Virginia Agricultural Experiment Station

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https://hdl.handle.net/10919/24235
The Virginia Agricultural Experiment Station conducts research on food and fiber systems, their impact on the environment, and their relation to the future needs of Virginia, the nation, and the world.

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Browsing Virginia Agricultural Experiment Station by Subject "0501 Ecological Applications"

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    Can the introduction of companion plants increase biological control services of key pests in organic squash?
    Lopez, Lorena; Liburd, Oscar (2021-07)
    Florida (USA) is a major producer of squash, Cucurbita pepo L. (Cucurbitaceae), with approximated 16% of the US production in 2019, valued at about 35 million USD. Major insect pests, including the sweetpotato whitefly MEAM1, Bemisia tabaci Gennadius (Hemiptera: Aleyrodidae), and the melon aphid, Aphis gossypii Glover (Hemiptera: Aphididae), jeopardize plant development and transmit viruses of economic importance that can cause up to 50% yield loss in squash crops. Pesticides are generally used for insect management in squash, but the development of insecticide resistance and their non-target effects are major concerns. A combination of non-pesticidal approaches was evaluated, including intercropping flowering plants, augmentation, and conservation biological control to manage key pests in organic squash. Refugia increased natural enemies around the squash; however, only a few beneficial arthropods moved from the companion plants towards the squash plants. Whitefly densities and squash silverleaf ratings were reduced, whereas natural enemies were more abundant when the predatory mite Amblyseius swirskii Athias-Henriot (Acari: Phytoseiidae) was released alone or together with sweet alyssum, Lobularia maritima (L.) Desv. (Brassicaceae). All companion plants used in this study increased natural enemies, but only African marigolds and sweet alyssum ultimately increased biological control activities.
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    Improved Trap Designs and Retention Mechanisms for Halyomorpha halys (Hemiptera: Pentatomidae)
    Rice, Kevin B.; Morrison, William R.; Short, Brent D.; Acebes-Doria, Angelita L.; Bergh, J. Christopher; Leskey, Tracy C. (Oxford University Press, 2018-10-01)
    Current monitoring systems for the invasive Halyomorpha halys (Stål) (Hemiptera; Pentatomidae) in orchard agroecosystems rely on ground-deployed tall black pyramid traps baited with the two-component H. halys aggregation pheromone and pheromone synergist. Pyramid traps are comparatively costly, require considerable time to deploy and service, and may not be best suited to grower needs. Therefore, we evaluated other traps for H. halys, including modified pyramid traps (lures deployed on the outside), a canopy-deployed small pyramid, a pipe trap, delta traps, and yellow sticky cards in 2015 and 2016 in commercial apple and peach orchards. We also compared various H. halys killing agents for use in standard pyramid trap collection jars, including VaporTape kill strips, cattle ear tags, and plastic netting treated with various pyrethroids. Finally, we evaluated the effect of positioning the lures inside versus outside the collection jar on standard pyramid traps on overall captures. Among trap types, modified pyramid and pipe traps were most effective, capturing more adults than all other trap designs. Adult captures in small canopy-deployed pyramid, delta, and yellow sticky traps were lower, but significantly correlated with the standard black pyramid. Placing lures on the outside of collection jars on pyramid traps resulted in significantly greater captures and insecticide-impregnated netting was as effective for retaining bugs as VaporTape strips. These studies demonstrate that trapping systems for H. halys can be simplified and improved by modifying the trap design, lure deployment location, and/or killing agent.
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    Influence of landscape factors and abiotic conditions on dispersal behavior and overwintering site selection by Halyomorpha halys (Hemiptera: Pentatomidae)
    Cullum, John; Nixon, Laura J.; Morrison, Wiilliam; Shrewsbury, Paula M.; Venugopal, V.; Martinson, Holly; Bergh, J. Christopher; Leskey, Tracy C. (2020-08-01)
    Since the initial detection of the invasive Halyomorpha halys (Stål) in the United States in the late 1990s, this insect has emerged as a severe agricultural and nuisance pest. Nuisance problems are due to adult dispersal to overwintering sites in the fall at which time they alight onto and eventually settle within humanmade structures in addition to natural harborage. This study examined how three factors, elevation, light, and moisture affected overwintering site selection by H. halys in the mid-Atlantic. Observational counts performed along elevational transects revealed elevation was significant predictor of H. halys abundance during both years of the study in 2014 and 2015 with more adults observed at higher elevations. Choice tests examining effects of moisture and light on settling behavior demonstrated H. halys settled within overwintering shelter boxes in significantly greater numbers when shelters were dry compared with those having moist conditions, and in darkened shelters compared with those augmented with LED lights. Our findings indicate that H. halys use cues at both landscape and very localized levels when seeking and selecting overwintering sites.
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    Sweet Corn Sentinel Monitoring for Lepidopteran Field-Evolved Resistance to Bt Toxins
    Dively, G. P.; Kuhar, Thomas P.; Taylor, Sally V.; Doughty, H. B.; Holmstrom, K.; Gilrein, D.; Nault, B. A.; Ingerson-Mahar, J.; Whalen, J.; Reisig, D.; Frank, Daniel L.; Fleischer, S. J.; Owens, David; Welty, C.; Reay-Jones, F. P. F.; Porter, P.; Smith, J. L.; Saguez, J.; Murray, S.; Wallingford, A.; Byker, H.; Jensen, B.; Burkness, E.; Hutchison, W. D.; Hamby, K. A. (Oxford University Press, 2021-02-01)
    As part of an insect resistance management plan to preserve Bt transgenic technology, annual monitoring of target pests is mandated to detect susceptibility changes to Bt toxins. Currently Helicoverpa zea (Boddie) monitoring involves investigating unexpected injury in Bt crop fields and collecting larvae from non-Bt host plants for laboratory diet bioassays to determine mortality responses to diagnostic concentrations of Bt toxins. To date, this monitoring approach has not detected any significant change from the known range of baseline susceptibility to Bt toxins, yet practical field-evolved resistance in H. zea populations and numerous occurrences of unexpected injury occur in Bt crops. In this study, we implemented a network of 73 sentinel sweet corn trials, spanning 16 U.S. states and 4 Canadian provinces, for monitoring changes in H. zea susceptibility to Cry and Vip3A toxins by measuring differences in ear damage and larval infestations between isogenic pairs of non-Bt and Bt hybrids over three years. This approach can monitor susceptibility changes and regional differences in other ear-feeding lepidopteran pests. Temporal changes in the field efficacy of each toxin were evidenced by comparing our current results with earlier published studies, including baseline data for each Bt trait when first commercialized. Changes in amount of ear damage showed significant increases in H. zea resistance to Cry toxins and possibly lower susceptibility to Vip3a. Our findings demonstrate that the sentinel plot approach as an in-field screen can effectively monitor phenotypic resistance and document field-evolved resistance in target pest populations, improving resistance monitoring for Bt crops.