Planting Date Effects on Heliothine Larval Numbers, Fruit Damage, and Yield of Transgenic B.t. Cotton in North Carolina

The susceptibility of Bollgard^® cotton and non-B.t. cotton to bollworm, Helicoverpa zea (Boddie), was examined under contrasting crop management strategies in northeastern North Carolina in 1995, 1996, and 1998. Specifically, planting date effects were observed in Edgecombe Co. in 1995 and 1996, in Martin Co. in 1996, and in Washington Co. in 1998. The bollworm was the only lepidopterous pest which occurred at damaging levels in these tests. Although no significant differences were detected in mean percent egg deposition, mean percent larval infestation, and mean percent damaged fruit between early-planted and late-planted plots in 1995 and 1996, yields were higher in early-planted cotton than in late-planted cotton. In 1998 mean percent damaged fruit was higher in early-planted cotton than in late-planted cotton, but early-planted cotton had significantly higher yields than late-planted cotton. Early planting may be an effective management strategy for Bollgard^® cotton in northeastern North Carolina.