A Seasonal Study of Diapause, Reproductive Activity and Seasonal Tolerance to Insecticides in the Boll Weevil1

Abstract

A seasonal study of reproductive activity, incidence of diapause and seasonal tolerance to toxaphene and Guthion® ( O, O - dimethyl S -(4-oxo-3 H -l,2,3-benzotriazine-3-methyl) phosphorodithioate) in the boll weevil was conducted in four cotton fields in central Texas. Diapausing weevils were first found in the various fields during the period from late July through August. Once diapausing weevils were found in a field, they occurred in all subsequent collections from the field. Reproductive activity was high from June until the onset of diapause. One peak of reproductive activity occurred in September on regrowth cotton. Overwintered weevils that emerged early in the season with fat content over 10% of the dry weight were harder to kill with toxaphene than weevils of the current season collected during June and early July. Seasonal tolerance to toxaphene of up to 100-fold occurred with the onset of diapause in the populations. No evidence of seasonal tolerance to Guthion was found.