Systemic delivery of insecticides in blueberries for control of blueberry stem gall wasp, hemadas nubilipennis / Amber Kay Bosch.

Blueberry stem gall wasp (Hemadas nubilipennis) is a pest of highbush blueberry and can pose a challenge to control with foliar sprays due to adult activity during bloom and larval development within the plant tissues. In this thesis, systemic delivery of insecticides in blueberry bushes was evaluated using three application methods on potted bushes, in blueberry shoot bioassays, and on a commercial blueberry farm. Each study aimed to evaluate impact on gall and gall wasp development, along with active ingredient residue delivery to plant tissues. I hypothesized that if the insecticide moved systemically within the blueberry vascular system to areas where the blueberry stem gall wasp larvae are developing, then the insecticide will kill the larvae leading to a reduction in gall formation and number of surviving adults per gall. In the potted bush study, applications were made by crown injection, soil drench and foliar sprays. Imidacloprid, flupyradifurone, and spirotetramat were recovered in shoot and leaf tissues, however there was no evidence of inhibited gall or gall wasp development. In the shoot bioassays, imidacloprid and spirotetramat were found to have the greatest potential for control of blueberry stem gall wasp. Active ingredient recovery in bioassay gall tissue revealed the concentration needed to get moribund/ lethal larval response. The on-farm study indicated there was successful movement of imidacloprid and flupyradifurone using chemigation, however, the impact on blueberry stem gall wasp was not great enough to provide control.

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