Reduction in Insecticide Use Associated with Cotton Resistant to Pink Bollworm

Cotton (Gossypium hirsutum L.) growers use significant quantities of insecticides to control pink bollworm (PBW), Pectinophora gossypiella (Saunders). The germplasm line WC‐12NL (nectariless, okra leaf, and early maturing) and ‘Deltapine 61’ (nectaried, normal leaf, and later maturing) were grown at Maricopa, AZ, and Brawley, CA, for three seasons. Irrigation water was terminated and plots were defoliated earlier than normal, a practice that favored the early maturing line. Insecticides were applied as needed, based on PBW egg infestations of cotton bolls. The major objective was to determine whether insecticide use can be reduced or eliminated by growing WC‐12NL. Other objectives were to compare WC‐12NL with Deltapine 61 for PBW resistance, yield, earliness, and fiber properties; to study location and seasonal effects; and to determine whether the growth‐regulating chemical ethephon (2‐chloroethylphosphonic acid) would cause bolls to open earlier. The mean number of insecticide applications was 41% lower for WC‐12NL than for Deltapine 61. First and last application dates averaged 21 d later and 10 d earlier, respectively, for WC‐12NL. WC‐12NL had significantly less seed damage caused by PBW, yielded significantly more lint, was significantly earlier, but had inferior fiber properties compared with Deltapine 61. Ethephon treatment increased earliness of Deltapine 61 but did not affect that of WC‐12NL, probably because it was applied too late. Location and seasonal effects and numerous interactions occurred, but did not alter the main conclusion that a cotton line such as WC‐12NL (but with improved fiber properties) could be valuable in areas where PBW is a problem.