How to Kill Grubs But Not Birds

Determine how bad the infestation is before applying an insecticide. Use a spade or shovel to lift various parts of your lawn and count the number of grubs you see. If you see more than two or three grubs in a 6-inch square patch, you probably need to treat that area of grass.

Use a microbial insecticide to reduce the risk of the toxin spreading to birds, animals and humans. The compounds contain microorganisms such as bacteria, protozoa or viruses that target specific insects and have a very low toxicity to nontargeted species.

Kill grubs with milky spore microbial insecticides. The products contain a bacterium that specifically targets grubs and is especially effective for Japanese beetle grubs. Milky spore penetrates the lawn and can last in an undisturbed area for up to 20 years, meaning you won’t have to continue applying the insecticide.

Spread the insecticide with a spreader for even coverage. Water the area extensively to ensure penetration under the top layer of sod so that it reaches the grubs. Soak the area with 1/4- to 1/2-inch of water for the most effective saturation.

Treat grubs in the late summer or early fall. If you wait until spring when you see the damage to your lawn, the insecticide will be ineffective because the larvae are at full maturity.