Evaluation of a preplant method for detecting damage to germinating corn seeds by multiple species of insects.

Field studies were conducted in Virginia cornfields from 1989 to 1991 to evaluate a preplant method for detecting damage to germinating corn seeds by multiple species of insect pests, including seedcorn maggots, Delia platura (Meigen); several species of wireworms in the genera Melanotus, Conoderus, and Aeolus; and several species of white grubs in the genera Popillia, Cyclocephala, Cotinis, and Maladera. The method used consisted of evaluating feeding damage to corn seeds in wire-mesh traps (i.e., baited wire traps) that were buried in cornfields for approximately 2 wk before planting. In the 1989 study conducted in a cornfield with a large infestation of wireworms, a significantly greater proportion of corn seeds exhibited feeding damage in the baited wire traps (38.3%) compared with corn seeds planted by hand at conventional plant spacings (i.e., simulated commercial plantings) (31.5%). Further evaluation in 47 cornfields in 1990 and 1991 revealed no significant difference between the proportion of damaged corn seeds in the baited wire traps (2.7%) and simulated commercial plantings (2.0%). A significantly greater proportion of corn seeds exhibited feeding damage in the commercial plantings (5.4%) compared with the baited wire traps; however, mean stand loss associated with insect feeding in the commercial plantings was only 0.4%, which was substantially less than the proportion of damaged corn seeds in the baited wire traps. Significant linear regressions were obtained between the proportion of damaged seeds in the baited wire traps and the proportion of damaged seeds in the simulated commercial plantings, commercial plantings, and proportion of stand loss in the commercial plantings. However, the lack of economic stand loss in the commercial plantings and low regression coefficient of determination precluded the development of a baited wire trap damage threshold to predict stand loss in fields subsequently planted with corn.