Beetles and Plants

Field and laboratory studies were conducted to examine the relationship between foliar feeding damage caused by striped cucumber beetle, Acalymma vittatum (F.) (Coleoptera: Chrysomelidae), and yield of pumpkin, Cucurbita pepo L. (var. Spookie). In field trials in 1996 and 1997, plants were artificially infested with varying numbers of beetles at the cotyledon-, first-, second-, or third-leaf stages. At harvest, fruit number, fruit mass, and fruit maturity were evaluated. Foliar feeding damage had little effect on yield other than a slight increase in number of fruit per plant for plants with 1 to 20% damage. The stage of plant development at infestation had no effect on yield, nor did the interaction of foliar feeding damage and growth stage. In a laboratory trial, varying numbers of A. vittatum were allowed to feed for 1, 2, 3, or 4 d on plants at cotyledon-, first-, second-, or thirdleaf stages. For all stages, significant and differing positive linear relationships were observed when the percentage of foliar feeding damage was regressed against beetle-days. The results indicated that small fruited, vining pumpkins can tolerate relatively high levels of striped cucumber beetle feeding injury. Foliar feeding damage thresholds are conservatively estimated to be similar to 60% during cotyledon through third leaf stage of growth