Bollworm (Lepidoptera: Noctuidae) Behavior on Transgenic Cotton Expressing Cry1Ac and Cry1F Proteins

Bollworm, Helicoverpa zea (Boddie), larvae are known to move away from Bollgard (TM) (Monsanto Co., St. Louis, MO) cotton terminals. Bollworm larvae are also found more frequently on flower buds (squares) and bolls of Bollgard as compared with those of nontransgenic cotton. However, data are not available for bollworm behavior on commercially available transgenic cotton varieties expressing 2 Bacillus thuringiensis Berliner proteins. Thus, field studies were conducted in Stoneville, MS, during 2007 and 2008 to determine whether bollworm behavior differed among cotton expressing the Cry1Ac and Cry1F proteins (Widestrike (R), Phytogen 485, PhytoGen Seed Co., LLC, Indianapolis, IN) and nonBt cotton (Phytogen 425, PhytoGen Seed Co., LLC, Indianapolis, IN). Two-day-old bollworm larvae were placed into terminals of either individual cotton plants or plants within 1-m plots during the flowering period. Comparison of larval movement away from cotton terminals between Widestrike and nonBt plants did not differ at 3, 6, 24, or 48 h after infestation. In addition, larval distribution on fruiting structures did not differ between Widestrike and nonBt cotton. These data indicate that different scouting methods for bollworm larvae should be used for the various Bt cotton technologies commercially available.