Early-Season Migratory Flights of Corn Earworm (Lepidoptera: Noctuidae)

Abstract

Studies were conducted to determine the frequency, intensity, and displacement of migratory Rights of adult com earworm, Helicoverpa zea (Boddie), from the lower Rio Grande Valley of southern Texas and northeastern Mexico during the citrus blooming period in February and March 1994. Samples of daily collections of adult male H. zea from pheromone traps in the valley (10) and southern Texas (21) were examined for the presence of citrus pollen using scanning electron microscopy. H. zea were captured at all locations except Alpine, TX. Based on samples of the daily collections, citrus pollen-contaminated H. zea were captured as far as 661 km from the valley. However, the valley is the nearest source of commercial citrus production. Insect Right trajectories from the valley were estimated using wind velocity data at 500 m above ground level and an assumed insect air speed of 5 m/s. Probability of daily capture of H. zea at locations that were 112–711 km from the valley were significantly related to duration of the estimated insect Right trajectory; minimum air temperature at the trap location; and daily average trap capture in the valley. The independent variables: duration of estimated insect Right trajectory, duration of estimated insect trap location, and the 1-d lag of minimum air temperature at the Right trajectory were significantly related to the daily capture of citrus pollen-contaminated H. zea . Wind trajectories measured by mylar balloons (tetroons) and hourly weather data (i.e., wind, precipitation, and air temperature) may explain some of the residual variance of the logistic regressions. The logistic regression equations can be used to estimate the probability of occurrence of daily capture of com earworm for use as an advisory to agriculturists, regulatory personnel, and research scientists.