Insecticides in the diamide class have a novel mode of action and have become a key component for management of agriculturally important lepidopteran pests since their introduction in 2008. Corn earworm, Helicoverpa zea (Boddie); and the armyworm complex including fall armyworm, Spodoptera frugiperda (J.E. Smith); and Spodoptera exigua (Hübner); are significant pests of agroecosystems in the Mid-southern and Southeastern regions of the United States. They have developed resistance to, and/or inconsistent control has occurred with most chemical classes. The objectives of this study were to establish susceptibility levels of field populations of H. zea, S. frugiperda, and S. exigua collected in the Mid-southern and Southeastern regions of the United States to flubendiamide and chlorantraniliprole. To achieve equivalent levels of mortality for each species, a higher concentration of flubendiamide was required compared to chlorantraniliprole. Furthermore, two experiments were conducted to determine the systemic and residual efficacy of chlorantraniliprole and flubendiamide against H. zea on vegetative and reproductive structures of soybean. Chlorantraniliprole moved systemically and had significantly greater control than flubendiamide in the systemic and residual study out to 31 DAT. Flubendiamide did not move systemically but provided significant residual control out to 31 DAT compared with the untreated control. Neither insecticide was detected in reproductive structures. Finally, to determine the risk of resistance development, a S. exigua colony, originating from a field collection in 2013, was separated into three cohorts that were independently selected with three concentrations (0.016, 0.020, and 0.025 ppm) of flubendiamide incorporated into a meridic diet. These concentrations were chosen from the LC30, LC60 and LC90 of the original colony. Resistance ratios never increased past 2.11old. The highest resistance ratios occurred after 18 generations for the LC30 colony, 19 generations for the LC60 colony, and 13 and 15 generations for the LC90 colony. After reaching their highest point of resistance, the colonies began to decline in egg production and larval survivability and did not recover. After 22 generations the selected colonies were terminated. The results from this portion of the study suggest that the potential for resistance development of beet armyworm to flubendiamide is unclear.
| Identifer | oai:union.ndltd.org:MSSTATE/oai:scholarsjunction.msstate.edu:td-1850 |
| Date | 07 May 2016 |
| Creators | Adams, Charles Andrew |
| Publisher | Scholars Junction |
| Source Sets | Mississippi State University |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Theses and Dissertations |
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