Browsing by Author "Hutchison, W. D."

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    Cold Tolerance of Halyomorpha halys (Hemiptera: Pentatomidae) Across Geographic and Temporal Scales
    Cira, Theresa M.; Venette, Robert C.; Aigner, John D.; Kuhar, Thomas P.; Mullins, Donald E.; Gabbert, Sandra E.; Hutchison, W. D. (2016-04)
    The brown marmorated stink bug, Halyomorpha halys (Stål), is native to eastern Asia and is presently invading North America. Little is known about the exposure to and effects of winter temperatures in newly invaded regions on H. halys. The overwintering habitats that this species utilizes vary greatly in their thermal buffering capacity. They naturally overwinter in aggregations beneath loose bark on trees and in cliff outcroppings, but will also commonly aggregate in buildings. Effects of cold temperatures such as mortality and freezing have yet to be quantified in the invading population. We report that H. halys is chill intolerant (i.e., dies before reaching its freezing point), and that the degree of cold tolerance of populations in North America differs by season, sex, and acclimation location. The mean winter supercooling point (+/- SEM) of individuals acclimated in Minnesota was -17.06A degrees C A +/- 0.13 and in Virginia was -13.90A degrees C A +/- 0.09. By using laboratory assays of lower lethal temperatures and ambient air temperature records, we accurately forecasted mortality for field experiments in Minnesota and Virginia. Temperature refugia provided by human-built structures are likely crucial for overwintering survival during atypically cold winters and possibly contribute to the northern geographic range expansion of this economically damaging insect in the temperate climates of North America.
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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.