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.