When grubs crash your lawn party, it’s a serious problem. As your lawn begins to green up in early spring, dead patches are usually a dead giveaway that these uninvited pests are lurking. Patches of grass that appear brown and lackluster can be a sign of various lawn pests, but a grub infestation is easy enough to diagnose — and treat.

    How to Diagnose a Grub Infestation

    • You noticed many beetles in the yard the summer before.
    • You see holes from armadillos, raccoons, and skunks digging in your yard, or birds patrolling your lawn regularly.
    • There are dead patches of turfgrass in the spring.
    • Your lawn feels spongy when you walk across it, a bit like freshly-laid sod.
    • You can peel back patches of grass easily, like a piece of loose carpet.
    • When you peel back dead, brown patches, you see grubs.
    • You see more than 10 lawn grubs in a 1 square foot of exposed soil.

    Grubs, or white grubs, are the larval form of many species of adult beetles. They look like a creature out of the movie “Alien.” Japanese beetles, June beetles, European chafers, and scarab beetles all begin life as wrinkly, white, C-shaped creepy crawlies that live beneath the thatch layer of your lawn. They live in this soil layer, feasting on the tender grass roots that anchor your lawn to the earth.

    What are Lawn Grubs?

    The grub life cycle lasts a year, except for the May and June beetles, which have a three-year life cycle. Female beetles lay eggs in the soil in July. Weeks later, in late summer, the eggs hatch and begin to feed on grass roots and organic matter in the uppermost layer of soil. In early fall, they burrow deeper to below the frost line, where they will remain until spring.

    In early spring, the grubs resurface to damage your garden yet again as they consume roots of grass and plants before entering a pupal stage. In late June to early July, pupae become adult beetles that crawl to the surface to find food and mate so that they can begin the cycle once more.

    How to Prevent Grub Problems

    The best way to control grub populations is to prevent them from becoming a problem in the first place. Always water deeply, rather than frequently. This will encourage grass to form deep roots that are less susceptible to grub damage. Mow grass high to keep your lawn healthy, and aerate annually to ensure good oxygen flow to your grass. A good lawn care routine can help make your lawn inhospitable to beetle larvae and protect your lawn from both grub damage and disease.

    If you suspect a grub problem, make sure it’s grubs, not moles or a lawn fungus disease, before you attempt to treat the issue. Once you determine that grubs are the blame, time your grub treatment appropriately. An insecticide applied in the spring can sometimes last up to three years.

    How to Get Rid of Grub Worms in a Lawn 

    Before choosing an insecticide, check the ingredients and directions. Peter Bowden, a New York gardening expert, reminds us to water in all products immediately following application.  “Don’t count on rain to do the job!” he says. “After you apply the grub control, get the sprinkler out and soak the area with an inch of water. Use an empty tuna fish or cat food can to measure the inch of water.” The insecticide must reach deep into the roots of your lawn.

    Biological Treatment

    Parasitic nematodes or milky spore offer a biological approach for homeowners who want a grub killer but wish to avoid chemicals. These beneficial nematodes will kill grubs without affecting earthworms and other beneficial soil organisms. Milky spore will suppress Japanese beetle grubs, but not many other species. Follow label directions carefully and know that it may take a few applications to achieve the grub control you desire.

    Neem oil is another natural way to suppress grubs, but it is applied as a preventive measure. It seems to inhibit the egg-laying of the insects.

    Preventative Chemical Treatment

    The next pest control approach is a chemical preventative product. Products that contain imidacloprid, thiamethoxam, or clothianidin will not control grubs in the spring. These products are best applied in June or July to kill grubs as they hatch. Mow the lawn before the application! This will help to protect bees and other pollinators by removing any flowering grasses or weeds. Immediately after application, water from between one half to an inch to increase the effectiveness of the treatment.

    Curative Chemical Treatment

    Carbaryl and trichlorfon are curative treatments that should only be used in the case of severe infestations. They are most effective when applied in September, with efficiency dropping by up to 25 percent by October. Always mow before applying chemicals to avoid killing bees or other pollinators.

    When these nasty pests crash your lawn party, it’s possible to kick them out, but it will take a little patience, good timing, and some dedication to restore a healthy lawn. A reminder, if you find only a few grubs, you may want to leave it up to Mother Nature. There’s a reason all those birds are hanging around. They’ll enjoy a good meal and take care of a few grubs. But if you’ve got more than the birds can handle, it’s time to kick the grubs to the curb.

    Image credit: “Curl grub,” CSIRO, CC 3.0