Assessing the impact of piercing-sucking pests on greenhouse-grown industrial hemp (Cannabis sativa L.).

Cannabis sativa or hemp, defined as <0.3% total tetrahydrocannabinol (THC), is a specialty crop in the United States, of particular interest among growers in the southeastern United States to replace tobacco production. Tetranychus urticae (twospotted spider mite), Aculops cannabicola (hemp russet mite), Polyphagotarsonemus latus (broad mites), and Phorodon cannabis (cannabis aphids) are considered the most significant pests in greenhouse grown hemp. Mite and aphid injury can cause cupping and yellowing of leaves, resulting in leaf drop, and reduced flower and resin production. We sought to understand the effects of feeding by T. urticae and Myzus persicae (green peach aphid), as a proxy for P. cannabis, on the concentration of economically significant cannabinoids through a series of experiments on greenhouse grown plants. First, we compared the variability of chemical concentrations in samples collected from individual plants versus pooled samples from 5 plants, and found that chemical concentrations in single plants were similar to those in pooled plant samples. Next, we compared chemical concentrations prior to arthropod infestation and post infestation. When evaluating the mite feeding damage in 2020, cannabinoids in plants infested with high densities of T. urticae increased more slowly than in uninfested control plants or plants infested with low T. urticae densities. In 2021, the concentration of tetrahydrocannabinol did not differ significantly between treatments. Cannabidiol increased more slowly in plants with low T. urticae densities when compared to uninfested controls but did not differ from the high T. urticae densities 14 days after infestation.

Moisture and soil type are primary drivers of Helicoverpa zea (Lepidoptera: Noctuidae) pupation.

Studies in the lab have demonstrated that evaluating the effect of soil moisture and other variables is essential for understanding the importance of environmental factors influencing the Heliothinae pupal stage, but simulated field studies are conducted infrequently. We compared the pupation of Helicoverpa zea (Boddie) (Lepidoptera: Noctuidae) under saturated and unsaturated conditions across 3 distinct soil types (coarse sand, high organic muck, and fine-textured clay) and observed adult emergence, as well as pupal depth and weight. The interaction between soil type and moisture had a significant effect on adult emergence. Fewer adults emerged from dry fine-textured clay soil than from dry coarse sand and high organic muck. However, there was no effect of soil type and no interaction between soil and moisture on pupal depth. Soil moisture was the primary driver of pupal depth, suggesting prepupae use moisture to mediate their position within the pupal chamber. In addition, pupal weight was unrelated to soil type, moisture, or their interaction. Our study demonstrates that soil moisture can be a greater driver of H. zea pupation than soil type, but additional observations are necessary to understand the mechanism by which moisture impacts pupation.

Comparing the effectiveness of different insecticide application orders for suppressing Drosophila suzukii Matsumura (Diptera: Drosophilidae) infestation: experimental and modeling approaches.

Drosophila suzukii Matsumura (Diptera: Drosophilidae) is a key pest of soft-skinned fruit such as blackberry and blueberry. Differing seasonal spray regimes are expected to have variable effects on D. suzukii populations. Semi-field cage trials were performed at three locations in the United States (Georgia, Oregon, and North Carolina) on blueberry and blackberry crops to evaluate this hypothesis. Insecticides with different efficacy rates (ZC - zeta-cypermethrin, SPI - spinetoram, CYAN - cyantraniliprole) were applied during field experiments conducted within large cages. Treatment schedules consisted of two insecticide applications which performed over three weeks. Seasonal treatment schedules were applied in the following order: ZC-CYAN and CYAN-ZC in rabbiteye and highbush blueberry with the addition of a ZC-SPI treatment applied in blackberry. In addition, a population model was applied to simulate the relative efficacy of the insecticide schedules in Oregon on D. suzukii population model based on previously published efficacy, biological, and weather parameters. Overall, all schedules resulted in reduced D. suzukii infestation compared to untreated control (UTC) treatments, with statistical differences in all three locations. The numerically lower infestation was found in some cases in ZC-CYAN schedule. Population modeling conducted exclusively for blueberry, and the simulations indicated no discernible differences between the two respective schedules (ZC-CYAN vs CYAN-ZC). The present study demonstrates that seasonal infestation of D. suzukii could be suppressed irrespective of application order. Additional research is required to assess the optimal timing and sequence of insecticide applications for controlling seasonal populations of D. suzukii in fruit crops. Such information could be invaluable for growers who are seeking to strategize their insecticide applications.

Plasticity in oviposition and foraging behavior in the invasive pest Drosophila suzukii across natural and agricultural landscapes.

The effects and extent of the impacts of agricultural insect pests in and around cropping systems is a rich field of study. However, little research exists on the presence and consequence of pest insects in undisturbed landscapes distant from crop hosts. Research in such areas may yield novel or key insights on pest behavior or ecology that is not evident from agroecosystem-based studies. Using the invasive fruit pest Drosophila suzukii (Matsumura) as a case study, we investigated the presence and resource use patterns of this agricultural pest in wild blackberries growing within the southern Appalachian Mountain range of North Carolina over 2 years. We found D. suzukii throughout the sampled range with higher levels of infestation (D. suzukii eggs/g fruit) in all ripeness stages in natural areas when compared with cultivated blackberry samples, but especially in under-ripe fruit. We also explored a direct comparison of oviposition preference between wild and cultivated fruit and found higher oviposition in wild berries when equal weights of fruit were offered, but oviposition was higher in cultivated berries when fruit number was equal. Forest populations laid more eggs in unripe wild-grown blackberries throughout the year than populations infesting cultivated berries. This suggests D. suzukii may change its oviposition and foraging behavior in relation to fruit type. Additionally, as D. suzukii exploits a common forest fruit prior to ripeness, further research is needed to explore how this affects wild food web dynamics and spillover to regional agroecosystems.

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.

Monitoring of Spotted-Wing Drosophila (Diptera: Drosophilidae) Resistance Status Using a RAPID Method for Assessing Insecticide Sensitivity Across the United States.

Drosophila suzukii (Matsumura) has spread rapidly, challenging berry and cherry crop production due to its ability to lay eggs into ripening fruit. To prevent infestation by this pest, insecticides are applied during fruit ripening and harvest. We field-tested the Rapid Assessment Protocol for IDentification of resistance in D. suzukii (RAPID) on seventy-eight populations collected across eight U.S. states in 2017 and 2018. Exposure to LC50 rates of malathion, methomyl, spinetoram, spinosad, and zeta-cypermethrin led to average female fly mortality of 25.0% in 2017, and after adjusting concentrations the average was 39.9% in 2018. Using LC99 × 2 discriminating concentrations in 2017 and LC90 × 8 rates in 2018, average female mortalities were 93.3% and 98.5%, respectively, indicating high overall susceptibility. However, using these high concentrations we found 32.0% of assays with survival of some female flies in 2017 and 27.8% in 2018. The adjustment in discriminating dose from 2017 to 2018 also reduced the proportion of assays with <90% survival from 17.6 to 2.9%. Populations with low mortality when exposed to spinosad were identified using this assay, triggering more detailed follow-up bioassays that identified resistant populations collected in California coastal region berry crops. Widespread evaluations of this method and subsequent validation in California, Michigan, and Georgia in 2019-2021 show that it provides a quick and low-cost method to identify populations of D. suzukii that warrant more detailed testing. Our results also provide evidence that important insecticide classes remain effective in most U.S. regions of fruit production.

Stakeholder engagement to inform the risk assessment and governance of gene drive technology to manage spotted-wing drosophila.

Emerging biotechnologies, such as gene drive technology, are increasingly being proposed to manage a variety of pests and invasive species. As one method of genetic biocontrol, gene drive technology is currently being developed to manage the invasive agricultural pest spotted-wing drosophila (Drosophila suzukii, SWD). While there have been calls for stakeholder engagement on gene drive technology, there has been a lack of empirical work, especially concerning stakeholder engagement to inform risk assessment. To help address this gap and inform future risk assessments and governance decisions for SWD gene drive technology, we conducted a survey of 184 SWD stakeholders to explore how they define and prioritize potential benefits and potential adverse effects from proposed SWD gene drive technology. We found that stakeholders considered the most important potential benefits of SWD gene drive technology to be: 1) Decrease in the quantity or toxicity of pesticides used, and 2) Decrease in SWD populations. Stakeholders were most concerned about the potential adverse effects of: 1) Decrease in beneficial insects, 2) Increase in non-SWD secondary pest infestations, and 3) Decrease in grower profits. Notably, we found that even stakeholders who expressed support for the use of SWD gene drive technology expressed concerns about potential adverse effects from the technology, emphasizing the need to move past simplistic, dichotomous views of what it means to support or oppose a technology. These findings suggest that instead of focusing on the binary question of whether stakeholders support or oppose SWD gene drive technology, it is more important to identify and assess the factors that are consequential to stakeholder decision making - including, for example, exploring whether and under what conditions key potential adverse effects and potential benefits would result from the use of SWD gene drive technology.

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.

Global patterns in genomic diversity underpinning the evolution of insecticide resistance in the aphid crop pest Myzus persicae.

The aphid Myzus persicae is a destructive agricultural pest that displays an exceptional ability to develop resistance to both natural and synthetic insecticides. To investigate the evolution of resistance in this species we generated a chromosome-scale genome assembly and living panel of >110 fully sequenced globally sampled clonal lines. Our analyses reveal a remarkable diversity of resistance mutations segregating in global populations of M. persicae. We show that the emergence and spread of these mechanisms is influenced by host-plant associations, uncovering the widespread co-option of a host-plant adaptation that also offers resistance against synthetic insecticides. We identify both the repeated evolution of independent resistance mutations at the same locus, and multiple instances of the evolution of novel resistance mechanisms against key insecticides. Our findings provide fundamental insights into the genomic responses of global insect populations to strong selective forces, and hold practical relevance for the control of pests and parasites.

Plasticity in Oviposition Site Selection Behavior in Drosophila suzukii (Diptera: Drosophilidae) in Relation to Adult Density and Host Distribution and Quality.

Flexibility in oviposition site selection under temporally shifting environmental conditions is an important trait that allows many polyphagous insects to flourish. Population density has been shown to affect egg-laying and offspring fitness throughout the animal kingdom. The effects of population density in insects have been suggested to be mutualistic at low densities, whereas intraspecific competition is exhibited at high densities. Here, we explore the effects of adult crowding and spatial resource variation on oviposition rate in the invasive pest Drosophila suzukii (Matsumura). In a series of laboratory experiments, we varied the density of adult males and females while holding oviposition substrate availability constant and measured per female oviposition rate using high and low-quality substrates. We found that oviposition behavior was affected more by substrate than adult density, though both variables had significant effects. When we varied the spatial arrangement of whole raspberries, we observed differences in oviposition rate and egg distribution between the grouped and solitary female treatments. Our results suggest that social interactions encourage oviposition, especially when exposed to unfamiliar or unnatural substrates. These results highlight the compensating effect of increased oviposition rate per female as adult populations decline. They will help researchers and crop managers better understand in-field population dynamics throughout the season as population densities change.

Susceptibility of North Carolina Chloridea (Heliothis) virescens (Lepidoptera: Noctuidae) Populations From Flue Cured Tobacco to Chlorantraniliprole.

The tobacco budworm, Chloridea (Heliothis) virescens (F.), has evolved resistance to numerous insecticides in the field. In tobacco, chlorantraniliprole can be applied as either a preventative systemic soil application at or near transplant, or a foliar application timed to current treatment thresholds. With a novel mode of action chlorantraniliprole provides an option for rotation with other insecticides to reduce the probability of insecticide resistance development. However, specific usage patterns in tobacco have the potential to increase the risk of resistance development to this insecticide. In particular, soil applied treatments may expose C. virescens to sublethal concentrations of the insecticide. We studied chlorantraniliprole susceptibility in nine field populations and one laboratory strain of C. virescens using a diet incorporation bioassay. Mortality was measured at 7, 10, and 14 d after exposure. Our results demonstrated that bioassays should be evaluated at 14 d after exposure to optimize interpretation of the dose-response due to the antifeeding properties of chlorantraniliprole. We observed low variation within field-collected populations. Field populations were as susceptible as the laboratory strain; the resistance ratio at the 14-d evaluation for field-collected populations ranged from 1.01 to 1.05. A discriminating dose of 0.117, 0.080, and 0.070 µg a.i./g diet could be used at 7, 10, and 14 d, respectively. Larval growth varied between field populations. Two field populations continued growing on diet containing chlorantraniliprole and differed in size from the laboratory and other populations. Further evaluation of growth inhibition will be necessary.

Cultural Control of Drosophila suzukii in Small Fruit-Current and Pending Tactics in the U.S.

Spotted-wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), a vinegar fly of Asian origin, has emerged as a devastating pest of small and stone fruits throughout the United States. Tolerance for larvae is extremely low in fresh market fruit, and management is primarily achieved through repeated applications of broad-spectrum insecticides. These applications are neither economically nor environmentally sustainable, and can limit markets due to insecticide residue restrictions, cause outbreaks of secondary pests, and select for insecticide resistance. Sustainable integrated pest management programs include cultural control tactics and various nonchemical approaches for reducing pest populations that may be useful for managing D. suzukii. This review describes the current state of knowledge and implementation for different cultural controls including preventative tactics such as crop selection and exclusion as well as strategies to reduce habitat favorability (pruning; mulching; irrigation), alter resource availability (harvest frequency; sanitation), and lower suitability of fruit postharvest (cooling; irradiation). Because climate, horticultural practices, crop, and market underlie the efficacy, feasibility, and affordability of cultural control tactics, the potential of these tactics for D. suzukii management is discussed across different production systems.

Social signals mediate oviposition site selection in Drosophila suzukii.

The information that female insects perceive and use during oviposition site selection is complex and varies by species and ecological niche. Even in relatively unexploited niches, females interact directly and indirectly with conspecifics at oviposition sites. These interactions can take the form of host marking and re-assessment of prior oviposition sites during the decision-making process. Considerable research has focused on the niche breadth and host preference of the polyphagous invasive pest Drosophila suzukii Matsumura (Diptera: Drosophilidae), but little information exists on how conspecific signals modulate oviposition behavior. We investigated three layers of social information that female D. suzukii may use in oviposition site selection-(1) pre-existing egg density, (2) pre-existing larval occupation, and (3) host marking by adults. We found that the presence of larvae and host marking, but not egg density, influenced oviposition behavior and that the two factors interacted over time. Adult marking appeared to deter oviposition only in the presence of an unmarked substrate. These results are the first behavioral evidence for a host marking pheromone in a species of Drosophila. These findings may also help elucidate D. suzukii infestation and preference patterns within crop fields and natural areas.

Determining the Effect of Postharvest Cold Storage Treatment on the Survival of Immature Drosophila suzukii (Diptera: Drosophilidae) in Small Fruits.

We evaluated the effect of postharvest cold storage temperature (0.0-2.2°C) and duration (3-5 d) on pupal emergence of single life stage populations of laboratory-generated Drosophila suzukii (Matsumura) and mixed-age populations collected in the field from blackberries, blueberries, strawberries, and raspberries. For field-infested fruit, cold storage at any temperature and duration resulted in less pupal emergence compared with the control held at 20°C, but D. suzukii subjected to higher temperatures and shorter storage durations in caneberries had higher survival. When a single life stage of D. suzukii was exposed to cold storage, pupal emergence was significantly reduced across all fruit types held at 0°C and for most life stages and fruit types held at 1.5 and 2.2°C, dependent on the substrate. Freshly laid eggs exposed to cold storage produced the lowest pupal emergence. Our results suggest using cold storage treatment is an effective postharvest management strategy for small-fruit growers to use on-farm as part of an integrated program to manage D. suzukii infestation. An economic assessment was made to examine the profit implications of an investment in cold storage units to counter pest pressure. Results suggest that investment in a cold storage unit would breakeven in about 4 yr. On farms that already have cold storage installed, we estimated a $0.11/kg decrease in blueberry market price for holding fruit for 3 d. Together, this cost assessment will provide growers with the knowledge to make decisions based on infestation risk and the seasonal sale price of blueberries.

Seasonal polyphenism of spotted-wing Drosophila is affected by variation in local abiotic conditions within its invaded range, likely influencing survival and regional population dynamics.

Overwintering Drosophila often display adaptive phenotypic differences beneficial for survival at low temperatures. However, it is unclear which morphological traits are the best estimators of abiotic conditions, how those traits are correlated with functional outcomes in cold tolerance, and whether there are regional differences in trait expression.We used a combination of controlled laboratory assays, and collaborative field collections of invasive Drosophila suzukii in different areas of the United States, to study the factors affecting phenotype variability of this temperate fruit pest now found globally.Laboratory studies demonstrated that winter morph (WM) trait expression is continuous within the developmental temperature niche of this species (10-25°C) and that wing length and abdominal melanization are the best predictors of the larval abiotic environment.However, the duration and timing of cold exposure also produced significant variation in development time, morphology, and survival at cold temperatures. During a stress test assay conducted at -5°C, although cold tolerance was greater among WM flies, long-term exposure to cold temperatures as adults significantly improved summer morph (SM) survival, indicating that these traits are not controlled by a single mechanism.Among wild D. suzukii populations, we found that regional variation in abiotic conditions differentially affects the expression of morphological traits, although further research is needed to determine whether these differences are genetic or environmental in origin and whether thermal susceptibility thresholds differ among populations within its invaded range.

Diurnal and Seasonal Activity Patterns of Drosophilid Species (Diptera: Drosophilidae) Present in Blackberry Agroecosystems With a Focus on Spotted-Wing Drosophila.

Drosophilid species with different life histories have been shown to exhibit similar behavioral patterns related to locating and utilizing resources such as hosts, mates, and food sources. Drosophila suzukii (Matsumura) is an invasive species that differs from other frugivorous drosophilids in that females lay eggs in ripe and ripening fruits instead of overripe or rotten fruits. We hypothesized that there may be diurnal and/or seasonal patterns associated with the movement of drosophilid species into and out of crop fields and their attraction to fermentation-odor-based monitoring traps, and that D. suzukii would conform to similar patterns. To test these hypotheses, we deployed passive, 2-headed Malaise traps between crop fields and wooded edges to simultaneously catch flies moving into and out of crop fields. We also deployed monitoring traps with a fermentation-based bait between crop fields and wooded edges and within crop rows. Traps were deployed weekly in June-August in 2014 and 2015 at two commercial blackberry farm in Cleveland County, NC, and were checked hourly for 24 h, except during darkness. Both D. suzukii and other drosophilid species moved between crop fields and wooded edges and were attracted to monitoring traps primarily during the morning and evening hours. Whereas other drosophilids were captured in traps throughout the season, few D. suzukii were caught in traps until early to mid-July in both years and increased as the season progressed. Understanding D. suzukii movement and activity patterns is essential for the development of effective management strategies.

Effects of Interspecific Larval Competition on Developmental Parameters in Nutrient Sources Between Drosophila suzukii (Diptera: Drosophilidae) and Zaprionus indianus.

Two invasive drosophilids, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae) and Zaprionus indianus (Gupta) (Diptera: Drosophilidae) are expanding their geographic distribution and cohabiting grape production in the Mid-Atlantic. The ecological and economic impact of these two species within vineyards is currently unknown. Zaprionus indianus was presumably not capable of ovipositing directly into grapes because they lack a serrated ovipositor and may use D. suzukii oviposition punctures for depositing their own eggs. Therefore, an interspecific larval competition assay was performed at varying larval densities using commercial medium and four commonly grown wine grapes in Virginia to investigate the impact Z. indianus larvae may have on the mortality and developmental parameters of D. suzukii larvae. Zaprionus indianus did not affect D. suzukii mortality or development parameters even at high interspecific densities when reared in commercial medium, but it did cause higher D. suzukii mortality within grapes. Mortality was also influenced by the variety of grape in which the larvae were reared, with smaller grapes having the highest D. suzukii mortality. Presence of Z. indianus also increased development time to pupariation and adult emergence for most interspecific competition levels compared with the intraspecific D. suzukii controls. Pupal volume was marginally affected at the highest interspecific larval densities. This laboratory study suggests that competition from Z. indianus and grape variety can limit D. suzukii numbers, and the implications on D. suzukii pest management be further verified in the field.

Olive Fruit Fly, Bactrocera oleae (Diptera: Tephritidae), Attraction to Volatile Compounds Produced by Host and Insect-Associated Yeast Strains.

The olive fruit fly, Bactrocera oleae (Rossi), is one of the most damaging insect pests of olives worldwide, requiring the use of insecticides for fruit protection in many orchards. Olive fruit flies are attracted to volatile composunds, including a female-produced pheromone, and host-plant and bacterial volatiles. Preliminary laboratory bioassays were conducted for olive fruit fly attraction to over 130 yeast strains from among 400 that were isolated from B. oleae adults and larvae or other insects, infested olives, and potential feeding sites. Kuraishia capsulata, Scheffersomyces ergatensis, Peterozyma xylosa, Wickerhamomyces subpelliculosus, and Lachancea thermotolerans appeared to attract B. oleae as well or better than did torula yeast pellets (Cyberlindnera jadinii; syn. Candida utilis). Volatile compounds emitted by these yeast strains were chemically identified, and included isobutanol, isoamyl alcohol, 2-phenethyl alcohol, isobutyl acetate, and 2-phenethyl acetate. The behavioral response of B. oleae adults to these volatile compounds at three concentrations was tested in a laboratory Y-tube olfactometer. The same volatile compounds were also tested in the field. Isoamyl alcohol was more attractive than the other compounds tested in both laboratory and field bioassays. Isobutanol was not attractive to B. oleae in either laboratory bioassay or field bioassay. Identifying yeast volatiles attractive to the olive fruit fly may lead to development of a more effective lure for detection, monitoring, and possibly control of B. oleae.

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.