September and October is the time to be scouting for signs of grub activity – this is when their feeding causes turf to wilt and die. Look for brown or dead areas of the lawn where the turf is easily lifted because the roots have been chewed. You will likely find grubs around the outer edge of the turf dieback. Raccoons and skunks will dig and flip the turf over to get a free grub meal. We often get frantic calls from homeowners who have had an animal dig up large areas of the lawn overnight.

 

What are Grubs?

Grubs are the larvae of several different beetles; there are over 30,000 different species worldwide. The ones that affect turf in our area include Japanese beetles, Asiatic or Oriental beetles, masked chafers, and May/June beetles (a.k.a. “June bugs”). The annual white grub is a “C” shaped larva and is identified by the hair pattern on its posterior.

The grub life cycle begins in our area with the over-wintering beetle larvae, often at depths of six feet or more. These larvae migrate to the surface in spring, pupate, and become adult beetles, typically around July 4th. They fly around and mate, laying eggs in the soil, which hatch in a few weeks to become grub larvae. These larvae devour turf roots in September/October for about six weeks before colder temperatures force them to go back down deeper into the soil, starting the process over again the following year.

 

What is the Treatment for Grubs?

Grubs like sunny, well irrigated lawns. Properties with a history of grub activity and/or with an irrigation system are usually treated with a preventative insecticide such as Merit, in June or July. If treating after the grubs emerge, a curative insecticide such as Dylox is very effective. Both products should be watered in within 3 days to ensure maximum efficacy and minimize future damage; ultra-violet light from the sun can degrade the insecticide toxicity if not watered in.

The main benefit to chemical treatments are the speed with which they work and the predictable control. There are also biological controls (milky spore and parasitic nematodes) that can be applied but may take several years to be effective. Applications of Milorganite can help reduce animals foraging for grubs.

After grub activity has dissipated, the lawn can usually recover on its own, though seeding may be needed in severe cases.

 

What About Killing the Beetles?

The grub larvae do most of the damage, though some adults like Japanese beetle cause a nuisance by feeding on ornamental plants and trees for a short period of time. They “skeletonize” foliage, leaving only the veins and mid rib. Their damage occurs too late in the season to cause any harm to the trees or shrubs they inhabit.

Beetle pheromone traps (the bags you hang from a stick) are not recommended for control as they often bring in many more beetles to a given area than would otherwise be there. We do offer a summer insect treatment for Japanese beetles and other pests on certain plants, but treating rose bushes for Japanese beetle is generally not effective as the beetles tend to return to the blooms right away. You can knock them off into a shallow container of soapy water and dispose of them. Rose & Floral dust or spray is effective for control on roses but repeat applications may be necessary.