Bollgard II Efficacy on the Heliothine Complex

Bollgard cotton (Gossypium hirsutum L.) containing the CryIAc endotoxin of Bacillus thuringiensis Berliner became commercially available to cotton producers in 1996. Bollgard cultivars since that time have provided excellent control of the tobacco budworm, Heliothis virescens F., for growers in Arkansas. Control of bollworm, Helicoverpa zea (Boddie), and other lepidopterous pests has been less dependable and foliar insecticide applications are sometimes needed for control. Bollgard II was developed to contain an additional toxin, CryX , to enhance the control of lepidopterous pests in cotton and hinder the development of resistance. Previous studies have shown Bollgard II to have increased efficacy for bollworm and soybean looper (Allen et al., 2000; Stewart et al., 2000; Ridge et al., 2000). The purpose of this study was to compare the efficacy of Bollgard II to Bollgard and conventional cotton for control of lepidopterous pests. Observations were also made to compare agronomic characteristics of these cultivars.