INFLUENCE OF PLANT MATURITY AND APPLICATION TIMING ON EFFICACY OF DICROTOPHOS FOR CONTROL OF COTTON APHID

Efficacy of dicrotophos for controlling the cotton aphid, Aphis gossyp ii Glover, was investigated at the Texas Agricultural Experiment Stati on at Chillicothe in 1992-1994. Cotton was planted in late April, late May, and late June each pear, and dicrotophos, at 0.5 Ib Al/acre, was applied as aphid numbers began increasing during August. A single app lication was made at different aphid densities within each planting da te. A treatment threshold of 35-50 aphids per leaf can be used for all three planting dates. A single application prevented development of h igh numbers for extended periods in the late April and late May planti ng dates; in some years populations of 50 aphids per leaf did not deve lop in these two plantings. Multiple applications will probably be nec essary to control aphids in late June cotton.