IMPROVED TIMING OF CONTROL FOR THE GRAPE BERRY MOTH, PARALOBESIA VITEANA, USING A DEGREE-DAY MODEL

The grape berry moth is the most destructive direct pest of grapes in that the larvae feed internally on grape berries resulting in loss of crop and often initiating bunch rot diseases. New York is the second largest and Pennsylvania is the fifth largest grape producing state in the US, and the vast majority of the grapes are grown along the shore of Lake Erie and in the Finger Lakes region of New York. In recent years, late season infestations of GBM have caught grape growers unaware, resulting in numerous load rejections at juice processing plants. These late season infestations have caused considerable consternation to grape growers and to the grape industry (see appendix document GBM Summit II for a summary of National Grape Cooperative sponsored workshop on this problem). Speculation as to why we are now experiencing problems with this insect in the late summer has considered the loss of broad-spectrum contact insecticides and/or insecticide resistance. It is apparent that the newer compounds available for GBM management are not contact poisons, but must be ingested in order to kill. Preliminary studies carried out at PSU have demonstrated that GBM larvae within grape berries are protected from insecticide sprays. Therefore, the only window of opportunity available for the control of GBM using insecticides that must be ingested is the brief time during which neonate GBM larvae are chewing their way through the grape skin and into the berry. Ensuring that active insecticide residues are covering the grape berry when the newly hatched GBM larvae are attempting to chew their way in requires a precise method for anticipating and timing insecticide applications. Without the intervention of this project, grower loads will continue to be rejected at the processing plants, the economic well being of grape growers will be negatively impacted, and insecticides will continue to be misapplied with concomitant non-target impacts including effects on biodiversity, ecosystem services, and human health.