BINOMIAL SAMPLING PLANS FOR ESTIMATING BEMISIA-TABACI POPULATIONS IN CANTALOUPES

Early season infestations of the sweet potato whitefly, Bemisia tabaci (Gennadius), on cantaloupes, Cucumis melo L., were determined by counts of the number of adults per leaf in fields near Yuma, Arizona. We used these data to develop binomial sampling plans based on the relationship between mean densities of whiteflies per leaf, m, and proportion of leaves infested with more than I whiteflies, P-I, according to the empirical model In m=a'+b' ln[-ln(1-P-I)]. The models were developed for the presence-absence approach (I=0) and for a cutoff value of three whiteflies per leaf (I=3). Four independent data sets were used to evaluate the models. Both methods yielded reliable predictions at low infestation levels, but some of the higher m values were overestimated. As the tentative economic threshold for B. tabaci is three adults per leaf, which corresponds to low P-I values, results of the binomial sampling were satisfactory for pest management purposes.