| European corn borer (ECB) oviposition and harvest infestation were examined in multiple sweet corn plantings from 1994--1996. Oviposition rates gradually increased during vegetative stages as new leaves appeared, but had sharp increases when reproductive plant parts appeared. Leaf area appeared to influence oviposition during the vegetative stages, but was of little influence after tassels emerged. Female moths alighted on plants identical to those favored for oviposition, whereas males showed little preference.; During vegetative stages, the mean leaf position of an egg mass within a plant was typically at or one leaf above the mid-point of available leaves, gradually increased from early to late stages as new leaves were added, and continued to increase during the first reproductive stage (green tassel). Mean position during the next (four) reproductive stages stabilized at or slightly above ear height. The egg mass distributions did not significantly deviate from a normal distribution.; Multiple regression indicated three periods of oviposition within a crop's development (DD prior to harvest) with differing correlation to harvest infestation: (1) 784-337 DD (prior to green tassel) had very low correlation; (2) 336-169 DD (green tassel to green silk) was highly correlated; and (3) the last 168 DD had low to moderate correlation. These results corroborate existing but untested guidelines for management of sweet corn insects, and indicate the optimum time to control ECB larvae.; Based on predicted ECB larval populations and empirical data, three periods of potential infestation were presented as a function of DD (Base 12.5°C) from January 1: (1) prior to 815 DD, first generation bivoltine ECB larvae would be present; (2) from 815--1096 DD, ECB would be in late fifth instar larva to egg stages of first generation bivoltine, and first through fifth larval instars of univoltine; and (3) from 1125 to 1515 DD, ECB would be in first through fifth instars of second generation bivoltine. Based on these periods and sweet corn development, a system was proposed which better anticipates ECB harvest infestation, and which plantings would benefit from the use of ECB control measures. |
