DIFFERENCES IN YIELD RESPONSE TO COTTON APHIDS (HOMOPTERA, APHIDIDAE)BETWEEN SMOOTH-LEAF AND HAIRY-LEAF ISOGENIC COTTON LINES

DES 119 cotton, Gossypium hirsutum L., and a smooth-leaf isoline were monitored for cotton aphid, Aphis gossypii Glover, densities and effec ts on yield in aphicide-treated and untreated plots. The interactions of cotton genotype and aphicide treatment regime were significant for aphid density and cotton yield. Aphids caused a yield loss (approximat e to 140 kg lint per hectare) in DES 119 cotton when it was not treate d with aphicide. No yield differences were observed between aphicide-t reated and untreated plots containing the smooth-leaf isoline of DES 1 19. Yields for DES 119 with aphicide, the smooth-leaf isoline without aphicide, the smooth-leaf isoline with aphicide, and DES 119 without a phicide were 1105.0, 996.3, 971.0, and 964.0 kg lint per hectare, resp ectively. DES 119 treated with aphicide yielded more cotton than each of the other treatments. No differences were observed in the densities of, nor damages caused by, other cotton pests, which could account fo r yield losses that we attributed to cotton aphid. The data also indic ated that the smooth-leaf isoline of DES 119 offers substantial resist ance to cotton aphid. Thus, high-yielding, smooth-leaf cotton lines th at do not respond to aphicide treatments might be viable alternatives to currently used chemical approaches to cotton aphid management.