COTTON APHID (HOMOPTERA, APHIDIDAE) RESPONSE TO NITROGEN FERTILITY INDRYLAND COTTON

Cotton aphid, Aphis gossypii Glover, response to nitrogen fertility an d planting date was investigated at the Texas Agricultural Experiment Station at Chillicothe in 1992-1994. Nitrogen was applied at 0, 32, 62 , and 88 lb./acre just prior to planting cotton in late April, late Ma y, and late June. Aphid density and percentage leaf nitrogen were esti mated once a week in top- and bottom-half leaves. There was a signific ant, positive linear correlation between aphid density and fertility l evel in the late May planting date only. In multiple regression analys es, planting date was the most important variable affecting aphid dens ity during August. Nitrogen fertility levels of 62-88, 32-62, and 0-32 lb/acre are recommended for cotton planted in late April, late May, a nd late June, respectively; these levels provided acceptable yields in each planting date without increasing severity of cotton aphid infest ations.