Corn earworm, Helicoverpa zea (Boddie), male catch in pheromone traps was monitored in western Oregon processing sweet corn, Zea mays L., fields during 1986-1990. Peaks in catches of males and degree-day calculations indicate only two generations per year. Using nominal values for the crop, treatment costs, and estimated loss of $16.63/ha per 10% infestation, an economic injury level was estimated at 27.4% infested ears. Correlation and regression were used to identify variables for predicting percentage ears infested on a per-field basis in 55 untreated fields in 1986-1989. A linear regression of date of 5% silk and moth catch from first tassel to 5% silk explained 63% of variation in infestations. Additionally, a variable accounting for a change in pheromone trap and lure type and two indicator variables accounting for relatively earlier beginning and higher increases of infestations for 1988 improved the model significantly (adjusted R2 = 0.73). Because July moth counts were higher in 1988 than in other years, the model was formulated so the indicator variables are used when moth captures are> 1.5 per trap per night during the month of July. A validation using 30 fields monitored in 1990 showed good correlation with model predictions (R2 = 0.69, P <0.001). Of nine fields with infestation levels >5%, the model overpredicfed damage by a mean of $5.63/ha in seven fields and underpredicted damage by a mean of $5.86/ha in two fields. Overall, the model tended to overpredict damage in 1990, which had very light infestations.
Document Type: Research Article
Publication date: February 1, 1992
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Journal of Economic Entomology is published bimonthly in February, April, June, August, October, and December. The journal publishes articles on the economic significance of insects and is divided into the following sections: apiculture & social insects; arthropods in relation to plant disease; forum; insecticide resistance and resistance management; ecotoxicology; biological and microbial control; ecology and behavior; sampling and biostatistics; household and structural insects; medical entomology; molecular entomology; veterinary entomology; forest entomology; horticultural entomology; field and forage crops, and small grains; stored-product; commodity treatment and quarantine entomology; and plant resistance. In addition to research papers, Journal of Economic Entomology publishes Letters to the Editor, interpretive articles in a Forum section, Short Communications, Rapid Communications, and Book Reviews.