Yield response of pumpkin and winter squash to simulated cucumber beetle (Coleoptera : Chrysomelidae) feeding injury

Field studies were conducted to characterize the yield responses of pumpkin , Cucurbita pepo L., and winter squash, Cucurbita maxima Duch., to simulate d striped cucumber beetle, Acalymma vittatum (F.), feeding damage. Prelimin ary studies in pumpkin ('Spookie') were conducted in 1993, and more complet e studies in 1994 and 1995 in pumpkin (Spookie), and in 1995 and 1996 in wi nter squash ('Waltham'). Plants were artificially injured 1 time at the cot yledon, 1st, 2nd, or 3rd true leaf stages by clipping specified percentages of leaf area from all leaves on the plant. Treatments consisted of a contr ol treatment with no simulated injury and 4 levels of simulated injury. Pum pkin treatments were 10, 20, 40, and 80% leaf area removal in 1993 and 1994 and 20, 40, 60, and 80% in 1995. Winter squash treatments were 20, 10, 60, and 80% leaf area removal in 1995 and 10, 20, 40, and 80% in 1996. In 1993 , 5 wk after planting, mean leaf, stem, and total dry weight were significa ntly lower on pumpkin plants subjected to greater than or equal to 20% simu lated leaf injury regardless of the growth stage when the injury occurred. Injury at the 3rd leaf stage resulted in a significant reduction in the mea n leaf and total dry weight of plant, across all levels of injury. At 2-3 w k before crop maturity, fruit weight and number of fruit per plant were sig nificantly lower with 80% leaf area removal. Ln 1994 and 1995, and when pum pkins were grown to full maturity and apparently able to compensate for the simulated damage, neither number nor weight of marketable fruit per plant were affected significantly by simulated injury at any stage of development nor level of simulated injury. In contrast, greater than or equal to 20% a nd 80% leaf area removal to winter squash resulted in significant reduction s in the weight of marketable fruit and/or number of marketable fruit, in 1 995 and 1996, respectively. The results of this study indicate that pumpkin s can tolerate relatively high levels of simulated defoliation, whereas win ter squash is less tolerant. Variable results across years in winter squash may indicate an interaction between injury and plant stress caused by abio tic factors such as soil moisture availability.