Effects of Ethephon on Boll Weevil (Coleoptera: Curculionidae) Population Development, Cotton Fruiting, and Boll Opening

Ethephon (2-chloroethyl) phosphonic acid) (“Prep”) was applied in 1985 and 1986 to cotton, Gossypium hirsutum (L.), during early to late September to remove late season fruiting forms and to determine the effects on boll weevil, Anthonomus grandis grandis Boheman, population development, cotton quality, lint yield, fiber quality, and boll opening. In 1985, boll weevils ranged from approximately one to five per 4 m of cotton row at the time of application on 6 and 13 September. Populations decreased in ethephon-treated plots thereafter, and average numbers found in infested bolls and squares were reduced >95% as compared with infestations in untreated check plots. In 1986, boll weevils ranged from zero to less than one per 4 m of row at the time of treatments on 15, 23, and 29 September. Populations increased in all plots thereafter, but were on average 9.5 times greater in check plots than in ethephon-treated plots 30 to 44 d following treatment. In 1985, ethephon at rates of 1.12 kg (AI)/ha applied 6 or 13 September did not affect cotton lint yield, but 2.24 kg (AI)/ha applied 6 September reduced yield significantly, possibly because of delayed cotton harvest. In 1986, ethephon at 1.68 kg (AI)/ha had no effect on cotton yields or cotton fiber quality characteristics, but the fiber-length uniformity ratio was significantly higher in the ethephon-treated plots. Ethephon accelerated mature boll opening in the experimental plots in both years, demonstrating the potential for earlier harvest, stalk destruction, and cotton plow down, which are desirable cultural practices that help reduce overwintering boll weevil populations.