Location: Southern Insect Management ResearchTitle: Mortality of bollworm and tobacco budworm larvae exposed to microbial and chemical insecticides in treated Bt and non-Bt cotton assays
Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 1/12/2016
Publication Date: 5/18/2016
Citation: Luttrell, R.G., Mullen, R.M., Little, N., Allen, K.C., Perera, O.P. 2016. Mortality of bollworm and tobacco budworm larvae exposed to microbial and chemical insecticides in treated Bt and non-Bt cotton assays. National Cotton Council Beltwide Cotton Conference. Memphis, TN. Pp. 168-174.
Interpretive Summary: The availability of purified or representative sources of Bt toxins for monitoring insect susceptibilities to transgenic crops is lacking. The purpose of this study was to demonstrate alternative methodologies for tracking bollworm and tobacco budworm susceptibilities to microbial and chemical insecticides. Therefore, we investigated plant-based larval assays as an option for tracking resistance evolution to multiple Bt insecticidal traits expressed in the newer Bt transgenic technologies, and determining insect susceptibilities to different classes of chemical insecticides. The quantitative estimates of insect mortality obtained in this study may be useful in estimating the value of various insect management options and the threat of future resistance problems in the MS Delta.
Technical Abstract: Laboratory colonies of bollworm (Helicoverpa zea Boddie) and tobacco budworm (Heliothis virescens F.) were exposed to microbial and chemical insecticides on non-Bt (DP1441) and Bt (DP1321) cotton leaves in spray-table and field-plot experiments. The microbial insecticides included commercial formulations of Bacillus thuringiensis (Dipel®) and Heliothis (Helicoverpa) nuclear polyhedrosis virus (Elcar®, Gemstar®, and Heligen®). A range of field application rates was evaluated with each microbial and chemical insecticide against neonate and 3rd instar larvae, and residual activity was measured in a small plot field experiment. Trends in activity provided quantitative assessments of insecticidal and Bt cotton activity against the susceptible laboratory strains of insects studied. These data may be useful as future benchmark comparisons for resistance management and strategic optimization of the need to spray non-Bt and Bt cotton.