BirdCast: Garden Pests: White Grubs

Pest: White Grubs, May/June Beetles (Phyllophaga spp.), Japanese Beetles (Popillia japonica) and others.

Discussion: Larval stages of various species of scarab beetles like the Japanese Beetle and June Beetle, live in the soil and feed on plant roots and can have pronounced effects on turf grass. As with other lawn pests, it's best to determine whether you actually have a grub problem before taking action. Grubs outbreaks are periodic in nature, making annual treatment unnecessary. The most frequently recommended method for grub detection is to take a look under your turf in August, when the grubs are large enough to detect easily. Using a trowel, cut three sides of a square with 1 foot sides. Leave the fourth side uncut, and open your little door to inspect the soil and roots of your turf. Take samples from different sections of your lawn. If you find an average of 6 grubs or less, you will probably not notice any problems. 10 to 15 grubs per square foot, and you may notice some damage towards the end of the summer if conditions are dry, and 40 to 60 per square foot would indicate an outbreak that could cause serious damage to your lawn.

Pesticides Commonly Applied: Bendiocarb (Ficam), Carbaryl (Sevin), Chlorpyrifos (Dursban), Diazinon, and others. Check the labels on your pesticide to see what active ingredients they contain.

Biological and Physical Controls: Plant resistant grass such as fescues. Milky spore disease (a microbial insecticide made up of two species of bacteria: Bacillus popilliae and B. lentimorbus ) will kill Japanese beetle grubs, and will remain and protect your soil well in to the future. Several nematodes can also be introduced to control grub populations. Use pheromone traps to attract and catch adults and prevent breeding.

Bird Facts: Robins and Flickers will often probe for grubs in the soil. Blackbirds, wrens, sparrows and Mallard Ducks have been killed by Bendiocarb (Ficam) use around the home. As previously mentioned, registered uses of both Diazinon and Chlorpyrifos have led to a large proportion of documented wildlife kills around the home and garden.