SEMIOCHEMICAL-INSECTICIDE BAIT PLACEMENT AND VERTICAL-DISTRIBUTION OF CORN-ROOTWORM (COLEOPTERA, CHRYSOMELIDAE) ADULTS - IMPLICATIONS FOR MANAGEMENT

Experiments were conducted in 1988 and 1989 to determine the effect and potential interaction of height of semiochemical-insecticide bait placement and within-canopy adult corn rootworm vertical distribution on beetle mortality in baited traps. Results of an experiment utilizing semiochemical-insecticide baited traps, and unbaited yellow sticky traps placed in a corn (Zea mays L.) field at 0 m and corn ear height indicated that D. virgifera virgifera LeConte mortality was significantly higher at ear height baited traps. In addition, more D. v. virgifera females were distributed near ear height than at 0 m. Results of subsequent experiments with baited, and unbaited traps placed at 0, 0.6, 1.2, 1.8, and 2.4-m height intervals within the canopy indicated that efficacy of starch baits increases with height of bait placement and the vertical distribution of corn rootworm beetles interacts with height of semiochemical-insecticide bait placement. Data from all experiments strongly indicate that semiochemical-insecticide granules placed at ground level will not effectively attract and kill female D. v. virgifera beetles. To optimize the effectiveness of corn rootworm semiochemical-insecticide baits, application of formulations should be restricted as much as possible to regions at or above the ear. Formulations need to be developed that will adhere to plants at the time of application.