Infestation of Germplasm Lines and Cultivars of Cotton in Arizona by Whitefly Nymphs (Homoptera: Aleyrodidae)

Seasonal abundance of whitefly nymphs, primarily sweetpotato whitefly, Bemisia tabaci (Gennadius), and bandedwinged whitefly, Trialeurodes abutilonea (Haldeman), on leaves of germplasm lines and cultivars of cotton, Gossypium hirsutum L., were determined in field plots at Maricopa, AZ, in 1987. In general, the germplasm lines with the greatest numbers of leaf trichomes (range 2 to 98 per cm²) had the greatest numbers of nymphs (range 0.4 to 11.3 nymphs per leaf on 23 September). The okra-leaf characteristic did not have a consistent effect on the numbers of nymphs. Deltapine 20, Centennial, and Stoneville 506 cultivars planted on 30 April had significantly greater infestations (range 20.3 to 121.3 nymphs per leaf) on 16 October than did the same cultivars planted 21 May (range 4.5 to 53.0) or 11 June (range 7.0 to 31.5). The nectariless okra-leaf line WC-12NL and cultivar Deltapine 61 had 1.1 and 1.5 nymphs per leaf on 22 September, respectively, not significantly different.