Anytime lawns show signs of damage or browning, it’s important to find the cause — and grubs are one possible culprit. Grubs are the larva or immature stage of various beetles like Japanese and chafer beetles.
There are about 10 species found across the country. Grubs eat roots, causing the grass to wilt, turn brown and increase the likeliness of turf loss. Experts say it’s important to follow these do’s and don’ts to properly control grubs.
DO
Check with the local cooperative extension office to find which grubs are common in your area. “This knowledge will guide when to start checking for larvae feeding damage and determining an insect control strategy,” says Ben Hamza, Ph.D., product development associate director for FMC.
Educate. Manufacturers can supply contractors with information about grub infestations to share with homeowners. “Contractors should also educate themselves on how to identify species of grubs by their pattern and characteristics,” says Mike Agnew, Ph.D., technical services manager for turf at Syngenta.
Know how the insecticide works. Contact insecticides work by coming in contact with the grub in the soil, Hamza says. Plant roots absorb systemic insecticides, and the grub comes in contact with the active ingredient as it ingests treated plant material.
Look for grub damage. “The lawn becomes spongy because the grubs have eaten the roots and churned the soil, making it a little soft. If you tug on the sod and it pulls up, you can tell if you have grubs,” Agnew says. “You might also see crows, raccoons, skunks or other animals digging up the lawn looking for grubs to eat.”
Time application around the peak egg hatch. “The smaller the insect is, the easier it is to control — and they’re relatively close to the surface after they hatch,” says Ian Rodriguez, Ph.D., technical services manager at Quali-Pro. “Make sure you’re getting the product down by June to mid-July.”
Control more than grubs. Consider a product that also covers other insects found on the property like sod webworms, billbugs and caterpillars. If you apply the insecticide early with the preventive compound chlorantraniliprole, you can control a variety of pests including grubs, Agnew says.
Apply preventively. Preventive treatments provide longevity of control. “It doesn’t have to be 100-percent precise with the day they hatch,” Rodriguez says.
Use a systemic product. Systemic applications will get into the soil and control the insect after it hatches. “You can apply an insecticide like (chlorantraniliprole) anytime between April to July for season-long control with a single application,” Agnew says.
Water in grub applications. It will help move the product down into the soil where the grubs are developing and increase the product performance, Hamza says.
Treat breakthroughs. Use contact insecticides for breakthroughs in the fall or for new accounts that weren’t previously treated, Rodriguez says.
DON’T
Treat for the wrong pest. Agnew says spraying an insecticide that only treats sucking insects, for example, won’t work on grubs. Check the label to ensure it will cover the intended insect.
Overirrigate. “That gives you less roots, so fewer grubs can do more damage, compared to having a dense root system,” Rodriguez says.
Apply the product too early. Agnew says if you apply a biological product before the insect is present, the application won’t work because it affects the insect only.
Expect grubs to die immediately. “Some products stop the insects from feeding,” Agnew says. “So, although they will cease to continue causing damage, it could take up to a few weeks for them to perish.”
Apply insecticides unnecessarily. Don’t assume every brown area on the lawn is from grubs or other turf insects. “Whether using contact or systemic insecticides, avoid applying them when there is no target pest present,” Hamza says.
