Submitted to: National Cotton Council Beltwide Cotton Conference
Publication Type: Proceedings
Publication Acceptance Date: 2/28/2007
Publication Date: 5/1/2007
Citation: Jackson, R.E., Gore, J., Catchot, A. 2007. Impact of Fall Armyworm Survival in Bt Crops on Survival and Damage Potential of Subsequent Generations. In: Proceedings of National Cotton Council Beltwide Cotton Conference, January 9-12, 2007, New Orleans, Louisiana . p. 1634-1637
Interpretive Summary: Fall armyworm populations in Mississippi were evaluated to determine whether development on Bt sweet corn or Bt cotton affected survival and damage potential of subsequent generations in Bt cottons. Results from this study indicated fall armyworm populations originating from Bt sweet corn may be less fit than those from non-Bt sweet corn. However, fall armyworm populations originating from Bt cottons appeared to be equally as fit as those from non-Bt cotton. Information generated from these experiments is important in that it provides a better understanding of the potential for fall armyworms to develop resistance to Bt toxins and may provide information necessary in making critical management decisions.
Technical Abstract: Fall armyworm, Spodoptera frugiperda (J. E. Smith), colonies were compared to determine whether development on Bt corn or Bt cotton impacted survival and damage potential of subsequent generations on Bt or non-Bt cotton. Late instars of fall armyworm were collected from Bt and non-Bt sweet corn to establish two separate colonies. Two-day old and 5-day old F1 larva(e) from each colony were confined to white flowers of two non-Bt cotton varieties, a WideStrike (Dow AgroSciences, Indianapolis, IN) variety, and a Bollgard II (Monsanto Co., St. Louis, MO) variety with cloth cages to evaluate damage potential. Two of three cage studies with 2-d old fall armyworm larvae on non-Bt cotton showed that the Bt corn strain damaged significantly fewer bolls as compared to the non-Bt corn strain, although a similar trend existed for all three studies. Conversely, no differences were detected between strains with respect to boll damage levels caused by 2-d old larvae in WideStrike or Bollgard II cottons. Studies conducted with 5-d old fall armyworm larvae demonstrated that boll damage caused by the Bt corn strain to non-Bt cotton was significantly less than that of the non-Bt strain in only one of three studies. However, as with 2-d old larvae, a similar trend was observed for all three studies. No differences in boll damage levels from 5-d old larvae were evident between strains on Bollgard II cotton. Leaf tissue bioassays were also conducted to compare survival of two fall armyworm strains that originated from either non-Bt or Bollgard II cotton. From infestations of 3-d old larvae, no differences in survival were detected between strains when fed either non-Bt or Bollgard II cotton. Results from these studies suggest that there may be some fitness cost(s) associated with fall armyworm development on Bt sweet corn. Because this same phenomenon was not associated with development on Bt cotton, further studies should be conducted to examine the impact of Bt crops on fall armyworm populations.