San Jose Scale (Homoptera: Diaspididae): Simulation of Seasonal Phenology in North Carolina Orchards

Abstract

Orchard temperatures and pheromone trap catch data and crawler hatch data for nine orchard-years were used to validate the accuracy of physiological time models in simulating the time intervals for one generation between male flight peaks, and crawler peaks, as well as the interval between male flight peaks and crawler peaks (embryonic development) of four seasonal generations of the San Jose scale, Quadraspidiotus perniciosus (Comstock) in North Carolina orchards. Linear (degree-days) models simulated within ±1 wk the interval for all male flight peaks between overwintering and F1 generations, while a nonlinear model simulated within ±1 wk all but one male flight peak between overwintering and F1 generations. The models were less accurate for simulating intervals of flight peaks between F1 to F2 and F2 to F3 generations. Likewise, model simulations of the time interval for one generation between crawler hatch peaks, and the time required for embryonic development, were more accurate for F1 and F2 than F3 and F4 generations. Simulation results of the linear and nonlinear models were similar with 40 of the 49 simulations comparing linear versus nonlinear models not differing by more than 6 d of each other. Validation of the models for San Jose scale was complicated in one apple orchard by the presence of Forbes scale, Quadraspidiotus forbesi (Johnson).