Evaluation of Three Sampling Methods for Estimating Adult Sweet potato Whitefly (Homoptera: Aleyrodidae) Abundance on Cantaloupes

Abstract

Three sampling techniques (yellow sticky trap, visual [Leafturn], and modified vacuum [Handvac]) were compared over a 2-yr period to determine sampling reliability for estimating adult sweet potato whitefly, Bemisia tabaci (Gennadius), population levels in cantaloupes, Cucumis melo L. In experimental plots, the 3 sampling methods indicated similar whitefly population trends throughout the season, and all methods were highly correlated with immature densities. There was a strong correlation of Leafturn samples with Handvac and sticky trap counts. In commercial 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 correlated 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 methods. In general, estimates of whitefly population trends measured with the Leafturn and Handvac methods were similar in commercial fields despite differences in cultivar planted, year of the test, and insecticide use patterns. Estimates of relative sampling variation (precision) indicated that sticky traps were more efficient in some cases, but, overall, precision did not differ among the sample methods. The relative net precision for adults was greater with the Leafturn and Handvac methods, which were less time consuming than the sticky trap. Comparison of sampling methods in small-plot chemical trials indicated that yellow sticky traps were not reliable for estimating treatment differences. Only the Leaftum and Handvac methods detected significant differences in adult numbers between treated and untreated plots after insecticide applications.