Browsing by Subject "crop protection"

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    Assessing practical resistance and fitness costs of pyrethroid resistant soybean aphid
    (2022-02) Menger, James
    The soybean aphid remains the most economically important arthropod pest of soybean in the Upper Midwest Region even twenty years after its arrival in the United States. After years of sustained insecticidal pressures placed on the aphid, anecdotal reports of insecticides failing to control soybean aphid began to emerge, and resistance to the pyrethroid class of insecticides has since been documented in the laboratory. The reduction in the efficacy of field applications of pyrethroids against soybean aphid has not been thoroughly examined, nor the effects of this resistance on aphid fitness. A time-series was created of data from insecticide efficacy trials performed at two locations in Minnesota spanning 2005 – 2020 and changepoint-regression models were used to evaluate percent control over time. Also, the fitness of aphid populations displaying resistant and susceptible phenotypes to pyrethroid insecticides were compared across several experiments over three soybean growing seasons.
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    Community Characterization and Development of a Sampling Plan for Stink Bugs (Hemiptera: Pentatomidae) in Soybean in the North Central Region of the U.S.
    (2018-09) Pezzini, Daniela
    Stink bugs are an emerging threat for soybean production in the North Central Region of the U.S., which accounts for 80% of the country’s total soybean production. However, there is a lack of literature on stink bug community composition and management recommendations for the region. Therefore, my research aimed to fill the gap of region-specific literature and management recommendations for stink bugs by using data from 9 states of the North Central Region of the U.S. My first chapter characterized the species composition, abundance and temporal dynamics of stink bugs in the region. We demonstrated that the stink bug community is dominated by Euschistus spp. and Chinavia hilaris, and the invasive Halyomorpha halys was among the most abundant species in the eastern part of the region. Economically damaging infestations of stink bugs occurred in soybean fields in southern areas, and higher densities occurred at later soybean growth stages. Further aspects of stink bug management are addressed in my second chapter, where I assessed spatial patterns and developed fixed-precision sequential sampling plans for stink bugs in the North Central soybean. Results showed that stink bugs were aggregated, but extent of aggregation varied by species, life stage and location. We showed that 40 sample units (i.e., sets of 25 sweeps) would be needed for reliable stink bug estimation under the conditions experienced across the region. However, sample size recommendations could vary significantly by state depending on densities of stink bugs typically encountered. Also, we demonstrated that current sampling recommendations of 6 to 10 sample units may provide unreliable density estimation in some states. Overall, this is the first study to 1) characterize the stink bug community composition in soybean across the region and 2) develop cost-effective, research-based scouting recommendations for these pests. Results obtained from this thesis will provide important insights for the implementation of IPM for stink bugs in soybean in the North Central Region of the U.S.