SEASONAL DISTRIBUTION OF BEMISIA-ARGENTIFOLII (HOMOPTERA, ALEYRODIDAE) HONEYDEW SUGARS ON PIMA AND UPLAND COTTON LINT AND LINT STICKINESS AT HARVEST

Bemisia argentifolii Bellows and Perring populations were higher on lo ng-staple Pima S-7 cotton, Gossypium barbadense L., compared with shor t-staple, upland cottons, G. hirsutum L., Deltapine (DPL) 50 and 5415 in 1995 and DPL 50 in 1996. Higher numbers of mature open cotton bells occurred earlier for DPL cultivars compared with Pima S-7. Also, numb ers of open bells for DPL cotton bells peaked 8 to 14 days before Pima S-7 and decreased dramatically by 15 September reflecting termination of the first fruiting cycle in August. In contrast, the indeterminate fruiting pattern of Pima S-7 showed that numbers of open bells per we ek declined gradually after the peak without a clear cut termination o ccurrence. Trehalulose and melezitose sugars produced by B. argentifol ii were found on lint for all weekly samples in both years for both co tton types. About 95 and 80% of the open cotton bells, of the Deltapin e and Pima S-7 cottons, respectively, occurred by mid-September. This suggests that defoliation timing and early harvest can be important ma nagement tools to avoid sticky cotton. For upland cotton in 1996, exte nding the cotton season after 95% of the crop matured (congruent to 15 September) resulted in development from non-sticky cotton to lightly- sticky cotton within 21 days following the occurrence of increasing wh itefly populations after 15 September. This could have been avoided wi th mid-September defoliation. Later fruiting and lack of a distinct en d of the first cotton fruiting cycle probably precludes using early de foliation for long-staple Pima cotton. At harvest, total amounts of tr ehalulose and melezitose and total thermodetector counts for all weekl y harvests were greater than amounts found in lint for randomly select ed 20 bell samples, and samples from all cotton picked from 4 m of row , except for thermodetector counts for spindle-machine-picked cotton. This probably occurred because weekly picked cotton escaped rainfall a nd exposure and other weathering, in 1995 but not 1996, and machine-pi cked cotton contains more honeydew-contaminated leaf trash. Except in one instance, thermodetector counts and lint trehalulose and melezitos e content for all sampling methods were significantly correlated.