Simulating the dynamics of Bemisia argentifolii (Homoptera: Aleyrodidae) in an organic cropping system with a spatiotemporal model

The dynamics of the whitefly Bemisia argentifolii Bellows & Perring were studied at a mixed-crop organic farm on Pine Island, FL, between September 1992 and January 1993. Whitefly populations on tomato, eggplant, zucchini, cucumber, and pepper were monitored weekly by beat-pan sampling and biweekly by visual counts, and parasitism was determined by rearing parasitoids from whitefly infested tomato and eggplant foliage. Analysis of the sampling data identified tomato and eggplant as the most attractive whitefly host plants followed by cucumber, zucchini, and pepper. Parasitism of whiteflies on tomato and eggplant reached 80% during the study. Two peaks in population numbers were observed on tomato and eggplant planted by late September, whereas only 1 peak occurred when the same crops were planted later. The suitability of a spatially explicit population model as a tool for investigating insect dynamics was demonstrated on whiteflies at the farm. Simulation experiments conducted to explain the trends in whitefly population numbers observed on early and late tomato indicated that these population peaks likely resulted from the interaction of planting date and temperature and not from the spatial heterogeneity of the crop system at the farm. Other simulation experiments showed that whitefly population levels could be lowered by grouping similar crops and maintaining barriers to whitefly movement between crops. The utility of this type of model for studying insect dynamics in systems where host plants vary spatially and temporally is illustrated.