Effect of striped cucumber beetle (Coleoptera:Chrysomelidae) foliar feeding on winter squash injury and yield

The relationship between leaf feeding injury caused by striped cucumber beetle, Acalymma vittatum (F.), and yield of winter squash, Cucurbita moschata Duch., was examined under field and laboratory conditions. In a field trial in 1998, individually-caged plants were artificially infested with varying numbers of beetles to create a range of injury levels. Treatments consisted of three levels of injury (1 to 25, 26 to 50, and >50%) and uninjured controls, each at the cotyledon-, first-, second-, and third-leaf stages of plant development. Under laboratory conditions, the leaf area consumed by known numbers of beetles for varying durations was quantified on cotyledon-, first-, second-, and third-leaf plants. In the field trial, winter squash was relatively tolerant of foliar injury. Total fruit mass was influenced by injury level and growth stage, but not by their interaction. Number of fruit, mass per fruit and number of marketable fruit were influenced by the interaction of factors. Maturity rating was affected by injury level alone. In the laboratory trial, response of winter squash to varying beetle-days (number beetles x number days) depended on plant age. Based on our results, we propose conservative action thresholds of 20% injury to cotyledon plants and 50% foliar damage to first-, second-, and third-leaf plants.