Submitted to: Extension Circular
Publication Type: Research Notes
Publication Acceptance Date: 12/7/2004
Publication Date: 3/12/2005
Citation: Reding, M.E., Zhu, H., Zondag, R. 2005. Application of imidacloprid through drip irrigation for control of white grubs in field-grown nursery crops. Extension Circular 195. p. 131-134.
Technical Abstract: The larval stages of exotic scarabs (white grubs) are serious pests of nursery crops in the midwestern and northeastern states. They injure and kill plants by feeding on the roots. Control can be achieved by applying treatments of reduced-risk insecticides such as imidacloprid to the soil surface. However, efficacy is dependent on applications of sufficient water to facilitate movement of the insecticide into the soil. Growers who use drip irrigation tend to have difficulty applying sufficient water to move insecticides off the surface into the soil. We tested drip irrigation as a delivery system for applying imidacloprid to control white grubs. Our agricultural engineering group designed a system which allowed us to inject insecticide (imidacloprid) into drip irrigation lines in a commercial nursery. The insecticide was applied to 6 Kousa dogwood trees in each of three rows on 1 July 2004. This timing targeted the egg and early larval (grub) stages of the scarabs. The trial was evaluated 21 September 2004. Trees were dug by hand, the root balls broken apart, and the soil and roots were searched for grubs. Four species of exotic white grubs were found with oriental beetle (Exomala orientalis) being the most common. The insecticide treatment reduced grub numbers by 62% in the treated trees compared to the untreated (water only) trees (3.6 versus 9.4 grubs per tree, respectively).