Olson Yellow Sticky Trap: Decision-Making Tool for Sampling Western Corn Rootworm (Coleoptera: Chrysomelidae) Adults in Field Corn

Abstract

Field studies were conducted in Virginia in 1992-1994 to evaluate the effectiveness of using counts of western corn rootworm Diabrotica virgifera virgifera LeConte, adults on Olson yellow sticky traps and in the ear-zone region of corn plants to predict subsequent root-feeding damage in corn. Western corn rootworm adults accounted for >97% of the total corn rootworm species sampled. Adult population estimates obtained at calendar week 33 (mid-August) had the highest correlations with subsequent root damage among all sampling intervals from July to August for both the Olson sticky trap and the ear-zone visual counts. Linear regression models for Olson sticky trap and ear-zone counts explained 65 and 41% of the variability in root ratings, respectively, and were used to calculate western corn rootworm economic thresholds for each sampling method. Various edaphic and agronomic variables, including planting date, years in continuous corn, percentage of sand in soil, and monthly precipitation levels were used to help improve the models of adult counts as a predictor of subsequent damage. Sampling plans and economic thresholds of 20 western corn rootworm adults per trap per week for the Olson sticky trap and 0.35 adults per ear zone were suggested. Olson sticky traps correctly predicted economic damage (root rating >3.5) to corn in 81% of the fields, and resulted in only one serious error of failing to predict economic damage. Ear-zone counts correctly predicted economic damage to corn in 74% of the fields but resulted in 6 (14%) serious prediction errors.