Treatment thresholds for the glassy-winged sharpshooter based on the local epidemiology of Pierce’s disease spread

The current treatment threshold for the glassy-winged sharpshooter (GWSS) as a vector of Pierce’s disease (PD) is one insect per tree in citrus. We developed a model to evaluate how the threshold might change in relation to various biological and ecological factors. The model was designed to determine the number of GWSS required to cause a single PD infection in grape. The primary model parameters were the proportion of GWSS carrying PD, GWSS transmission efficiency of PD, proportion of GWSS that will move from citrus to grape, the number of grapevines that a single GWSS will visit, grape varietal susceptibility, and the probability of an infection event resulting in disease. As these factors varied in the model, the GWSS treatment threshold changed. A major limitation of implementing treatment thresholds calculated from the model is that key data for some parameters are lacking. The model is a useful tool for identifying research areas that are needed to further refine a GWSS treatment threshold