Efficacy of Dimilin® (diflubenzuron) and transgenic Bt cotton on several lepidopteran species.
A laboratory bioassay was used to evaluate the effect of Dimilin in combination with transgenic cotton (Bollgard), which incorporates the genes to manufacture the Bacillus thuringiensis (Bt) endotoxin, on several lepidopteran species. Bollgard was highly effective in minimizing leaf feeding and causing mortality of third instar larvae of tobacco budworm (Heliothis virescens), cotton bollworm (Helicoverpa zea) and soybean looper (Pseudoplusia includens [Chrysodeixis includens]), but was less efficacious for beet armyworm (Spodoptera exigua) and fall armyworm (Spodoptera frugiperda). For S. exigua diflubenzuron (Dimilin) in combination with Bt cotton was more effective in reducing larval leaf feeding and increasing larval mortality than either diflubenzuron or Bt cotton alone. Instances of synergistic responses to diflubenzuron and Bt cotton for both larval feeding and mortality were found for this species. Although diflubenzuron alone was highly effective on fall armyworm, the advantage of diflubenzuron on Bt cotton over diflubenzuron on non-Bt cotton was not evident for this species.