Download or read book Characterization of Western Corn Rootworm coleoptera Chrysomelidae Susceptibility to Foliar Insectivides in Northeast Nebraska written by Timothy B. Dang and published by . This book was released on 2021 with total page 98 pages. Available in PDF, EPUB and Kindle. Book excerpt: The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte (Coleoptera: Chrysomelidae), is a major pest of maize in the United States. A variety of tactics are used to manage this pest such as crop rotation, insecticides, and transgenic maize expressing insecticidal proteins from Bacillus thuringiensis (Bt). WCR populations are highly adaptive and have evolved resistance to these management tactics. Management options are limited as few new tactics are available. Research is needed to evaluate the value of existing tactics used within an integrated framework to manage densities/injury and mitigate resistance. This study evaluated the field performance of formulated foliar insecticides (bifenthrin, chlorpyrifos) targeting adult WCR populations in northeast Nebraska during 2019-2020 with the focus on short and longer-term effects on density. Cohorts of fields were treated with a single application of foliar insecticide or left untreated as controls during the peak adult activity period, then sampled for WCR density before and after treatment. WCR densities, sex ratio, and proportion gravid females were not significantly different in treated and untreated fields prior to insecticide application. Results indicated within-season efficacy of insecticides was excellent as mean adult density was significantly reduced post-application in treated fields compared to control fields. An emergence cage study was conducted the following season to document the effect of foliar insecticides on adult survival. Total adult emergence was significantly reduced the following season in treated fields. Results suggest a single, properly timed insecticide application can reduce build-up of WCR density in continuous maize which would also reduce selection pressure on Bt maize where resistance occurs. A positive relationship between the sampling methods, whole plant counts and unbaited Pherocon AM sticky traps, was derived from the sample data. Susceptibility of adult WCR populations in northeast Nebraska was further characterized by conducting laboratory vial bioassays with bifenthrin, chlorpyrifos, and dimethoate to develop dose-response curves. Results confirmed that the WCR populations were relatively susceptible to the active ingredients with exception of a few populations exhibiting low levels of resistance. These data will serve as a baseline for comparison in future bioassays and inform WCR management programs.

Download or read book Characterization of Esterase mediated Insecticide Resistance in the Western Corn Rootworm Diabrotica Virgifera Virgifera LeConte Coleoptera Chrysomelidae written by Xuguo Zhou and published by . This book was released on 2002 with total page 344 pages. Available in PDF, EPUB and Kindle. Book excerpt:

Download or read book Spatial Variation in Western Corn Rootworm Coleoptera Chrysomelidae Susceptibility to Bacillus Thuringiensis Corn Events in Nebraska written by Jordan D. Reinders and published by . This book was released on 2017 with total page 112 pages. Available in PDF, EPUB and Kindle. Book excerpt: The western corn rootworm (WCR), Diabrotica virgifera virgifera LeConte, is an economically important pest species of field corn (Zea mays L.) in the U.S. Corn Belt. Yield losses and control costs exceed greater than $1 billion annually. Over the past 10+ years, growers have adopted transgenic corn hybrids expressing rootworm-active Bacillus thuringiensis (Bt) proteins as a primary WCR management tactic. Field-evolved resistance to Cry3Bb1 and mCry3A proteins expressed in single-trait Bt hybrids has been confirmed in some areas of Nebraska. Growers have used different tactics as needed to prevent or mitigate resistance, resulting in a mosaic of selection pressure placed on local populations. Currently, research is needed to characterize WCR susceptibility to these Bt toxins on a local spatial scale. Therefore, this study was conducted to characterize spatial variation in WCR susceptibility to Bt corn events in two corn-intensive production areas of Nebraska. Single-plant larval bioassays were conducted in 2016 and 2017 to characterize the susceptibility of populations from pre-established grids in Keith and Buffalo counties to single-trait Cry3Bb1 and mCry3A proteins. Bioassay results confirmed a mosaic of susceptibility to Cry3Bb1 and mCry3A existed within the two landscapes. Patterns at several spatial scales were observed and some gene flow of resistant alleles was indirectly documented in the landscape. A field history index, comprised of additive and weighted WCR management tactics and agronomic practices was developed in an attempt to explain variation in WCR susceptibility. Regression analyses indicated a strong relationship between past management practices and WCR survival on Cry3Bb1, indicating that localized selection pressure is a major contributing factor in determining current susceptibility. These two study areas can be viewed as model systems to draw potential inferences about the relationship of susceptibility to past Bt management histories. These retrospective case histories will inform use of current rootworm-Bt technologies and contribute to the future development of sustainable rootworm management strategies conducted within an IPM framework..