Lawn Insect Pests

Lawns have a place in many landscapes; they provide space for outdoor activities and can also increase the aesthetic and economic value of the landscape. Additionally, lawns aid in erosion control, filter pollutants, and provide oxygen. For your lawn to function best it needs to be healthy.

It's not just people who like a nice green lawn. Several insects feed on grass and their roots, and can ruin a perfectly good yard. As with so much, an ounce of prevention is worth a pound of treatment. Lawns are no different and the best way to keep your lawn healthy and looking great means mowing to the correct height, watering efficiently, and fertilize appropriately. If you think a pest has been munching on your lawn be sure you discover who the culprit is before you work to remedy the situation. Knowing which pest you are dealing with will determine which course of treatment is best.

White stubby wormlike grub

White grub

White grub is a general term for all scarab beetle larvae. These grubs feed on the roots of all turfgrass species and live at or just below the soil-thatch interface. All white grubs rest in a curled C-shape and are about ½ to 2 inches long; chafer beetle grubs are the most common in Florida lawns, and are on the small end of that range.

Initial, mild damage from the grubs will leave areas of turf yellow, which is a symptom that is hard to correctly diagnose. Major damage will result in large areas of dead turf; this kind of damage usually becomes noticeable in late summer to early fall, particularly when the turf is stressed, for example by drought. Read more about white grubs.

Fall armyworm

Fall armyworm

Fall armyworms are actually the larval stage of a moth. These small, light-colored caterpillars with dark heads will eat many types of grassy weeds and lawn grasses, including bermudagrass. Despite their name, fall armyworms cause damage to turfgrass in spring and fall. Damage from fall armyworms is uniform across a large area and results in bare spots in a lawn. They rarely kill lawns, but can do damage. Fall armyworms are often controlled by their natural predators, like wasps and other predatory bugs. Be aware that pesticide applications can affect these natural predators, so keeping your lawn healthy and well maintained is the best to prevent rather than treat for a pest. Read more about fall armyworms.

Chinch damage

Chinch bug damage

In your St. Augustine lawn, look for yellow or brown chinch bug-damaged areas found first in the hotter, drier parts of your landscape. Damaged areas appear as yellow to brown patches, and injury typically occurs first in grass that’s water-stressed or in full sun. If you suspect you have chinch bugs, inspect the border between the brown and green grass for the tiny, black-and-white adults. Treat with an appropriate pesticide in the spring, or try non-chemical options like reducing thatch or minimizing fertilizer use.

In a Bahia lawn, tunnels may indicate the presence of mole crickets. Mole crickets are a serious pest problem in Florida. They tunnel through the roots and eat the shoots of grass (and munch on the foliage of other plants as well). There are three species of mole crickets considered pests in the Southeast: tawny, southern, and short-winged mole crickets. Mole crickets can damage any grass cultivar, but prefer Bahia and Bermuda grass.

Their tunneling near the soil surface dislodges plants or causes them to dry out. If you suspect you have mole crickets in your lawn, you can check their presence by pouring a solution of liquid detergent and water onto a few square feet of turf. If multiple mole crickets appear, you may want to consider a control. Or you can purchase special nematodes for your soil that infect and kill mole crickets.

In the summertime, tropical sod webworms can attack the grasses in many Florida lawns. These hungry pests can quickly make a lawn look scalped. The gray-green caterpillars grow up to an inch long and prefer feeding on St. Augustine, bermuda, and zoysia grasses. They feed at night and then curl up on the soil surface during the day.

If you think your lawn could be affected by tropical sod webworms, kneel down and check the grass blades for signs of chewing or scraping. Poke around in the grass to see if you can spot any webworms. You can also do a soap drench test to help flush out any insects hiding in the thatch. The good news is that the grass should recover from the damage, as long as you continue to irrigate it properly and keep it healthy. Read more about tropical sod webworms.

Hunting billbug

Hunting billbug

Hunting billbugs are small but damaging weevils that often infest zoysia and bermuda grasses. Adults chew on the stems, rhizomes, and stolons, while larvae bore into stems and feed on roots. Heavily infested grass turns yellow and dies. Symptoms may be misdiagnosed as disease, drought, or a slow spring green-up.

If you suspect billbugs, start with a "tug test" to see if the damaged grass easily pulls free. Then look for sawdust-like debris inside the damaged grass tissue or small, legless white larvae in the plants or the top two inches of soil.

Keeping grass watered may help it tolerate light infestations. But if you find more than ten billbugs per square foot, an insecticide will be needed. Be sure to read the label and follow all instructions.

Fire ants are also a pest that lurks in the lawn. Read more about fire ants.

Insects aren’t the only cause of lawn damage. Make sure you correctly identify the problem before applying any treatments. Spot-treat only the infected areas, and remember to follow all label instructions.

Once you have an idea of what pest you are dealing with, you can contact your local county Extension office for information on treatments.

UF/IFAS Publications