ARS | Publication request: Supplemental control of lepidopterous pests on BT transgenic sweet corn with biologically based spray treatments

Submitted to: Journal of Insect Science
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: January 24, 2008
Publication Date: March 19, 2009
Citation: Farrar, R.R., Shepard, M.B., Shapiro, M., Hassel, R., Schaffer, M., Smith, C. 2009. Supplemental control of lepidopterous pests on BT transgenic sweet corn with biologically based spray treatments. Journal of Insect Science. 9:8.

Interpretive Summary: Fall armyworm and corn earworm caterpillars are major pests of corn in much of the United States. Corn that has been genetically engineered with proteins from the bacterium Bacillus thuringiensis (Bt) resists insects and is widely grown. Bt corn provides good control of the corn earworm in most situations, but fall armyworms may survive on it and can damage the crop. Bt corn may thus still need supplemental treatments to control this pest. In addition, when infestations of corn earworm are particularly bad, supplemental treatments for it may also be needed. For five growing seasons, we field tested several low risk, environmentally friendly sprays as supplemental controls for the fall armyworm and corn earworm on Bt sweet corn. We found that spinosad, a substance produced by a natural bacterium, gave good control of both pests. Neem, which is a plant extract, and natural insect-specific viruses also improved control. These materials could provide the additional control needed to protect Bt corn from damage by the fall armyworm and corn earworm while causing few side effects. We expect this information to be used by other scientists and by extension personnel developing better and safer ways to control pests of corn.

Technical Abstract: Biologically based spray treatments, including nucleopolyhedroviruses, neem, and spinosad, were evaluated as supplemental controls for the fall armyworm, Spodoptera frugiperda (J. E. Smith), and corn earworm, Helicoverpa zea (Boddie), on transgenic sweet corn, Zea mays (L.), expressing a Cry1Ab toxin from Bacillus thuringiensis Berliner (BT). Overall, transgenic corn supported lower densities of both pests than did nontransgenic corn. Control of the fall armyworm was improved in both whorl-stage and tassel-stage corn by the use of a nucleopolyhedrovirus and neem, but the greatest improvement was seen with spinosad. Only spinosad consistently reduced damage to ears, which was caused by both pest species. In general, efficacy of the spray materials did not differ greatly between transgenic and nontransgenic corn.