A 2-component blend of coconut oil-derived fatty acids as an oviposition deterrent against Drosophila suzukii (Drosophilidae: Diptera).

Coconut free fatty acid (CFFA), a mixture of 8 fatty acids derived from coconut oil, is an effective repellent and deterrent against a broad array of hematophagous insects. In this study, we evaluated the oviposition deterrent activity of CFFA on spotted-wing drosophila (SWD; Drosophila suzukii), a destructive invasive pest of berries and cherries, and identified bioactive key-deterrent compounds. In laboratory 2-choice tests, CFFA deterred SWD oviposition in a dose-dependent manner with the greatest reduction (99%) observed at a 20-mg dose compared with solvent control. In a field test, raspberries treated with 20-mg CFFA received 64% fewer SWD eggs than raspberries treated with the solvent control. In subsequent laboratory bioassays, 2 of CFFA components, caprylic and capric acids, significantly reduced SWD oviposition by themselves, while 6 other components had no effect. In choice and no-choice assays, we found that a blend of caprylic acid and capric acid, at equivalent concentrations and ratio as in CFFA, was as effective as CFFA, while caprylic acid or capric acid individually were not as effective as the 2-component blend or CFFA at equivalent concentrations, indicating the 2 compounds as the key oviposition deterrent components for SWD. The blend was also as effective as CFFA for other nontarget drosophilid species in the field. Given that CFFA compounds are generally regarded as safe for humans, CFFA and its bioactive components have potential application in sustainably reducing SWD damage in commercial fruit operations, thereby reducing the sole reliance on insecticides.

Coconut oil derived five-component synthetic oviposition deterrent for oriental fruit fly, Bactrocera dorsalis.

BACKGROUND: Bactrocera dorsalis, oriental fruit fly (OFF), is one of the most destructive agricultural pests. Although bait sprays can effectively control OFF, resistance development has been a concern. We evaluated the oviposition deterrent activity of coconut free fatty acids (CFFA), a mixture of eight coconut oil-derived fatty acids known to repel hematophagous insects and deter their feeding and oviposition, against OFF females. RESULTS: In laboratory 72-h two-choice assays using guava-juice infused-agar as an oviposition substrate, CFFA deterred OFF oviposition in a dose-dependent manner with the greatest reduction of 87% at 20 mg dose compared to the control. When the eight CFFA components were tested individually, four compounds (caprylic, capric, oleic, and linoleic acids) significantly reduced OFF oviposition ('negative-compounds'), two (lauric and myristic acids) had no effect ('neutral-compounds'), and two (palmitic and stearic acids) stimulated OFF oviposition ('positive-compounds'). In two-choice tests, the 'negative-compounds' blend failed to elicit the same level of oviposition reduction as CFFA at equivalent concentrations found in CFFA. Adding the two 'neutral-compounds' recovered the oviposition deterrence similar to CFFA. Subsequent subtraction tests showed that four 'negative-compounds' plus lauric acid was as effective as CFFA in reducing OFF oviposition in guava-juice agar. This five-component key-deterrent blend also reduced OFF oviposition by 95 and 72% on papaya and tomato fruit, respectively. CONCLUSION: CFFA acts as an oviposition deterrent for OFF. Given that CFFA compounds are generally regarded as safe for humans and the environment, CFFA and its bioactive components have potential use in behavioral control strategies against OFF. © 2023 Society of Chemical Industry. This article has been contributed to by U.S. Government employees and their work is in the public domain in the USA.

Selection for, and characterization of, malathion and zeta-cypermethrin resistance in vineyard-collected Drosophila melanogaster.

BACKGROUND: Drosophila melanogaster is a pest in vineyards because of its role in sour rot disease. Insecticides are commonly used, particularly late in the season, to control D. melanogaster and thus sour rot. Use of insecticides in vineyards and neighboring fruit production systems has led to the evolution of insecticide resistance in D. melanogaster, which is now widespread to commonly used insecticides like zeta-cypermethrin and malathion. Implementation of resistance management strategies is facilitated by an understanding of the mechanisms and genetics underlying the resistance. RESULTS: Starting with a vineyard-collected strain of D. melanogaster (NY18), we selected for a strain that was 1100-fold resistant to zeta-cypermethrin and one that was 40-fold resistant to malathion. Resistance was inherited as an incompletely dominant trait for zeta-cypermethrin. Resistance to malathion was inherited differently between reciprocal crosses. Insecticide bioassays using insecticide synergists found resistance to zeta-cypermethrin was partly suppressible with either piperonyl butoxide or S,S,S-tributylphosphorotrithionate, while resistance to malathion was unchanged by the synergists and mutations in Ace associated with the resistance were found. CONCLUSIONS: Resistance to zeta-cypermethrin is most likely due to enhanced detoxification, while the results with malathion were associated with two Ace alleles. How the newly selected strains can facilitate diagnostic tools for the identification of the mutations causing the resistance is discussed. © 2022 Society of Chemical Industry.

Using Red Panel Traps to Detect Spotted-Wing Drosophila and its Infestation in US Berry and Cherry Crops.

Spotted-wing drosophila (SWD), Drosophila suzukii Matsumura (Diptera: Drosophilidae), is an invasive pest of thin-skinned fruits in the United States. Monitoring traps are an integral part of SWD integrated pest management, allowing early detection and timely management of this pest. An ideal monitoring trap should be easy to use, effective in capturing SWD, sensitive and selective to male SWD which are easy to identify due to their spotted wings, and able to predict fruit infestation from trap captures. Deli-cup-based liquid traps (grower standard), which make in-situ observations difficult, were compared with red-panel sticky traps, both baited with commercial lures (Scentry, Trécé Broad-Spectrum (BS), and Trécé High-Specificity (HS)), across several US states in blueberries (lowbush and highbush), blackberry, raspberry, and cherry crops during 2018 and 2021. Results showed that red-panel traps effectively captured SWD, were able to detect male SWD early in the season while also being selective to male SWD all season-long, and in some cases linearly related male SWD trap captures with fruit infestation. Scentry and Trécé BS lures captured similar numbers of SWD, though Trécé BS and Trécé HS were more selective for male SWD in red panel traps than liquid traps in some cases. In conclusion, due to its ease of use with less processing time, red-panel traps are promising tools for detecting and identifying male SWD in-situ and for predicting fruit infestation. However, further research is needed to refine the trap captures and fruit infestation relationship and elucidate the trap-lure interactions in berry and cherry crops.

Effects of SmartWater, a fluorescent mark, on the dispersal, behavior, and biocontrol efficacy of Phytoseiulus persimilis.

New marking methods for studying small biocontrol agents (especially predatory mites) are needed because many current techniques are expensive, ineffective or not applicable to small organisms. The objective of this study was to determine whether SmartWater, a liquid and permanent fluorescent dye, can be used to mark Phytoseiulus persimilis for experimentation without any deleterious effects on its dispersal, behavior, reproduction, and biocontrol efficacy. Our results show that there were no significant differences in movement, inter-plant dispersal, feeding behavior, survivability, and reproduction between marked P. persimilis and control individuals sprayed with water. We also found that the SmartWater mark lasted for the duration of the mites' life, indicating strong durability over time. Marking efficacy may be reduced, due to a trade-off between batch marking efficacy and the possibility of drowning study organisms. However, we feel future research could improve liquid marking techniques that would reduce this risk. Overall, this study concludes that SmartWater could be a useful marking tool for predatory mites in both laboratory and field studies.

The effect of UVB-blocking plastics on the efficacy of Beauveria bassiana and a conventional product against Lygus lineolaris on low tunnel strawberry.

BACKGROUND: Effective, safe and practical biocontrol options are greatly needed for combating Lygus lineolaris on protected culture strawberry. This study demonstrated how ultaviolet (UV)-selective plastics can improve the efficacy of the fungal biocontrol agent Beauveria bassiana (Mycotrol) compared to the conventional insecticide acetamiprid (Assail) against L. lineolaris on low tunnel strawberry. RESULTS: We found that UVB-blocking treatments improved B. bassiana spore viability in both in vitro and in vivo laboratory experiments. In the field, survival of Mycotrol-treated sentinel L. lineolaris was lowest under UVB-blocking low tunnels, but this did not translate into significant differences among covering treatments in local L. lineolaris density or fruit damage. In contrast, applying the product Assail resulted in the lowest L. lineolaris density and highest quality yield compared to Mycotrol sprays. This was especially pronounced under low tunnels of any UV-limiting plastic. CONCLUSIONS: This study indicates that growing under low tunnels is a useful tool to improve the efficacy of conventional products and biopesticides containing microbial biocontrol agents. The efficacy of both products was improved under low tunnels, and specifically under UVB-blocking plastics for Mycotrol containing B. bassiana. However, there was little evidence that UVB plastics resulted in lower L. lineolaris densities and proportion of damaged fruit for either product in the field. Therefore we conclude that growing under any plastic covering is likely to benefit growers, but the economic value of growing under UVB tunnels is unclear. © 2022 Society of Chemical Industry.

Insecticide resistance in Drosophila melanogaster in vineyards and evaluation of alternative insecticides.

BACKGROUND: Cultivation of grapes is a major crop globally, particularly in support of the wine production industry which has significant economic impact in numerous countries. Sour rot is an economically important disease of grapes. It is caused by an interaction of yeast + acetic acid bacteria, and vectored by Drosophila spp. Substantial control of sour rot in wine grape vineyards has been achieved by control of Drosophila using insecticides such as zeta-cypermethrin. An outbreak of sour rot and high populations of Drosophila melanogaster were observed in 2018 in a vineyard in New York (Finger Lakes region), USA. Flies from this population were found to be resistant to zeta-cypermethrin (the active ingredient in Mustang Maxx®), but whether or not this was a widespread problem was not known. To determine if resistance was geographically limited, we surveyed populations of D. melanogaster collected from 11 vineyards across New York State and one in Missouri (USA). We also evaluated 19 alternative insecticides for their potential use for control of D. melanogaster, by determining their toxicity to a susceptible strain and by examining cross-resistance using a field-collected population. RESULTS: There were high levels of resistance to zeta-cypermethrin, malathion, and acetamiprid found in all populations sampled. Resistance to zeta-cypermethrin and malathion was stable over 33 months. Results from two vineyards also suggested that resistance to spinetoram was starting to evolve. The alternative insecticides we evaluated had LC50 values to the susceptible strain ranging from 0.65 to 15 000 ng·cm-2 . CONCLUSION: Resistance to zeta-cypermethrin, malathion, and acetamiprid is geographically widespread and the levels of resistance are similar between early season and late season collections. Cross-resistance was detected against all the insecticides tested, with the lowest levels seen for broflanilide, fipronil, and flumethrin. These patterns of resistance/cross-resistance/multiple resistance are discussed in terms of selection within and outside of vineyards. The implications of these results to insecticide resistance monitoring and management are discussed.

Population genomics of Drosophila suzukii reveal longitudinal population structure and signals of migrations in and out of the continental United States.

Drosophila suzukii, or spotted-wing drosophila, is now an established pest in many parts of the world, causing significant damage to numerous fruit crop industries. Native to East Asia, D. suzukii infestations started in the United States a decade ago, occupying a wide range of climates. To better understand invasion ecology of this pest, knowledge of past migration events, population structure, and genetic diversity is needed. In this study, we sequenced whole genomes of 237 individual flies collected across the continental United States, as well as several sites in Europe, Brazil, and Asia, to identify and analyze hundreds of thousands of genetic markers. We observed strong population structure between Western and Eastern US populations, but no evidence of any population structure between different latitudes within the continental United States, suggesting that there are no broad-scale adaptations occurring in response to differences in winter climates. We detect admixture from Hawaii to the Western United States and from the Eastern United States to Europe, in agreement with previously identified introduction routes inferred from microsatellite analysis. We also detect potential signals of admixture from the Western United States back to Asia, which could have important implications for shipping and quarantine policies for exported agriculture. We anticipate this large genomic dataset will spur future research into the genomic adaptations underlying D. suzukii pest activity and development of novel control methods for this agricultural pest.

Drosophila suzukii (Diptera: Drosophilidae): A Decade of Research Towards a Sustainable Integrated Pest Management Program.

Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) also known as spotted-wing drosophila (SWD), is a pest native to Southeast Asia. In the last few decades, the pest has expanded its range to affect all major European and American fruit production regions. SWD is a highly adaptive insect that is able to disperse, survive, and flourish under a range of environmental conditions. Infestation by SWD generates both direct and indirect economic impacts through yield losses, shorter shelf life of infested fruit, and increased production costs. Fresh markets, frozen berries, and fruit export programs have been impacted by the pest due to zero tolerance for fruit infestation. As SWD control programs rely heavily on insecticides, exceedance of maximum residue levels (MRLs) has also resulted in crop rejections. The economic impact of SWD has been particularly severe for organic operations, mainly due to the limited availability of effective insecticides. Integrated pest management (IPM) of SWD could significantly reduce chemical inputs but would require substantial changes to horticultural management practices. This review evaluates the most promising methods studied as part of an IPM strategy against SWD across the world. For each of the considered techniques, the effectiveness, impact, sustainability, and stage of development are discussed.

Field and Laboratory Testing of Feeding Stimulants to Enhance Insecticide Efficacy Against Spotted-Wing Drosophila, Drosophila suzukii (Matsumura).

The invasive spotted-wing drosophila, Drosophila suzukii (Matsumura), is a key insect pest of berries globally, causing lost revenues and increased production costs associated with applications of insecticides. The insecticides utilized are commonly broad-spectrum pyrethroids, organophosphates, or carbamates in conventionally managed fields and spinosad in organically managed fields. Adoption of more selective insecticides has been limited due to their lower residual activity, and the requirement that some must be ingested to be effective. We investigated the use of feeding stimulants for D. suzukii as a method to improve longevity and efficacy in a range of insecticides. In laboratory bioassays, sugar increased the efficacy of all chemical classes tested; however, the inclusion of yeast only showed a benefit with malathion. Feeding stimulants had a limited effect in some cases under field conditions. Similarly, infestation in field plots and a semifield bioassay showed no significant decreases in infestation with the inclusion of feeding stimulants for the insecticides tested in these trials. We discuss the implications of these findings for managing D. suzukii in fruit crops to help ensure the harvest of marketable fruit.

Winter warm-up frequency and the degree of temperature fluctuations affect survival outcomes of spotted-wing drosophila winter morphotypes.

Among overwintering Drosophila suzukii, discrete environmental changes in temperature and photoperiod induce a suite of biochemical changes conferring cold tolerance. However, little is known regarding how temperature fluctuations, which can influence metabolic and cellular repair activity, affect survival outcomes in this species. For that reason, we designed three experiments to test the effects of intermittent warm-up periods and the degree of temperature fluctuation on winter-morphotype (WM) D. suzukii survival. We found that at 5 °C, a temperature sufficient to induce reproductive diapause, but warm enough to allow foraging, increasing warm-up frequency (warmed to 25 °C at various interval schedules) was associated with decreased survival. In contrast, when the nightly low temperature was 0 °C, daily fluctuations that warmed the environment to temperatures above freezing (5, or 15 °C) appeared beneficial and resulted in improved survival compared to flies held at 0 °C during day and night. When we next evaluated cold tolerance using a 24-hour stress test assay (-5 °C), we found that again, thermal fluctuations improved survival compared to static freezing conditions. However, we also found that WM D. suzukii exposed to freezing temperatures during acclimation were less cold tolerant, regardless of the thermal fluctuation schedule, indicating that there may be tradeoffs between adequate acclimation temperature, which is required to induce cold tolerance, and the ensuing effects of incidental chill injury. Moving forward, these data, which account for the nuanced interactions between the thermal environment and in the internal physiology of D. suzukii, may help refine seasonal populations models, which aim to forecast pest pressure based on conditions the previous winter.

Grapevine Red Blotch Virus Is Transmitted by the Three-Cornered Alfalfa Hopper in a Circulative, Nonpropagative Mode with Unique Attributes.

The transmission mode of grapevine red blotch virus (GRBV, genus Grablovirus, family Geminiviridae) by Spissistilus festinus, the three-cornered alfalfa hopper, is unknown. By analogy with other members in the family Geminiviridae, we hypothesized circulative, nonpropagative transmission. Time-course experiments revealed GRBV in dissected guts, hemolymph, and heads with salivary glands after a 5-, 8-, and 10-day exposure to infected grapevines, respectively. After a 15-day acquisition on infected grapevines and subsequent transfer on alfalfa, a nonhost of GRBV, the virus titer decreased over time in adult insects, as shown by quantitative PCR. Snap bean proved to be a feeding host of S. festinus and a pseudosystemic host of GRBV after Agrobacterium tumefaciens-mediated delivery of an infectious clone. The virus was efficiently transmitted by S. festinus from infected snap bean plants to excised snap bean trifoliates (90%) or grapevine leaves (100%) but less efficiently from infected grapevine plants to excised grapevine leaves (10%) or snap bean trifoliates (67%). Transmission of GRBV also occurred trans-stadially but not via seeds. The virus titer was significantly higher in (i) guts and hemolymph relative to heads with salivary glands, and (ii) adults emanating from third compared with first instars that emerged on infected grapevine plants and developed on snap bean trifoliates. This study demonstrated circulative, nonpropagative transmission of GRBV by S. festinus with an extended acquisition access period compared with other viruses in the family Geminiviridae and marked differences in transmission efficiency between grapevine, the natural host, and snap bean, an alternative herbaceous host.

Identification of natural pathogens from wild Drosophila suzukii.

BACKGROUND: Drosophila suzukii (Matsumura, 1931) (spotted wing drosophila), an invasive species, has recently become a significant global pest of soft-skinned fruits such as berries. Unlike other Drosophila species, female D. suzukii have evolved a specialized sharp, serrated ovipositor that pierces and penetrates ripe and ripening fruits, causing them to lose commercial value and preventing their sale. A first step for the development of biological control agents for pest management may be achieved through the identification of microbes infectious for D. suzukii in the wild. RESULTS: We first determined that D. suzukii is susceptible to chemicals commonly used to rear Drosophilids in the laboratory and established a diet able to sustain healthy D. suzukii growth. Using this diet, we demonstrated that of 25 species of culturable bacteria and fungi isolated from field-collected D. suzukii, eight microbes decreased host survival when injected. Three of the eight bacteria (Alcaligenes faecalis, Achromobacter spanius and Serratia marcescens) were acutely pathogenic to both D. suzukii and Drosophila melanogaster adults by injection. Feeding of these bacteria resulted in susceptibility only in larvae. CONCLUSION: We successfully identified multiple microbes from field-collected D. suzukii that are pathogenic to both larvae and adults through different routes of infection, some of which could be candidates for biocontrol of this species. © 2020 Society of Chemical Industry.

Automated aerosol puffers effectively deliver 1-OCTEN-3-OL, an oviposition antagonist useful against spotted-wing drosophila.

BACKGROUND: Automated aerosol puffers releasing behaviorally active volatile organic compounds can deter insect pests in crops. During 2016, we tested the efficacy of aerosol puffer arrays emitting 1-octen-3-ol at reducing Drosophila suzukii oviposition in fall-bearing raspberries in Western New York State. During 2017, we compared the performance of aerosol puffers with a passive diffusion release method (vial dispensers), as well as puffer timing and placement within the field. RESULTS: During 2016, we found that octenol application in the field via aerosol puffer systems resulted in a 20% decrease in D. suzukii oviposition compared to control plots. During 2017, we found that aerosol puffers releasing octenol were 42-55% more effective than vial dispensers at deterring oviposition. We also found that a discontinuous application of octenol during dawn and dusk was sufficient to deter D. suzukii oviposition equivalent to continuous applications throughout the day. Although we observed no differences in infestation depending on puffer placement, low fly populations at the time of the trial may have affected the data. CONCLUSIONS: Our data indicate that automated aerosol puffer systems may reduce D. suzukii infestation to a greater extent than vial dispensers. If adopted, a discontinuous puffer release schedule may protect both economic and ecological interests by reducing the amount of material required to achieve efficacy. Further research on puffer placement is needed to determine whether perimeter applications are effective in larger scale field research and in combination with attractants as part of a push-pull management system.

2-Pentylfuran: a novel repellent of Drosophila suzukii.

BACKGROUND: Drosophila suzukii (Matsumura), spotted-wing drosophila (SWD), is a major invasive pest of soft-skinned fruits in North America and Europe. Although insecticides are currently the primary method of SWD control, it is imperative to develop alternative management approaches, such as behavioral control through the use of repellents and attractants. This study explores the repellent properties of 2-pentylfuran as an oviposition deterrent on raspberries. RESULTS: 2-Pentylfuran was found to be aversive to SWD in laboratory multiple-choice tests. When co-released from a vial (loaded as neat compound) with a synthetic SWD lure, 2-pentylfuran reduced SWD attraction to the SWD lure by 98% and the effect appeared 17% stronger compared to 1-octen-3-ol, a known SWD repellent. Releasing 50% 2-pentylfuran mixed with mineral oil from a vial located near ripe raspberries resulted in 30% reduction in SWD oviposition in the field. In laboratory no-choice assays, 2-pentylfuran reduced SWD oviposition on raspberries above 2.5 mg h-1 with greater repellency achieved at higher release rates. A release rate of 10 mg h-1 from a polyethylene sachet reduced egg-laying on raspberries by 60% in a semifield cage choice experiment. In a field experiment using fruiting raspberry clusters, 14 mg h-1 release rate of 2-pentylfuran was effective at reducing SWD infestations by 56% compared to untreated plots. CONCLUSION: 2-Pentylfuran acts as a repellent for SWD and can significantly reduce fruit infestations under field conditions and high SWD pressure. Given that 2-pentylfuran is a registered food additive and generally regarded as safe, 2-pentylfuran has a potential use in behavioral control strategies against SWD. Published 2020. This article is a U.S. Government work and is in the public domain in the USA.

The effectiveness of flower strips and hedgerows on pest control, pollination services and crop yield: a quantitative synthesis.

Floral plantings are promoted to foster ecological intensification of agriculture through provisioning of ecosystem services. However, a comprehensive assessment of the effectiveness of different floral plantings, their characteristics and consequences for crop yield is lacking. Here we quantified the impacts of flower strips and hedgerows on pest control (18 studies) and pollination services (17 studies) in adjacent crops in North America, Europe and New Zealand. Flower strips, but not hedgerows, enhanced pest control services in adjacent fields by 16% on average. However, effects on crop pollination and yield were more variable. Our synthesis identifies several important drivers of variability in effectiveness of plantings: pollination services declined exponentially with distance from plantings, and perennial and older flower strips with higher flowering plant diversity enhanced pollination more effectively. These findings provide promising pathways to optimise floral plantings to more effectively contribute to ecosystem service delivery and ecological intensification of agriculture in the future.

Behavioral evidence for contextual olfactory-mediated avoidance of the ubiquitous phytopathogen Botrytis cinerea by Drosophila suzukii.

Herbivorous insects may benefit from avoiding the smell produced by phytopathogens infecting plant host tissue if the infected tissue reduces insect fitness. However, in many cases the same species of phytopathogen can also infect host plant tissues that do not directly affect herbivore fitness. Thus, insects may benefit from differentiating between pathogen odors emanating from food and nonfood tissues. This is based on the hypothesis that unnecessarily staying attentive to pathogen odor from nonfood tissue may incur opportunity costs associated with not responding to other important survival functions. In this study adults of Drosophila suzukii Matsumura, an invasive larval frugivore, showed reduced attraction to the odor of raspberry fruit, a food tissue, when infected with Botrytis cinerea Pers., a ubiquitous phytopathogen, in favor of odors of uninfected raspberry fruit. Moreover, D. suzukii oviposited fewer eggs on infected raspberry fruit relative to uninfected raspberry fruit. Larval survival and adult size after eclosion were significantly reduced when reared on B. cinerea-infected raspberry relative to uninfected fruit. Interestingly, when the behavioral choice experiment was repeated using Botrytis-infected vs. -uninfected strawberry leaves, a nonfood tissue, in combination with fresh raspberry fruit, odor from B. cinerea-infected leaves did not reduce D. suzukii attraction to raspberries relative to raspberries with uninfected leaves. These behavioral results illustrate the important role context can play in odor-mediated interactions between insects, plants and microbes. We discuss implications of our findings for developing a repellent that can be useful for the management of D. suzukii.

Proximate Mechanisms of Host Plant Location by a Specialist Phytophagous Insect, the Grape Berry Moth, Paralobesia Viteana.

There are contrasting hypotheses regarding the role of plant volatiles in host plant location. We used the grape berry moth (GBM; Paralobesia viteana)-grape plant (Vitis spp.) complex as a model for studying the proximate mechanisms of long distance olfactory-mediated, host-plant location and selection by a specialist phytophagous insect. We used flight tunnel assays to observe GBM female in-flight responses to host (V. riparia) and non-host (apple, Malus domestica; and gray dogwood, Cornus racimosa,) odor sources in the form of plant shoots, extracts of shoots, and synthetic blends. Gas chromatography-electroantennographic detection and gas chromatography/mass spectrometry analyses were used to identify antennal-active volatile compounds. All antennal-active compounds found in grape shoots were also present in dogwood and apple shoots. Female GBM flew upwind to host and non-host extracts and synthetic blends at similar levels, suggesting discrimination is not occurring at long distance from the plant. Further, females did not land on sources releasing plant extracts and synthetic blends, suggesting not all landing cues were present. Additionally, mated and unmated moths displayed similar levels of upwind flight responses to all odor sources, supporting the idea that plant volatiles are not functioning solely as ovipositional cues. The results of this study support a hypothesis that GBM females are using volatile blends to locate a favorable habitat rather than a specific host plant, and that discrimination is occurring within the habitat, or even post-landing.

A QTL associated with leaf trichome traits has a major influence on the abundance of the predatory mite Typhlodromus pyri in a hybrid grapevine population.

The abundance of predatory phytoseiid mites, Typhlodromus pyri, important biological control agents of spider mite pests in numerous crops, is positively influenced by the density of leaf trichomes and tuft-form domatia in vein axils. Identification of the genetic regions controlling both trophic levels could facilitate the improvement of predatory mite habitat in breeding programs. The abundance of T. pyri and non-glandular trichomes was measured in a segregating F1 family derived from the cross of the complex Vitis hybrid, 'Horizon', with Illinois 547-1 (V. rupestris B38 × V. cinerea B9), finding positive correlation among traits. High density genetic maps were used to localize one major quantitative trait locus (QTL) on chromosome 1 of Illinois 547-1 associated with both predatory mite abundance and leaf trichomes. This QTL explained 23% of the variation in phytoseiid abundance and similar amounts of variance in domatia rating (21%), domatia size (16%), leaf bristle density (37% in veins and 33% in blades), and leaf hair density (20% in veins and 15% in blades). Another nine QTL distributed among chromosomes 1, 2, 5, 8, and 15 were associated solely with trichome density, and explained 7-17% of the phenotypic variation. Combined, our results provide evidence of the genetic architecture of non-glandular trichomes in Vitis, with a major locus influencing trichome densities, domatia size and predatory mite abundance. This information is relevant for breeding grapevines with a more favorable habitat for biological control agents.

Laboratory and Field Evaluation of Host-Related Foraging Odor-Cue Combinations to Attract Drosophila suzukii (Diptera: Drosophilidae).

The invasive spotted-wing drosophila, Drosophila suzukii (Matsumura), is a major pest of soft-skinned fruits. Since its introduction into North America and Europe, significant progress has been made in understanding the volatile cues used by this fly during food, oviposition site, and mate finding. Despite this progress, commercially available lures are non-selective. Here, we tested two Hanseniaspora uvarum (Niehaus) yeast compounds (isoamyl acetate and isobutyl acetate) and a leaf compound ß-cyclocitral alone and in combination with a blend of four fermentation compounds ('Fermentation lure': acetic acid, ethanol, methionol, and acetoin) to improve D. suzukii attraction and selectivity. In laboratory assays, males and females were attracted to all seven individual compounds, although in electrophysiological assays, their antennae exhibited a dose-dependent response to only four of these compounds. In two-choice cage studies, the Fermentation lure was more attractive to D. suzukii than water controls, whereas ß-cyclocitral and the mixture of isoamyl acetate and isobutyl acetate were not attractive in this larger-cage study. Moreover, adding the two-component H. uvarum compound blend to the Fermentation lure reduced D. suzukii attraction to the Fermentation blend. When these experiments were repeated in blueberry, raspberry, blackberry, and cherry orchards across several states in the United States over 2 yr, similar outcomes were observed: ß-cyclocitral or the mixture of the H. uvarum blend did not improve the attractiveness of the Fermentation lure or its selectivity. This study demonstrates that cues from different sources may interfere with each other and reduce D. suzukii attraction to otherwise attractive odor combinations.