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Browsing by Author "Fleischer, S. J."

Now showing 1 - 3 of 3
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    Distribution of Cotesia rubecula (Hymenoptera: Braconidae) and its displacement of Cotesia glomerata in eastern North America
    Herlihy, M. V.; Van Driesche, R. G.; Abney, M. R.; Brodeur, J.; Bryant, A. B.; Casagrande, R. A.; Delaney, D. A.; Elkner, T. E.; Fleischer, S. J.; Groves, R. L.; Gruner, D. S.; Harmon, J. P.; Heimpel, G. E.; Hemady, K.; Kuhar, Thomas P.; Maund, C. M.; Shelton, A. M.; Seaman, A. J.; Skinner, M.; Weinzierl, R.; Yeargan, K. V.; Szendrei, Z. (Florida Entomological Society, 2012-06)
    A survey was conducted from May to Oct of 2011 of the parasitoid community of the imported cabbageworm, Pieris rapae (Lepidoptera: Pieridae), in cole crops in part of the eastern United States and southeastern Canada. The findings of our survey indicate that Cotesia rubecula (Hymenoptera: Braconidae) now occurs as far west as North Dakota and has become the dominant parasitoid of P. rapae in the northeastern and north central United States and adjacent parts of southeastern Canada, where it has displaced the previously common parasitoid Cotesia glomerata (Hymenoptera: Braconidae). Cotesia glomerata remains the dominant parasitoid in the mid-Atlantic states, from Virginia to North Carolina and westward to southern Illinois, below latitude N 38 degrees 48'. This pattern suggests that the released populations of C. rubecula presently have a lower latitudinal limit south of which they are not adapted.
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    Egg mass sampling plans for gypsy moth management programs
    Carter, Jane Louise (Virginia Tech, 1992-09-05)
    The goal of this research was to develop gypsy moth egg mass sampling plans that reflect the influence of habitat, changes in egg mass distribution, and provide populations densities or density categories for making control decisions. Sequential egg mass sampling plans for gypsy moth management programs in urban and suburban habitats were developed from 0.01 ha fixed-radius plot samples collected in Loudoun, Fairfax, and Arlington Counties, Virginia. The sampling plans were develop from Wald's sequential probability ratio test and is based on a negative binomial distribution. Operating characteristic and average sample number curves were used to determine the acceptability of the sampling plans. Three sampling plans were developed for the action thresholds of 618, 1,236, and 2,471 egg masses/ha. The use of binomial sampling for low density (<618 egg masses/ha) gypsy moth populations in continuously forested habitats was examined. Fixed- and variable-radius plot egg mass samples were collected in 28 study areas in Virginia, Maryland, and Massachusetts. The relationship between egg mass density and the proportion of trees with zero egg masses was developed. Binomial sampling resulted in a higher relative variability and lower relative efficiency than the fixed- and variable-radius plot sampling method. Binomial sampling was determined not to be an effective sampling method for gypsy moth populations below 618 egg masses/ha. Fixed- and variable-radius plot egg mass samples were taken when leaves were present (summer) and absent (winter) in 136 sample sites in Virginia. A significant difference between summer and winter counts was determined. The relationship between summer and winter counts was quantified using nonparametric Statistics. Winter egg mass counts were found to be 14 to 34 percent higher than summer egg mass counts . The probability of a summer egg mass count exceeding an action threshold was constructed by fitting a logistic curve to empirical data for the action thresholds of 618 and 1,236 egg masses/ha. Egg mass counts need to compensate for differences between summer and winter counts. Alternatively, the probability of a summer egg mass count exceeding an action threshold should be utilized.
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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.