Quantifying Apple Maggot (Diptera: Tephritidae) Preference for Apples to Optimize the Distribution of Traps Among Trees

The spatial and temporal distribution pattern of apple maggot, Rhagoletis pomonella (Walsh), fly captures was monitored among trees within an unmanaged apple orchard. Each tree within the orchard was monitored weekly for the presence of flies using sticky traps. Fruit maturity was monitored weekly to determine percentage soluble solids. Significantly more apple maggot were captured on trees with mature fruit than on trees with immature fruit. A selective predation model was used to quantify the effect of fruit preference on apple maggot captures. Two hypotheses were evaluated. The first hypothesis was that fly capture among trees is a function of the relative sequence or phenology of fruit maturation (tree category hypothesis). The second hypothesis was that fly capture among trees is a function of apple maturity among trees, regardless of the phenology of fruit maturation (fruit maturity hypothesis). Both models explained the distribution of fly capture among trees early in the growing season, but the fruit maturity hypothesis best explained the entire season. The use of the model for predicting the distribution pattern of apple maggot captures and the optimum placement of traps for apple maggot detection are discussed.