You might not be able to see lawn grubs, but the damage they cause to your yard can be pretty obvious. Grubs are insects that are typically white in color and resemble a caterpillar. They are immature scarab beetles that work inside the soil, eating the roots of your grass, thereby killing it.
Damage from lawn grubs appears as sections of brown turf throughout your lawn. The damage is different than other types of brown spots, however, because the damaged turf from lawn grubs peels easily away from the soil, almost like peeling a piece of carpet away from the floor. The patch of turf lifts easily because most of the roots connecting it to the soil are gone as a result of the lawn grubs' work.
When attempting to destroy an infestation of lawn grubs, your lawn care options are rather straightforward. First of all, you should know that if you wait too long to treat the lawn grubs, the infestation can become advanced. If its gotten too widespread, your only option may be to replant the entire lawn.
In most cases, you'll want to apply a fertilizer-insecticide granule combination that will destroy the grubs. You'll usually want to apply this treated fertilizer in the late summer or early fall, when lawn grubs are most active. Depending on how common grubs infestations are where you live, you may want to incorporate an annual lawn application that limits grub populations. You can also treat small areas of your lawn that show heavy infestation with concentrated chemicals. In some areas, using a natural grub control option, such as parasitic nematodes, might be the best solution.
Before deciding what to do, you'll want to determine the level of risk before deciding whether to treat them at all. A few grubs are not going to destroy your lawn. However, a large number of grubs can cause damage quickly once they begin to feed.
Taking a sample count of grubs in your lawn is easy. In middle-to-late summer, stake out a few sample areas in your lawn. Using a garden shovel, carefully cut into a few sections of grass, peeling it back. Search the soil for grubs, calculating how many grubs you may have per square foot (about 929 square cm) of turf. If you average four or fewer grubs in that amount of space, your lawn should be fine. Averaging five to nine grubs is cause for concern. If you're averaging 10 or more grubs in your samples, you need to take action. Keep in mind that a strong, healthy lawn with a good root structure can withstand more grubs more efficiently than a sickly lawn.
If you have a large number of grubs in your lawn, you may attract animals such as raccoons, birds, moles, and even skunks. These animals feed on the grubs. In doing so, they'll dig to reach the grubs, further damaging your lawn.