EVALUATION OF 3 SAMPLING METHODS FOR ESTIMATING ADULT SWEET-POTATO WHITEFLY (HOMOPTERA, ALEYRODIDAE) ABUNDANCE ON CANTALOUPES

Three sampling techniques (yellow sticky trap, visual [Leafturn], and modified vacuum [Handvac]) were compared over a 2-yr period to determi ne sampling reliability for estimating adult sweetpotato whitefly, Bem isia tabaci (Gennadius), population levels in cantaloupes, Cucumis mel o L. In experimental plots, the 3 sampling methods indicated similar w hitefly population trends throughout the season, and all methods were highly correlated with immature densities. There was a strong correlat ion of Leafturn samples with Handvac and sticky trap counts. In commer cial fields, however, seasonal patterns of population levels detected with sticky traps differed from those detected with the other sampling methods. Adult counts from the Leafturn procedure were more closely c orrelated with counts from Handvac samples than with those from sticky traps. Estimates of adult abundance measured by Leafturn counts also provided a higher correlation with immature densities than the other m ethods. In general, estimates of whitefly population trends measured w ith the Leafturn and Handvac methods were similar in commercial fields despite differences in cultivar planted, year of the test, and insect icide use patterns. Estimates of relative sampling variation (precisio n) indicated that sticky traps were more efficient in some cases, but, overall, precision did not differ among the sample methods. The relat ive net precision for adults was greater with the Leafturn and Handvac methods, which were less time consuming than the sticky trap. Compari son of sampling methods in small-plot chemical trials indicated that y ellow sticky traps were not reliable for estimating treatment differen ces. Only the Leafturn and Handvac methods detected significant differ ences in adult numbers between treated and untreated plots after insec ticide applications.