Gonzales, John David (2019-08). Evaluation of Commercial Grain Sorghum Hybrids and Commercial Insecticides for Control of the Sugarcane Aphid Melanaphis sacchari (Zehntner, 1897) (Hemiptera: Aphididae). Master's Thesis.
Thesis
Since the sugarcane aphid's (SCA) introduction in the United States in 2013 many management strategies have been evaluated and used for its control. In this study we evaluated hybrid resistance through a field screening, seedling screen, and reproduction study. For chemical control we found it necessary to develop baseline susceptibility data for two main insecticides used to control the SCA (Sulfoxaflor and Flupyradifurone). We also evaluated the residual activity of these insecticides with the addition of chlorpyrifos. Results from the hybrid field screen revealed ATx2752/RTx2783, R84353, R9813, SP6929, SP73B12, SP7715, SPX760, SP78M30, P-83P17, W-844-E, and DKS 37-07 exhibited resistance, showing no statistical differences in yield or cumulative aphid days between sprayed and non-sprayed plots. The seedling screen showed similar results to the field screen with most of the same hybrids showing tolerance to SCA colonization at a highly susceptible stage; however P-83P17 appeared to be susceptible to aphid colonization at the seedling stage. Results from the reproduction study showed that DKS 37-07 was the most resistant hybrid of the hybrids evaluated, with reduced intrinsic rate of increase compared to the other hybrids. DGM75GB39 appeared to be the most susceptible hybrid in all three evaluations. In the baseline susceptibility study the SCA appeared to be highly susceptible to both sulfoxaflor and flupyradifurone from 2014-2017, with slight shifts in susceptibility appearing due to environmental conditions and other factors besides potential resistance. In the residual activity study all three insecticides appeared to offer very good initial kill, however flupyradifurone offered the longest residual control providing approximately 10 days in 2015 and 7 days in 2016. Sulfoxaflor was similar in initial kill, however it only provided approximately 5 days in 2015 and 2 days in 2016. Chlorpyrifos was similar to sulfoxaflor providing approximately 5 days in 2015 and 3 days in 2016.
