Everyone loves having a lush green lawn, and if the lawn starts to look unhealthy many people will call a professional lawn care service in to check it out. People in the lawn care business perform many tasks, and one of those tasks is finding out what could be killing a customer’s lawn. A common problem lawn owners face is grub infestation. Knowing the symptoms and how to identify a grub infestation is a great way to head off the problem before the entire lawn needs a complete reseeding.

What are Grubs

Grubs are the larvae of some types of beetles. Masked chafers and Japanese beetles are two of the beetle types that can cause a grub infestation. After the beetle eggs hatch into grubs in late summer, the immature beetles begin consuming the organic matter just under the surface of the soil. Most plants can survive this damage, but turf grass can become extremely damaged. The grubs will eat until the cold months set in, and then they will hibernate until spring. The larger grubs will then continue to eat until they emerge from the ground as adults. The adults will then breed and lay more eggs that will hatch into grubs.

The C-shaped grubs  have grey to white bodies and brown heads. They can be anywhere from 3/8 to 1 inch long.


If the lawn owner has a lot of adult beetles flying around their yard in the spring and summer, then there is a chance of having a grub infestation. Symptoms of this infestation resemble drought stress and may prompt owners to over water their lawns. The grass may appear off color, can wilt in the sun, could thin, or even die off in large areas. The lawn will also feel spongy, and because the organic roots are being eaten away the grass can be peeled back like carpet.

Checking for Grubs

A simple test to check for a grub infestation should be preformed before treating, as the symptoms do resemble drought stress. Several square feet of the turf should be peeled back. Look for and count the number of grubs that are found. If fewer than five grubs are found per square foot then they are not a problem. Healthy lawns may withstand five to ten grubs per square foot for a short time, but a sickly lawn should be treated. If more than ten grubs are found the lawn should be treated as soon as possible.


Lawns with a small population of grubs face no threat from the immature beetles, but moles, raccoons, skunks, and other insect eating animals will be attracted. If the grubs are not the problem then the lawn should not be treated for them. Instead the lawn owner should take measures to detour the animals that could hurt their lawn.

Fertilizer insecticides or biological insecticides can be used to treat for grubs. The most effective time to treat the lawn is in late summer or early fall. Grubs will be smaller and easier to kill at this time. There are also spot treatments that can be used if the grub infestation is still small.