Crop Pests Research Articles

Whole-genome sequence of Enterobacter hormaechei, isolate jjbc recovered from the gut of Plutella xylostella feeding on cabbage.

We present the whole-genome sequence of Enterobacter hormaechei (previously Enterobacter cloacae) obtained from long and short reads. It is a dominant gut symbiont of the notorious crop pest Plutella xylostella, highly prevalent in lepidopteran midguts and a useful model for the evolution of resistance to antimicrobials.

Development of a sequential sampling plan for classifying Thrips tabaci (Thysanoptera: Thripidae) populations in onion fields.

Onion thrips, Thrips tabaci Lindeman, is a global pest of onion crops, causing substantial economic damage by diminishing bulb yields and transmitting plant pathogens. Insecticides are used to manage T. tabaci infestations with control decisions traditionally based on action thresholds that require visually counting thrips on a fixed, predetermined number of onion plants per field. However, this approach for treatment decisions is inefficient when thrips populations are well above or below the action threshold. The aim of this research was to develop a sequential sampling plan that would provide a rapid and reliable classification of thrips populations in commercial onion fields above or below prespecified management thresholds. The study was conducted in a total of 24 commercial onion fields in New York in 2021 and 2022. Taylor's power law and Wald's Sequential Probability Ratio Test were used in concert to develop each sampling plan. Simulated and historical field data of thrips populations were used to further validate the efficacy of each sampling plan. Results demonstrated the sequential sampling plan required an average of 78% fewer samples to make a control decision compared with the traditional fixed-sampling approach. Treatment decisions were reached in 72% of cases after inspecting only 10 plants, while only 6% of the cases required examining more than 25 plants. Comparisons with fixed-sample sizes ranging from 23 to 68 plants revealed a 96% agreement in decision-making and a 78% reduction in sampling effort when using the sequential sampling plans.

Causality-inspired crop pest recognition based on Decoupled Feature Learning.

Ensuring the efficient recognition and management of crop pests is crucial for maintaining the balance in global agricultural ecosystems and ecological harmony. Deep learning-based methods have shown promise in crop pest recognition. However, prevailing methods often fail to address a critical issue: biased pest training dataset distribution stemming from the tendency to collect images primarily in certain environmental contexts, such as paddy fields. This oversight hampers recognition accuracy when encountering pest images dissimilar to training samples, highlighting the need for a novel approach to overcome this limitation. We introduce the Decoupled Feature Learning (DFL) framework, leveraging causal inference techniques to handle training dataset bias. DFL manipulates the training data based on classification confidence to construct different training domains and employs center triplet loss for learning class-core features. The proposed DFL framework significantly boosts existing baseline models, attaining unprecedented recognition accuracies of 95.33%, 92.59%, and 74.86% on the Li, DFSPD, and IP102 datasets, respectively. Extensive testing on three pest datasets using standard baseline models demonstrates the superiority of DFL in pest recognition. The visualization results show that DFL encourages the baseline models to capture the class-core features. The proposed DFL marks a pivotal step in mitigating the issue of data distribution bias, enhancing the reliability of deep learning in agriculture. © 2024 Society of Chemical Industry.

Optimizing the production of dsRNA biocontrols in microbial systems using multiple transcriptional terminators.

Crop pests and pathogens annually cause over $220 billion in global crop damage, with insects consuming 5%-20%of major grain crops. Current crop pest and disease control strategies rely on insecticidal and fungicidal sprays, plant genetic resistance, transgenes, and agricultural practices. Double-stranded RNA(dsRNA) is emerging as a novel sustainable method of plant protection as an alternative to traditional chemical pesticides. Successful commercialization of dsRNA-based biocontrols requires the economical production of large quantities of dsRNA combined with suitable delivery methods to ensure RNAi efficacy against the target pest. In this study, we have optimized the design of plasmid DNA constructs to produce dsRNA biocontrols in Escherichia coli, by employing a wide range of alternative synthetic transcriptional terminators before measurement of dsRNA yield. We demonstrate that a 7.8-fold increase of dsRNA was achieved using triple synthetic transcriptional terminators within a dual T7 dsRNA production system compared to the absence of transcriptional terminators. Moreover, our data demonstratethat batch fermentation production dsRNA using multiple transcriptional terminators is scalable and generates significantly higher yields of dsRNA generated in the absence of transcriptional terminators at both small-scale batch culture and large-scale fermentation. In addition, we show that application of these dsRNA biocontrols expressed in E. coli cells results in increased insect mortality. Finally, novel mass spectrometry analysis was performed to determine the precise sites of transcriptional termination at the different transcriptional terminators providing important further mechanistic insight.

Biopesticide effect on crops for the bioactive components extracted from Tagetes erecta and Tagetes patula

Botanicals from Marigold, Chrysanthemum, Basil, Rosemary and other medicinal plants have been analysed as potential replacements of chemical pesticides as they are effective and non-hazardous to the environment. The bioactive components thiophene is present in large amount in Tagetes sp. which have a wide range of biocidal properties. In this study the crude extracts of different parts of Tagetes erecta and Tagetes patula were obtained by Soxhlet extraction method. The leaf extracts were subjected to GC–MS to identify their components and to confirm the presence of thiophenes. Two major disastrous crop pests namely, Spodoptera litura and Corcyra cephalonica belongs to Order Lepidoptera, Family Noctuidae and Pyralidae were used for the experimental study. The effect of bioactive extract was tested by direct and indirect methods for their larvicidal effect. The S. litura larvae was allowed to feed on castor leaves coated with spraying different concentrations of methanolic sample extracts as indirect method. In the direct spraying method, the S. litura and C. cephalonica larvae were sprayed with low and high concentrations of crude sample extracts of both T. patula and T. erecta. Significant decrease in larval activity and survival rate within 24 h to 48 h were recorded for both the methods. The trials were performed using variousvolumes from 10 to 1000 µl to check larvicidal activity. The roots and stem extracts of T. erecta for 25 µl kill 100% larvae within 24 h whereas 50 µl of T. patula flowers, roots and stem extract effectively kill only 50% of the larvae in 48 h. A mini nursery evaluation were conducted by direct spraying method on larvae growing on jowar saplings, which displayed 100% mortality of larvae within 24 h for 25 µl of T. erecta leaf and flower extracts and T. patula flower extract. From these trials, it can be inferred that the extracts of T. patula and T. erecta provided effective outcomes as larvicides of S. litura and C. cephalonica.

Control Efficacy of the Bt Maize Event DBN3601T Expressing Cry1Ab and Vip3Aa Proteins against Beet Armyworm, Spodoptera exigua (Hübner), in China.

The beet armyworm, Spodoptera exigua (Hübner), is a major pest of maize, cotton, soybean, and many other crops globally. Despite the widespread deployment of Bt transgenic maize for pest control worldwide, the efficacy of Bt lepidopteran-resistant transgenic maize in managing S. exigua remains rarely studied. In this study, we quantified the expression level of pyramided Cry1Ab and Vip3Aa toxins in Bt maize (event DBN3601T) and evaluated their control efficiency against S. exigua under both laboratory and field conditions. The enzyme-linked immunosorbent assay (ELISA) results showed that the expression levels of Cry1Ab and Vip3Aa proteins in DBN3601T maize tissues followed a decreasing order as follows: V5-leaf > V8-leaf > VT-tassel > R2-kernel > R1-silk. Diet-overlay assay results showed that the LC50 values of Cry1Ab and Vip3Aa proteins against S. exigua larvae were 11.66 ng/cm2 and 27.74 ng/cm2, respectively, with corresponding GIC50 values at 1.59 ng/cm2 and 7.93 ng/cm2. Bioassay using various tissues of the DBN3601T maize indicated that after 7 days of infestation, mortality rates of neonates and third-instar larvae ranged from 86% to 100% and 58% to 100%, respectively. Mortality was highest on V5 and V8 leaves, followed by R2-kernel, VT-tassel, and R1-silk. Field trials demonstrated that DBN3601T maize exhibited significantly lower larval density, damage rate, and leaf damage score compared to non-Bt maize. Field cage trial showed that the control efficacy of DBN3601T maize at the vegetative stage could reach 98%. These findings provide a theoretical basis for utilizing Bt transgenic maize to enhance the sustainable management of S. exigua in Asia.

Comparative proteomic analysis of resistant and susceptible cotton genotypes in response to leaf hopper infestation

The cotton leaf hopper is a major pest in cotton, causing a hopper burn in leaves. In this study, a comparative proteomic analysis of NDLH2010 (Resistant) and LRA5166 (Susceptible), infected with leaf hopper, was employed using a nano LC-MS/MS approach. A total of 1402 proteins varied significantly between leaf hopper-infected and control plants. The resistant and susceptible genotypes had differentially expressed proteins (DEPs) of 743 and 659, respectively. Functional annotation of DEPs revealed that the DEPs were primarily associated with stress response, hormone synthesis, photosynthesis, cell wall, and secondary metabolites. Notably, DEPs such as polyphenol oxidase, carboxypeptidase, heat shock proteins, protein BTR1-like isoform X2, chaperone protein ClpB1, and β glucosidase factors associated with environmental stress response were also detected. Quantitative real-time PCR (qRT-PCR) analysis confirmed a positive correlation between protein abundances and transcripts for all genes. Collectively, this study provides the molecular mechanisms associated with cotton defense responses against leaf hopper. Significance statementCotton, a natural fiber, assumes a pivotal role as a raw material for textile industries, thereby bearing significant importance in the global economy. The cotton production sector is considerably affected by both biotic and abiotic stresses. The cotton leaf hopper (Amrasca biguttula biguttula (Ishida)) stands as a polyphagous insect, emerging as a dominant sap-feeding pest of the cotton crop. The continuous onslaught of sap-feeding insects on cotton plants has a detrimental impact, with leaf hoppers potentially causing yield reductions of up to 50%. Therefore, comprehending the molecular interplay between cotton and leaf hopper, elucidated at the proteome level, holds promise for more effective pest management strategies. This approach holds the potential to offer insights that contribute to the development of leaf hopper-resistant cotton varieties.

Expression and Functional Characterization of Oryzacystatin II Protein from Oryza sativa L. Indica Rice and Its Potential Role as a Bioinsecticide Against Major Insects of Rice.

Rice (Oryza sativaL.) is a crucial staple food crop globally, facing significant challenges from various pests that affect crop productivity and quality. Conventional pesticide usage has limitations, necessitating the development of sustainable pest management strategies. This study focuses on the expression, purification, and functional characterization of Oryzacystatin II (OC-II), a protein derived from O. sativaL. Indica rice, with the intent to evaluate its potential as a bioinsecticide against rice pests. The OC-II gene was expressed and purified, and purification confirmed its molecular weight (∼12 kDa) and protein sequence through LC-MS/MS analysis and Western blotting. The IC50 value of OC-II was calculated as 0.06 μM, and the inhibition was identified as a competitive inhibition. The protein exhibited efficient control of both pests at the nymph and adult stages, with lower probing marks observed on treated plants. The inhibition of cathepsin B enzyme activity in insects further confirmed the bioactivity of the OC-II protein. Molecular docking and molecular dynamics simulations provided insights into the interaction between the OC-II protein and cathepsin enzymes reported in BPH and WBPH. Further investigations can focus on optimizing production methods and exploring the specificity and efficacy of the OC-II protein against other crop pests to enhance its practical applications.

Exogenous systemin peptide treatment in olive alters Bactrocera oleae oviposition preference

AbstractThe olive fruit fly, Bactrocera oleae (Rossi), is a key pest of the olive crop, whose control relies mostly on the use of insecticides. Plant peptides may represent a more environmentally-friendly tool to manage olive fly, due to their recognized role to activate and/or prime plant defence responses against pests. In this work, behavioural experiments (no-choice and two-choice) and analysis of volatile compounds were carried out to evaluate the impact of the exogenous application of the peptide systemin to olive tree on olive fly infestation, and to elucidate its mode of action to prime plant defence. The treatment of olive branches with 10 nM systemin showed to confer protection against olive fly, by reducing significantly the ovipositions (up to 3.0-fold) and the number of infested fruits (up to 2.9-fold) when compared to non-treated branches. This protective effect was even detected in neighbouring non-treated branches, suggesting the ability of systemin to trigger plant-to-plant communication. The deterrent activity of the primed olives was associated with the emission of the volatiles 2-ethyl-1-hexanol, 4-tert-butylcyclohexyl acetate and 1, 2, 3-trimethyl-benzene, which were negatively correlated with oviposition and fly infestation. Systemin has also showed to trigger the biosynthesis of specific volatiles (esters) in olives in response to fly attacks. Overall, the observed protection conferred by systemin against olive fly is likely due to the emission of specific volatiles that can act as a defence and/or as signalling molecules to upregulate the plant defence response. Thus, systemin represents a novel and useful tool to manage olive fruit fly.

A comparative approach for life history and functional response demonstrates similar survival strategies for Trichogramma evanescens and T. pintoi.

Egg parasitoids are important biological control agents of lepidopteran pests of agricultural crops. Trichogramma evanescens Westwood and T. pintoi Voegele (Hymenoptera: Trichogrammatidae) are egg parasitoids with worldwide importance. The parasitoid selection necessitates comparative assessment of the life table traits and functional response analysis to provide insights into their effectiveness in pest control. In this study, we examined theirlife table traits including survivorship and reproductivity, and functional response and associated parameters i.e., attack coefficient and handling time. Life table parameters, using age-stage, two-sex theory, revealed similar survival and reproductive strategies for both species. For example, the female longevity, oviposition days and fecundity did not differ between both species. Exceptionally, the male longevity of T. evanescens was shorter than that of T. pintoi. The population growth parameters such as gross reproductive rate (GRR), net reproductive rate (R0), intrinsic rate of increase (r), finite rate of increase (λ), and mean generation time (T) did not differ between species. The polynomial logistic regression yielded a type III functional response and a non-linear least square analysis revealed different attack coefficient and similar handling time. However, their parasitism rate differed between the lowest (five eggs) and highest (80 eggs) initial host egg densities such that T. evanescens had a lower parasitism rate at the lowest density and higher parasitism rate at the highest density. The similarity in survival strategies and minor differences in host handling of both parasitoids are discussed in terms of relevance to applied biological control applications and evolutionary traits. © 2024 The Author(s). Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Development of bioinsecticide based on Streptomyces griseoflavus PAL114 for control of black bean aphids Aphis fabae

ABSTRACT This research highlights the efficiency of a bioinsecticide based on Streptomyces griseoflavus PAL114 in controlling black bean aphids and its effect on fava beans. Three actinobacterial strains were tested in vitro for their aphicidal activity. The PAL114 strain was then formulated in talc powder and tested again. Formulation processes were performed with four spore suspension densities (102, 104, 106 and 108 spore ml−1) at a rate of 25 ml per 100 g of talc powder. Furthermore, the in vivo effect of bioinsecticide on fava bean plants was studied in pot experiments using two application methods: spray and spray + soil amendment. The results showed that only the PAL114 strain had a highly significant effect on mortality (p = .001). Their high-density formulations at 106 and 108 spore ml−1 induced very highly significant activity (p < .001) for both, with no influence difference exceeding 90% after 58 h. In contrast, the other low-density formulations at 102 and 104 spore ml−1 had no significant effect (p = .322 and p = 1.000, respectively). There was no adverse effect of the bioinsecticide on fava bean; instead, there was an improvement in growth, especially when the spray application was combined with soil amendment. The present study opens up prospects for field studies on the biocontrol of this crop pest.

Novel Mito-Nuclear Combinations Facilitate the Global Invasion of a Major Agricultural Crop Pest.

A fundamental understanding of the underlying mechanisms involved in biological invasions is crucial to developing effective risk assessment and control measures against invasive species. The fall armyworm (FAW), Spodoptera frugiperda, is a highly invasive pest that has rapidly spread from its native Americas into much of the Eastern Hemisphere, with a highly homogeneous nuclear genetic background. However, the exact mechanism behind its rapid introduction and propagation remains unclear. Here, a systematic investigation is conducted into the population dynamics of FAW in China from 2019 to 2021 and found that FAW individuals carrying "rice" mitochondria (FAW-mR) are more prevalent (>98%) than that with "corn" mitochondria (FAW-mC) at the initial stage of the invasion and in newly-occupied non-overwintering areas. Further fitness experiments show that the two hybrid-strains of FAW exhibit different adaptions in the new environment in China, and this may have been facilitated by amino acid changes in mitochondrial-encoded proteins. FAW-mR used increases energy metabolism, faster wing-beat frequencies, and lower wing loadings to drive greater flight performance and subsequent rapid colonization of new habitats. In contrast, FAW-mC individuals adapt with more relaxed mitochondria and shuttle energetics into maternal investment, observed as faster development rate and higher fecundity. The presence of two different mitochondria types within FAW has the potential to significantly expand the range of damage and enhance competitive advantage. Overall, the study describes a novel invasion mechanism displayed by the FAW population that facilitates its expansion and establishment in new environments.

Smartphone-Based Citizen Science Tool for Plant Disease and Insect Pest Detection Using Artificial Intelligence

In recent years, the integration of smartphone technology with novel sensing technologies, Artificial Intelligence (AI), and Deep Learning (DL) algorithms has revolutionized crop pest and disease surveillance. Efficient and accurate diagnosis is crucial to mitigate substantial economic losses in agriculture caused by diseases and pests. An innovative Apple® and Android™ mobile application for citizen science has been developed, to enable real-time detection and identification of plant leaf diseases and pests, minimizing their impact on horticulture, viticulture, and olive cultivation. Leveraging DL algorithms, this application facilitates efficient data collection on crop pests and diseases, supporting crop yield protection and cost reduction in alignment with the Green Deal goal for 2030 by reducing pesticide use. The proposed citizen science tool involves all Farm to Fork stakeholders and farm citizens in minimizing damage to plant health by insect and fungal diseases. It utilizes comprehensive datasets, including images of various diseases and insects, within a robust Decision Support System (DSS) where DL models operate. The DSS connects directly with users, allowing them to upload crop pest data via the mobile application, providing data-driven support and information. The application stands out for its scalability and interoperability, enabling the continuous integration of new data to enhance its capabilities. It supports AI-based imaging analysis of quarantine pests, invasive alien species, and emerging and native pests, thereby aiding post-border surveillance programs. The mobile application, developed using a Python-based REST API, PostgreSQL, and Keycloak, has been field-tested, demonstrating its effectiveness in real-world agriculture scenarios, such as detecting Tuta absoluta (Meyrick) infestation in tomato cultivations. The outcomes of this study in T. absoluta detection serve as a showcase scenario for the proposed citizen science tool’s applicability and usability, demonstrating a 70.2% accuracy (mAP50) utilizing advanced DL models. Notably, during field testing, the model achieved detection confidence levels of up to 87%, enhancing pest management practices.

Assay of Front-Line Demonstration on Integrated Pest and Disease Management (IPDM) in Rice in the Vikarabad District of Telangana, India

Rice crop is attacked by various insects and diseases in spite of using pesticides, but relaying only on synthetic pesticides usage resulted into disrupt the natural balance between crop pests and their existed natural enemies. Integrated pest and disease management (IDPM) is a concept which is blended with all possible proven technologies like Cultural, Mechanical, Biological and Chemical methods. Front line demonstration on Integrated Pest and Disease Management in rice was taken up in farmers fields during kharif season of two consecutive years of 2021 and 2022 by DAATTC, Tandur in Vikarabad district of Telangana. Study revealed that seed treatment with Carbendazim @3gm/kg seed, seedling root dip with Pseudomonas species 10gm /lit of water, application of Carbofuran granules @160g/cent nursery, installation of pheromone traps, formation of alley ways and need based application of fertilizers and pesticides reduced the pest like Stem borer, BPH, Leaf folder and Blast disease significantly compared to farmers practice. Mean higher yield was recorded in demo field 6065 kg/ha compared to 5795 kg/ha in check, and showed 4.6 per cent yield increases in demonstration fields.

Retrotransposon-mediated disruption of a chitin synthase gene confers insect resistance to Bacillus thuringiensis Vip3Aa toxin.

The vegetative insecticidal protein Vip3Aa from Bacillus thuringiensis (Bt) has been produced by transgenic crops to counter pest resistance to the widely used crystalline (Cry) insecticidal proteins from Bt. To proactively manage pest resistance, there is an urgent need to better understand the genetic basis of resistance to Vip3Aa, which has been largely unknown. We discovered that retrotransposon-mediated alternative splicing of a midgut-specific chitin synthase gene was associated with 5,560-fold resistance to Vip3Aa in a laboratory-selected strain of the fall armyworm, a globally important crop pest. The same mutation in this gene was also detected in a field population. Knockout of this gene via CRISPR/Cas9 caused high levels of resistance to Vip3Aa in fall armyworm and 2 other lepidopteran pests. The insights provided by these results could help to advance monitoring and management of pest resistance to Vip3Aa.

Bio-inoculant consortia modulated plantain (Musa × paradisiaca L.) growth, rhizosphere pH, acid phosphatase and urease activity

Fertilizers influence biochemical interactions in the rhizosphere that can affect crop performance. This study evaluated the interaction of plantain (Musa × paradisiaca) growth with soil pH, acid phosphatase and urease activities under different fertilizer amendments in Buea with mono-modal and Akonolinga with bi-modal rainfall patterns in Cameroon. The two experiments were setup in June 2021 following a randomized complete block design with NPK (nitrogen, phosphorus, and potassium), bio-inoculant consortia (plant growth-promoting bacteria – PGPB, Beauveria, Trichoderma, PGPB + Trichoderma), and untreated control, with four replications each. Soil samples were collected on 30th September 2021 and 30th April 2022 for analyses of soil physico-chemical and biological properties. Higher plantain performance occurred in Buea than Akonolinga across samplings, while treatments modulated plantain performance. Significant correlations occurred between plantain height or stem girth with rhizosphere pH, acid phosphatase and urease activities. The soil in Akonolinga is clayey with 38 % higher clay content than Buea, while Buea was clay-loamy with two times more silt than Akonolinga. The pre- and post-planting soil pH in Buea were strongly acidic as compared to extremely acidic soil in Akonolinga, with significant variation of post-planting pH across treatments, sampling time, and field sites. The positive correlation of soil pH, acid phosphatase and urease activities with plantain growth strongly indicate functional relationships that highlight fertilizer effects, sampling time or site-specific variations, and their interactions on plantain performance. Thereby, highlighting the role of locally formulated bio-inoculants in improving crop performance. These findings open up avenues for further studies on the role of bio-inoculants on crop nutrient uptake, and control of crop pests and diseases, in order to promote a holistic management approach that integrates bio-inoculants, crop type, and site-specific factors.

Potential insect threats to pennycress, Thlaspi arvense (Brassicales: Brassicaceae), an emerging oilseed cover crop.

Pennycress (Thlaspi arvense L.) is an annual plant in temperate regions that often grows as a weed. Pennycress is being domesticated as a new winter cover crop and oilseed crop for incorporation in the Midwest United States corn-soybean rotation, where it could offer economic and environmental benefits. While pennycress is gaining attention as a promising new crop, there remains a significant gap in understanding its interaction with insect communities and agroecosystems. This review compiles available information on insect herbivores (potential pests) and beneficial insects associated with pennycress growing in the wild (natural areas) or as a weed in agricultural areas. The limited knowledge on the response of pennycress to stressors (defoliation, stem injury and stand loss) similar to injury that could be caused by insects is also compiled here. By shedding light on the insects associated with pennycress and how pennycress might respond to injury from insectpests, this review sets the stage for further research and development of integrated pest management programs for insect pests of this new crop.

Radioactivity and GMO-Free Sterile Insect Technology for the Sustainable Control of the Invasive Pest Drosophila suzukii.

Drosophila suzukii (D. suzukii), commonly known as the spotted wing drosophila, is a highly invasive crop pest that is difficult to control using chemical insecticides. To address the urgent need for alternative and more sustainable control strategies, the sterile insect technique (SIT) is improved, which involves the release of sterilized male insects to mate with fertile conspecifics, thereby reducing the size of the pest population in the subsequent generation. The three critical aspects that influence the success of SIT programs in D. suzukii are addressed. First, an accurate and nondestructive method is established to determine the sex of individual insects based on the differential weight of male and female pupae. Second, conditions for X-ray sterilization are systematically tested and an optimal dose (90kV/40Gy) is identified that ensures the efficient production of sterile D. suzukii for release. Finally, the inherent thermosensitivity of D. suzukii males is exploited to develop a temperature-based sterilization technique, offering an alternative or additional SIT method for this pest. These advances will contribute to the development of a comprehensive and effective strategy for the management of D. suzukii populations, reducing their impact on agriculture and helping to safeguard crop yields.

Rapid Adaptation and Interspecific Introgression in the North American Crop Pest Helicoverpa zea.

Insect crop pests threaten global food security. This threat is amplified through the spread of nonnative species and through adaptation of native pests to control measures. Adaptations such as pesticide resistance can result from selection on variation within a population, or through gene flow from another population. We investigate these processes in an economically important noctuid crop pest, Helicoverpa zea, which has evolved resistance to a wide range of pesticides. Its sister species Helicoverpa armigera, first detected as an invasive species in Brazil in 2013, introduced the pyrethroid-resistance gene CYP337B3 to South American H. zea via adaptive introgression. To understand whether this could contribute to pesticide resistance in North America, we sequenced 237 H. zea genomes across 10 sample sites. We report H. armigera introgression into the North American H. zea population. Two individuals sampled in Texas in 2019 carry H. armigera haplotypes in a 4 Mbp region containing CYP337B3. Next, we identify signatures of selection in the panmictic population of nonadmixed H. zea, identifying a selective sweep at a second cytochrome P450 gene: CYP333B3. We estimate that its derived allele conferred a ∼5% fitness advantage and show that this estimate explains independently observed rare nonsynonymous CYP333B3 mutations approaching fixation over a ∼20-year period. We also detect putative signatures of selection at a kinesin gene associated with Bt resistance. Overall, we document two mechanisms of rapid adaptation: the introduction of fitness-enhancing alleles through interspecific introgression, and selection on intraspecific variation.

The perfect pesticide?

Insecticides made of RNA could offer a safer and more targeted weapon against crop pests