Browsing by Author "Weber, Donald C."

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    Ancient origin and conserved gene function in terpene pheromone and defense evolution of stink bugs and hemipteran insects
    Rebholz, Zarley; Lancaster, Jason; Larose, Hailey; Khrimian, Ashot; Luck, Katrin; Sparks, Michael E.; Gendreau, Kerry L.; Shewade, Leena; Koellner, Tobias G.; Weber, Donald C.; Gundersen-Rindal, Dawn E.; O'Maille, Paul; Morozov, Alexandre, V; Tholl, Dorothea (Pergamon-Elsevier Science, 2023-01)
    Insects use diverse arrays of small molecules such as metabolites of the large class of terpenes for intra-and inter -specific communication and defense. These molecules are synthesized by specialized metabolic pathways; however, the origin of enzymes involved in terpene biosynthesis and their evolution in insect genomes is still poorly understood. We addressed this question by investigating the evolution of isoprenyl diphosphate synthase (IDS)-like genes with terpene synthase (TPS) function in the family of stink bugs (Pentatomidae) within the large order of piercing-sucking Hemipteran insects. Stink bugs include species of global pest status, many of which emit structurally related 15-carbon sesquiterpenes as sex or aggregation pheromones. We provide evidence for the emergence of IDS-type TPS enzymes at the onset of pentatomid evolution over 100 million years ago, coinciding with the evolution of flowering plants. Stink bugs of different geographical origin maintain small IDS -type families with genes of conserved TPS function, which stands in contrast to the diversification of TPS genes in plants. Expanded gene mining and phylogenetic analysis in other hemipteran insects further provides evidence for an ancient emergence of IDS-like genes under presumed selection for terpene-mediated chemical interactions, and this process occurred independently from a similar evolution of IDS-type TPS genes in beetles. Our findings further suggest differences in TPS diversification in insects and plants in conjunction with different modes of gene functionalization in chemical interactions.
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    Biology of Chauliognathus spp. (Hentz) (Coleoptera: Cantharidae) in Virginia agroecosystems
    Catron, Katlyn Amos (Virginia Tech, 2021-05-17)
    Chauliognathus pensylvanicus (De Geer) and C. marginatus (Fabr.) are two of the most common species of cantharid beetles observed in agroecosystems in Virginia. Despite their widespread abundance and early recognition and description in the 1700s, little is known about their phenology and ecological role in agricultural systems. Immatures have been recorded feeding upon soft-bodied insects such as lepidopteran larvae, and adults frequently visit flowering plants, where they eat nectar and/or pollen. Beyond those observations, relatively little is known about these species, which are conspicuous elements on and around farms, though there is considerable potential for their use as pollinators and predators in a biological pest control context. I employed a phenological study to determine the period of C. marginatus activity in Southwestern Virginia, and found adults active on a variety of flowers from mid-May to late July. On these flowers, they spent a large percentage of their day mating or feeding, with significant differences in the percentage of beetles participating in behaviors based on time of day and beetle sex, but not based on month. The majority of C. marginatus observations occurred on narrowleaf mountain mint (Pycnanthemum tenuifolium Schrad.), poison hemlock (Conium maculatum L.), and wild bergamot (Monarda fistulosa L.). I also used a community science-based approach to evaluate the usage of host plants and flower colors by C. marginatus and C. pensylvanicus. Chauliognathus marginatus utilized white flowers more than expected based on their potential availability, while C. pensylvanicus utilized yellow flowers over all other flower colors and more than expected based on their potential availability. Communities of flowers available to and observed with C. marginatus and C. pensylvanicus differed significantly at the family and genus levels. Laboratory bioassays supported these conclusions regarding C. pensylvanicus color preference, but not C. marginatus color preference. Lastly, because of their susceptibility to nontarget chemical exposure in agroecosystems, I tested the efficacy of both organic and conventional vegetable insecticides against C. marginatus adults. The highest mortality was seen in the acetamiprid, flupyridifurone, sulfoxaflor, and imidacloprid treatments, which reached 97-100% mortality at two days after treatment. High mortality (60-97% two days after treatment) was also seen in the organic treatments containing azadirachtins, pyrethrins, and Chromobacterium subtsugae strain PRAA4-1T. Mortality in the Burkholderia spp. strain A396 and spinosad treatments was not significantly different from that of the controls, however, control mortality was relatively high in both assays.
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    Both the Squash Bug Anasa tristis and Horned Squash Bug Anasa armigera (Hemiptera: Coreidae) are Attracted to Vittatalactone, the Aggregation Pheromone of Striped Cucumber Beetle
    Weber, Donald C.; Haber, Ariela I.; Pasteur, Kayla; Boyle, Sean M.; Kuhar, Thomas P.; Cornelius, Mary L. (Oxford University Press, 2022-12)
    Vittatalactone, the aggregation pheromone of the striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae), is attractive to two species of squash bugs (Hemiptera: Coreidae), the squash bug Anasa tristis (DeGeer) and horned squash bug Anasa armigera (Say). In field trapping experiments in Maryland and Virginia, clear sticky traps baited with 1 mg of a synthetic 8-isomer mix of vittatalactone captured similar to 9x more of female A. tristis and of both sexes of A. armigera, whereas male A. tristis were not significantly attracted, compared to unbaited traps. A. armigera showed a distinct dose-response to vittatalactone lure loading in the late season, and this species was more attracted than A. tristis, based on comparison to captures from underneath wooden boards emplaced in adjacent fields. Results suggest that vittatalactone could be a 'keystone semiochemical' in colonization of cucurbit hosts by specialist herbivores, and may offer the opportunity for multi-species behavioral control as a component of integrated pest management in cucurbit crops.
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    Effect of Plastic Mulch Colors on Anasa tristis (Hemiptera: Coreidae) Population Dynamics in Summer Squash, Cucurbita pepo (Cucurbitales: Cucurbitaceae)
    Boyle, Sean M.; Alford, Adam M.; McIntyre, Kelly C.; Weber, Donald C.; Kuhar, Thomas P. (Oxford University Press, 2022-06)
    The squash bug, Anasa tristis (De Geer), is a serious pest of cucurbit crops across the United States, especially within summer squash (Cucurbita pepo L.) systems. Using their piercing sucking mouthparts, squash bugs feed on both leaf tissue and fruits, often leading to leaf necrosis, marketable fruit loss, and even plant death. To date, the relationship between squash bug presence and plasticulture has not been adequately investigated. This 2-yr study evaluated the effects of white, black, and reflective plastic mulch colors on the occurrence of all squash bug life stages and marketable zucchini yield in Virginia. In both years, A. tristis adults and egg masses were more numerous on zucchini plants grown in white and reflective plastic mulch compared to bare ground plants. Greater nymphal densities and marketable fruit yield were observed in certain plastic mulch treatments versus the bare ground treatment, yet these differences were not consistent in both years. Contrary to the repellency effects reflective mulches have on other cucurbit insect pests, our research suggests that reflective and other plastic mulch colors can negatively impact squash bug management, especially in regions with high A. tristis pressure. Our study offers new insights for cucurbit growers to use when considering whether they should implement plasticulture in their growing systems.
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    Effects of Selective Hemipteran-Targeting Insecticides and One Broad-Spectrum Insecticide on Squash Bug, 2018
    Boyle, Sean; Kuhar, Thomas P.; Weber, Donald C. (Oxford University Press, 2022-01-01)
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    Effects of Some Selective Hemipteran-Targeting Insecticides and One Broad-Spectrum Insecticide on the Parasitoid Hadronotus Pennsylvanicus, 2018
    Boyle, Sean; Kuhar, Thomas P.; Wilson, James; Weber, Donald C. (Oxford University Press, 2022-01-01)
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    Indigenous arthropod natural enemies of the invasive brown marmorated stink bug in North America and Europe
    Abram, Paul K.; Hoelmer, Kim A.; Acebes-Doria, Angelita L.; Andrews, Heather; Beers, Elizabeth H.; Bergh, J. Christopher; Bessin, Ric; Biddinger, David J.; Botch, Paul; Buffington, Matthew L.; Cornelius, Mary L.; Costi, Elena; Delfosse, Ernest S.; Dieckhoff, Christine; Dobson, Rachelyn; Donais, Zachary; Grieshop, Matthew; Hamilton, George; Haye, Tim; Hedstrom, Christopher; Herlihy, Megan V.; Hoddle, Mark S.; Hooks, Cerruti R. R.; Jentsch, Peter; Joshi, Neelendra K.; Kuhar, Thomas P.; Lara, Jesus; Lee, Jana C.; Legrand, Ana; Leskey, Tracy C.; Lowenstein, David; Maistrello, Lara; Mathews, Clarissa R.; Milnes, Joshua M.; Morrison, William R. III; Nielsen, Anne L.; Ogburn, Emily C.; Pickett, Charles H.; Poley, Kristin; Pote, John; Radl, James; Shrewsbury, Paula M.; Talamas, Elijah; Tavella, Luciana; Walgenbach, James F.; Waterworth, Rebeccah; Weber, Donald C.; Welty, Celeste; Wiman, Nik G. (2017-09)
    Since the establishment of the brown marmorated stink bug, Halyomorpha halys (Stal) (Hemiptera: Pentatomidae) in North America and Europe, there has been a large, multi-group effort to characterize the composition and impact of the indigenous community of arthropod natural enemies attacking this invasive pest. In this review, we combine 98 indigenous natural enemy datasets spanning a variety of sampling methods, habitats, and geographic areas. To date, the vast majority of H. halys biological control research has focused on the egg stage, using sentinel egg masses to characterize indigenous parasitoid and predator communities and their contribution to H. halys egg mortality. Although egg parasitism and predation levels by indigenous natural enemies are low (typically <10% each) in most surveys, total egg mortality attributable to natural enemies can be higher (typically between 5 and 25%; up to 83%)-even though these values were likely underestimated in most cases because some mortality due to biological control was not recognized. In North America, where the most data are available, it appears that the relative prevalence of different indigenous parasitoid species varies among habitat types, particularly between crop and non-crop habitats. Predator species responsible for egg mortality are much less commonly identified, but appear to include a wide variety of generalist chewing and sucking predators. To date, studies of natural enemies attacking H. halys nymphs and adults are relatively rare. Based on our review, we identify a number of key research gaps and suggest several directions for future research.
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    Integrated pest management of squash bug, Anasa tristis, for conventional and organic cucurbit systems in Virginia
    Boyle, Sean Michael (Virginia Tech, 2022-06-07)
    The squash bug, Anasa tristis De Geer (Hemiptera: Coreidae), is a serious pest of cucurbit crops across the US, especially within summer squash (Cucurbita pepo L.) systems. Using its piercing sucking mouthparts, squash bug feeds on both leaf tissue and fruits, potentially leading to leaf necrosis, seedling death, and yield loss. Currently, A. tristis management strategies in summer squash focus exclusively on insecticide applications. Given that continuous use of insecticides imposes negative side effects on many non-target species, the major objective of this dissertation was to identify new and understudied management strategies for minimizing A. tristis damage in Virginia summer squash. To accomplish this goal, we first performed experiments to test the effects of colored mulches on squash bug density. A two-year field replicated study conducted in 2019 and 2020 in southwest Virginia found that black, white, and reflective plastic mulch colors had no effect on squash bug adult, egg mass, or nymphal densities. Overall, we observed a broad plastic mulch effect, as summer squash plants grown in any plastic mulch color tended to harbor greater densities of squash bug life stages than plants grown on bare ground. Next, the potential of augmentative releases of egg parasitoid, Hadronotus pennsylvanicus Ashmead (Hymenoptera: Scelionidae) was assessed by deploying lab-reared parasitoids on organic farms growing summer squash in southeastern Virginia in 2020 and 2021. In both years, we found higher levels of A. tristis egg parasitism at H. pennsylvanicus release sites compared to sites where the parasitoids were not released. Further, higher egg parasitism at the release sites was observed within two weeks of the field deployment date. The third goal of this dissertation research was to characterize the relationship between squash bug life stages and marketable summer squash yield. In 2020 and 2021, summer squash fields were established in Whitethorne, Virginia and individual plants were labeled as either 'managed' or 'infested'. Managed plants were subject to weekly manual removal of all squash bug egg masses and nymphs, while infested plants were left to have natural densities of squash bug life stages. We performed weekly A. tristis surveys on all infested plants in both years and added H. pennsylvanicus surveys on infested and managed plants in 2021. Also, we collected all fruit produced by each plant. Managed plants were found to produce more marketable fruit and fewer squash bug-damaged fruit than infested plants. Linear regression analyses of initial two-week accumulated squash bug life stage counts displayed adult and nymph densities to be significantly associated with marketable fruit yield per plant. However, nymphs showed a considerably stronger relationship with marketable yield than did adults. Hadronotus pennsylvanicus was visually sampled during each of the eight sampling weeks, but did not exhibit high egg parasitism until the latter half of the sampling interval. Lastly, we evaluated the toxicity of reduced risk insecticides on A. tristis nymphs and H. pennsylvanicus adults. To do so, we conducted laboratory bioassays exposing nymphs to insecticide treated summer squash fruit and parasitoids to treated filter paper, and recorded mortality at 24, 48, and 72 h following initial exposure. Only one reduced risk insecticide, flupyradifurone, was found to be highly toxic to squash bug nymphs and nontoxic to the parasitoids. Overall, the results of these studies will offer much needed information to improve the success and sustainability of squash bug management programs, as well as provide a fundamental basis and spark motivation for future research in squash bug biological control.
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    Murgantia histrionica (Hahn): new trapping tactics and insights on overwintering survival
    DiMeglio, Anthony S. (Virginia Tech, 2018-12-19)
    Harlequin bugs are orange and black aggregation pheromone emitting stink bug pests, specifically of cole crops such as kale, broccoli and collards. This nearly loyal crop preference makes an interesting challenge for trapping them and helping farmers predict pest severity. Harlequin bugs can be found in much of North America, and are a serious problem in the southeastern United States. Presumably their persistence into northern regions is limited by extreme winters. In 2014 and 2015 the arctic polar vortex extended into mid-latitudes bringing a blanket of sustained sub-freezing temperatures to much of the United States. We used these events to determine effects of extreme winter weather on harlequin bug survival. In both years we observed nearly identical low temperatures of -15oC and this linked to high (80-96%) harlequin bug mortality. In the lab we measured exact lethal freezing temperatures in harlequin bugs (i.e. supercooling points) to see if a physiological metric could be used to predict overwinter survival. Harlequin bug adults froze and died at -10.4oC, and similarly, their larger juvenile stages freeze at -11.0oC. Freshly hatched harlequin bugs and unhatched eggs froze at considerably lower temperatures with eggs forming ice crystals at -23.2oC and recent hatches at -21.6oC. Now with an understanding of how harlequin bugs likely survive winter extreme, we can then work on developing a trap to tally their populations in the spring and predict summer and fall pest severity. In the lab and field, harlequin bug adults and large nymphs were more likely found on green and black colors, and statistically less frequently on yellow, white, purple or red colors with the exception of adult females, which were most attracted to red and green in the lab, but green and black in the field. To increase harlequin bug attraction to and termination at traps square corrugated plastic panels were wrapped with an insecticide netting and baited with harlequin bug aggregation pheromone, murgantiol. Bugs were effectively drawn to the panels, with green panels having significantly more dead harlequin bugs and fewer dead beneficial lady beetles (Coleoptera: Coccinellidae) at their base than yellow panels. Thus, green was chosen as the ideal trap color to use for another field experiment that evaluated three trap types -- a corrugated plastic square panel, pyramidal trap, and ramp trap -- each with three lure treatments, murgantiol alone or murgantiol plus a low or high rate of mustard oil. More bugs were killed with the pyramidal trap than with the panel trap or the ramp trap, and more bugs were killed at traps containing murgantiol combined with benzyl isothiocyanate than at those with murgantiol alone. This research demonstrated that with the proper visual elements and odors, harlequin bugs can be drawn to traps and effectively killed after contact with insecticide-incorporated netting.
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    De novo formation of an aggregation pheromone precursor by an isoprenyl diphosphate synthase-related terpene synthase in the harlequin bug
    Lancaster, Jason; Khrimian, Ashot; Young, Sharon; Lehner, Bryan; Luck, Katrin; Wallingford, Anna K.; Ghosh, Saikat Kumar B.; Zerbe, Philipp; Muchlinski, Andrew; Marek, Paul E.; Sparks, Michael E.; Tokuhisa, James G.; Tittiger, Claus; Köllner, Tobias G.; Weber, Donald C.; Gundersen-Rindal, Dawn E.; Kuhar, Thomas P.; Tholl, Dorothea (2018-09-11)
    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 (15,6S,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.
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    Parental host species affects behavior and parasitism by the pentatomid egg parasitoid, Trissolcus japonicus (Hymenoptera: Scelionidae)
    Boyle, Sean M.; Weber, Donald C.; Hough-Goldstein, Judith; Hoelmer, Kim A. (2020-10)
    The samurai wasp, Trissolcus japonicus, is the primary natural enemy of the invasive brown marmorated stink bug, Halyomorpha halys, in its native range of Asia. Laboratory tests have found that the wasp can parasitize numerous native pentatomid species in North America, yet many potentially influential factors involved with T. japonicus host acceptance and host suitability are understudied. In this study we evaluated the effects of host related semiochemicals and parental host species on T. japonicus host foraging behavior and host parasitism. To address possible influences of parental host species, separate parasitoid lines were established using H. halys and native predatory pentatomid Podisus maculiventris eggs as hosts. Female T. japonicus from both host types were exposed to soybean (Glycine max) leaf surfaces contaminated by adult kairomones of either host species in behavioral assays. Females from each host type were also subject to no-choice tests in which they were exposed to either H. halys or P. maculiventris egg masses in large mesh cages. Each female used in the no-choice tests was weighed and their right hind tibiae were measured to identify possible phenotypic plasticity. Results from the behavioral assays suggest that T. japonicus exhibits some degree of host fidelity while searching for hosts. Females which emerged from P. maculiventris eggs resided for equal amounts of time on leaves contaminated with kairomones from either stink bug species. Differences in no-choice test performance were not found between the two host types, as parasitism rates and host suitability were determined to be dependent on exposed host species and not the parasitoid parental host species. T. japonicus which emerged from H. halys possessed longer right hind tibiae and weighed roughly twice as much as wasps which emerged from P. maculiventris.
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    Sesquiterpene pheromone biosynthesis in stink bugs: An isopentenyl diphosphate synthase like protein produces the cyclic sesquiterpene alcohol precursor of the aggregation pheromone murgantiol in harlequin bug (Murgantia histrionica)
    Lancaster, Jason; Khrimian, Ashot; Young, Sharon; Lehner, Bryan; Luck, Katrin; Wallingford, Anna K.; Ghosh, Saikat Kumar B.; Zerbe, Philipp; Muchlinski, Andrew; Marek, Paul E.; Sparks, Michael E.; Tokuhisa, James G.; Tittiger, Claus; Köllner, Tobias G.; Weber, Donald C.; Gundersen-Rindal, Dawn E.; Kuhar, Thomas P.; Tholl, Dorothea (2018-08-23)
    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.
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    Spotted cucumber beetle (Diabrotica undecimpunctata howardi) is attracted to vittatalactone, the pheromone of striped cucumber beetle (Acalymma vittatum)
    Haber, Ariela I.; Pasteur, Kayla; Guzman, Filadelfo; Boyle, Sean M.; Kuhar, Thomas P.; Weber, Donald C. (Springer, 2023-01-01)
    Spotted cucumber beetle (Diabrotica undecimpunctata howardi; also known as southern corn rootworm) is a pest feeding on many crops, including cucurbits, corn (maize), peanuts, beans, and other crops and wild plants in North America. On cucurbit crops, where it co-occurs with striped cucumber beetle (Acalymma vittatum), both are key pests that vector Erwinia tracheiphila, a destructive pathogen that causes bacterial wilt. Here we deployed synthetic vittatalactone, the male-produced aggregation pheromone of A. vittatum, as lures in the field, to measure attraction of the target and non-target insects. Both sexes of D. u. howardi were strongly attracted to the vittatalactone lures (5–7.5-fold compared to blank trap) throughout the growing season in Maryland and Virginia, USA. Moreover, D. u. howardi was more attracted to live A. vittatum males feeding on squash plants than to plants with females or without any beetles, confirming the genuine organismal cross-attraction between these two key pests. The kairomonal attraction to vittatalactone suggests that it functions as a “keystone semiochemical,” mediating the colonization of cucurbits by multiple herbivore species. Such cross attraction could allow for use of vittatalactone in management of multiple pest species, with potential reduction of pesticide use in cucurbit crops.
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    Supercooling Points of Murgantia histrionica (Hemiptera: Pentatomidae) and Field Mortality in the Mid-Atlantic United States Following Lethal Low Temperatures
    DiMeglio, Anthony S.; Wallingford, Anna K.; Weber, Donald C.; Kuhar, Thomas P.; Mullins, Donald E. (2016-10)
    The harlequin bug, Murgantia histrionica (Hahn), is a serious pest of brassicaceous vegetables in southern North America. While this insect is limited in its northern range of North America, presumably by severe cold winter temperatures, specific information on its cold hardiness remains unknown. We determined the supercooling points (SCPs) for Maryland and Virginia adult populations and found no significant difference among these populations. SCPs were similar for adults ( = -10.35 A degrees C; 2.54) and early and late instar 11.00 C; rX 4.92) and between adult males and females. However, SCPs for first instars 21.56 C; rX 1.47) and eggs (X 23.24 C; rX1.00) were significantly lower. We also evaluated field survival of overwintering harlequin bug adults during extreme cold episodes of January 2014 and January 2015, which produced widespread air temperatures lower than -15 A degrees C and subfreezing soil temperatures in the Mid-Atlantic Region. After the 48-h episode in 2014, bug mortality in exposed field sites averaged 88%, compared to < 5% mortality of bugs sheltered in an unheated greenhouse (recorded minimum temperature 4.4 A degrees C). After the 2015 episode, 80% of adults that were established in the field the previous November and then sheltered in an unheated garage during the episode, died, in contrast to 96% mortality in exposed field sites. Our results provide new information on M. histrionica overwintering biology, and thermal limitations to its distribution, which leads to improved predictive capabilities to forecast pest severity.
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    Toward developing pheromone emitting trap crops: Metabolic engineering of an aggregation pheromone for enhanced attraction of Phyllotreta cruciferae
    LeBlanc, Sophie M. (Virginia Tech, 2021-09-08)
    Pheromone lures and trap crops are appealing pest management tools that use insect and/or plant volatiles to reduce pest populations on crops of interest. Generating pheromone-emitting trap plants may allow for a continuing and highly-specific attraction of insect pests without repeated and costly application of synthetic pheromones. These trap plants may also be used to develop area-wide pest management strategies. As a proof-of-principle study we tested the possibility of producing the pheromone of the crucifer flea beetle Phyllotreta cruciferae in transgenic plants. P. cruciferae is an important pest of Brassica crops. In the presence of a host plant, males emit an aggregation pheromone, which attracts both males and females. Himachaladiene, a sesquiterpene, has been identified as a key component of the aggregation pheromone of P. cruciferae. In a close relative, Phyllotreta striolata, the compound is synthesized by a two-step pathway with an isoprenyl diphosphate synthase (PsIDS3) making (Z,E)-farnesyl diphosphate (FPP), which is converted by a terpene synthase (PsTPS1) to himachaladiene. Transient transformation of N. benthamiana with PsIDS3-TPS1 co-localized to the plastid resulted in the emission of himachaladiene and other known PsTPS1 products. Daily emissions of himachaladiene were approximately 1 µg per plant, which is six-fold higher than emissions from individual male flea beetles. Stable transformation of Arabidopsis thaliana with the same vector construct resulted in transgenic plants that expressed PsTPS1 and PsIDS3 transcripts, but no himachaladiene or other PsTPS1 products were present in volatile collections or leaf extracts of these plants. Moreover, no PsTPS1 enzyme activity was observed, indicating that post-transcriptional/translational effects prevent proper expression or targeting of functional PsIDS3 and/or PsTPS1 proteins in A. thaliana. Overall, this study demonstrates that the key component of the P. cruciferae aggregation pheromone, himachaladiene, can be transiently produced and emitted in a plant system at rates that are biologically relevant for insect attraction. However, further work is required for the stable production of the pheromone in plants. In addition, preliminary results are presented for the development of simple two-choice arenas that may allow for assessment of the movement of beetles toward host plant leaf tissue. This work can inform future efforts in developing methods for the economic production of himachaladiene in a plant system or the establishment of transgenic plants for the production and deployment of himachaladiene in a field setting.
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    A Transcriptome Survey Spanning Life Stages and Sexes of the Harlequin Bug, Murgantia histrionica
    Sparks, Michael E.; Rhoades, Joshua H.; Nelson, David R.; Kuhar, Daniel; Lancaster, Jason; Lehner, Bryan; Tholl, Dorothea; Weber, Donald C.; Gundersen-Rindal, Dawn E. (MDPI, 2017-05-25)
    The harlequin bug, Murgantia histrionica (Hahn), is an agricultural pest in the continental United States, particularly in southern states. Reliable gene sequence data are especially useful to the development of species-specific, environmentally friendly molecular biopesticides and effective biolures for this insect. Here, mRNAs were sampled from whole insects at the 2nd and 4th nymphal instars, as well as sexed adults, and sequenced using Illumina RNA-Seq technology. A global assembly of these data identified 72,540 putative unique transcripts bearing high levels of similarity to transcripts identified in other taxa, with over 99% of conserved single-copy orthologs among insects being detected. Gene ontology and protein family analyses were conducted to explore the functional potential of the harlequin bug’s gene repertoire, and phylogenetic analyses were conducted on gene families germane to xenobiotic detoxification, including glutathione S-transferases, carboxylesterases and cytochrome P450s. Genic content in harlequin bug was compared with that of the closely related invasive pest, the brown marmorated stink bug, Halyomorpha halys (Stål). Quantitative analyses of harlequin bug gene expression levels, experimentally validated using quantitative real-time PCR, identified genes differentially expressed between life stages and/or sexes.
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    Trapping of Crucifer-Feeding Flea Beetles (Phyllotreta spp.) (Coleoptera: Chrysomelidae) With Pheromones and Plant Kairomones
    Weber, Donald C.; Konstantinov, Alexander S.; Khrimian, Ashot; Bier, Alexander D.; Lubenow, Lesley A.; Knodel, Janet J.; Haber, Ariela; Wallingford, Anna K.; Mason, James A. C.; Kuhar, Thomas P. (Oxford University Press, 2022-04-13)
    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.