Master of Science (MS)
The soybean looper, Chrysodeixis includens (Walker), is a defoliating insect pest of soybean in the Mid-South and Texas. In 2008, Louisiana producers reported unsatisfactory control of soybean loopers in soybean with methoxyfenozide. In 2009 and 2010, field collections from Louisiana, Missouri, Mississippi and Texas were exposed to discriminating concentrations (0.020 to 5.000 ai ìg/ml) of methoxyfenozide in diet incorporation bioassays. All field colonies were compared to a reference strain LC50 of 0.007 ìg/ml for 2009 and 0.008 ìg/ml for 2010. Louisiana populations exhibited LC50’s of 0.079 ìg/ml and 0.122 ìg/ml for 2009 and 2010, respectively, which were the highest values among all field collections during three years. The Missouri collections demonstrated the lowest LC50’s with 0.025 ìg/ml in 2009 and 0.011 ìg/ml in 2010. In general, results of these discriminating concentration tests indicated that all field collections showed elevated LC50’s compared to the reference colony. Additional field experiments were conducted to evaluate the efficacy of foliar insecticides against Louisiana soybean loopers. Significant differences among treatments for defoliation area were determined between lepidopteran specific and broad spectrum insecticides. For the 2009-10 experiment chlorantraniliprole had the lowest defoliation 3,7,14,21 and 28 days after treatment (DAT) (0.20, 0.20, 0.50, 0.57, 0.97 cm2) while lambda-cyhalothrin had the highest (1.12, 2.38, 2.06, 2.79, 2.25 cm2). In 2011, defoliation and days to 100% mortality were evaluated at two locations for R3 and R5 development stages. Chlorantraniliprole provided the lowest days to mortality (2.3) at R3 and (1.0) at R5 while oxadiazine resulted in the highest (5.7 and 6.0).
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Brown, Sebe Anthony, "Evaluating the efficacy of methoxyfenozide on Louisiana, Texas and the mid-southern soybean looper populations" (2012). LSU Master's Theses. 2781.