A common urban landscape problem in California is animals digging up turf during late summer and autumn. The vertebrate pests causing the damage are raccoons, skunks, wild pigs, and geese. The real culprit, however, is underground. The skunks and other vertebrates are digging to eat fat, juicy beetle grubs in the soil. These white grubs, larvae of scarab beetles such as the masked chafer, also directly damage plants and turf by feeding on their roots.
Insecticides can be used to kill white grubs, but potential negative impacts include surface water, soil, and groundwater contamination; harm to human health; disruption of the ecosystem; economic costs; and negative public perception. For instance, urban surface water contamination with pesticides has been recorded at levels two to three times higher than that in production agricultural areas. Some of the culprits found in urban surface waters include insecticides and herbicides like diazinon, chlorpyrifos, pyrethroids, fipronil, 2,4-D, triclopyr, diuron, MCPA, bifenthrin, imidacloprid, and malathion.
Area Urban IPM Advisor Andrew Sutherland teaches no grubs = no digging = no problem. By managing white grubs in the spring and early summer, vertebrate damage to turf in the summer and autumn can be prevented. He suggests preventive tactics first to lessen grub feeding damage, such as planting more tolerant warm season grasses, providing proper irrigation, and removing thatch. Sutherland tested two insecticides against white grubs in municipal turf areas: one containing a bacterium, Bacillus thuringiensis galleriae, and one containing the active ingredient chlorantraniliprole. These insecticides were applied at two different sites, one newly-planted and one with a chronic white grub infestation. Insecticide application timing was based on the monitoring of adults via light traps or according to the traditional calendar-based schedules of cooperating municipalities. At each site, both treatments, whether they were applied on a calendar basis or when monitoring indicated a need, reduced the numbers of grubs when compared to untreated plots.
Sutherland’s research will improve knowledge about preventing damage from grubs feeding on roots as well as from vertebrates digging for the grubs in turf areas. His outreach efforts will improve IPM skills of professional turf managers to correctly identify grub pests, monitor for grubs, and make decisions about when an insecticide might be needed. It is anticipated that increased knowledge and improved skills will facilitate the adoption of IPM programs for white grubs in turf.
Long-Term Impacts
