EFFECTS OF IMIDACLOPRID SEED TREATMENT OF CORN ON FOLIAR FEEDING AND ERWINIA-STEWARTII TRANSMISSION BY THE CORN FLEA BEETLE

The effects of imidacloprid seed treatment (a systemic insecticide) on corn flea beetle leaf feeding and transmission of Erwinia stewartii t o corn were studied in greenhouse experiments. Seed of corn inbred A63 2 was treated with imidacloprid at 6.0, 3.0, 1.5, or 0 g a.i./kg seed and planted in 15-cm pots. Corn flea beetles were allowed to feed on E . stewartii-infected corn plants for 9 to 10 days and were transferred to insect cages containing the 2- or 3-week-old seedlings grown from treated seeds. Beetles were allowed to feed on the treated plants for 2 to 4 weeks. Flea beetle feeding damage, Stewart's disease symptoms, E. stewartii infection (detected by enzyme-linked immunosorbent assay) , and plant growth were evaluated. Imidacloprid seed treatment at 6.0 and 3.0 g a.i./kg seed significantly reduced the total number of flea beetle feeding scars, the number of feeding scars >3 mm in length, the number of leaves with Stewart's disease symptoms, and the number of p lants infected by E. stewartii, compared with the control plants. Resu lts indicate that imidacloprid seed treatment at greater than or equal to 3.0 g a.i./kg seed can be an effective control practice for Stewar t's disease in young corn plants.