Showing papers in "Pest Management Science in 2019"

Molecular mechanisms influencing efficiency of RNA interference in insects

Abstract: RNA interference (RNAi) is an endogenous, sequence-specific gene-silencing mechanism elicited by small RNA molecules. RNAi is a powerful reverse genetic tool, and is currently being utilized for managing insects and viruses. Widespread implementation of RNAi-based pest management strategies is currently hindered by inefficient and highly variable results when different insect species, strains, developmental stages, tissues, and genes are targeted. Mechanistic studies have shown that double-stranded ribonucleases (dsRNases), endosomal entrapment, deficient function of the core machinery, and inadequate immune stimulation contribute to limited RNAi efficiency. However, a comprehensive understanding of the molecular mechanisms limiting RNAi efficiency remains elusive. Recent advances in dsRNA stability in physiological tissues, dsRNA internalization into cells, the composition and function of the core RNAi machinery, as well as small-interfering RNA/double-stranded RNA amplification and spreading mechanisms are reviewed to establish a global understanding of the obstacles impeding wider understanding of RNAi mechanisms in insects. © 2018 Society of Chemical Industry.

Review: Endophytic microbes and their potential applications in crop management.

Abstract: Endophytes are microbes (mostly bacteria and fungi) present asymptomatically in plants. Endophytic microbes are often functional in that they may carry nutrients from the soil into plants, modulate plant development, increase stress tolerance of plants, suppress virulence in pathogens, increase disease resistance in plants, and suppress development of competitor plant species. Endophytic microbes have been shown to: (i) obtain nutrients in soils and transfer nutrients to plants in the rhizophagy cycle and other nutrient-transfer symbioses; (ii) increase plant growth and development; (iii) reduce oxidative stress of hosts; (iv) protect plants from disease; (v) deter feeding by herbivores; and (vi) suppress growth of competitor plant species. Because of the effective functions of endophytic microbes, we suggest that endophytic microbes may significantly reduce use of agrochemicals (fertilizers, fungicides, insecticides, and herbicides) in the cultivation of crop plants. The loss of endophytic microbes from crop plants during domestication and long-term cultivation could be remedied by transfer of endophytes from wild relatives of crops to crop species. Increasing atmospheric carbon dioxide levels could reduce the efficiency of the rhizophagy cycle due to repression of reactive oxygen used to extract nutrients from microbes in roots. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Recent advances in allelopathy for weed control: from knowledge to applications

Abstract: Allelopathy is the biological phenomenon of chemical interactions between living organisms in the ecosystem, and must be taken into account in addressing pest and weed problems in future sustainable agriculture. Allelopathy is a multidisciplinary science, but in some cases, aspects of its chemistry are overlooked, despite the need for a deep knowledge of the chemical structural characteristics of allelochemicals to facilitate the design of new herbicides. This review is focused on the most important advances in allelopathy, paying particular attention to the design and development of phenolic compounds, terpenoids and alkaloids as herbicides. The isolation of allelochemicals is mainly addressed, but other aspects such as the analysis and activities of derivatives or analogs are also covered. Furthermore, the use of allelopathy in the fight against parasitic plants is included. The past 12 years have been a prolific period for publications on allelopathy. This critical review discusses future research areas in this field and the state of the art is analyzed from the chemist's perspective. © 2019 Society of Chemical Industry.

Pesticidal natural products - status and future potential.

Abstract: There is a long history of using natural products as the basis for creating new pesticides but there is still a relatively low percentage of naturally derived pesticides relative to the number of pharmaceuticals derived from natural sources. Biopesticides as defined and regulated by the US Environmental Protection Agency (EPA) have been around for 70 years, starting with Bacillus thuringiensis, but they are experiencing rapid growth as the products have got better and more science-based, and there are more restrictions on synthetic chemical pesticides. As such, biopesticides are still a small percentage (approximately US$3-4 billion) of the US$61.3 billion pesticide market. The growth of biopesticides is projected to outpace that of chemical pesticides, with compounded annual growth rates of between 10% and 20%. When integrated into crop production and pest management programs, biopesticides offer the potential for higher crop yields and quality than chemical-only programs. Added benefits include reduction or elimination of chemical residues, therefore easing export, enabling delay in the development of resistance by pests and pathogens to chemicals and shorter field re-entry, biodegradability and production using agricultural raw materials versus fossil fuels, and low risk to non-target organisms, including pollinators. Challenges to the adoption of biopesticides include lack of awareness and education in how to deploy their unique modes of action in integrated programs, testing products alone versus in integrated programs, and lingering perceptions of cost and efficacy. © 2019 Society of Chemical Industry.

Identification and risk assessment of spinosad resistance in a California population of Drosophila suzukii.

Abstract: BACKGROUND The bioinsecticide spinosad is among the most widely used insecticides for managing spotted-wing drosophila, Drosophila suzukii (Matsumura), and is critical for preventing fruit infestation in organic berry production. Recent reports, however, have raised concerns that the efficacy of this material is declining in fields near Watsonville, CA, a major hub of commercial berry production in the USA and the first location where D. suzukii was reported in North America. RESULTS In this study, we performed dose-response analyses on D. suzukii from commercial raspberry plantings near Watsonville as well as a second untreated site in California using a widely implemented bioassay protocol. We found that Watsonville flies exhibited spinosad LC50 values 4.3-7.7 times higher than those from the untreated location and 11.6-22.4 times higher than previously reported susceptible baselines. Additionally, tolerance to spinosad continued to increase after additional selection for five generations, though this result was only statistically significant after prolonged exposure to residues. CONCLUSIONS These findings confirm that spinosad resistance is emerging in the Watsonville area and document the first known occurrence in the USA, presenting an urgent need for the development of alternative management strategies to control this pest. Additional work is needed to resolve the underlying molecular mechanism(s) that confers spinosad resistance in D. suzukii and assess the potential for this trait to spread into new populations. © 2018 Society of Chemical Industry.

Field evaluation of an unmanned aerial vehicle (UAV) sprayer: effect of spray volume on deposition and the control of pests and disease in wheat.

Abstract: BACKGROUND Unmanned aerial vehicles (UAVs) are a recently developed aerial spraying technology. However, the effect of spray volume variation on deposition and pesticide control efficacy is unknown. The effect of three UAV spray volumes (9.0, 16.8 and 28.1 L ha-1 ) using three different nozzle sizes on droplet deposition and wheat aphid and powdery mildew control efficacy was assessed. An electric air-pressure knapsack (EAP) sprayer was used as a comparison. RESULTS Different spray volumes significantly influenced the deposition and control efficacy of the UAV and EAP. For the UAV, a low spray volume of 9.0 L ha-1 with a fine nozzle (nozzle LU120-01) resulted in lower deposition and control efficacy. Optimal control efficacy was achieved with coarser nozzles (nozzles LU120-02, -03) at > 16.8 L ha-1 volume with systemic insecticide, and at 28.1 L ha-1 with contact insecticide and fungicide. For EAP, a high spray volume led to run-off, and a spray volume of 225 L ha-1 achieved better deposition and control efficacy. CONCLUSION The UAV had comparable deposition and efficacy control to the EAP at a higher spray volume (> 16.8 L ha-1 ) with coarse nozzles, but exhibited inferior deposition and efficacy control at a lower spray volume (<9.0 L ha-1 ) with fine nozzles. © 2019 Society of Chemical Industry.

Selection and characterization of the inheritance of resistance of Spodoptera frugiperda (Lepidoptera: Noctuidae) to chlorantraniliprole and cross-resistance to other diamide insecticides.

Abstract: Background Understanding the genetic basis of insect resistance to insecticides can help to implement insecticide resistance management (IRM) strategies. In this study, we selected a strain of Spodoptera frugiperda (J. E. Smith) (Lepidoptera: Noctuidae) resistant to chlorantraniliprole using the F2 screen method, characterized the inheritance of resistance and evaluated patterns of cross-resistance to other diamide insecticides. Results The chlorantraniliprole-resistant strain (Chlorant-R) was selected from a field-collected population with an estimated allele frequency of 0.1316. The estimated median lethal concentration (LC50 ) values were 0.011 and 2.610 µg a.i. cm-2 for the susceptible (Sus) and Chlorant-R strains, respectively, resulting in a resistance ratio (RR) of 237-fold. The LC50 values of the reciprocal crosses were 0.155 and 0.164 µg a.i. cm-2 , indicating that resistance is autosomally inherited. Resistance was characterized as incompletely recessive and monogenic at concentrations close to the recommended field rates of chlorantraniliprole. Survival of the resistant strain and heterozygous larvae in maize plants treated at the field rate was ∼ 60 (similar to the susceptible strain on untreated maize) and 15%, respectively. The Chlorant-R strain showed low cross-resistance to cyantraniliprole (RR ∼ 27-fold) and very high cross-resistance to flubendiamide (RR > 42 000-fold). Conclusions The frequency of chlorantraniliprole resistance allele was moderately high in a field-collected population of S. frugiperda. The inheritance of chlorantraniliprole resistance was characterized as autosomal, incompletely recessive and monogenic. S. frugiperda showed cross-resistance to other diamide insecticides. These results provide essential information for the implementation of IRM programs to preserve the useful life of diamide insecticides for controlling S. frugiperda in Brazil. © 2019 Society of Chemical Industry.

A polymer/detergent formulation improves dsRNA penetration through the body wall and RNAi-induced mortality in the soybean aphid Aphis glycines.

Abstract: Background It is difficult to efficiently silence gene expression in some insects, probably because of the degradation of dsRNA by enzymes present in the gut and hemolymph post-oral feeding or body injecting of dsRNA. We previously developed a nanocarrier delivery system that can systemically deliver dsRNA into chewing mouthpart insects by oral feeding and efficiently silence gene expression. For the purpose of pest control in the field, there is a great demand to develop a spray method to apply dsRNA formulation. Results A formulation of the nanocarrier/dsRNA/detergent was developed and could be easily applied just by dropping it on the notum of the aphid. The formulation penetrated the body wall into the hemocoel and then spread into various tissues within 1 h. The delivered dsRNA efficiently silenced the target gene expression at a high knockdown effect (95.4%) and the aphid population was largely suppressed (80.5%). Conclusion A novel dsRNA formulation was developed with the help of a nanocarrier and detergent that can quickly penetrate the insect body wall and efficiently silence gene expression. The formulation may provide a fast and easy tool for gene silence in some tough insects and for pest control in the field. © 2019 Society of Chemical Industry.

Liposome encapsulation and EDTA formulation of dsRNA targeting essential genes increase oral RNAi‐caused mortality in the Neotropical stink bug Euschistus heros

Abstract: Background The Neotropical stink bug Euschistus heros is a major pest in soybean fields. Development of highly species-specific pesticides based on RNA interference (RNAi) could provide a new sustainable and environmentally friendly control strategy. Results Here, the potential of RNAi as a pest control tool against E. heros was assessed. First, target gene selection using a microinjection approach was performed. Seven of the 15 candidate genes tested exhibited > 95% mortality after hemolymph injection of 27.5 ng dsRNA. Subsequently, dsRNA was administered orally using different formulations: naked dsRNA, liposome-encapsulated-dsRNA and dsRNA formulated with EDTA. Liposome-encapsulated dsRNA targeting vATPase A and muscle actin led to significant mortality after 14 days (45% and 42%, respectively), whereas EDTA-formulated dsRNA did so for only one of the target genes. Ex vivo analysis of the dsRNA stability in collected saliva indicated a strong dsRNA-degrading capacity by E. heros saliva, which could explain the need for dsRNA formulations. Conclusion The results demonstrate that continuous ingestion of dsRNA with EDTA or liposome-encapsulated dsRNA can prevent dsRNA from being degraded enzymatically and suggest great potential for using these formulations in dsRNA delivery to use RNAi as a functional genomics tool or for pest management of stink bugs. © 2018 Society of Chemical Industry.

Safe nanotechnologies for increasing the effectiveness of environmentally friendly natural agrochemicals

Abstract: Natural compounds and living organisms continue to play a limited role in crop protection, and few of them have reached the market, despite their attractiveness and the efforts made in research. Very often these products have negative characteristics compared to synthetic compounds, e.g., higher costs of production, lower effectiveness, lack of persistence, and inability to reach and penetrate the target plant. Conversely, nanotechnologies are having an enormous impact on all human activities, including agriculture, even if the production of some nanomaterials is not environmentally friendly or could have adverse effects on agriculture and the environment. Thus, certain nanomaterials could facilitate the development of formulated natural pesticides, making them more effective and more environmentally friendly. Nanoformulations can improve efficacy, reduce effective doses, and increase shelf-life and persistence. Such controlled-release products can improve delivery to the target pest. This review considers certain available nanomaterials and nanotechnologies for use in agriculture, discussing their properties and the feasibility of their use in sustainable crop protection, in particular, in improving the effectiveness of natural bio-based agrochemicals. © 2019 Society of Chemical Industry.

Arbuscular mycorrhizal fungi and their response to pesticides.

Abstract: Arbuscular mycorrhizal fungi (AMF) form symbioses with the majority of plant species and can provide multiple benefits to the host plant. In agro-ecosystems, the abundance and community structure of AMF are affected by agricultural management practices. This review describes and discusses current knowledge on the effects of inorganic and organic chemical pesticides on AMF in the conflicting area between agricultural use and environmental concerns. Variable effects have been reported following chemical pesticide use, ranging from neutral to positive and negative. Moreover, a species-specific reaction has been documented. The reported effects of pesticides on arbuscular mycorrhizal symbiosis are very diverse, and even when the same substance is investigated, the results are often contradictory. These effects depend on many parameters, such as the active substance, the mode of action, the mode of application and the dosage. In the field, determinants such as the physico-chemical behavior of the active substances, the soil type and other soil microorganisms contribute to the fate of pesticides and thus the amount of active substances to which AMF are exposed. This review highlights that the fate of AMF following pesticide use needs to be addressed in a broader agro-ecosystem context. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Characterization of sulfoxaflor resistance in the brown planthopper, Nilaparvata lugens (Stål).

Abstract: Background Sulfoxaflor is a new insecticide for controlling Nilaparvata lugens in the field. This study was conducted to investigate the risk of resistance development, the cross-resistance spectrum and the mechanisms of sulfoxaflor resistance in N. lugens. Results A sulfoxaflor-resistant strain was obtained from a field population by successive selection with sulfoxaflor for 39 generations in the laboratory. Sulfoxaflor-resistant populations showed significant levels of cross-resistance to dinotefuran, nitenpyram, thiamethoxam, clothianidin, imidacloprid and cycloxaprid. However, they exhibited only minor or no cross-resistance to isoprocarb, etofenprox, chlorpyrifos, triflumezopyrim and buprofezin. Sulfoxaflor was synergized by the inhibitor piperonyl butoxide (PBO) in the sulfoxaflor-resistant strain (SFX-SEL) with 2.69-fold relative synergistic ratios compared with the unselected strain (UNSEL). Compared with UNSEL, the P450 enzyme activity of SFX-SEL was increased 3.50 times, and eight P450 genes were upregulated more than 2.0-fold in SFX-SEL. RNAi reduced the expression of CYP6ER1 (36.87-fold change) and significantly enhanced the susceptibility of SFX-SEL to sulfoxaflor. Conclusion Resistance development and cross-resistance risk of sulfoxaflor-resistance in N. lugens is evident. The enhanced detoxification of P450 enzymes caused by upregulation of several P450 genes is considered to be the metabolic resistance mechanism. These results suggest that CYP6ER1 might play an important role in sulfoxaflor resistance in N. lugens. © 2018 Society of Chemical Industry.

Integrated weed management (IWM): why are farmers reluctant to adopt non-chemical alternatives to herbicides?

Abstract: Implementation of integrated weed management (IWM) has been poor, with little evidence of concomitant reductions in herbicide use. Non-chemical methods are often adopted as a means of compensating for reduced herbicide efficacy, due to increasing resistance, rather than as alternatives to herbicides. Reluctance to adopt non-chemical methods is not due to a lack of research or technology but to a lack of farmer motivation and action. Justifiably, herbicides are often seen as the easier option - their convenience outweighs the increased complexity, costs and management time associated with non-chemical alternatives. Greater use of non-chemical alternatives to herbicides will only occur if the following seven aspects are addressed: (i) better recognition of the reasons why farmers are reluctant to use non-chemical alternatives; (ii) encouraging farmers to adopt a longer-term approach to weed control; (iii) changing farmers' attitudes to pesticides; (iv) paying more attention to the individual farmer's perspective; (v). greater involvement of economists, social scientists and marketing professionals; (vi) re-evaluating research and extension priorities; and (vii) changing the mindset of funders of research and extension. If 'persuasion' fails to deliver greater implementation of IWM, authorities may resort to greater use of financial and other incentives combined with tougher regulations. © 2018 Society of Chemical Industry.

Farmer perception of fall armyworm (Spodoptera frugiderda J.E. Smith) and farm-level management practices in Zambia.

Abstract: Background This paper documents farmer perceptions and management practices for fall armyworm (Spodoptera frugiderda J.E. Smith), providing a baseline for the development of sustainable pest management strategies. Results 91% of farmers correctly identified fall armyworm, and reported it as the most important maize pest during 2016/2017 cropping season, affecting nearly half of cultivated area. Estimated maize yield loss during the season, attributed to fall armyworm was 28%. A majority of farmers (60%) used pesticides for fall armyworm control, along with other cultural/physical practices - hand picking and crushing egg masses/caterpillars (36%), and application of ash/sand in the funnel (19%). Farmers used various pesticide active ingredients, and protective measures were inadequate; >50% of farmers did not use any protective measures while spraying. Significantly more male than female farmers used pesticides (P = 0.05), and the reverse was true for cultural practices. Significant maize yield differences (P = 0.001) were observed by gender, attributed to differences in utilization of production inputs/practices. At least 77% of farmers received and shared agricultural advice, which can be optimized to spread information on fall armyworm management options. Conclusion Increased use of pesticides to manage fall armyworm poses health and environmental risks, besides the high cost for farmers and governments. Research into cultural and indigenous practices used by farmers will offer opportunities for alternative and sustainable management practices. Research efforts should pay attention to gender differences in access to resources and inputs. Tackling fall armyworm at the farm level, and averting yield losses will require integrated messaging addressing other production risks. © 2019 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Climate change exacerbates pest damage through reduced pesticide efficacy

Abstract: Pesticide efficacy is strongly associated with environmental conditions. Conditional resistance defined as a reduction in pesticide sensitivity under changed environmental conditions has been widely detected under climatic changes such as elevated temperatures and CO2 enrichment. Given the effects of environmental conditions on pesticide sensitivity, many of the putative resistance reports made by farmers may be due to pesticide application followed by non-optimal environmental conditions rather than the evolution of resistance. This type of conditional resistance may be the result of phenotypic plasticity or epigenetic changes in response to environmental changes. Elevated temperatures and CO2 enrichment can directly lead to reduced pesticide efficacy by altering pesticide metabolism and translocation, or indirectly increasing pesticide detoxification in host-plants thus reducing pesticide availability for the target pest. Stress-related signal transduction pathways, as well as physiological changes, can both be associated with accelerated pesticide detoxification under climatic changes. The possibility for parallel mechanisms controlling these responses in different pest species should be considered. It is proposed that the same mechanisms leading to non-target site resistance in pests may also play a role in conditional resistance, suggesting we can predict the pesticides to which pests are likely to be less responsive under changing climatic conditions. Using adjuvants to improve pesticide translocation or reduce pesticide metabolism, alongside with new technologies such as using nanoparticles may result in higher pesticide functionality under the projected climate change. Exploring the physiological, transcriptional and biochemical basis underlying conditional resistance is crucial in maintaining future pest management under changing environmental conditions. © 2018 Society of Chemical Industry.

Novel 4‐pyrazole carboxamide derivatives containing flexible chain motif: design, synthesis and antifungal activity

Abstract: Background In recent years, carboxamide fungicides, targeting succinate dehydrogenase (SDH), have shown highly efficient and broad spectrum fungicidal activity. Structure-activity relationship (SAR) results for these commercial fungicides show that the carboxamide group was a key active group. This is useful information for the discovery of new pyrazole carboxamide derivatives with fungicidal activity. Results Twenty-seven novel pyrazole carboxamides were designed and synthesized. Their fungicidal activities against Gibberella zeae, Phytophthora infestans, Phytophthora capsici, Rhizoctonia solani, Alternaria solani, Botrytis cinerea, Fusarium oxysporum, Cercospora arachidicola, Sclerotinia sclerotiorum and Physalospora piricola were tested; derivatives possessed excellent inhibitory at 50 mg L-1 in particular. Furthermore, some pyrazole carboxamides exhibited remarkably high activities against Sclerotinia sclerotiorum in vitro with EC50 values of 2.04 to 15.2 μg mL-1 . In addition, some compounds also exhibited high activities against Physalospora piricola, Cercospora arachidicola and Phytophthora capsici. Inhibition activities against SDH proved that the designed analogues were effective at the enzyme level. The SAR of these pyrazole carboxamides was studied by using the docking method. Conclusion It is possible that pyrazole carboxamides, which exhibit good activity against Sclerotinia sclerotiorum, can be further optimized as a lead compounds of carboxamide fungicides. © 2019 Society of Chemical Industry.

A comparison of the EU and US regulatory frameworks for the active substance registration of microbial biological control agents.

Abstract: Background Microbial biological control agents (MBCA) are biopesticides based on living microbes. They have huge potential for the control of pests and diseases, but have trouble reaching the European Union (EU) market. According to several authors, this is caused by the regulatory regime, which is less supportive compared with that in the USA. The main objective of this paper is to present regulatory differences between the USA and the EU, and the resulting effects and developments of registration in both regions. Results Results show that EU registration is more complex due to differences between EU- and Member State (MS)-level processes, large actor heterogeneity and low flexibility. As a result, EU registration takes, on average, ∼ 1.6 years longer than US registration. Regulatory amendments have improved EU-level processes and led to a significant contraction of procedural time spans, but processes at the MS level have not improved and have become a larger procedural obstacle. Conclusion The results correspond with the idea that EU registration is complex and lengthy compared with that in the USA. To improve regulation, national-level processes should be targeted for amendment. To that end, the authors suggest various ways of expanding the registration capacity of MS. © 2018 The Authors. Pest Management Science published by John Wiley & Sons Ltd on behalf of Society of Chemical Industry.

Responses of two ladybird beetle species (Coleoptera: Coccinellidae) to dietary RNAi.

Abstract: BACKGROUND: One concern with the adoption of RNAi‐based genetically engineered (GE) crops is the potential harm to valued non‐target organisms. Species of Coccinellidae (Coleoptera) are important natural enemies and might be exposed to the insecticidal dsRNA produced by the plant. To assess their susceptibility to dietary RNAi, we fed Adalia bipunctata and Coccinella septempunctata with a dsRNA designed to target the vATPase A of the western corn rootworm, Diabrotica virgifera virgifera (Dvv dsRNA). Specific dsRNAs designed to target the vATPase A of the two ladybird beetle species served as positive controls. RESULTS: Our results revealed that both species were sensitive to dietary RNAi when ingesting their own dsRNAs, with C. septempunctata being more sensitive than A. bipunctata. Dvv dsRNA also adversely affected the two ladybird beetles as indicated by a significantly (but marginally) prolonged developmental time for A. bipunctata and a significantly reduced survival rate for C. septempunctata. These results, however, were obtained at Dvv dsRNA concentrations that were orders of magnitude higher than expected to occur in the field. Gene expression analyses confirmed the bioactivity of the dsRNA treatments and the results from the feeding bioassays. These results are consistent with the bioinformatics analyses, which revealed a higher number of 21‐nucleotide‐long matches, a requirement for effective RNAi, of the Dvv dsRNA with the vATPase A of C. septempunctata (34 matches) than with that of A. bipunctata (six matches). CONCLUSION: Feeding bioassays revealed that two ladybird species are responsive to dietary RNAi. The two species, however, differed in their sensitivity. © 2019 Society of Chemical Industry

Natural products: a strategic lead generation approach in crop protection discovery.

Abstract: With the anticipated population growth in the coming decades, the changing regulatory environment, and the continued emergence of resistance to commercial pesticides, there is a constant need to discover new lead chemistries with novel modes of action. We have established a portfolio of approaches to accelerate lead generation. One of these approaches capitalizes on the rich bioactivity of natural products (NPs), highlighted by the numerous examples of NP-based crop protection compounds. Within Corteva Agriscience and the affiliated preceding companies, NPs have been a fruitful approach, for nearly three decades, to identifying and bringing to the market crop protection products inspired by or originating from NPs, . Included in these NP-based crop protection products are the spinosyns family of insecticides, and those from more recent areas of NP-based fungicidal chemistry, as highlighted in this perspective. © 2019 Society of Chemical Industry.

Projecting the current and future potential global distribution of Hyphantria cunea (Lepidoptera: Arctiidae) using CLIMEX.

Abstract: Background The international invasive and quarantined defoliating insect Hyphantria cunea Drury (Lepidoptera: Arctiidae) causes huge ecological and economic losses in the world. Furthermore, future climate change may alter the distribution of H. cunea and aggravate the damage. In the present study, we used CLIMEX to project the potential global distribution of H. cunea according to both historical climate data (1961-1990) and future climate warming estimates (2011-2100) to define the impact of climate change. Results Under the historical climate scenario, we found that H. cunea can survive on every continent, and temperature is the main factor that limits its establishment. With climate change, suitability will increase in middle and high latitude regions, while decrease in the low latitude regions. Moreover, tropic regions will be the most sensitive to climate change impacts for the pest to survive. The impacts of climate change will also increase over time, whether they be positive impacts or negative impacts. Conclusion The projected potential distributions provide a theoretical basis for quarantine and control strategies for the management of this pest in each country. Furthermore, these results provide substantial guidance for studies of the effects of climate change on other major forest pests. © 2018 Society of Chemical Industry.

Advances in insect phototaxis and application to pest management: a review.

Abstract: Many insects, especially nocturnal insects, exhibit positive phototaxis to artificial lights. Light traps are currently used to monitor and manage insect pest populations, and play a crucial role in physical pest control. Efficient use of light traps to attract target insect pests is an important topic in the application of integrated pest management (IPM). Phototactic responses of insects vary among species, light characteristics and the physiological status of the insects. In addition, light can cause several biological responses, including biochemical, physiological, molecular and fitness changes in insects. In this review, we discuss several hypotheses on insect phototaxis, factors affecting insect phototaxis, insect-sensitive wavelengths, biological responses of insects to light, and countermeasures for conserving beneficial insects and increasing the effect of trapping. In addition, we provide information on the different sensitivities to wavelengths causing positive phototactic behavior in > 70 insect pest and beneficial insect species. The use of advanced light traps equipped with superior light sources, such as light-emitting diodes (LEDs), will make physical pest control in IPM more efficient. © 2019 Society of Chemical Industry.

Tying pest insects in knots: the deployment of spider‐venom‐derived knottins as bioinsecticides

Abstract: Spider venoms are complex chemical arsenals that contain a rich variety of insecticidal toxins. However, the major toxin class in many spider venoms is disulfide-rich peptides known as knottins. The knotted three-dimensional fold of these mini-proteins provides them with exceptional chemical and thermal stability as well as resistance to proteases. In contrast with other bioinsecticides, which are often slow-acting, spider knottins are fast-acting neurotoxins. In addition to being potently insecticidal, some knottins have exceptional taxonomic selectivity, being lethal to key agricultural pests but innocuous to vertebrates and beneficial insects such as bees. The intrinsic oral activity of these peptides, combined with the ability of aerosolized knottins to penetrate insect spiracles, has enabled them to be developed commercially as eco-friendly bioinsecticides. Moreover, it has been demonstrated that spider-knottin transgenes can be used to engineer faster-acting entomopathogens and insect-resistant crops. © 2019 Society of Chemical Industry.

Topical dsRNA delivery induces gene silencing and mortality in the pea aphid

Abstract: BACKGROUND With the growing number of available aphid genomes and transcriptomes, an efficient and easy-to-adapt tool for gene function study is urgently required. RNA interference (RNAi), as a post-transcriptional gene silencing mechanism, is important as a research tool for determining gene functions and has potential as a novel insect control strategy. However, these applications have been hampered by the lack of effective dsRNA delivery approaches in aphids. RESULTS Here, we developed a convenient and efficient dsRNA delivery method, topical RNAi, in aphids. An investigation of its dose and time-dependent RNAi efficiencies revealed that with as little as 60 ng dsRNA per adult pea aphid (Acyrthosiphon pisum), the indicator gene, Aphunchback, could be significantly silenced within 2 h of exposure. The method was further validated by successfully silencing other different genes, and it was also efficient toward two other aphid species, Aphis citricidus and Myzus persicae. Furthermore, a noticeable mortality was also observed in pea aphids using topical RNAi-mediated gene silencing, within 4 days post-dsRNA application for four out of seven tested genes. CONCLUSION Compared with the currently used dsRNA delivery methods in aphids, microinjection and ingestion, topical RNAi is time- and cost-effective, which could greatly influence RNAi-based gene functional studies and potential candidate gene selection for developing RNAi-based aphid control strategies in the future. © 2019 Society of Chemical Industry.

Assessing the impact of climate change on the worldwide distribution of Dalbulus maidis (DeLong) using MaxEnt

Abstract: Background For the first time, a model was applied at the global scale to investigate the effects of climate change on Dalbulus maidis. D. maidis is the main vector of three plant pathogens of maize crops and has been reported as one of the most important maize pests in Latin America. We modelled the effects of climate change on this pest using three Global Climate Models under two Representative Concentration Pathways (RCPs) using MaxEnt software. Results Overall, climate change will lead to a decrease in suitable areas for D. maidis. In South America, climate change will decrease the areas suitable for the pest, especially in Brazil. However, Argentina, Chile, Colombia, Ecuador, Peru and Venezuela will have small areas that are highly suitable for the corn leafhopper. Outside the pest's range, Ethiopia, Kenya, Rwanda, Burundi and South Africa also should be concerned about the risk of corn leafhopper invasions in the future because they are projected to have conditions that are highly suitable for this insect in some areas. Conclusion This study allows the relevant countries to increase their quarantine measures and guide researchers to develop new Zea mays varieties that are resistant or tolerant to D. maidis. In addition, the maize-stunting pathogens for the areas are highlighted in this modelling. © 2019 Society of Chemical Industry.

Target site mutations and cytochrome P450s confer resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl in Alopecurus aequalis

Abstract: BACKGROUND: Shortawn foxtail (Alopecurus aequalis Sobol.) is a competitive grass weed infesting winter wheat‐ and canola‐growing fields in China. In May 2016, a suspected A. aequalis resistant population AHTC‐06 that survived fenoxaprop‐P‐ethyl and mesosulfuron‐methyl applied at their field‐recommended rates was collected from a wheat field in Jinji County, Anhui Province, China. This study aimed to determine the resistance profile of this AHTC‐06 population to ACCase‐ and ALS‐inhibitors, and to investigate its mechanisms of resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl. RESULTS: Two mutations, a common Ile‐2041‐Asn (ACCase gene) and a very rare Pro‐197‐Tyr (ALS1 gene), were both identified in resistant individual plants. The homozygous subpopulation AHTC‐06F1 for the two mutations was generated, and it showed broad‐spectrum resistance to APPs, DENs, and ALS‐inhibiting herbicides of all five chemical families tested, with resistance index (RI) values that ranged from 2.2 to 36.5. In vitro ALS activity assays showed the ALS from the resistant population was insensitive to all the tested ALS inhibitors, with RI values ranging from 3.10 to 22.51. Pre‐treatment with piperonyl butoxide (PBO) and malathion significantly (P < 0.05) reversed the weed's resistance to fenoxaprop‐P‐ethyl and mesosulfuron‐methyl, respectively. Two P450 genes, c21190_g1 and c43350_g3, were constitutively overexpressed and mesosulfuron‐methyl‐induced upregulated in resistant plants, for which c43350_g3 was also fenoxaprop‐P‐ethyl‐induced upregulated. CONCLUSION: This study confirms the first case of a grass weed featuring broad‐spectrum resistance to ALS‐inhibiting herbicides due to a Pro‐197‐Tyr mutation in the ALS gene. Fenoxaprop‐P‐ethyl and mesosulfuron‐methyl resistances in AHTC‐06 plants were conferred by target site mutations and P450s‐based metabolism. © 2018 Society of Chemical Industry

Contributions of dsRNases to differential RNAi efficiencies between the injection and oral delivery of dsRNA in Locusta migratoria.

Abstract: Background The efficiency of RNA interference (RNAi) varies considerably among different insect species, and there is growing evidence to suggest that degradation of double-stranded (dsRNA) prior to uptake is an important factor that limits the efficiency of RNAi in insects. In Locusta migratoria, RNAi is highly efficient when dsRNA is delivered by injection, but not by feeding. However, detailed mechanisms causing such differential RNAi efficiency are still elusive. Results We identified and characterized the full-length complementary DNAs (cDNAs) of two new dsRNA nuclease (dsRNase) genes from L. migratoria, which were named LmdsRNase1 and LmdsRNase4. Transcript analyses revealed that LmdsRNase1 and LmdsRNase4 were highly expressed in hemolymph with relatively lower expression in other tested tissues. Our study using heterologously expressed LmdsRNase1 and LmdsRNase4 fusion proteins showed that LmdsRNase1 can degrade dsRNA rapidly at an optimal pH of 5, whereas LmdsRNase4 had no activity at any of the pH values examined. In comparing the substrate specificity of the four LmdsRNases, we found that only LmdsRNase1 and LmdsRNase2 digested dsRNA; however, our experiments suggested that the physiological pH of hemolymph (7.0) suppresses LmdsRNase1 activity permitting significant dsRNA stability in this tissue. Conversely, the physiological pH of midgut juice (6.8) is ideal for LmdsRNase2 activity, resulting in degradation of dsRNA in midgut. Conclusion The physiological pH of different insect tissues or compartments can significantly alter the stability of dsRNA by influencing LmdsRNase activity in L. migratoria. Thus, new strategies to overcome such obstacles are expected to help implement RNAi-based technologies for insect pest management. © 2018 Society of Chemical Industry.

Robotic weeders can improve weed control options for specialty crops.

Abstract: Specialty crop herbicides are not a priority for the agrochemical industry, and many of these crops do not have access to effective herbicides. High-value fruit and vegetable crops represent small markets and high potential liability in the case of herbicide-induced crop damage. Meanwhile, conventional and organic specialty crop producers are experiencing labor shortages and higher manual weeding costs. Robotic weeders are promising new weed control tools for specialty crops, because they are cheaper to develop and, with fewer environmental and human health risks, are less regulated than herbicides. Now is the time for greater investment in robotic weeders as new herbicides are expensive to develop and few in number, organic crops need better weed control technology and governments are demanding reduced use of pesticides. Public funding of fundamental research on robotic weeder technology can help improve weed and crop recognition, weed control actuators, and expansion of weed science curricula to train students in this technology. Robotic weeders can expand the array of tools available to specialty crop growers. However, the development of robotic weeders will require a broader recognition that these tools are a viable path to create new weed control tools for specialty crops. © 2019 Society of Chemical Industry.

A novel triple amino acid substitution in the EPSPS found in a high-level glyphosate-resistant Amaranthus hybridus population from Argentina.

Abstract: Background The evolution of herbicide-resistant weeds is one of the most important concerns of global agriculture. Amaranthus hybridus L. is a competitive weed for summer crops in South America. In this article, we intend to unravel the molecular mechanisms by which an A. hybridus population from Argentina has become resistant to extraordinarily high levels of glyphosate. Results The glyphosate-resistant population (A) exhibited particularly high parameters of resistance (GR50 = 20 900 g ai ha-1 , Rf = 314), with all plants completing a normal life cycle even after 32X dose application. No shikimic acid accumulation was detected in the resistant plants at any of the glyphosate concentrations tested. Molecular and genetic analyses revealed a novel triple substitution (TAP-IVS: T102I, A103V, and P106S) in the 5-enol-pyruvylshikimate-3-phosphate synthase (EPSPS) enzyme of population A and an incipient increase on the epsps relative copy number but without effects on the epsps transcription levels. The novel mechanism was prevalent, with 48% and 52% of the individuals being homozygous and heterozygous for the triple substitution, respectively. In silico conformational studies revealed that TAP-IVS triple substitution would generate an EPSPS with a functional active site but with an increased restriction to glyphosate binding. Conclusion The prevalence of the TAP-IVS triple substitution as the sole mechanism detected in the highly glyphosate resistant population suggests the evolution of a new glyphosate resistance mechanism arising in A. hybridus. This is the first report of a naturally occurring EPSPS triple substitution and the first glyphosate target-site resistance mechanism described in A. hybridus. © 2018 Society of Chemical Industry.

Insect midgut structures and molecules as targets of plant-derived protease inhibitors and lectins.

Abstract: The midgut of insects is involved in digestion, osmoregulation and immunity. Although several defensive strategies are present in this organ, its organization and function may be disturbed by some insecticidal agents, including bioactive proteins like lectins and protease inhibitors (PIs) from plants. PIs interfere with digestion, leading to poor nutrient absorption and decreasing amino acid bioavailability. Intake of PIs can delay development, cause deformities and reduce fertility. Ingestion of PIs may lead to changes in the set of proteases secreted in the insect gut, but this response is often insufficient and results in aggravation of the malnutrition status. Lectins are proteins that are able to interact with glycoconjugates, including those linked to cell surfaces. Their effects on the midgut include disruption of the peritrophic matrix, brush border and secretory cell layer; induction of apoptosis and oxidative stress; interference with nutrient absorption and transport proteins; and damaging effects on symbionts. In addition, lectins can cross the intestinal barrier and reach the hemolymph. The establishment of resistant insect populations due to selective pressure resulting from massive use of a bioactive protein is an actual possibility, but this can be minimized by the multiple mode-of-action of these proteins, mainly the lectins. © 2018 Society of Chemical Industry.

Detection of broadleaf weeds growing in turfgrass with convolutional neural networks

Abstract: BACKGROUND Weed infestations reduce turfgrass aesthetics and uniformity. Postemergence (POST) herbicides are applied uniformly on turfgrass, hence areas without weeds are also sprayed. Deep learning, particularly the architecture of convolutional neural network (CNN), is a state-of-art approach to recognition of images and objects. In this paper, we report deep learning CNN (DL-CNN) models that are remarkably accurate at detection of broadleaf weeds in turfgrasses. RESULTS VGGNet was the best model for detection of various broadleaf weeds growing in dormant bermudagrass [Cynodon dactylon (L.)] and DetectNet was the best model for detection of cutleaf evening-primrose (Oenothera laciniata Hill) in bahiagrass (Paspalum notatum Flugge) when the learning rate policy was exponential decay. These models achieved high F1 scores (>0.99) and overall accuracy (>0.99), with recall values of 1.00 in the testing datasets. CONCLUSION The results of the present research demonstrate the potential for detection of broadleaf weed using DL-CNN models for detection of broadleaf weeds in turfgrass systems. Further research is required to evaluate weed control in field conditions using these models for in situ video input in conjunction with a smart sprayer. © 2019 Society of Chemical Industry.