Advances in Attract-and-Kill for Agricultural Pests: Beyond Pheromones

Potential use of pinenes to improve localized insecticide injections targeting the western drywood termite (Blattodea: Kalotermitidae)

The western drywood termite, Incisitermes minor (Hagen), causes significant economic damage to wood structures in the United States of America, especially California. When infestation is not widespread, localized insecticide injections may be useful for remedial control. However, the extensive gallery structure of drywood termites and their tendency to aggregate at specific parts of the galleries can impact the efficacy of localized insecticide injection. Chemicals that attract termites from a distance may improve the localized insecticide injection by increasing the number of termites contacting the insecticide residues. Two volatile terpenes, α-pinene and β-pinene, commonly found in many coniferous timber trees, were applied to artificial termite galleries to determine if termites were attracted from their original aggregation site. Furthermore, we examined if adding these pinenes would improve the overall efficacy of some insecticide products for drywood termite control. Behavioral assay results showed that the treatment with pinenes increased the likelihood that drywood termites would leave their original aggregation site and contact the treated part of the gallery. When tested with the pesticide products applied in a small area away from the termite aggregation, β-pinene significantly accelerated the time course of mortality for the aqueous fipronil. The efficacy of disodium octaborate tetrahydrate dust was not influenced by the addition of pinenes. Implications for drywood termite management and future research directions are discussed.

Exploration of D-limonene as a sex pheromone for males of Bactrocera minax (Diptera: Tephritidae)

BACKGROUND

Bactrocera minax is a devastating pest of citrus fruits. However, there have been no effective control measures before. Few reports on the sex pheromones of B. minax are available.

RESULTS

In this study, nine of the volatile compounds in adult females were identified using headspace solid-phase microextraction (HS-SPME) in combination with gas chromatography-mass spectrometry (GC-MS). Among them, d-limonene, caprolactam, 2-Nitro-1H-imidazole, and creatinine could evoke antennal responses in males. Field bioassays showed that only d-limonene could lure male flies, with a relative lure rate of 78.18% in all tested samples, which was significantly higher than that of paraffin oil control, while all volatile compounds did not have any lure effective to female flies. Moreover, d-limonene was diluted with paraffin oil into differential concentrations, the lure effect on males was better at 100, 500, and 800 μL d-limonene mL-1 than pure d-limonene (1000 μL mL-1 ). The relative male lure rate of d-limonene at 100 μL mL-1 was 85.88%, which was significantly higher than that of food-baits (14.12%) on day 3. However, d-limonene was unattractive to female and male Bactrocera dorsalis and Zeugodacus tau. Further kinetic analysis showed that female adults released d-limonene around 15-day post eclosion. Electroantennography 1 results showed that 500 μL mL-1 d-limonene evoked the strongest responses to antennae of 10- to 25-day-old male flies.

CONCLUSION

Our results indicated that d-limonene could be a sex pheromone from female flies of B. minax, and it could be used as a male-specific sex attractant for B. minax. © 2023 Society of Chemical Industry.

Harvest load transfer sites influence sugarcane billbug (Coleoptera: Curculionidae) spatiotemporal injury in sugarcane

BACKGROUND

The sugarcane billbug, Sphenophorus levis Vaurie 1978, is a key soil-dwelling insect pest of sugarcane in Brazil and greatly affects plant development and yield. This insect presents an aggregated distribution pattern in production fields. The reasons for such behavior include intraspecific communication and attractivity due to the fermentation of sugar in stalk residues. During mechanized harvesting, part of the harvested material usually falls in the load transfer sites, becoming a potential source for increasing the infestation. We therefore evaluated whether producing areas near the harvest load transfer sites are more prone to S. levis injury.

RESULTS

There are greater chances of finding billbug injury within a radius of 740 m from the harvest load transfer site. Additionally, injured areas are estimated to expand 11.96% each growing season. Our spatiotemporal models support higher injured areas surrounding the harvest load transfer site and show clear and significant signs of increased injury levels compared to the initial growing season surveyed.

CONCLUSION

Our results reinforce the importance of harvest transfer sites in the dispersion and propagation of the sugarcane billbug. Based on this knowledge, sugarcane millers and growers can adopt preventive and remedial practices within the loading sites that can potentially contribute to the successful management of this insect pest. © 2023 Society of Chemical Industry.

An odorant receptor mediates the avoidance of Plutella xylostella against parasitoid

BACKGROUND

Ecosystems are brimming with myriad compounds, including some at very low concentrations that are indispensable for insect survival and reproduction. Screening strategies for identifying active compounds are typically based on bioassay-guided approaches.

RESULTS

Here, we selected two candidate odorant receptors from a major pest of cruciferous plants-the diamondback moth Plutella xylostella-as targets to screen for active semiochemicals. One of these ORs, PxylOR16, exhibited a specific, sensitive response to heptanal, with both larvae and adult P. xylostella displaying heptanal avoidance behavior. Gene knockout studies based on CRISPR/Cas9 experimentally confirmed that PxylOR16 mediates this avoidance. Intriguingly, rather than being involved in P. xylostella-host plant interaction, we discovered that P. xylostella recognizes heptanal from the cuticular volatiles of the parasitoid wasp Cotesia vestalis, possibly to avoid parasitization.

CONCLUSIONS

Our study thus showcases how the deorphanization of odorant receptors can drive discoveries about their complex functions in mediating insect survival. We also demonstrate that the use of odorant receptors as a screening platform could be efficient in identifying new behavioral regulators for application in pest management.

The greening-causing agent alters the behavioral and electrophysiological responses of the Asian citrus psyllid to a putative sex pheromone

The Asian Citrus Psyllid (ACP), Diaphorina citri, is a vector of the pathological bacterium Candidatus Liberibacter asiaticus (CLas), which causes the most devastating disease to the citrus industry worldwide, known as greening or huanglongbing (HLB). Earlier field tests with an acetic acid-based lure in greening-free, 'Valencia' citrus orange groves in California showed promising results. The same type of lures tested in São Paulo, Brazil, showed unsettling results. During the unsuccessful trials, we noticed a relatively large proportion of females in the field, ultimately leading us to test field-collected males and females for Wolbachia and CLas. The results showed high rates of Wolbachia and CLas infection in field populations. We then compared the olfactory responses of laboratory-raised, CLas-free, and CLas-infected males to acetic acid. As previously reported, CLas-uninfected males responded to acetic acid at 1 µg. Surprisingly, CLas-infected males required 50 × higher doses of the putative sex pheromone, thus explaining the failure to capture CLas-infected males in the field. CLas infection was also manifested in electrophysiological responses. Electroantennogram responses from CLas-infected ACP males were significantly higher than those obtained with uninfected males. To the best of our knowledge, this is the first report of a pathogen infection affecting a vector's response to a sex attractant.

Comparison of multimodal attract-and-kill formulations for managing Drosophila suzukii: Behavioral and lethal effects

Attract-and-kill (A&K) is a potential alternative control tactic for managing the invasive spotted-wing drosophila, Drosophila suzukii Matsumura. Here, we compared the efficacy of two novel A&K formulations based on proprietary blends-ACTTRA SWD OR1 (henceforth OR1) and ACTTRA SWD TD (henceforth TD)-in managing D. suzukii. Using two-choice bioassays, we compared OR1 and TD for their relative attractiveness to adult D. suzukii. Additionally, we tested how the addition of (1) a red dye (visual cue) and (2) the insecticide spinosad (Entrust™) to the OR1 and TD formulations influenced the attraction of adult D. suzukii in the presence of blueberry fruits. Finally, complementary laboratory efficacy (no-choice) bioassays were conducted to assess the mortality of adult D. suzukii exposed to OR1 and TD. A direct comparison between TD and OR1 formulations indicated the TD formulation was ~8 times more attractive than OR1. Adding a red dye to the TD or OR1 formulation did not significantly alter the attraction or mortality of adult D. suzukii compared to the formulation without a dye. Similarly, irrespective of dye status, adding spinosad to either the TD or OR1 formulation did not alter the adult D. suzukii behavioral response to these formulations but resulted in significantly higher D. suzukii mortality. Overall, the TD formulations resulted in significantly higher, or at least comparable, mortality to the OR1 formulations. In summary, our laboratory results demonstrated the higher efficacy of a TD-based A&K product in managing D. suzukii over its well-tested predecessor, the OR1 formulation, confirming its potential as a new behavioral tactic against this pest.

Large-area field application confirms the effectiveness of toxicant-infused bait for managing Helicoverpa armigera (Hübner) in maize fields

BACKGROUND

Maize is one of the world's most important crops, so its stable production and supply is crucial for food security and socioeconomic development. The cotton bollworm, Helicoverpa armigera (Hübner), is one of the major pests in maize. We evaluated the control effect of a bio-bait, an adult attractant, combined with insecticide, a 'toxicant-infused bait', on H. armigera populations in maize fields, as well as the impact on crop yield and quality through large-scale field applications in Hebei Province, China over a period spanning 2019 to 2021.

RESULT

The number of male and female H. armigera adults killed by strip application ranged from 1 to 37 and 4 to 36 per strip, respectively, of which female moths were 53%. Following the application of toxicant-infused bait, we observed a significant reduction in the populations of eggs and larvae, with the average adjusted decrease range from 58% to 63% for eggs and from 34% to 62% for larvae. The application of toxicant-infused bait also resulted in a notable reduction in the proportion of damaged maize plants, with an adjusted decline rate ranging from 59% to 69%. Concurrently, we observed an increase in yield by 4% to 8%. The concentration of aflatoxin in harvested maize grains was significantly reduced from an initial level of 1.24 to 0.1 ug/kg.

CONCLUSION

By applying toxicant-infused bait, there was a significant reduction in the population of H. armigera adults and their offspring, resulting in an improved yield and quality of maize. Toxicant-infused bait has great application potential in the integrated pest management of H. armigera. © 2023 Society of Chemical Industry.

A meta-analytic investigation of the potential for plant volatiles and sex pheromones to enhance detection and management of Lepidopteran pests

Effective early detection, monitoring and management methods are critical for reducing the impacts of insect pests in agriculture and forestry. Combining host plant volatiles with sex pheromones could enhance trapping methodologies, whilst the use of non-host volatiles could improve the effectiveness of pest management through repellency effects. In this meta-analysis approach, we analysed 51 studies that used electroantennograms (EAG), wind tunnels and/or field traps to evaluate the antennal and behavioural responses of Lepidoptera to sex pheromones combined with attractant or repellent plant volatiles. Proposed attractant plant volatiles had a positive association with female Lepidoptera responses to sex pheromone, but effects on males were highly variable, with unexpected repellency reported in some studies. Proposed repellent plant volatiles were significantly or near-significantly negatively associated with male attraction to sex pheromones but were scarcely studied. Sub-group analysis identified that male responses to sex pheromone were reduced when the dose of attractant plant volatile relative to sex pheromone was increased. Green-leaf volatiles were associated with the strongest positive effects for males in field traps. Multiple-compound attractant plant volatile blends were less effective than single compounds in field studies. Our analysis demonstrates, (i) the potential value of combining host plant volatiles with sex pheromones to capture females rather than only males, (ii) the importance of identifying appropriate host plant volatiles and optimal relative doses, and (iii) the potential for non-host plant volatile use in pest management strategies.

Sustainable Pest Management in Date Palm Ecosystems: Unveiling the Ecological Dynamics of Red Palm Weevil (Coleoptera: Curculionidae) Infestations

The red palm weevil (RPW) poses a significant threat to date palm ecosystems, highlighting the necessity of sustainable pest management strategies that carefully consider the delicate ecological balance within these environments. This comprehensive review delves into innovative approaches to sustainable pest management, specifically focusing on date palm, and seeks to unravel the intricate ecological dynamics underlying RPW infestations. We thoroughly analyze biocontrol methods, eco-friendly chemical interventions, and integrated pest management (IPM) strategies, aiming to minimize the ecological impact while effectively addressing RPW infestations. By emphasizing the interplay of both living organisms (biotic) and environmental factors (abiotic) in shaping RPW dynamics, we advocate for a holistic and sustainable management approach that ensures the long-term resilience of date palm ecosystems. This review aims to contribute to an ecologically sound framework for pest management, promoting the sustainability and vitality of date palm ecosystems amidst the challenges posed by the RPW.

The Effect of Cuelure on Attracting and Feeding Behavior in Zeugodacus tau (Walker) (Diptera: Tephritidae)

As a vital pest control strategy, trapping plays an important role in the system of monitoring, catching and killing fruit flies. Cuelure (4-(4-acetoxyphenyl)-2-butanone, CL) is a male lure that attracts Zeugodacus tau and also stimulates feeding in this species. In this study, the attraction of Z. tau to CL and its subsequent feeding behavior were investigated. Under the significant influence of age and time of day, the attraction of CL to Z. tau was found to be optimal when flies were 14 days old, and the number of flies trapped increased with trapping duration. It was determined that consumption can improve the mating success and female adult fertility of Z. tau. After the observation period, the mating success rate of flies that ingested CL was significantly higher than that of the control group and was maintained at a higher level. It was found that parental consumption of CL could accelerate the development of eggs and larvae, resulting in increased pupation and emergence rates. The results of this study will further clarify the dynamic relationship between pest and lure, and provide a research basis for navigating the integrated management of Z. tau in the field.

The attractive host volatiles can enhance oviposition of Anoplophora glabripennis on a non-host tree

BACKGROUND

The Asian longhorned beetle (ALB), Anoplophora glabripennis, is a serious wood borer of hardwood trees. Populus deltoides 'Shalinyang' (PdS) is attractive to ALB adults for oviposition but highly resistant to their offspring. Investigation of the chemicals regulating ALB oviposition is scarce in previous studies until now. To determine which chemicals emitted by PdS were attractive and induced oviposition behavior by ALB on non-host poplar tree species, we first: collected and identified the bio-active volatiles produced by PdS using coupled gas chromatography-mass spectrometry (GC-MS) and coupled gas chromatography-electroantennographic detector (GC-EAD); then evaluated which chemicals were attractive in a Y-tube olfactometer bioassay; and finally screened key compounds affecting ALB oviposition using a 'chemical-stimulated oviposition on non-host tree' bioassay.

RESULTS

(E)-2-Hexenal, hexyl acetate, (Z)-3-hexenol acetate, 1-hexanol, (Z)-3-hexenol, β-caryophyllene, and salicylaldehyde emitted from PdS were attractive to ALB. When (E)-2-hexenal, 1-hexanol, (Z)-3-hexenol acetate, and (Z)-3-hexenol were applied to the non-host tree Populus tomentosa, oviposition by ALB females was significantly increased. Furthermore, the mean number of oviposition pits increased as the (Z)-3-hexenol concentrations increased. Further tests on synergy between pairs of chemicals showed that (Z)-3-hexenol stimulated production of the most oviposition pits, but that the percentage of effective oviposition pits (those containing an egg and larva and not empty) decreased.

CONCLUSION

(Z)-3-Hexenol is the main chemical component inducing ALB oviposition. These results increase understanding about the oviposition behavior of ALB and could help improve management strategies that regulate ALB behavior by planting mixed-species forests resistant to ALB. © 2023 Society of Chemical Industry.

Volatiles produced by symbiotic yeasts improve trap catches of Carpophilus davidsoni (Coleoptera: Nitidulidae): an important pest of stone fruits in Australia

Carpophilus davidsoni (Dobson) is an important pest of Australian stone fruit. Current management practices for this beetle include the use of a trap that contains an attractant lure comprised of aggregation pheromones and a 'co-attractant' mixture of volatiles from fruit juice fermented using Baker's yeast, Saccharomyces cerevisiae (Hansen). We explored whether volatiles from yeasts Pichia kluyveri (Bedford) and Hanseniaspora guilliermondii (Pijper), which are closely associated with C. davidsoni in nature, might improve the effectiveness of the co-attractant. Field trials using live yeast cultures revealed that P. kluyveri trapped higher numbers of C. davidsoni compared to H. guilliermondii, and comparative GC-MS of volatile emissions of the two yeasts led to the selection of isoamyl acetate and 2-phenylethyl acetate for further investigation. In subsequent field trials, trap catches of C. davidsoni were significantly increased when 2-phenylethyl acetate was added to the co-attractant, compared to when isoamyl acetate was added, or both isoamyl acetate and 2-phenylethyl acetate. We also tested different concentrations of ethyl acetate in the co-attractant (the only ester in the original lure) and found contrasting results in cage bioassays and field trails. Our study demonstrates how exploring volatile emissions from microbes that are ecologically associated with insect pests can result in more potent lures for use in integrated pest management strategies. Results from laboratory bioassays screening volatile compounds should be treated with caution when making inferences regarding attraction under field conditions.

Attraction, mobility, and preference by Lasioderma serricorne (Coleoptera: Ptinidae) to microbially-mediated volatile emissions by two species of fungi in stored grain

Insects and microbes are known to interact in a variety of ways at food facilities, compounding damage. However, little research has explicated how specific common fungal species affect the behavior of the cosmopolitan secondary stored product pest, Lasioderma serricorne. Enhanced knowledge about attraction to microbially-produced volatile organic compounds (MVOCs) may be used to manipulate insect behavior. Aspergillus flavus and Fusarium verticillioides are two common, widespread pre- and postharvest fungi on small cereals that produce aflatoxins and fumonisins, respectively, while directly competing with each other for nutrients. Our goals were to (1) characterize the volatile emissions from grain inoculated by A. flavus or F. verticillioides derived from the cuticle of L. serricorne compared to uninoculated and sanitized grain, and (2) understand how MVOCs from each fungal species affects mobility, attraction, and preference by L. serricorne. Headspace collection revealed that the F. verticillioides- and A. flavus-inoculated grain produced significantly different volatiles compared to sanitized grain or the positive control. Changes in MVOC emissions affected close-range foraging during an Ethovision movement assay, with a greater frequency of entering and spending time in a small zone with kernels inoculated with A. flavus compared to other treatments. In the release-recapture assay, MVOCs were found to be attractive to L. serricorne at longer distances in commercial pitfall traps. There was no preference shown among semiochemical stimuli in a still-air, four-way olfactometer. Overall, our study suggests that MVOCs are important for close- and long-range orientation of L. serricorne during foraging, and that MVOCs may have the potential for inclusion in behaviorally-based tactics for this species.

Potential Alternatives to Spinosad as the Killing Agent Mixed With Two Attractant Products in Attract-and-Kill Formulations Used to Manage the Spotted-Wing Drosophila, Drosophila suzukii (Diptera: Drosophilidae)

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a key pest of many berry and fruit crops worldwide. The primary method of controlling this pest is the application of insecticides. Attract-and-kill is a management tactic that may reduce the number of insecticide applications needed to manage D. suzukii. ACTTRA SWD OR1 and ACTTRA SWD TD, developed by ISCA Technologies Inc., combine D. suzukii attractants with a gel matrix. Growers add an insecticide as a killing agent. The only USDA National Organic Program approved organic insecticide that has been shown to be effective as a killing agent is spinosad. This study aimed to determine the efficacy of other USDA National Organic Program approved organic insecticides, including Grandevo 30 WDG (Chromobacterium subtsugae strain PRAA4-1 30%), MBI-203 SC2 (C. subtsugae strain PRAA4-1 98%), Venerate XC (Burkholderia spp. Strain A396 94.45%), MBI-306 SC1 (B. rinojensis Strain A396 94.45%), Azera (azadirachtin 1.2% + pyrethrins 1.4%), and PyGanic (pyrethrins 1.4%), when used as the killing agent with the two ACTTRA SWD products. Lab and cage bioassays were conducted. Entrust (spinosad 22.5%) and PyGanic were the only compounds that showed some efficacy when used with ACTTRA SWD OR1 and ACTTRA SWD TD.

Insights into insecticide-resistance mechanisms in invasive species: Challenges and control strategies

Threatening the global community is a wide variety of potential threats, most notably invasive pest species. Invasive pest species are non-native organisms that humans have either accidentally or intentionally spread to new regions. One of the most effective and first lines of control strategies for controlling pests is the application of insecticides. These toxic chemicals are employed to get rid of pests, but they pose great risks to people, animals, and plants. Pesticides are heavily used in managing invasive pests in the current era. Due to the overuse of synthetic chemicals, numerous invasive species have already developed resistance. The resistance development is the main reason for the failure to manage the invasive species. Developing pesticide resistance management techniques necessitates a thorough understanding of the mechanisms through which insects acquire insecticide resistance. Insects use a variety of behavioral, biochemical, physiological, genetic, and metabolic methods to deal with toxic chemicals, which can lead to resistance through continuous overexpression of detoxifying enzymes. An overabundance of enzymes causes metabolic resistance, detoxifying pesticides and rendering them ineffective against pests. A key factor in the development of metabolic resistance is the amplification of certain metabolic enzymes, specifically esterases, Glutathione S-transferase, Cytochromes p450 monooxygenase, and hydrolyses. Additionally, insect guts offer unique habitats for microbial colonization, and gut bacteria may serve their hosts a variety of useful services. Most importantly, the detoxification of insecticides leads to resistance development. The complete knowledge of invasive pest species and their mechanisms of resistance development could be very helpful in coping with the challenges and effectively developing effective strategies for the control of invasive species. Integrated Pest Management is particularly effective at lowering the risk of chemical and environmental contaminants and the resulting health issues, and it may also offer the most effective ways to control insect pests.

Lethal and sublethal effects of chlorantraniliprole on the migratory moths Agrotis ipsilon and A. segetum: New perspectives for pest management strategies

BACKGROUND

Agrotis ipsilon and A. segetum are major migratory pests of many crops in China, and frequent regional outbreaks cause severe yield losses. Use of food attractants is one of the most promising control methods against adult lepidoptera, notably through the attract-and-kill strategy. Chlorantraniliprole's acute toxicity and sublethal effects on both moths were evaluated.

RESULTS

Chlorantraniliprole showed high activity against both adults of both species, with LC₂₀ and LC₅₀ values of 0.08 and 0.21 mg L^-1 (A. ipsilon), and 0.14 and 0.51 mg L^-1 (A. segetum). The fecundity, effective oviposition rate, and egg hatching rate of both species in dual-sex exposure treatments were all significantly reduced compared with the control, and the population growth coefficients in the LC₅₀ ♀ × LC₅₀ ♂ treatments were only 0.32% (A. ipsilon) and 3.35% (A. segetum) that of the control. Furthermore, the flight distance was significantly suppressed from 6.67 km (control) to 0.01 km (LC₅₀ ) for A. ipsilon, and from 7.39 km (control) to 0.78 km (LC₅₀ ) for A. segetum. The proportions of robust- and medium-flight individuals of A. ipsilon and A. segetum in exposure treatments were greatly reduced.

CONCLUSIONS

Low lethal concentration exposures to chlorantraniliprole can drastically reduce the reproduction and flight performance of A. ipsilon and A. segetum, while inhibiting the production of offspring, suggesting chlorantraniliprole would be an excellent compound for use in combination with food attractants. Chlorantraniliprole has good potential for management of the two long-range migratory pests tested using an attract-and-kill strategy. © 2022 Society of Chemical Industry.

Pollen and nectar have different effects on the development and reproduction of noctuid moths

Although many noctuid insects are agricultural pests that threaten food production, they are also the major nocturnal pollinators of flowering plants. Larval foods of noctuid pest insects have been well studied for developing control strategies, but knowledge on host plants for the adults is rather scarce. Here, the impact of plant-derived foods on adult survival, fecundity and reproductive physiology of four global species of noctuid pests (Mythimna separata Walker, Mythimna loreyi Duponchel, Athetis lepigone Möschler, and Hadula trifolii Hufnagel) was assessed in laboratory experiments. Our results indicated that nectar slowed testis decay and prolonged the oviposition period and lifespan, increasing fecundity. Acacia nectar increased the longevity of male and female adults by 3.2∼10.9 and 2.4∼5.0 days, respectively, and fecundity of females by 1.22∼3.34 times compared to water-fed individuals. The fitness among the different species of noctuid moths differed on specific pollen diets. On pine pollen, the fecundity of female moths of M. separata, A. lepigone and H. trifolii was 10.06, 33.52, and 28.61%, respectively, lower than those of the water-fed females, but the fecundity of female moths of M. loreyi on pine pollen was 2.11 times greater than for the water-fed individuals. This work provides valuable information on the nutritional ecology for noctuid moths, which can aid the development and design of nutritional attractants within noctuid pests-infected cropping systems and provide a basis for effective and targeted management of global noctuid pests.

Optimization and field evaluation of sex-pheromone of potato tuber moth, Phthorimaea operculella Zeller (Lepidoptera: Gelechiidae)

BACKGROUND

The potato tuber moth, Phthorimaea operculella is a key pest of potato and tobacco in China. We compared the sex pheromone titers released by P. operculella female, and the electroantennogram (EAG) responses of male antennae to pheromone compounds under laboratory conditions. Then, the optimal sex pheromone ratio was screened in the field.

RESULTS

The P. operculella sex pheromone feeding on potato or tobacco was extracted by solvent-extraction method. Main sex pheromone compounds including E4, Z7-13: AC (PTM1) and E4, Z7, Z10-13: AC (PTM2) were found in gland. The titer and relative ratio of P. operculella sex pheromone compounds secreted by female adult moths differ between host populations, while the relative EAG responses trend of P. operculella males to the pheromone components were the same when directly stimulated. In field trials, PTM1:PTM2 = 8:1-4:1 and PTM1:PTM2 = 1:4-1:7 was the most attractive ratio to P. operculella males in tobacco and potato fields, respectively. During 2019-2020, after 8 weeks of mass trapping for each year, the sex pheromone could reduce the population of P. operculella in the potato and tobacco fields.

CONCLUSIONS

In this study, fixed property and quantity analyzing methods were adopted to compare sex pheromones from feeding on potato versus tobacco. EAG tests then were carried out on P. operculella males. Finally, we optimized the ratio of two sex pheromone compounds in potato and examined how this influenced field trapping. By further improving the parameters of sex pheromone application in the field, we demonstrate that deployment of sex pheromones can provide effective control of P. operculella. © 2021 Society of Chemical Industry.

Factors Influencing the Efficacy of Novel Attract-and-Kill (ACTTRA SWD) Formulations Against Drosophila suzukii

In the continental United States, the invasive spotted-wing drosophila (SWD), Drosophila suzukii Matsumura, has become a primary pest of multiple stone and soft-skinned fruits. A new innovative adjuvant formulation, ACTTRA SWD, mixed with a suitable insecticide, constitutes a novel attract-and-kill tactic to manage D. suzukii in fruit crops. We hypothesized that background odors present in crop fields, particularly odors from host fruits, negatively affect the effectiveness of this attract-and-kill formulation, as odors from these sources can compete for insect attraction. Additionally, we evaluated the influence of adult D. suzukii sex and physiological status (age and mating status), and fruit ripeness on its response to the ACTTRA SWD formulation. For this, we used two-choice bioassays to test the response of adult D. suzukii to three ACTTRA SWD formulations (named OR1, TD, and HOOK SWD) in the presence and absence of host fruits (blueberries, raspberries, blackberries, and strawberries). Odors from raspberries were significantly more attractive than those from the TD formulation mixed with spinosad (Entrust). For the HOOK SWD formulation and OR1+Entrust formulation, odors from all the fruit types tested were significantly more attractive than the adjuvants. Compared with females, male D. suzukii were more attracted to the TD formulation over the blueberry fruits. Additionally, age and female mating status but not fruit ripeness influenced D. suzukii attraction to both OR1 and TD formulations. The results from this study indicate that D. suzukii physiological status and host fruit availability impact the efficacy of new attract-and-kill adjuvants such as ACTTRA SWD.

Odor Perception in the Cotton Bollworm, Helicoverpa armigera, Exposed to Juglans regia, a Marginal Host Plant

The cotton bollworm, Helicoverpa armigera, is one of the most destructive agricultural pests in the world, infesting cotton, maize, soybean, and many other crops. In recent years, H. armigera has been observed damaging walnuts, Juglans regia, in Xinjiang China. Here we examine the chemical perception by H. armigera of the marginal host J. regia. In Y-tube olfactometer tests, we found H. armigera females and males both showed significant behavioral responses to odors from walnut branches. Furthermore, nine electrophysiologically active volatiles (α-pinene, β-pinene, myrcene, limonene, eucalyptol, ocimene, β-caryophyllene, (E)-β-farnesene, and germacrene D) were identified from walnuts with gas chromatography coupled with electroantennography (GC-EAD) and gas chromatography-mass spectrometry (GC-MS). Among these volatiles, β-pinene and eucalyptol were released in relatively higher amounts. In electroantennogram (EAG) dose-dependent trials, all compounds evoked responses in H. armigera adults when tested at high concentrations, with germacrene D evoking the greatest response. In wind tunnel tests, H. armigera females preferred eight of the electrophysiologically active volatile dilutions compared with clean air, while males showed preference for only five compounds. As such we describe the chemical recognition of H. armigera for walnut, a marginal host. This study contributes to understanding the interaction between polyphagous pests and their host plants.

Bisexual Attract-and-Kill: A Novel Component of Resistance Management for Transgenic Cotton in Australia

In Australia, destruction of overwintering pupae of Helicoverpa armigera (Hübner) and Helicoverpa punctigera (Wallengren) (Lepidoptera: Noctuidae) has been a key component of mandatory resistance management schemes to constrain development of resistance to Bt toxins in transgenic cotton. This has been accomplished by tillage ('pupae busting'), but it is expensive and can interfere with farming operations. Bisexual attract-and-kill technology based on plant volatile formulations offers a potential alternative in some circumstances. We discuss strategies for using such products and describe two trials in which three applications of an attract-and-kill formulation substantially reduced the numbers of Helicoverpa spp. moths and the numbers of potentially overwintering eggs they laid. One trial tested a curative strategy in which the last generation of moths emerging from transgenic cotton was targeted. The other tested a preventive strategy which aimed to reduce the numbers of eggs in the last generation. The preventive strategy reduced egg numbers by about 90% and is now included as an optional alternative to pupae busting in resistance management strategies for Australian cotton. It is limited to fields which have not been defoliated prior to 31 March and was developed to be used primarily in southern New South Wales. In the 2020-2021 cotton season, it was adopted on approximately 60% of the eligible cotton area. We describe the process whereby the strategy was developed in collaboration with the transgenic technology provider, supported by the cotton industry, and approved by the regulatory authority.

Evaluation of Selected Plant Volatiles as Attractants for the Stick Tea Thrip Dendrothrips minowai in the Laboratory and Tea Plantation

Simple Summary

The stick tea thrip Dendrothrips minowai is a key pest in tea plantations in China. In recent years, plant-derived semiochemicals have attracted considerable attention as promising attractants for the management of thrips, due to their safety and low cost. In this study, compounds that have been reported to attract other thrips or emitted from tea plants were evaluated for their electroantennogram (EAG), behavioral tests and field trapping efficacy for D. minowai. The EAG relative response value of D. minowai evoked by p-anisaldehyde, 3-methyl butanal, (E)-β-ocimene, farnesene, nonanal, eugenol, (+)-α-pinene, limonene, (−)-α-pinene, and γ-terpinene was significantly higher than the other compounds. Meanwhile, p-anisaldehyde, eugenol, farnesene, methyl benzoate, 3-methyl butanal, (E)-β-ocimene, (−)-α-pinene, (+)-α-pinene, and γ-terpinene led to attraction or repellency responses of female D. minowai. In addition, trap capture numbers of female D. minowai on sticky traps baited with p-anisaldehyde, eugenol, farnesene, and 3-methyl butanal were significantly higher than the control in tea plantations. Overall, our results highlight the potential application of plant volatiles in the development of effective, eco-friendly lure formulations for use in the monitoring and management of thrips.

Abstract

The stick tea thrip (Dendrothrips minowai Priesner) is the main pest thrip in tea (Camellia sinensis) plantations in China, and seriously affects the quality and yield of tea. Plant-derived semiochemicals provide an alternative to pheromones as lures and these compounds possess powerful attractiveness. In this study, we selected 20 non-pheromone semiochemicals, including compounds that have been reported to attract other thrips and some volatiles emitted from tea plants as the potential attractant components for D. minowai. In electroantennogram (EAG) assays, 10 synthetic compounds (p-anisaldehyde, 3-methyl butanal, (E)-β-ocimene, farnesene, nonanal, eugenol, (+)-α-pinene, limonene, (−)-α-pinene, and γ-terpinene) elicited significant antennal responses in female D. minowai. In addition, a two-choice H-tube olfactometer bioassay showed that D. minowai displayed significant positive responses to eight compound dilutions (p-anisaldehyde, eugenol, farnesene, methyl benzoate, 3-methyl butanal, (E)-β-ocimene, (−)-α-pinene, and (+)-α-pinene) when compared with the solvent control at both 1 and 2 h. Moreover, γ-terpinene exhibited a significantly deterrent effect on D. minowai. Finally, trap catches of four compounds (p-anisaldehyde, eugenol, farnesene, and 3-methyl butanal, respectively) significantly increase in tea plantations. Among these, the maximum number of D. minowai collected by blue sticky traps baited with p-anisaldehyde was 7.7 times higher than the control. In conclusion, p-anisaldehyde, eugenol, farnesene, and 3-methyl butanal could significantly attract D. minowai in the laboratory and under field conditions, suggesting considerable potential as commercial attractants to control D. minowai populations.

Electroantennogram and machine learning reveal a volatile blend mediating avoidance behavior by Tuta absoluta females to a wild tomato plant

Tomato cultivation is threatened by the infestation of the nocturnal invasive tomato pinworm, Tuta absoluta. This study was based on field observations that a wild tomato plant, Solanum lycopersicum var. cerasiforme, grown in the Mount Kenya region, Kenya, is less attacked by T. absoluta, unlike the cultivated tomato plants like S. lycopersicum (var. Rambo F1). We hypothesized that the wild tomato plant may be actively avoided by gravid T. absoluta females because of the emission of repellent allelochemical constituents. Therefore, we compared infestation levels by the pest in field monocrops and intercrops of the two tomato genotypes, characterized the headspace volatiles, then determined the compounds detectable by the insect through gas chromatography-linked electroantennography (GC-EAG), and finally performed bioassays using a blend of four EAG-active compounds unique to the wild tomato. We found significant reductions in infestation levels in the monocrop of the wild tomato, and intercrops of wild and cultivated tomato plants compared to the monocrop of the cultivated tomato plant. Quantitative and qualitative differences were noted between volatiles of the wild and cultivated tomato plants, and between day and night volatile collections. The most discriminating compounds between the volatile treatments varied with the variable selection or machine learning methods used. In GC-EAG recordings, 16 compounds including hexanal, (Z)-3-hexenol, α-pinene, β-myrcene, α-phellandrene, β-phellandrene, (E)-β-ocimene, terpinolene, limonene oxide, camphor, citronellal, methyl salicylate, (E)-β-caryophyllene, and others tentatively identified as 3,7,7-Trimethyl-1,3,5-cycloheptatriene, germacrene D and cis-carvenone oxide were detected by antennae of T. absoluta females. Among these EAG-active compounds, (Z)-3-hexenol, α-pinene, α-phellandrene, limonene oxide, camphor, citronellal, (E)-β-caryophyllene and β-phellandrene are in the top 5 discriminating compounds highlighted by the machine learning methods. A blend of (Z)-3-hexenol, camphor, citronellal and limonene oxide detected only in the wild tomato showed dose-dependent repellence to T. absoluta females in wind tunnel. This study provides some groundwork for exploiting the allelochemicals of the wild tomato in the development of novel integrated pest management approaches against T. absoluta.

Comparative Adult Mortality and Relative Attractiveness of Spotted-Wing Drosophila (Diptera: Drosophilidae) to Novel Attract-and-Kill (ACTTRA SWD) Formulations Mixed With Different Insecticides

Since its first appearance in California in 2008 and subsequent spread across the continental United States, the spotted-wing drosophila, Drosophila suzukii Matsumura, has become an economically damaging pest of multiple stone and soft-skinned fruits in the United States. The adjuvant ACTTRA SWD, when mixed with a suitable insecticide, constitutes an innovative attract-and-kill tactic that can be applied as a sprayable bait to manage D. suzukii. As an adjuvant, growers can mix ACTTRA SWD with any insecticide recommended for D. suzukii management in a specific crop; however, to achieve this, the efficacy of this adjuvant incorporated with various insecticides needs testing. This research aims to test the suitability of nine insecticides added to two ACTTRA SWD formulations (named OR1 and TD) to maintain the formulation’s attractiveness to D. suzukii adults and in resulting mortality. We conducted a series of two-choice bioassays to test the relative attraction of D. suzukii to ACTTRA SWD formulations prepared with and without a specific insecticide. Additionally, we tested the efficacy of ACTTRA SWD formulations mixed with insecticides in managing D. suzukii by using no-choice efficacy bioassays. Adding Mustang Maxx (zeta-cypermethrin) to ACTTRA SWD OR1 significantly improved D. suzukii adult attraction to the formulation, while Azera (azadirachtin + pyrethrins) significantly reduced attraction to both ACTTRA SWD formulations. Among the insecticides tested, we identified Danitol (fenpropathrin), Exirel (cyantraniliprole), Malathion (malathion), Mustang Maxx, and Entrust (spinosad) as suitable insecticide additives for both ACTTRA SWD formulations. The results from this study will assist growers in selecting proper insecticide components when preparing attract-and-kill formulations of the new adjuvant ACTTRA SWD.

Electrophysiological and behavioral responses of blister beetle Mylabris pustulata to plant volatiles

Plant volatiles, constitutive or induced, are perceived by insect pests to locate the host plant and also by natural enemies to locate the host insect. These plant volatiles can be utilized to develop attractive or repellant lures for pest management. Studies were carried out to identify the plant volatiles which are induced in pigeonpea, Cajanus cajan (L.) Huth due to the herbivory of blister beetle, Mylabris pustulata. The volatiles from healthy uninfested pigeonpea plants and blister beetle-infested plants were collected using the dynamic headspace collection method with Porapaq Q (80-100 mesh) as adsorbent. Using gas chromatography-mass spectrometry, 28 compounds were identified from uninfested pigeonpea plants whereas 16 compounds were identified from infested plants. A qualitative analysis showed that α-pinene and 3-hexen-2-one were exclusively detected in infested plants and (Z)-3-hexen-1-yl acetate and acetophenone were released in higher quantities from infested plants than from uninfested one. Electrophysiological evaluation of these volatiles along with other plant volatiles showed that blister beetle antennae eliciting higher responses to eucalyptol at a 1-μg dose, to nerol at a 10-μg dose and to benzyl acetate at 100- and 1000-μg doses. Beetle traps with lures of eucalyptol, benzaldehyde, benzyl acetate, and nerol attracted a very small number of blister beetle adults, suggesting the need for further efforts to standardize lure load and trap design.

From tissue engineering to mosquitoes: biopolymers as tools for developing a novel biomimetic approach to pest management/vector control

Background

Pest management has been facing the spread of invasive species, insecticide resistance phenomena, and concern for the impact of chemical pesticides on human health and the environment. It has tried to deal with them by developing technically efficient and economically sustainable solutions to complement/replace/improve traditional control methods. The renewal has been mainly directed towards less toxic pesticides or enhancing the precision of their delivery to reduce the volume employed and side effects through lure-and-kill approaches based on semiochemicals attractants. However, one of the main pest management problems is that efficacy depends on the effectiveness of the attractant system, limiting its successful employment to semiochemical stimuli-responsive insects. Biomaterial-based and bioinspired/biomimetic solutions that already guide other disciplines (e.g., medical sciences) in developing precision approaches could be a helpful tool to create attractive new strategies to liberate precision pest management from the need for semiochemical stimuli, simplify their integration with bioinsecticides, and foster the use of still underemployed solutions.

Approach proposed

We propose an innovative approach, called “biomimetic lure-and-kill”. It exploits biomimetic principles and biocompatible/biodegradable biopolymers (e.g., natural hydrogels) to develop new substrates that selectively attract insects by reproducing specific natural environmental conditions (biomimetic lure) and kill them by hosting and delivering a natural biopesticide or through mechanical action. Biomimetic lure-and-kill-designed substrates point to provide a new attractive system to develop/improve and make more cost-competitive new and conventional devices (e.g. traps). A first example application is proposed using the tiger mosquito Aedes albopictus as a model.

Conclusions

Biomaterials, particularly in the hydrogel form, can be a useful tool for developing the biomimetic lure-and-kill approach because they can satisfy multiple needs simultaneously (e.g., biomimetic lure, mechanical lethality, biocompatibility, and bioinsecticide growth). Such an approach might be cost-competitive, and with the potential for applicability to several pest species. Moreover, it is already technically feasible, since all the technologies necessary to design and configure materials with specific characteristics are already available on the market.

Graphical Abstract

Mutualism between Gut-Borne Yeasts and Their Host, Thaumatotibia leucotreta, and Potential Usefulness in Pest Management

Thaumatotibia leucotreta is endemic to southern Africa and is highly significant for various fruit industries, including the South African citrus industry, due to its classification as a phytosanitary pest. Mutualistic associations between C. pomonella, closely related to T. leucotreta, and yeasts have previously been described and reported to reduce larval mortality and enhance larval development. Here, we determined which yeast species occur naturally in the gut of T. leucotreta larvae and investigated whether any of the isolated yeast species affect their behaviour and development. Navel oranges infested with T. leucotreta larvae were collected from geographically distinct provinces in South Africa, and the larvae were processed for analysis of naturally occurring associated yeasts. Six yeast species were isolated and identified from the guts of these T. leucotreta larvae via PCR amplification and sequencing of the ITS region of rDNA and D1/D2 domain of large ribosomal subunit. Larval development and attraction assays were conducted, and T. leucotreta larvae that fed on Navel oranges inoculated with yeast had accelerated developmental periods and reduced mortality rates. Neonate T. leucotreta were also attracted to YPD broth cultures inoculated with yeast for feeding. Oviposition preference assays were conducted with adult T. leucotreta females. Navel oranges inoculated with yeast were shown to influence the oviposition preference of adult females. Yeasts harbour the potential for use in biocontrol, especially when combined with other well-established control methods. This study provides a platform for future research into incorporating yeast with current biological control agents as a novel option for controlling T. leucotreta in the field.

Compatibility of a Beta-cyfluthrin-Based 'Attract-and-Kill' Device with Tamarixia radiata (Hymenoptera: Eulophidae) for Suppression of Diaphorina citri (Hemiptera: Liviidae) on Residential Citrus

The Asian citrus psyllid, Diaphorina citri Kuwayama (Hemiptera: Liviidae), is a serious threat to the U.S. citrus industry because it spreads huanglongbing (HLB), a bacterial and incurable citrus disease. The nymphal parasitoid, Tamarixia radiata Waterston (Hymenoptera: Eulophidae), has been extensively released for biological control of D. citri in South Texas since 2010 but provides insufficient control. An 'attract-and-kill' (AK) device was evaluated for its compatibility with T. radiata for suppression of D. citri on dooryard citrus. The AK device is visually attractive to D. citri adults because it is the same color as young citrus flush and kills individuals on contact with the toxicant beta-cyfluthrin. This study evaluated 1) lethality of AK devices to T. radiata adults under lab conditions; 2) efficacy of AK devices for year-round psyllid suppression on individual dooryard lemon trees; 3) discovery and parasitism of D. citri colonies by T. radiata on lemon trees with or without AK devices. Contact with AK devices for 5 s or more was lethal to adult parasitoids. Deployment of 20 AK devices per tree provided significant year-round suppression of D. citri on infested lemon trees and reduced mean attack intensity (cumulative psyllid-days) of adults by 66% and nymphs by 82%. Discovery and parasitism rates of D. citri colonies by T. radiata were similar on control trees and trees protected by AK devices. An AK device that targets adult psyllids could be used to effectively complement biological control of D. citri by T. radiata in residential landscapes.

Influence of Sunlight Incidence and Fruit Chemical Features on Oviposition Site Selection in Mango by Anastrepha obliqua: Implications for Management

With the aim of identifying key factors that determine oviposition decisions by Anastrepha obliqua for management purposes, we conducted a behavioral study under natural/semi-natural field conditions to identify where exactly in the fruit (upper, middle, or lower sections) females preferred to lay eggs in a highly susceptible mango cultivar (“Criollo”), and whether sunlight incidence and fruit chemical compounds influenced oviposition site selection by this pestiferous fly. Females oviposited in shaded, upper fruit sections where pulp had higher total carbohydrate concentrations but similar total protein, lipid, and polyphenol concentrations than non-oviposited sections. Peel had higher overall nutrient and mangiferin/quercetin-3-D-galactoside (polyphenols) concentrations. An untargeted metabolomic analysis of oviposited and non-oviposited fruit sections identified abscisic acid (ABA) and dihydrophaseic acid glucoside, a by-product of ABA catabolism, as potential chemical markers that could play a role in fruit acceptance behaviors by female flies. We conclude that females preferentially oviposit in fruit sections with optimal chemical and environmental conditions for larval development: more carbohydrates and antioxidants such as mangiferin and ferulic acid and lesser sunlight exposure to avoid lethal egg/larval desiccation/overheating. We make specific recommendations for A. obliqua management based on female host selection behavior, a tree pruning scheme exposing fruit to direct sunlight, application of a host marking pheromone, and the use of egg sinks in the orchard.

Volatile Organic Compound Profiles From Wheat Diseases Are Pathogen-Specific and Can Be Exploited for Disease Classification

Plants and fungi emit volatile organic compounds (VOCs) that are either constitutively produced or are produced in response to changes in their physico-chemical status. We hypothesized that these chemical signals could be utilized as diagnostic tools for plant diseases. VOCs from several common wheat pathogens in pure culture (Fusarium graminearum, Fusarium culmorum, Fusarium avenaceum, Fusarium poae, and Parastagonospora nodorum) were collected and compared among isolates of the same fungus, between pathogens from different species, and between pathogens causing different disease groups [Fusarium head blight (FHB) and Septoria nodorum blotch (SNB)]. In addition, we inoculated two wheat varieties with either F. graminearum or P. nodorum, while one variety was also inoculated with Blumeria graminis f.sp. tritici (powdery mildew, PM). VOCs were collected 7, 14, and 21 days after inoculation. Each fungal species in pure culture emitted a different VOC blend, and each isolate could be classified into its respective disease group based on VOCs with an accuracy of 71.4 and 84.2% for FHB and SNB, respectively. When all collection times were combined, the classification of the tested diseases was correct in 84 and 86% of all cases evaluated. Germacrene D and sativene, which were associated with FHB infection, and mellein and heptadecanone, which were associated with SNB infection, were consistently emitted by both wheat varieties. Wheat plants infected with PM emitted significant amounts of 1-octen-3-ol and 3,5,5-trimethyl-2-hexene. Our study suggests that VOC blends could be used to classify wheat diseases. This is the first step toward a real-time disease detection in the field based on chemical signatures of wheat diseases.

Nanomaterials and nanotechnology for the delivery of agrochemicals: strategies towards sustainable agriculture

Nanomaterials (NMs) have received considerable attention in the field of agrochemicals due to their special properties, such as small particle size, surface structure, solubility and chemical composition. The application of NMs and nanotechnology in agrochemicals dramatically overcomes the defects of conventional agrochemicals, including low bioavailability, easy photolysis, and organic solvent pollution, etc. In this review, we describe advances in the application of NMs in chemical pesticides and fertilizers, which are the two earliest and most researched areas of NMs in agrochemicals. Besides, this article concerns with the new applications of NMs in other agrochemicals, such as bio-pesticides, nucleic acid pesticides, plant growth regulators (PGRs), and pheromone. We also discuss challenges and the industrialization trend of NMs in the field of agrochemicals. Constructing nano-agrochemical delivery system via NMs and nanotechnology facilitates the improvement of the stability and dispersion of active ingredients, promotes the precise delivery of agrochemicals, reduces residual pollution and decreases labor cost in different application scenarios, which is potential to maintain the sustainability of agricultural systems and improve food security by increasing the efficacy of agricultural inputs.

Insect pest management in the age of synthetic biology

Arthropod crop pests are responsible for 20% of global annual crop losses, a figure predicted to increase in a changing climate where the ranges of numerous species are projected to expand. At the same time, many insect species are beneficial, acting as pollinators and predators of pest species. For thousands of years, humans have used increasingly sophisticated chemical formulations to control insect pests but, as the scale of agriculture expanded to meet the needs of the global population, concerns about the negative impacts of agricultural practices on biodiversity have grown. While biological solutions, such as biological control agents and pheromones, have previously had relatively minor roles in pest management, biotechnology has opened the door to numerous new approaches for controlling insect pests. In this review, we look at how advances in synthetic biology and biotechnology are providing new options for pest control. We discuss emerging technologies for engineering resistant crops and insect populations and examine advances in biomanufacturing that are enabling the production of new products for pest control.

Production of Volatile Moth Sex Pheromones in Transgenic Nicotiana benthamiana Plants

Plant-based bioproduction of insect sex pheromones has been proposed as an innovative strategy to increase the sustainability of pest control in agriculture. Here, we describe the engineering of transgenic plants producing (Z)-11-hexadecenol (Z11-16OH) and (Z)-11-hexadecenyl acetate (Z11-16OAc), two main volatile components in many Lepidoptera sex pheromone blends. We assembled multigene DNA constructs encoding the pheromone biosynthetic pathway and stably transformed them into Nicotiana benthamiana plants. The constructs contained the Amyelois transitella AtrΔ11 desaturase gene, the Helicoverpa armigera fatty acyl reductase HarFAR gene, and the Euonymus alatus diacylglycerol acetyltransferase EaDAct gene in different configurations. All the pheromone-producing plants showed dwarf phenotypes, the severity of which correlated with pheromone levels. All but one of the recovered lines produced high levels of Z11-16OH, but very low levels of Z11-16OAc, probably as a result of recurrent truncations at the level of the EaDAct gene. Only one plant line (SxPv1.2) was recovered that harboured an intact pheromone pathway and which produced moderate levels of Z11-16OAc (11.8 μg g-1 FW) and high levels of Z11-16OH (111.4 μg g-1). Z11-16OAc production was accompanied in SxPv1.2 by a partial recovery of the dwarf phenotype. SxPv1.2 was used to estimate the rates of volatile pheromone release, which resulted in 8.48 ng g-1 FW per day for Z11-16OH and 9.44 ng g-1 FW per day for Z11-16OAc. Our results suggest that pheromone release acts as a limiting factor in pheromone biodispenser strategies and establish a roadmap for biotechnological improvements.

Physiological Synchrony of the Broad Bean Weevil, Bruchus rufimanus Boh., to the Host Plant Phenology, Vicia faba L

The aims of the study were to understand the physiological and phenological relationship between Bruchus rufimanus and Vicia faba in the perspective of IPM strategies. V. faba, an important food resource for humans and livestock is the main host plant of B. rufimanus. Adults feed on the pollen, females lay eggs on pods, and larvae develop into the seeds. Pending the blooming phase, the weevil may feed on the pollen from wild plants. Depending on the sowing date, the phenological time lag should lead the plant parts, most utilized by the weevil, less or more available during the key life stages of the pest. The aims of the study were therefore (1) to assess the impact of the sowing date (i.e., cultivars) on the phenological relationship between B. rufimanus and V. faba, and (2) to identify alternative pollen resources during the vegetative phase. Insects were collected weekly on two cultivars: winter-sown and spring-sown fields. Ovarian development, fecundity, and diet were monitored using dissected adults. Results showed that immature adults colonized the blooming winter-sown field and then 2 weeks later, the blooming spring-sown field. Sexual maturity of the weevils is related with V. faba pollen consumption. The sexual maturity of females increased with the growing density of flowers and the first pods were quickly covered with eggs. In spring-sown field, first pods grew 19 days later, while collected females in winter sown field had already laid most of their eggs. Feeding tests were carried using flowers collected from plants growing close to the fields: wild chervil, oilseed rape and wild Prunus. All this pollen were consumed by the weevils. The study showed a perfect synchrony between the host and the pest. Late sowing date and control of the early blooming wild plants surrounding the crops might reduce the attacks in field beans. More broadly, the study helps to understand the eco-ethology of the insect in cultivated areas.

Population Dynamics and Reproductive Developmental Analysis of Helicoverpa armigera (Lepidoptera: Noctuidae) Trapped Using Food Attractants in the Field

Monitoring adult populations of Helicoverpa armigera (Hübner) (Lepidoptera: Noctuidae), a major agricultural pest, provides data useful for its control. Food attractants, considered as adult insect behavior regulators based on the preference of an herbivorous pest for food sources or their volatiles, also have great potential for monitoring populations. To study the feasibility of monitoring the population dynamics and reproductive development of H. armigera in the field using food attractants, we quantitatively analyzed reproductive organ development of adults in a laboratory population as a way to predict the reproductive development of adults trapped using food attractants in the field in 2019 and 2020. The adults trapped using food attractants had obvious generational changes and the same trends in variation for females and males. The extent of ovarian development in trapped females tended to increase within each generation, and the major axis length of testis in trapped males tended to decrease. Reproductive developmental status of trapped adults also differed significantly among months. This study shows that by trapping H. armigera with food attractants, the population dynamics of adults in the field can be monitored, and reproductive anatomy can also be used to monitor adult reproductive status. These approaches are a new way to forecast the population dynamics of this pest.

The Future of Organic Insect Pest Management: Be a Better Entomologist or Pay for Someone Who Is

Simple Summary

The Federal National Organic Program (NOP) guidelines for pest management can be viewed as constraining to certified organic growers giving them a “limited toolbox” relative to non-organic crop production systems. Certifying agencies work with individual growers in setting boundaries for acceptable pest management tactics and enforce compliance for annual certification, but the knowledge required to have a successful insect pest management program can be overwhelming for growers. Traditional grower educational programs are challenged in providing the needed one-on-one training and follow up to ensure growers successfully master current and adopt newly developed pest management tactics. Gaps in the guidelines, such as monitoring, if included, could aid in grower adoption of practices that inform better decision-making and efficacy. This review promotes the idea that these issues can be overcome by utilizing experiential learning programs to educate growers and paid professionals, such as a pest control advisor. If the pest control advisor is a valued partner in the educational and extension process, they can be an effective advocate, educator, mentor, and assessor reaching more growers than education/extension programs alone, thus, achieving the NOP’s philosophical goal of a production system managed to respond to site-specific conditions.

Abstract

Insect pest management in certified organic production systems presents considerable challenges for growers. The Federal National Organic Program (NOP) guidelines list acceptable tactics, but their effective use requires a considerable knowledgebase in entomology. The range of tactics allowed by the NOP are viewed as limiting by many growers and there are important elements missing from the list such as pest monitoring and identification. Educational programs must consider utilizing instructional methods and additional means of outreach that introduce new pest management tactics that are individualized, regionally appropriate and emphasize grower adoption and collaboration with local professionals. This review describes the challenges and knowledge burden associated with the listed NOP pest management guidelines, provides an educational model that includes an additional level of professional support for enhanced adoption of novel pest management tactics, or refinement of current practices, with a special emphasis on the importance of insect pest population monitoring.

Optimization and field demonstration of the Lygus pratensis (Hemiptera: Miridae) sex pheromone

BACKGROUND

The plant bug Lygus pratensis Linnaeus is a widely distributed polyphagous herbivore that increasingly attains outbreak population levels on cotton in northwestern China. Although the sex pheromone of L. pratensis from the United Kingdom has been identified as hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal, at a ratio of 100:25:24, this volatile blend does not prove attractive to Chinese field populations.

RESULTS

In this study, we identified and optimized the sex pheromone of L. pratensis strains from northwestern China. In coupled gas chromatography and electro-antennogram detection (GC-EAD) assays, three compounds within whole-body extracts of virgin L. pratensis females elicited antennal responses: hexyl butyrate, (E)-2-hexenyl butyrate and (E)-4-oxo-2-hexenal. In field trials, a 20:1:30 ratio blend was the most attractive to L. pratensis males.

CONCLUSION

Traps baited with this synthetic pheromone blend present considerable advantages over traditional sweep-net sampling for L. pratensis population monitoring. It can readily be incorporated into monitoring schemes and integrated pest management packages.

Sublethal Effects of Chlorantraniliprole on Spodoptera litura (Lepidoptera: Noctuidae) Moth: Implication for Attract-And-Kill Strategy

The integrated use of plant-derived volatile attractants and synthetic insecticides in attract-and-kill programs is a useful tool for integrated pest management programs reducing pesticide input. Efficient alternative insecticides are critically needed to replace methomyl, which has been banned on cruciferous vegetables in China because it is also highly toxic to nontarget organisms. In the present study, among 15 commonly used insecticides were screened for toxicity against S. litura moths, where chlorantraniliprole, flubendiamide, and emamectin benzoate was found to have the highest levels of toxicity (LC₅₀ of 0.56, 3.85, and 6.03 mg a.i. L⁻¹ respectively). After exposure to the low lethal concentration LC₅₀ of chlorantraniliprole, fecundity of the moths was substantially reduced. Egg-hatching was lower for LC₂₀- and LC₅₀-treated moth pairs than for untreated control pairs. Net reproductive rate (R₀), intrinsic rate of increase (r), and finite rate of increase (λ) were significantly reduced in LC₅₀♀ × LC₅₀♂ cohorts. Larval mortality was significantly higher in subsequent generations in pairs of LC₅₀-treated moths. Chlorantraniliprole, which was most toxic and had significant sublethal effects on moths, can be used as an alternative insecticide to methomyl in the attracticide for controlling S. litura moths, and the LC₅₀ indicated a high potential for efficacy in the control S. litura through attract-and-kill schemes.

Long-Lasting Insecticide-Incorporated Netting and Interception Traps at Pilot-Scale Warehouses and Commercial Facilities Prevents Infestation by Stored Product Beetles

At any point along the post-harvest supply chain, commodities are vulnerable to insect infestation. This is due to a variety of factors, but includes landscape-scale movement of stored product insects to and from food facilities and natural refugia. Long-lasting insecticide-incorporated netting (LLIN) is an innovative tactic that may be used to intercept immigrating insects. LLIN can be used to cover gaps in architecture (e.g., vents, windows, eaves, or over pallets of goods) at food facilities. Another novel approach would be to use LLIN as a kill mechanism in attract-and-kill inspired interception traps on the perimeter of facilities. Furthermore, employing these two LLIN-based approaches together would create multiple protective barriers to reduce infestation in commodities. Therefore, the goal of the current study was to (1) examine the ability of interception traps to capture stored product insects at commercial wheat and rice food facilities, (2) assess whether LLIN deployment method affected efficacy in preventing infestation by stored product insects in pilot-scale warehouses, and (3) determine the success of using LLIN alone, interception traps alone, or both together to prevent infestations. Over 2 years, interception traps deployed for 48-h periods on the perimeter of commercial food facilities captured over 3,000 insects, representing 14 stored product insect taxa. Warehouses deploying LLIN exhibited an 89–93% and 98–100% reduction in insects reaching and progeny production in commodities, even after the release of 3,600 insects of three species over 12 weeks. The combined use of LLIN and interception traps did not improve control above LLIN alone, but this may be because insects could fly unencumbered, highlighting the importance of covering gaps with LLIN on food facilities.

Evaluating Behavioral Responses of Selected Stink Bugs (Hemiptera: Pentatomidae) to Spinosad

Southern green stink bug, Nezara viridula (L.) and redbanded stink bug, Piezodorus guildinii (Westwood) are two of the most important seed sucking pests affecting Louisiana soybean production and rice stink bug, Oebalus pugnax (F.) is an important late season pest in Louisiana rice. Exploration of chemicals that exhibit attraction or repellent activities toward major stink bug species would be beneficial in developing push-pull strategies. Spinosad is a commercially available natural insecticide that may have arrestant, attractant, or phagostimulant properties against stink bugs. To test this, a series of laboratory experiments were conducted to investigate the tactile, olfactory, and feeding responses of these stink bugs toward two commercial spinosad products (Entrust and Tracer) and technical grade spinosad. In tactile assays, female and male redbanded stink bug were arrested by Entrust, Tracer, and technical grade spinosad, whereas only rice stink bug and southern green stink bug males were arrested by Entrust. Y-tube assays revealed no attraction to any of the products by either male or female rice stink bug, redbanded stink bug, or southern green stink bug. In paired (treated or untreated soybean seed) feeding preference experiments, southern green stink bug showed no preference for any treatment, whereas redbanded stink bug fed more on Entrust- and Tracer-treated seed. From these results, spinosad appears to have an arrestant and phagostimulant effect on redbanded stink bug in the laboratory.

Progress Toward an Attract-and-Kill Device for Asian Citrus Psyllid (Hemiptera: Liviidae) Using Volatile Signatures of Citrus Infected With Huanglongbing as the Attractant

Asian citrus psyllid, Diaphorina citri (Kuwayama), preferentially orient toward citrus hosts infected with the phytopathogenic bacterium, Candidatus liberibacter asiaticus (CLas) the agent of citrus greening (Huanglongbing, HLB), compared to uninfected counterparts. We investigated whether this preference for the odors of infected plants could be useful for the development of an attract-and-kill (AK) device for D. citri. Twenty-nine blends of volatile organic compounds derived from the odor of citrus infected with CLas were tested in laboratory olfactometer tests, and two blends were also assessed under field conditions. A seven component blend of tricosane: geranial: methyl salicylate: geranyl acetone: linalool: phenylacetaldehyde: (E)-β-ocimene in a 0.40: 0.06: 0.08: 0.29: 0.08: 0.06: 0.03 ratio released from a proprietary slow-release matrix attracted twice more D. citri to yellow sticky traps compared with blank control traps. The attractive blend was subsequently co-formulated with spinosad insecticide into a slow-release matrix to create a prototype AK formulation against D. citri. This formulation effectively reduced the population density of D. citri up to 84% as measured with tap counts when deployed at a density of eight 2.5 g dollops per tree as compared with untreated controls in small plot field trials conducted in citrus orchards. Psyllid populations were not statistically affected at a deployment rate of four dollops per tree. Our results indicate that an AK formulation incorporating spinosad and a volatile blend signature of citrus greening into a slow-release matrix may be useful to suppress D. citri populations.

Visually and olfactorily enhanced attractive devices for thrips management

'Lure-and-infect' is an insect pest management strategy with high potential but so far there are few examples of its application. Using traps as surrogates for auto-dissemination devices, we tested the attractiveness to naturally occurring thrips (Thysanoptera: Thripidae) of three trap types differing in colour and structure, with and without the thrips lure methyl isonicotinate (MI), and sticky plate traps as a control. The aim was to find more effective traps that could be further developed into devices for auto-dissemination and lure-and-infect of thrips. The number of thrips captured varied substantially with trap type and the presence of the MI lure. We found a high visual response to a sticky 'white ruffle' trap (i.e., a 30-cm-long cylindrical outline of folded fabric), compared to a commonly used blue sticky plate trap (Bug-scan) as the control. This effect was seen both in a greenhouse with roses (Rosa spp.), where we encountered western flower thrips, Frankliniella occidentalis (Pergande), and in a grass field, where we encountered onion thrips, Thrips tabaci Lindeman, and New Zealand flower thrips, Thrips obscuratus (Crawford). In the absence of MI, the white ruffle trap caught 7-22× more thrips than the control Bug-scan trap. A similarly designed blue ruffle trap and a modified Lynfield trap caught lower thrips numbers than the white ruffle and the control Bug-scan traps. Presence of MI substantially increased the captures of T. tabaci in all three trap types in the field (2.5-18×). In the greenhouse, without MI the white ruffle trap caught 3.5-14× more thrips than the Bug-scan, blue ruffle, or modified Lynfield traps. Presence of MI increased the captures of F. occidentalis males and females in the Lynfield and blue ruffle traps (1.4-2.8×), but not in the white ruffle trap in the greenhouse (ca. 1.1×). The importance of visual and olfactory factors for the design of effective auto-dissemination and lure-and-infect strategies for thrips management is discussed.

Attract and kill: spinosad containing spheres to control onion maggot (Delia antiqua)

BACKGROUND

Onion maggot (Delia antiqua) is a pest of onions worldwide. Current means of managing this pest rely heavily on prophylatic insecticide treatments at planting. These options may not be viable in organic production systems or situations where insecticide-resistant populations occur. Here we explore the efficacy of an attract and kill strategy for control of D. antiqua evaluating the ability of attractive, spinosad containing spheres to kill adult D. antiqua and reduce crop losses.

RESULTS

Spinosad containing spheres were able to consistently kill D. antiqua adults over the course of the field season (mortality range: between 49% and 59% on average). Pairing spinosad spheres with Delia Lure increased efficacy by 72% compared with the spheres alone. Performance of this attract and kill strategy also can reduce damage by D. antiqua larvae in the field, but it did not achieve a level of control comparable to the level provided by a conventional insecticide treatment.

CONCLUSION

Implementation of this attract and kill strategy could be a valuable tool in situations where conventional pesticides are either not available or desired, where additional control techniques are needed, or to provide a season-long option for control of D. antiqua populations. © 2020 Society of Chemical Industry.

Exposure to essential oils and ethanol vapors affect fecundity and survival of two frugivorous fruit fly (Diptera: Tephritidae) pest species

Plant-derived compounds can be an environmentally friendly alternative to synthetic pesticide use for pest management. Essential oils (EOs) in several plant families have been found to be toxic to various pest species of insects through topical application, ingestion, and as fumigants. Previous studies revealed that, among various environmentally friendly insecticides, the EOs of Baccharis dracunculifolia and Pinus elliottii and an ethanol extract of Solanum granulosoleprosum plus Ricinus communis, were toxic to Ceratitis capitata and Anastrepha fraterculus (Diptera: Tephritidae) when applied topically to pupae or when ingested by adults. Here, we aimed to examine the potentially toxic effects of these plant-derived compounds when these two pestiferous fruit fly species were exposed to their vapors. We also examined their fumigant effect on female fecundity and fertility and compared it with water and ethanol controls. Exposure of C. capitata and A. fraterculus sexually mature adults to volatiles and vapors of both B. dracunculifolia and P. elliottii EOs resulted in lower longevity (half-life), survivorship, and female fecundity than the water vapor control. Toxicity of C. capitata was greater for P. elliottii than for B. dracunculifolia while the reverse was true for A. fraterculus. Exposure to vapors of S. granulosoleprosum + R. communis (S + R) had no effect on longevity but reduced survivorship of adults of both species. Interestingly, exposure to vapors of S + R, 50% (v/v) and pure ethanol resulted in greater fecundity of females of both frugivorous fly species than the water control. By contrast, fertility (% egg hatch) was in all cases high (>85%) and not different than the water control. Exposure to ethanol vapors appears to have similar effects on frugivorous tephritids as those reported on saprophagous and frugivorous species of Drosophila, a novel finding that may have important practical implications.

Odorant receptor phylogeny confirms conserved channels for sex pheromone and host plant signals in tortricid moths

The search for mates and food is mediated by volatile chemicals. Insects sense food odorants and sex pheromones through odorant receptors (ORs) and pheromone receptors (PRs), which are expressed in olfactory sensory neurons. Molecular phylogenetics of ORs, informed by behavioral and functional data, generates sound hypotheses for the identification of semiochemicals driving olfactory behavior. Studying orthologous receptors and their ligands across taxa affords insights into the role of chemical communication in reproductive isolation and phylogenetic divergence. The female sex pheromone of green budworm moth Hedya nubiferana (Lepidoptera, Totricidae) is a blend of two unsaturated acetates, only a blend of both elicits male attraction. Females produce in addition codlemone, which is the sex pheromone of another tortricid, codling moth Cydia pomonella. Codlemone also attracts green budworm moth males. Concomitantly, green budworm and codling moth males are attracted to the host plant volatile pear ester. A congruent behavioral response to the same pheromone and plant volatile in two tortricid species suggests co-occurrence of dedicated olfactory channels. In codling moth, one PR is tuned to both compounds, the sex pheromone codlemone and the plant volatile pear ester. Our phylogenetic analysis finds that green budworm moth expresses an orthologous PR gene. Shared ancestry, and high levels of amino acid identity and sequence similarity, in codling and green budworm moth PRs offer an explanation for parallel attraction of both species to the same compounds. A conserved olfactory channel for a sex pheromone and a host plant volatile substantiates the alliance of social and habitat signals in insect chemical communication. Field attraction assays confirm that in silico investigations of ORs afford powerful predictions for an efficient identification of behavior-modifying semiochemicals, for an improved understanding of the mechanisms of host plant attraction in insect herbivores and for the further development of sustainable insect control.

Host Plant and Antibiotic Effects on Scent Bouquet Composition of Anastrepha ludens and Anastrepha obliqua Calling Males, Two Polyphagous Tephritid Pests

In insects, the quality of sex pheromones plays a critical role in mating success and can be determined by the ability of larvae/adults to accrue chemical precursors. We tested the host-quality-effect hypothesis by analyzing the chemical composition of scent bouquets emitted by calling males of two polyphagous tephritid species (Anastrephaludens and A. obliqua) that originated from 13 fruit species representing diverse plant families. In A. ludens, we worked with an ancestral host (Rutaceae), nine exotic ones (Rutaceae, Anacardiaceae, Rosaceae, Solanaceae, Lythraceae), and two species never attacked in nature but that represent candidates for host-range expansion (Solanaceae, Myrtaceae). In A. obliqua, we tested an ancestral, a native, and an exotic host (Anacardiaceae), one occasional (Myrtaceae), and one fruit never attacked in nature (Solanaceae). We identified a core scent bouquet and significant variation in the bouquet’s composition depending on the fruit the larvae developed in. We also tested the possible microbial role on the scent bouquet by treating adults with antibiotics, finding a significant effect on quantity but not composition. We dwell on plasticity to partially explain our results and discuss the influence hosts could have on male competitiveness driven by variations in scent bouquet composition and how this could impact insect sterile technique programs.

Effects of advanced age on olfactory response of male and female Queensland fruit fly, Bactrocera tryoni (Froggatt) (Diptera: Tephritidae)

Olfaction is an essential sensory modality of insects which is known to vary with age. In short-lived insects odour response generally declines rapidly with increasing age, but how increasing age affects the olfactory response of long-lived insects is less known and there may be different life-time patterns of olfactory response. Here, we examine the effect of age on olfactory response and exploratory activity of a long-lived tephritid fruit fly, Bactrocera tryoni from sexual maturity (3 weeks) to advanced age (15 weeks). Males were tested against a male-specific attractant, cue-lure, which is associated with courtship and sexual selection in this species; while females were tested against guava-juice, a highly attractive oviposition host fruit odour. Trials were done in the laboratory using a Y-tube olfactometer at three weekly intervals. The probability of olfactory response of both males and females to tested odours declined with age. Males retained a constant attraction to cue-lure until 12 weeks of age, but then showed a significant drop in olfactory response at 15 weeks. However, females showed the highest attraction to guava-juice odour until six weeks of age and declined gradually thereafter. The change on odour response over time can be associated with an age-related change in initial locomotor activity for females as there was no change, over the life of the experiment, in selective female orientation to the odour source once flies started exploring within the olfactometer. However, for 15 week-old males, there was a simultaneous drop in both locomotor activity and selective olfactory orientation. The consistent attraction of male to cue-lure might be related to life-long reproductive activities of males, as males are thought to mate continuously during life. On the other hand, females' highest attraction to guava-juice odour in early life followed by a gradual decline might be linked with their oviposition rate which peaks in early life.

Drones: Innovative Technology for Use in Precision Pest Management

Arthropod pest outbreaks are unpredictable and not uniformly distributed within fields. Early outbreak detection and treatment application are inherent to effective pest management, allowing management decisions to be implemented before pests are well-established and crop losses accrue. Pest monitoring is time-consuming and may be hampered by lack of reliable or cost-effective sampling techniques. Thus, we argue that an important research challenge associated with enhanced sustainability of pest management in modern agriculture is developing and promoting improved crop monitoring procedures. Biotic stress, such as herbivory by arthropod pests, elicits physiological defense responses in plants, leading to changes in leaf reflectance. Advanced imaging technologies can detect such changes, and can, therefore, be used as noninvasive crop monitoring methods. Furthermore, novel methods of treatment precision application are required. Both sensing and actuation technologies can be mounted on equipment moving through fields (e.g., irrigation equipment), on (un)manned driving vehicles, and on small drones. In this review, we focus specifically on use of small unmanned aerial robots, or small drones, in agricultural systems. Acquired and processed canopy reflectance data obtained with sensing drones could potentially be transmitted as a digital map to guide a second type of drone, actuation drones, to deliver solutions to the identified pest hotspots, such as precision releases of natural enemies and/or precision-sprays of pesticides. We emphasize how sustainable pest management in 21st-century agriculture will depend heavily on novel technologies, and how this trend will lead to a growing need for multi-disciplinary research collaborations between agronomists, ecologists, software programmers, and engineers.

Natural Product Discovery by Direct Analysis in Real Time Mass Spectrometry

Direct analysis in real time mass spectrometry (DART MS) is one of the first ambient ionization methods to be introduced and commercialized. Analysis by DART MS requires minimal sample preparation, produces nearly instantaneous results, and provides detection over a broad range of compounds. These advantageous features are particularly well-suited for the inherent complexity of natural product analysis. This review highlights recent applications of DART MS for species identification by chemotaxonomy, chemical profiling, genetic screening, and chemical spatial analysis from plants, insects, microbes, and metabolites from living systems.