Submitted to: Florida Entomologist
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/1/2011
Publication Date: 7/6/2011
Citation: Armstrong, J.S., Gore, J., Adamczyk Jr, J.J. 2011. Efficacy of single and dual gene cotton Gossypium hirsutum (L.) events on yellowstriped armyworm (Lepidoptera: Noctuidae) in South Texas and the Mississippi Delta. Florida Entomologist. 94(3):594-598.
Interpretive Summary: The yellowstriped armyworm (YSAW) is a one of several caterpillar species that attack a variety of crops including cotton. We evaluated this particular species to the ingestion of different traits of Bt cotton tissue from varieties grown in Stoneville, MS and Weslaco, TX and compared it to a conventional variety with no Bt. The results of the bioassays using leaves collected from the lower, middle, and top canopy from Stoneville revealed that YSAW are no more susceptible to Bollgard I® than no technology in the cotton plant. However, YSAW were susceptible to Bollgard II®, and highly susceptible to the Widestrike™ traits. No live larvae were collected from the WideStrike™ replicated plots; only 2 larvae were collected from Bollgard II® cotton that weighed <200 mg. Results from these assays indicate that cotton producers have very effective options for controlling YSAW even late in the growing season.
Technical Abstract: The yellowstriped armyworm (YSAW), Spodoptera ornithogalli (Guenée), has a broad host range and can be an economic threat to cotton in southern growing regions of the United States by consuming leaves and damaging fruiting forms. Field grown cotton varieties containing the endotoxins from Bacillus thuringiensis, (Cry1Ac = Bollgard ®; Cry1Ac + Cry2Ab = Bollgard II®; Cry1F + Cry1Ac = Widestrike™) and a non-Bt cotton were evaluated for YSAW susceptibility to cotton leaf tissue. Bioassays conducted at Stoneville, MS, from leaves collected from the lower, middle, and top canopy leaves showed that YSAW were highly susceptible to Bollgard II®, and Widestrike™ traits. No live larvae were collected from the WideStrike replicated plots; only 2 larvae were collected from Bollgard II® cotton that weighed <200 mg. Larvae collected from Bollgard and non-Bt cotton were plentiful and averaged 900 and 800 mg respectively. Additional bioassays from late-season cotton plots in physiological cut-out at both Stoneville, MS, and Weslaco, TX, indicate that WideStrike™ is very active against YSAW larvae, followed by Bollgard II®. Results from these assays indicate that cotton producers have very effective options for controlling YSAW even late in the growing season.