between the cotton pest control strategies and the frequency of kdr L1014F. These results confirm the worrying status of insecticide multi-resistance within the vector mosquito species from Burkina Faso. Supplemental data for this article is available online at https://doi.org/10.1080/09670874.2022.2051642 .

Pest Biological Control: Goals Throughout My Life.

This autobiography documents the life and accomplishments of Li Liying. Born into a poor family in China, she eventually became director of Guangdong Entomological Institute. After graduating middle school (1949), she was admitted to the Agronomy Faculty at Beijing Agricultural University but was shortly after redirected by the Chinese Government to Timiryazev Agricultural Academy, Moscow, Russia. The last year of her study at Timiryazev Agricultural Academy was a pivotal experience. She had the opportunity to conduct fieldwork on cotton pest control and became aware of the harmful practice of aerially spraying highly toxic organophosphates with workers present. She decided to dedicate herself to finding safer alternatives and became a leader in the development of mass-rearing techniques for insects beneficial to agriculture. She traveled to laboratories in several foreign countries to foster collaboration and exchange of ideas among colleagues. She is recognized for her service to entomological societies, teaching at universities, and love of entomology.

Control of cotton pests and diseases by intercropping: A review

Cotton (Gossypium hirsutum L.) is a globally important crop that is often damaged by pests and diseases. Current cotton pests and diseases management is dependent on chemical pesticides. Although chemical pesticides are usually effective, long-term application of these pesticides often leads to increased insecticide resistance in the pests, fewer natural enemies, reduced natural control, and a degraded environment. Because of increased environmental awareness and the need for sustainable cotton production, the control of cotton pests and diseases using biological means like intercropping is increasingly receiving attention. Intercropping of cotton with other crops can often boost the total yield and output of the intercropping system and provide significant economic benefits without sacrificing cotton quality. Intercropping also increases the number of natural enemies, and reduces the occurrence of cotton pests and diseases by altering the ecological structure and environmental conditions in the fields. Cotton-based intercropping is an effective strategy to reduce the competition between cotton and grain or other economic crops for arable land. It is also an important way to increase the populations of natural enemies in cotton fields for the management of pests and diseases. However, inappropriate intercropping can also increase labor requirements and even result in inadequate control of pests and diseases. This review focuses on the performance and the mechanisms of intercropping for reducing cotton pests and disease as well as on the effective management of intercropping systems. The risks and limitations, as well as the study approaches needed and the prospects of intercropping for the control of cotton pests and diseases, are also discussed. This information is intended to aid researchers and growers in designing economically viable and ecologically friendly pest and disease management strategies that will reduce the use of chemicals and the cost of cotton production.

Efficacy of three biopesticides against cotton pests under field conditions in South Africa

Cotton is a major fibre crop grown in South Africa; and is subjected to pest attacks, which reduce its yield and profitability for farmers. Field trials were conducted in 2017 and 2018 to evaluate three biopesticides, namely, Eco-Bb®, Bb endophyte, and Metarhizium rileyi in comparison with the insecticides Chlorpyrifos® 480 EC, Karate® EC, and Bandit® 350 SC. The objective was to determine their efficacy against sucking pests, leafhoppers Jacobiella facialis, aphids Aphis gossypii, thrips Thrips tabaci, whiteflies Bemisia tabaci, red spider mite Tetranychus urticae, and cotton stainers Dysdercus spp. Karate® significantly reduced the leafhopper population and outperformed all the other treatments. Eco-Bb® and Bb endophyte did not control the aphids in 2017. However, in 2018 the best aphid control resulted from the biopesticides used. In 2017 plots treated with Eco-Bb® had the lowest number of thrips, while in 2018 plots treated with Bandit® had the least thrips, followed by treatments with M. rileyi and Karate®. There were no significant differences in the populations of whiteflies, however, insecticides were more effective than the biopesticides. All the treatments, except for Bandit®, significantly reduced the number of spider mites compared in 2017.Applications of Eco-Bb® and Bb endophyte significantly reduced spider mites in 2017, while in 2018 plots treated with Karate®, followed by M. rileyi, resulted in the lowest number of spider mites. Application of Bb endophyte, Chlorpyrifos®, and Karate® resulted in the lowest number of cotton stainers. The highest mean cottonseed yields of 6395 kg ha−1, 6295 kg ha−1, and 6141 kg ha−1 were recorded in plots sprayed with Bandit®, Bb endophyte, and Eco-Bb®, respectively. Biopesticides and chemical insecticides can be combined or alternated for future IPM programmes to control cotton pests.

Pyramiding of cry toxins and methanol producing genes to increase insect resistance in cotton

ABSTRACT The idea of enhanced methanol production from cell wall by pectin methyl esterase enzymes (PME) combined with expression of cry genes from Bacillus thuringiensis as a strategy to improve insect pest control in cotton is presented. We constructed a cassette containing two cry genes (cry1Fa and Cry32Aa) and two pme genes, one from Arabidopsis thaliana (AtPME), and other from Aspergillus. niger (AnPME) in pCAMBIA1301 plant expression vector using CAMV-35S promoter. This construction was transformed in Eagle-2 cotton variety by using shoot apex-cut Agrobacterium-mediated transformation. Expression of cry genes and pme genes was confirmed by qPCR. Methanol production was measured in control and in the cry and pme transformed plants showing methanol production only in transformed plants, in contrast to the non-transgenic cotton plants. Finally, insect bioassays performed with transgenic plants expressing cry and pme genes showed 100% mortality for Helicoverpa armigera (cotton bollworm) larvae, 70% mortality for Pectinophora gossypiella (pink bollworm) larvae and 95% mortality of Earias fabia, (spotted bollworm) larvae, that was higher than the transgenic plants expressing only cry genes that showed 84%, 49% and 79% mortality, respectively. These results demonstrate that Bt. cry-genes coupled with pme genes are an effective strategy to improve the control of different insect pests.

Buckwheat strip crops increase parasitism of Apolygus lucorum in cotton

Cropping system diversification, including the in-field establishment of strip crops can improve the effectiveness of natural enemies and enhance biological control of pestiferous herbivores. In China, habitat management such as the in-field establishment of alfalfa strips is used for pest control in cotton. However, their effect on other economically important pests, such as the mirid bug Apolygus lucorum (Meyer-Dur), has not been evaluated. In this study, we first assessed parasitism of A. lucorum within plots of 13 different host plant species. Next, we established strips of one suitable plant species within a commercial cotton field and evaluated its effect on A. lucorum parasitism level. The results showed that two A. lucorum parasitoids, i.e., Peristenus spretus Chen et van Achterberg and Peristenus relictus Ruthe, responded differently to host plant species. In 2014, the parasitism levels of P. spretus were highest on buckwheat Fagopyrum esculentum Moench, while parasitism levels of P. relictus were generally low and did not differ between the various plants. Furthermore, A. lucorum attained low population levels on buckwheat. In 2016, A. lucorum parasitism levels in buckwheat plots were higher than in cotton. When (2 m wide) buckwheat strips were established in cotton fields, P. spretus parasitism of A. lucorum on cotton plants increased 2.4-fold in 2016 and 8.5-fold in 2017 compared to cotton monocrops. In conclusion, the establishment of buckwheat strips in commercial cotton fields enhances A. lucorum parasitism. By deploying these habitat management tactics, parasitoid-mediated biological control may complement existing management schemes for the polyphagous mirid bug in China and abroad.

UDP-glucosyltransferases potentially contribute to imidacloprid resistance in Aphis gossypii glover based on transcriptomic and proteomic analyses

The cotton aphid, Aphis gossypii Glover, is a destructive global crop pest. Control of A. gossypii has relied heavily on the application of chemical insecticides. The cotton aphid has developed resistance to numerous insecticides, including imidacloprid, which has been widely used to control cotton pests in China since the 1990s. Our objective was to investigate the potential role of UDP-glycosyltransferases (UGTs) in imidacloprid resistance based on transcriptomic and proteomic analyses of field-originated imidacloprid-resistant (IMI_R) and -susceptible (IMI_S) A. gossypii clones. The transcriptomic and proteomic analyses revealed that 12 out of 512 differentially expressed genes and three out of 510 differentially expressed proteins were predicted as UDP-glycosyltransferase (UGT). Based on quantitative real-time PCR analysis, nine UGT genes, UGT343A4, UGT344A15, UGT344A16, UGT344B4, UGT344C7, UGT344C9, UGT344N4, UGT 24541, and UGT7630, were up-regulated in the IMI_R clone compared to the IMI_S clone. Meanwhile, UGT344A16, UGT344B4, UGT344C7, and UGT344N4 were overexpressed at the protein level based on western blot analysis. Furthermore, knockdown of UGT344B4 or UGT344C7 using RNA interference (RNAi) significantly increased sensitivity to imidacloprid in the IMI_R clone. In conclusion, UGTs potentially contributed to imidacloprid resistance in A. gossypii originating from cotton-growing regions of China. These results provide insights into the way we study insecticide resistance in cotton aphids.

Cotton extrafloral nectaries as indirect defence against insect pests

Knowledge about indirect defences that mediate the ecological interactions between plants and their beneficial and harmful insects are needed to better incorporate pest resistance traits in breeding programs. “Top-down” pest control by natural enemies has not been considered in most plant breeding strategies and, in many cases, beneficial interactions of crops with the third trophic level have been reduced through breeding processes. Extrafloral nectaries (EFNs) are plant structures that provide indirect defences to plants through nectar rewards attracting arthropods that may act as predators of pests. Recent studies have demonstrated that EFNs may play an important role in herbivore suppression in agricultural systems. The main objectives of this study were to quantify the leaf extrafloral nectar production of cotton plants, to identify natural enemies of crop pests visiting these EFNs, and to assess the biological control and occurrence of various cotton pests. To address these objectives, we performed both greenhouse and field experiments in which we compared three wild varieties of cotton plants with EFNs, two cultivated varieties with EFNs and two nectariless varieties. Results showed that wild cotton varieties produced greater quantity of nectar per leaf than cultivated varieties. In addition, wild varieties bearing EFNs enhanced the diversity of natural enemies (especially ants) which could, in turn, increase biological control under certain conditions. However, the association between the community of insects visiting EFNs and pest suppression was not clear and depended on the pest species. Indirect defences associated to EFN need to be better explored to enhance selection of pest-resistant cotton cultivars.

Phytophagous insects in cotton crop residues during the fallow period in the state of Mato Grosso do Sul, Brazil

Abstract: The objective of this work was to analyze the faunistic composition of the insect pests that occur during the fallow period in cotton (Gossypium hirsutum) crop residues in the state of Mato Grosso do Sul, Brazil. The study sites were the municipalities of Alcinópolis, Chapadão do Sul, Costa Rica, Aral Moreira, Dourados, and Sidrolândia. A sampling design with two replicates per municipality was used. Each replicate comprised 100 random points, and each point corresponded to a cotton plant that was entirely inspected, to count the insect pests on it. The obtained fauna was analyzed and a rarefaction curve of the species was generated. During the evaluation period, a total of 23 species were recorded in the cotton crop residue, and the most frequent and abundant were Bemisia tabaci, Aphis gossypii, Frankliniella schultzei, and Anthonomus grandis. The caterpillars were predominantly found on the non-Bt cotton crops in Dourados, and Chapadão do Sul was the municipality that exhibited the greatest species diversity. Despite being mandatory, the destruction of cotton stalks during the fallow period was not able to completely eliminate the insect pests during the study period; among these insect pests, A. grandis stands out, a species that affects the dynamics of cotton pest control.

Short-term toxicity of insecticides residues to key predators and parasitoids for pest management in cotton

The cotton ecosystem comprises various arthropod pest and natural enemies with simultaneous occurrence irrespective of growing region. The use of insecticides with reduced impact on natural enemies is a major goal to conserve them and, therefore, to reduce populations of arthropod pests. The survival of twelve key natural enemies for cotton pest management exposed to dried residues using the highest and lowest recommended rates representing old and new insecticides recommended to control cotton pests (chlorantraniliprole, chlofernapyr, spinosad, lambda-cyhalotrin, methidathion, pymetrozine, and thiamethoxam) was determined. The study included parasitoids [Aphelinus gossypii Timberlake, Bracon vulgaris Ashmead, Lysiphlebus testaceipes (Cresson), Telenomus podisi (Ashmead), Trichogramma pretiosum (Riley)] and predators [Hippodamia convergens Guerin-Meneville, Euborellia annulipes (Lucas), Podisus nigrispinus (Dallas), Solenopsis invicta Buren), Orius insidiosus (Say), Chrysoperla externa Hagen and Eriopis connexa (Germar)], with two different cohorts for these last two species. All natural enemies exposed to methidathion exhibited 100% mortality. Thiamethoxam, lambda-cyhalothrin and chlorfenapyr also caused high mortality of P. nigrispinus, S. invicta, H. convergens, O. insidiosus and all tested parasitoids. Among the natural enemies, E. annulipes exhibited high survival when exposed to all tested insecticides, except methidathion. Chlorantraniliprole and pymetrozine caused overall lower impact on the natural enemies tested followed by spinosad; hence, they are options for cotton pest management. Furthermore, the outcomes highlight the implication of knowing the background susceptibility of the species tested when addressing the impact of insecticides on natural enemies.

Cotton pest control awareness in farmers of the Punjab, Pakistan and its impact on whitefly resistance against available insecticides

A farmers survey was conducted to perceive their knowledge of pest control and its impact on resistance to insecticides in whitefly. Most farmers had some school education and were able to identify the major pests of cotton, but they used descriptive rather than specific names when defining a pest. They exclusively relied on chemical pest control and sprayed 4–5 active ingredients in almost 7–8 applications. The majority of them applied insecticide mixtures at doses higher than recommended and followed a calendar spraying schedule. Laboratory bioassays indicated a low level of resistance of B. tabaci to imidacloprid, acetamiprid, nitenpyram, buprofezina, pyriproxyfen, diafenthiuron, spirotetramat, and flonicamid with resistance ratios of 5.13-, 3.0-, 4.90-, 4.14-, 3.42-,4.73-, 3.08- and 1.93- fold, respectively compared with a susceptible population. However, the bioassays showed a medium level of resistance (16.4- fold) to bifenthrin. In conclusion, B. tabaci showed a low level of resistance to the insecticides used and for the attainment of satisfactory pest control, farmers should be educated on the correct use of insecticides and also about alternatives to chemical control.

Impact of pest management practices on the frequency of insecticide resistance alleles in Bemisia tabaci (Hemiptera: Aleyrodidae) populations in three countries of West Africa

In West Africa, the use of organophospates and pyrethroid insecticides to control cotton pests has led to the evolution of resistance in field populations of Bemisia tabaci Gennadius. Three pest management programs have been commonly recommended: the Conventional Program (CP) where 6 treatments are applied, the use of Bt cotton plants for which only 2 applications of neonicotinoids are required and that has been adopted in many countries, and a biological program (BP) without any chemical treatment. The present study aimed to determine the influence of these practices on the frequency of mutations that confer resistance to pyrethroids (mutation L925I in the para-type voltage-gated sodium channel gene) and organophosphates (mutation F331W in the acetylcholinesterase enzyme ace1: allele Ace1R) in B. tabaci populations using Bt cotton and CP areas in Pô and Saria (Burkina Faso), CP and BP areas in Kandi (Benin) and only CP areas in Tové and Infa (Togo). All individuals sampled belonged to the MED (biotypes MED-Q1) and Africa Silver Leafing (ASL) species. MED-Q1 was found in sympatry with ASL in Burkina Faso both on CP and Bt cotton areas at variable frequencies. In Togo and Benin, only ASL was found, except in Tové where MED-Q1 was also detected, but at low frequency. Frequencies of mutations that confer resistance varied between localities and species but we did not find any strong evidence of a relationship between the pest management program and these frequencies except for the allele Ace1R in Burkina Faso for which the frequencies decrease when chemical applications are reduced. This study provides valuable information for the development of efficient integrated pest management programs.

Microbial control of cotton pests: use of the naturally occurring entomopathogenic fungus Aspergillus sp. (BC 639) in the management of Bemisia tabaci (Genn.) (Hemiptera: Aleyrodidae) and beneficial insects on transgenic cotton crops

ABSTRACTThe commercial adoption of transgenic Bacillus thuringiensis (Bt) cotton (Bollgard II®) reduced the use of insecticides to control Helicoverpa spp. However, the ineffectiveness of the Bt toxin against sucking pests such as silverleaf whiteflies (Bemisia tabaci) resulted in a marked increase in B. tabaci populations and in the use of insecticides to control this pest. The effect of the entomopathogenic fungus Aspergillus sp. BC 639 on B. tabaci and beneficial insects (predominantly predatory insects) was studied in commercial cotton field trials. The results showed that oil-based extracts of the entomopathogenic fungus BC 639 control the number of B. tabaci adults and nymphs in commercial transgenic cotton crops. The BC 639 fungus caused 60.0%, 67.2%, and 68.8% mortality in adults, and 54.6%, 62.3%, and 51.7% in nymphs at 7, 14, and 21 days after treatment, respectively, relative to the unsprayed controls. The effect of BC 639 at concentrations of 125, 250, and 500 ml/ha on low-density B. tabaci (∼10 nymphs/leaf) did not differ significantly from that of the commercial insecticide (pyriproxifen). However, at higher densities (>50 nymphs per leaf), low concentrations of BC 639 (125 and 250 ml/ha) were not as effective as 500 ml/ha BC 639 in successfully controlling the pest. A simple graphic analysis suggested that the more B. tabaci nymphs per leaf, the fewer adults per leaf, and that once the number of nymphs increased to ∼70 per leaf, a negative feedback regulatory effect reduced the survivorship of the nymphs and adults and/or caused the emigration of the adults from the contaminated leaves in search of new resources. Therefore, the ability of BC 639 to control B. tabaci adults and nymphs with minimal effects on predatory insects indicates its potential utility in supplementing integrated pest management programmes for cotton crops.

Managing pests after 15 years of Bt cotton: Farmers' practices, performance and opinions in northern China

In China, a substantial amount of literature addresses pest control in Bt cotton, which is genetically engineered to resist some target pests but which had no direct effects on many other pests. The impact of this technology was positive a few years after the commercial release, but this impact was subsequently found to have reversed. The reversal was made known to the international community about ten years after the commercial release of Bt cotton in China, as a consequence of a pest complex shift phenomenon. Nevertheless, all the existing literature seldom took farmers' practices in spraying chemicals into account; farmers' opinions about using Bt cotton were not reported, nor were their opinions of their performance in growing cotton.Our study compensates for this lack through a specific and holistic approach in appraising farmers' practices, performance and opinions 15 years after the commercial release of Bt cotton in northern China. It focused on the topic of pest control by combining a survey of farmers' characteristics and opinions about Bt cotton effectiveness and profitability, as well as on their cotton cropping characteristics, with participatory detailed record-keeping of insecticide spraying by farmers. It is a holistic approach as it took into account the farming context when analyzing the results.Our results indicated that farmers used chemicals somewhat intensively, carrying out 11 insecticide sprayings on average, involving an average of 2 pest target-oriented insecticide controls. The pest complex shift phenomenon was confirmed as farmers aimed 60% of target-oriented insecticide controls at sucking pests, principally aphids even more than Lygus bugs. Three quarters of farmers were not content with Bt cotton profitability while providing a shorter protection time and most of them displayed a lack of proficiency in implementing chemical pest control. The remaining quarter of contented farmers carried out more pest target-oriented insecticide controls. Four spraying strategy factors were found and were associated notably with farmers' attitudes in controlling bollworms, aphids and Lygus bugs. The observed strategies were connected with distinct farming efficiency in a country where farming has lost its attractiveness. Sustainable use of Bt cotton calls for locally adapted actions to improve farmers' proficiency in pest control.

Improving spatio-temporal benefit transfers for pest control by generalist predators in cotton in the southwestern US

ABSTRACTGiven rapid changes in agricultural practice, it is critical to understand how alterations in ecological, technological, and economic conditions over time and space impact ecosystem services in agroecosystems. Here, we present a benefit transfer approach to quantify cotton pest-control services provided by a generalist predator, the Mexican free-tailed bat (Tadarida brasiliensis mexicana), in the southwestern United States. We show that pest-control estimates derived using (1) a compound spatial–temporal model – which incorporates spatial and temporal variability in crop pest-control service values – are likely to exhibit less error than those derived using (2) a simple-spatial model (i.e., a model that extrapolates values derived for one area directly, without adjustment, to other areas) or (3) a simple-temporal model (i.e., a model that extrapolates data from a few points in time over longer time periods). Using our compound spatial–temporal approach, the annualized pest-control value was $12.2 million, in contrast to an estimate of $70.1 million (5.7 times greater), obtained from the simple-spatial approach. Using estimates from one year (simple-temporal approach) revealed large value differences (0.4 times smaller to 2 times greater). Finally, we present a detailed protocol for valuing pest-control services, which can be used to develop robust pest-control transfer functions for generalist predators in agroecosystems.EDITED BY Neville Crossman