Drip Chemigation with Imidacloprid and Nematodes for Control of Scarab Larvae in Nursery Crops

Abstract

Abstract Larvae of scarabs, also known as white grubs, are subterranean insects that damage ornamental nursery crops when they feed on roots. Management is generally based on application of chemical insecticides to the soil surface, followed by supplemental water to leach the toxicants into the soil. Drip irrigation systems have the potential to deliver insecticides and insect pathogens to the root zones of crops to control subterranean insects. From 2004 through 2006, we tested the efficacy of imidacloprid (2004–2006), clothianidin (2006), or entomopathogenic nematodes (EPN) + imidacloprid (2005) applied through drip irrigation to control white grubs in an ornamental nursery. Insecticides (imidacloprid or clothianidin) or EPN + imidacloprid were injected into drip irrigation lines at the upstream end of rows in a commercial nursery. EPN + imidacloprid was also injected into the root zone of trees or applied as a surface drench. In 2004 and 2005, imidacloprid applied at a preventive timing through drip irrigation lines significantly reduced the numbers of white grubs in the root zones of Kousa dogwood (Cornus kousa Hance) trees. In 2006, variation in the data resulted in no significant differences at the P = 0.05 level, although, the percentage reductions of grubs by imidacloprid and clothianidin applied through drip irrigation were similar to trials in 2004 and 2005. EPN + imidacloprid applied through drip irrigation, injected into the soil, and surface drenched at a curative timing all significantly reduced the numbers of grubs compared to untreated trees. These data indicate drip irrigation is a viable delivery system for controls of white grubs in nursery crops.