Effects of Imidacloprid Seed Treatment of Corn on Foliar Feeding and Erwinia stewartii Transmission by the Corn Flea Beetle. G. P. Munkvold, Assistant Professor, Department of Plant Pathology; Iowa State University, Ames 50011. D. C. McGee, Professor, and A. Iles, Research Technician, Seed Science Center and Department of Plant Pathology, Iowa State University, Ames 50011. Plant Dis. 80:747-749. Accepted for publication 18 March 1996. Copyright 1996 The American Phytopathological Society. DOI: 10.1094/PD-80-0747.

The effects of imidacloprid seed treatment (a systemic insecticide) on corn flea beetle leaf feeding and transmission of Erwinia stewartii to corn were studied in greenhouse experiments. Seed of corn inbred A632 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 plants infected by E. stewartii, compared with the control plants. Results indicate that imidacloprid seed treatment at ≥3.0 g a.i./kg seed can be an effective control practice for Stewart’s disease in young corn plants.

Keyword(s): Pantoea stewartii, Stewart’s bacterial wilt