Evaluation of transgenic corn for resistance to corn earworm (Lepidoptera: Noctuidae), fall armyworm (Lepidoptera: Noctuidae), and southwestern corn borer (Lepidoptera: Crambidae) in a laboratory bioassay.

Abstract

The development of crop plants expressing genes that encode insecticidal proteins isolated from the bacterium lJacillus thuringiellsis Berliner (Et) has provided a tremendous opportunity for improved control of insect pests. Although corn, Zea mays L., gennplasm with resistance in the whorl stage to fall armyworm, Spodoptera (rugipcrda (J. E. Smith), and southwestern corn borer, Diatraca grandiosella Dyar, larval feeding has been identified and released, little progress has becn made in identif~'ing resis~ncc to ear damage by these insects. Husks and silks were collected 3 to 4 dafter anthesis from nontransgenic and transgenic corn hybrids and used in laboratory bioassays to determine the effects of the Bt insecticidal protein on larval survival and growth of fall armyworm, southwestern com borer, and com eaTWorm, Helico~'erpa zca (Boddie). Southwestern corn borer larvae that fed on diets containing husks of transgenic plants did not survive. Com earworm larvae fed on diets containing husks or silks from transgenic plants died, and those that fed on diets containing silks harvested from transgenic plants exhibited reduced survival and growth. Fall armyworm larvae were least susceptible to the Bt protein. but larval survh'al and gro ..... th on diets containing husks of transgenic plants were reduced. Larval growth also was reduced on diets containing silks from transgenic plants. The bioassays indicated that expression in husks and silks or genes encoding Bt insecticidal proteins could be useful in reducing insect damage in ears of com.