Water Stress Influences Phytoestrogen Levels in Red Clover (Trifolium pratense) but Not Kura Clover (T. ambiguum).

Some forage legumes synthesize phytoestrogens. We conducted a glasshouse study to investigate how water stress (drought and waterlogging) influences phytoestrogen accumulation in red clover and kura clover. Compared to the red clover control, the 20 day drought resulted in an over 100% increase in the phytoestrogens formononetin and biochanin A, which together accounted for 91-96% of the total phytoestrogens measured. Waterlogging resulted in elevated concentrations of daidzein, genistein, and prunetin but not formononetin or biochanin A. Concentrations of phytoestrogens in kura clover were low or undetectable, regardless of water stress treatment. Leaf water potential was the most explanatory single-predictor of the variation in concentrations of formononetin, biochanin A, and total phytoestrogens in red clover. These results suggest that drought-stressed red clover may have higher potential to lead to estrogenic effects in ruminant livestock and that kura clover is a promising alternative low- or no-phytoestrogen perennial forage legume.

A Field Survey of Syrphid Species and Adult Densities on Annual Flowering Plants in the Northeastern United States.

With the long-term goal of exploring the viability of conservation biological control of cabbage aphid Brevicoryne brassicae (L.) (Hemiptera: Aphididae) in the northeastern United States, adult syrphid flies (Diptera: Syrphidae) were observed on several species of annual insectary plants at farm sites in Connecticut, Massachusetts, and New Hampshire. Insectary plant species included alyssum, Lobularia maritima (L.) (Brassicales: Brassicaceae), buckwheat, Fagopyrum esculentum (Moench) (Caryophyllales: Polygonaceae), phacelia, Phacelia tanacetifolia (Bentham) (Boraginales: Hydrophyllaceae), calendula, Calendula officinalis (L.) (Asterales: Asteraceae) and ammi, Ammi majus (L.) (Apiales: Apiaceae). Among these insectary plants, alyssum had the longest bloom period and attracted the most syrphids. We identified 21 species of syrphid flies from insectary plants. The three most prevalent species collected were the aphidophagous Toxomerus marginatus (Say) (Diptera: Syrphidae) (70.1% of samples) and T. geminatus (Say) (Diptera: Syrphidae) (8.8% of samples), as well as the non-aphidophagous Syritta pipiens (L.) (Diptera: Syrphidae) (13.1% of samples). The benefits of including these insectary plant species as a companion to Brassica (L.) (Brassicales: Brassicaceae) cropping systems are discussed.

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.

Trapping of Crucifer-Feeding Flea Beetles (Phyllotreta spp.) (Coleoptera: Chrysomelidae) With Pheromones and Plant Kairomones.

Flea beetles (Coleoptera: Chrysomelidae) of the genus Phyllotreta are major pests of cole crops, canola, and related crops in the mustard family (Brassicaceae). Adults may damage seedlings or larger crop plants, impairing crop growth, rendering crops unmarketable, or killing seedlings outright. The two major North American crucifer pest species, Phyllotreta striolata (F.) and Phyllotreta cruciferae (Goeze), have male-produced pheromones attractive to both female and male adults. We tested the racemic synthetic pheromones, himachaladiene and hydroxyhimachalanone, as well as the host-plant-produced allyl isothiocyanate, alone and in combination, with experimental trapping in Maryland, Virginia, and North Dakota, using clear and yellow sticky traps and the ground-based 'rocket' trap (modified from boll weevil trap). Phyllotreta striolata was consistently attracted to the hydroxyketone, and captures were often enhanced by allyl isothiocyanate (AITC), but its response to pheromones, AITC, and trap color were variable from state to state. Phyllotreta cruciferae was strongly attracted to AITC, but its response to pheromone components varied by state, and this species was found rarely at the Maryland site. Phyllotreta bipustulata (F.) was attracted to the diene component, a new finding for this species. Several other genera of flea beetles were captured, some showing response to the semiochemicals and/or color. Results will be helpful in monitoring and possibly population suppression; however, further research is necessary to develop more efficient syntheses, optimal lure loadings, combinations, and controlled release methods.

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.

Trap Cropping Harlequin Bug: Distance of Separation Influences Female Movement and Oviposition.

To evaluate perimeter trap crops for management of harlequin bug, Murgantia histrionica (Hahn), we undertook greenhouse and field experiments with mustard greens as trap crop for a collard cash crop. We confirmed that harlequin bugs prefer to immigrate to and reside on mustard. Females, however, in greenhouse cage experiments, 'commuted' to collards to lay their eggs. In separate spring and fall field plantings, using replicated 12 m by 12 m collard plots in 1-ha fields, we tested mustard planted as an adjacent perimeter trap crop, or a perimeter trap crop separated by 2 unplanted rows (2.3 m), or with no trap crop. Adults accumulated on the spring mustard crop but overall numbers remained low, with all collards sustaining <1% leaves damaged. In the fall, the separation of 2.3 m reduced oviposition on collards fourfold, and feeding damage approximately 2.5-fold, compared to collards with an adjacent trap crop. Fall control plots with no border trap crop showed even lower foliar damage; likely result of preferential immigration of harlequin bugs to mustard at the field scale, resulting in fewer bugs near the control treatment plots. Thus, the spatial arrangement of the mustard trap crop, and its separation from the cash crop, influences pest abundance and damage. A separated mustard border can reduce bug movement including female commuting and egg-laying, thus better protecting the collard cash crop. Future research should address reduction in area of trap crops, deployment of semiochemicals, and possible changes in timing, to promote trap cropping that is practical for grower implementation.

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.

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.

Toward the Integration of an Attract-and-Kill Approach with Entomopathogenic Nematodes to Control Multiple Life Stages of Plum Curculio (Coleoptera: Curculionidae).

Efforts to reduce insecticide inputs against plum curculio, Conotrachelus nenuphar, a key pest of apples in eastern North America, include perimeter-row insecticide sprays applied after the whole-orchard petal fall spray to manage dispersing adults and, more recently, insecticide sprays confined to odor-baited trap trees. Entomopathogenic nematodes (EPNs) are virulent to ground-dwelling stages of C. nenuphar, and may be applied to the ground underneath trap-tree canopies. Here, we (1) compared the efficacy of the odor-baited trap tree approach with grower-prescribed (=grower standard) sprays to manage C. nenuphar populations over a six-year period in seven commercial apple orchards in New England; and (2) assessed the performance of the EPN Steinernema riobrave at suppressing ground-dwelling stages of C. nenuphar. In addition, the performance of S. riobrave was compared against that of S. carpocapsae and S. feltiae in one year. Across the six years, percent fruit injury on trap tree plots averaged 11.3% on odor-baited trap trees and 1.4% on unbaited trees in grower standard plots, highlighting the ability of trap trees to aggregate C. nenuphar activity and subsequent injury. Mean percentage injury on fruit sampled from interior trees, the strongest measure of treatment performance, in trap tree plots did not differ significantly from that recorded on interior trees in grower standard spray plots (0.95 vs. 0.68%, respectively). Steinernema riobrave consistently reduced C. nenuphar populations as indicated by the significantly lower number of adult C. nenuphar that emerged from the soil, when compared to water control. Steinernema carpocapsae and S. riobrave performed similarly well, and both EPN species outperformed S. feltiae. Our combined findings indicate that an IPM approach that targets multiple life stages of C. nenuphar has the potential to manage this pest more sustainably in a reduced-spray environment.

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.

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.

Interactions among morphotype, nutrition, and temperature impact fitness of an invasive fly.

Invasive animals depend on finding a balanced nutritional intake to colonize, survive, and reproduce in new environments. This can be especially challenging during situations of fluctuating cold temperatures and food scarcity, but phenotypic plasticity may offer an adaptive advantage during these periods. We examined how lifespan, fecundity, pre-oviposition periods, and body nutrient contents were affected by dietary protein and carbohydrate (P:C) ratios at variable low temperatures in two morphs (winter morphs WM and summer morphs SM) of an invasive fly, Drosophila suzukii. The experimental conditions simulated early spring after overwintering and autumn, crucial periods for survival. At lower temperatures, post-overwintering WM lived longer on carbohydrate-only diets and had higher fecundity on low-protein diets, but there was no difference in lifespan or fecundity among diets for SM. As temperatures increased, low-protein diets resulted in higher fecundity without compromising lifespan, while high-protein diets reduced lifespan and fecundity for both WM and SM. Both SM and WM receiving high-protein diets had lower sugar, lipid, and glycogen (but similar protein) body contents compared to flies receiving low-protein and carbohydrate-only diets. This suggests that flies spend energy excreting excess dietary protein, thereby affecting lifespan and fecundity. Despite having to recover from nutrient depletion after an overwintering period, WM exhibited longer lifespan and higher fecundity than SM in favorable diets and temperatures. WM exposed to favorable low-protein diet had higher body sugar, lipid, and protein body contents than SM, which is possibly linked to better performance. Although protein is essential for oogenesis, WM and SM flies receiving low-protein diets did not have shorter pre-oviposition periods compared to flies on carbohydrate-only diets. Finding adequate carbohydrate sources to compensate protein intake is essential for the successful persistence of D. suzukii WM and SM populations during suboptimal temperatures.

Interactions Between Biotic and Abiotic Factors Affect Survival in Overwintering Drosophila suzukii (Diptera: Drosophilidae).

Drosophila suzukii Matsumura is an invasive species affecting berry crops and cherries throughout North America, South America, and Europe. Previous research suggests that in temperate climates, the overwintering success of D. suzukii is likely dependent on access to food, shelter, and adequate cold hardening. We performed a multi-state study under field conditions for two winters to determine whether D. suzukii sex, phenotype (summer-morphotype, winter-morphotype), and life stage (adults, pupae) affected survival over time while recording naturally-occurring spatial and temporal variation in temperature. Access to food was provided and the flies were buried under leaf litter. Baited traps were deployed to determine whether local populations of D. suzukii were active throughout the winter season. The duration of exposure, mean daily temperature, and cumulative time below freezing significantly affected survival. Below freezing, D. suzukii survival was significantly reduced, particularly in northern locations. In contrast, we observed sustained survival up to 10 wk in southern locations among adults and pupae. Biotic factors also significantly affected survival outcomes: female survival was greater than male survival, winter-morphotype survival was greater than summer-morphotype survival, and adult survival was greater than pupal survival. In the north, wild D. suzukii were captured only in early winter, while in the south they were found throughout the winter. These data suggest that although adult D. suzukii may overwinter in sheltered microclimates, this ability may be limited in regions where the ground temperature, or site of overwintering, falls below freezing for extended durations.

Overwintering Behavior of Drosophila suzukii, and Potential Springtime Diets for Egg Maturation.

Spotted wing drosophila, Drosophila suzukii (Matsumura) (Diptera: Drosophilidae), is a serious agricultural pest, which lays eggs in ripe and ripening fruits of several cultivated and wild host plants. Here we explore several factors that may be critical to winter survival and improve D. suzukii's ability to successfully overwinter in northern climates and reestablish populations in the spring. Cold acclimation improved mobility in low-temperature laboratory mobility assays and improved survivorship in two wintertime field studies. Acclimation improved survivorship in experiments where overwintering habitats were above ground level and where habitats were at soil level by 1.9- and 13.7-fold, respectively. Soil acts to buffer changes in temperature, and the groundcovers investigated here provided microclimates that were 1-2°C warmer than bare soil during chilling events, and roughly 5°C cooler than bare soil during warm spells. Acclimated flies preferred overwintering substrates with a food source (dropped apple) over any other substrate (leaf litter, barky sticks, or bare soil). Pigeon (Columba livia L.) droppings and mushrooms (Peziza sp.) were identified as potential overwintering protein sources in laboratory feeding studies. Laboratory-simulated winter stress negatively influenced return of female reproduction, so future assays should consider biologically relevant subjects.

De novo formation of an aggregation pheromone precursor by an isoprenyl diphosphate synthase-related terpene synthase in the harlequin bug.

Insects use a diverse array of specialized terpene metabolites as pheromones in intraspecific interactions. In contrast to plants and microbes, which employ enzymes called terpene synthases (TPSs) to synthesize terpene metabolites, limited information from few species is available about the enzymatic mechanisms underlying terpene pheromone biosynthesis in insects. Several stink bugs (Hemiptera: Pentatomidae), among them severe agricultural pests, release 15-carbon sesquiterpenes with a bisabolene skeleton as sex or aggregation pheromones. The harlequin bug, Murgantia histrionica, a specialist pest of crucifers, uses two stereoisomers of 10,11-epoxy-1-bisabolen-3-ol as a male-released aggregation pheromone called murgantiol. We show that MhTPS (MhIDS-1), an enzyme unrelated to plant and microbial TPSs but with similarity to trans-isoprenyl diphosphate synthases (IDS) of the core terpene biosynthetic pathway, catalyzes the formation of (1S,6S,7R)-1,10-bisaboladien-1-ol (sesquipiperitol) as a terpene intermediate in murgantiol biosynthesis. Sesquipiperitol, a so-far-unknown compound in animals, also occurs in plants, indicating convergent evolution in the biosynthesis of this sesquiterpene. RNAi-mediated knockdown of MhTPS mRNA confirmed the role of MhTPS in murgantiol biosynthesis. MhTPS expression is highly specific to tissues lining the cuticle of the abdominal sternites of mature males. Phylogenetic analysis suggests that MhTPS is derived from a trans-IDS progenitor and diverged from bona fide trans-IDS proteins including MhIDS-2, which functions as an (E,E)-farnesyl diphosphate (FPP) synthase. Structure-guided mutagenesis revealed several residues critical to MhTPS and MhFPPS activity. The emergence of an IDS-like protein with TPS activity in M. histrionica demonstrates that de novo terpene biosynthesis evolved in the Hemiptera in an adaptation for intraspecific communication.

Phenotypic Plasticity Promotes Overwintering Survival in A Globally Invasive Crop Pest, Drosophila suzukii.

Spotted wing drosophila, Drosophila suzukii Matsumura, is a major pest of small fruit worldwide in temperate and subtropical growing regions. In Northern climates, D. suzukii likely overwinters locally under leaf litter and snow pack, but our understanding of the factors affecting thermal susceptibility is limited. While previous investigations of thermal susceptibility in this species have employed conventional static acclimation protocols, we aimed to determine whether gradual cooling, or dynamic acclimation, may extend the limits of known thermal tolerance by more closely approximating naturally occurring shifts in temperature. First, we assessed survival among adult and pupal D. suzukii using static acclimation. Then, we re-assessed survival using a novel dynamic acclimation method. We found that while static acclimation was sufficient to induce cold tolerance, dynamic acclimation significantly improved survival at temperatures as low as -7.5 °C. Following static acclimation, the lower lethal limit of adult D. suzukii was -1.1 °C in winter morphotype (WM) adults compared to 1.7 °C in non-acclimated summer morphotype (SM) adults. Dynamic acclimation reduced the lower limit to -5 °C in SM flies. At the end of our study 50% of WM flies survived 72 h at -7.5 °C. Below 0 °C pupal survival declined significantly regardless of acclimation procedure. However, pupal acclimation improved survival outcomes significantly compared to non-acclimated pupae, suggesting that while juvenile diapause is unlikely, cold hardening likely benefits those flies which may develop into the overwintering WM population. These data suggest that the degree of cold hardening is proportional to the thermal environment, a finding previously unrecognized in this species. Given the economic impact of this pest, these data may have important implications for offseason population monitoring and management. We discuss how phenotypic plasticity may drive geographical range expansion, and the impact of climate change on the spread of this species.

Avoiding Unwanted Vicinity Effects With Attract-and-Kill Tactics for Harlequin Bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae).

In the development of an attract-and-kill approach for the management of harlequin bug (HB), Murgantia histrionica (Hahn), we evaluated attraction and retention of HB by pheromone-baited traps in the field. In release-recapture and on-farm experiments, traps with collard plants with lures-containing HB aggregation pheromone (murgantiol = 10,11-epoxy-1-bisabolen-3-ol) arrested and retained more HB than traps with either plant or lure. In order to avoid unwanted vicinity effects (increased feeding injury to neighboring crop plants due to halo or spillover effects), we also investigated two methods of retaining HB that were attracted to traps: a systemic toxicant (neonicotinoid applied to the trap plant as a drench) and a contact toxicant (long-lasting insecticidal netting [LLIN] with incorporated pyrethroid). More HB adults and more HB-feeding injury were observed on collard plants in the vicinity of lures compared with those neighboring lures in combination with a systemic toxicant. This difference indicates that improvements to trap retention acted to mitigate spillover effects, thereby avoiding unwanted vicinity effects. We also conducted laboratory assays in order to estimate the length of exposure to LLIN necessary to knock down HB adults and nymphs, calculating a knockdown time (KDT50) of 78.3, 2.6, and 2.1 s for females, males, and nymphs, respectively.

Fooling the Harlequin Bug (Hemiptera: Pentatomidae) Using Synthetic Volatiles to Alter Host Plant Choice.

Harlequin bug, Murgantia histrionica (Hahn) (Hemiptera: Pentatomidae), is a widespread pest that feeds on a variety of brassicaceous crops and other plants. To understand olfactory cues that mediate host-finding, and their possible utility in pest management, we deployed aggregation pheromone (mixed murgantiols = 10,11-epoxy-1-bisabolen-3-ols) and/or isothiocyanate (ITC) host plant volatiles with potted host plants and nonhost soybean, in field choice bioassays. Adults of both sexes were strongly attracted (10-31×) to collard host plants baited with pheromone lures, compared with unbaited collards, as were nymphs. Collard plants baited with lures containing allyl and/or benzyl-ITC showed a 1.3× and 1.9× increase in attractiveness, respectively, neither differing by life-stage nor sex; multiple lures showed additive attraction. Nonhost soybean, baited with pheromone lure, was 4.6-7.5× more attractive to adults than unbaited collard; conversely, baited collard was 124× more attractive than unbaited soybean. The stark difference in observed effect of pheromone lure between unpoisoned plants, and those poisoned with imidacloprid, indicated that attraction was underestimated by circa-daily counts of unpoisoned plants, presumably because if not poisoned, bugs rapidly abandoned the baited nonhost soybean plant. Results indicate that harlequin bugs can be misled to encounter and feed on nonhosts by their aggregation pheromone, but additional means may be needed to retain them. Attraction to hosts is increased both by the aggregation pheromone, and at least two host plant volatiles, allyl and benzyl-ITC. These results contribute to our knowledge of host finding in harlequin bug, and to possible trapping and trap cropping schemes for pest management.