Capture of corn earworm (Lepidoptera: Noctuidae) in pheromone traps and hand nets: relationship to egg and adult densities in field corn, Texas Brazos River Valley
Temporal patterns of capture of corn earworm, Helicoverpa zea (Boddie), in pheromone traps and by hand nets and the relationship of numbers caught to egg and adult densities were studied for 35 and 44 nights during 1988 and 1989, respectively, in four commercial corn fields near College Station, TX. The percentage of nightly pheromone-trap catch, divided into hourly periods, was highest between 2100 and 2200 hours (CDT). Coefficient of determination between number of males caught in traps between 2100 and 2200 hours and egg densities determined the following morning (R2 = 37%) was also higher than for other time periods. However, stepwise regression showed that trap catch between 0400 and 0500 hours in combination with number of fresh silks per hectare provided the best equation for predicting egg densities (R2 = 51%). Of the total numbers of moths captured by hand net, 62% were females. The percentage of nightly hand-net catch of females was highest between 2100 and 2400 hours and of males was nearly uniform throughout the night. The percentage of nightly capture of mating pairs by hand net was highest between 0300 and 0400 hours. Overall, the temporal patterns of capture of males in the pheromone traps and of mating pairs by hand net did not reflect competition between the pheromone-baited traps and native females; there was no decrease in fraction of males captured in pheromone traps when mating activity was highest. There were significant linear regression relationships between the number of corn earworm male moths caught per pheromone trap per night and density of females (R2 = 67%) and males (R2 = 69%) estimated by hand nets.
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