Even if you follow strict lawn maintenance procedures and plant the right type of grass for your climate, you can still run into trouble. Following are seven of the most troublesome and common lawn insect pests with tips on how to identify and control them:
Armyworms and cutworms: Armyworms are most common in cool, moist spring weather. Cutworms prefer new lawns. To see whether you have cutworms, drench the soil with a soapy water solution (2 tablespoons of dish soap in a gallon of water).
Armyworms and cutworms are both moth larvae. Armyworms are light green to greenish brown caterpillars with three lighter colored stripes down the back and sides. The middle stripe ends up as an inverted Y on the head. They often look greasy. Cutworms are almost always curled into a tight circle when you find them. They are plump, usually brown to black, and sometimes with lighter colored stripes or spots.
Bacillus thuringiensis (Bt)is an effective control. Beneficial nematodes and pyrethrin sprays are also effective. You also can reseed with grass varieties that include endophytes. Several traditional insecticides are labeled for control of armyworms and cutworms.
Billbugs: Billbug adults and larvae feed on lawns. You can recognize the 1/4 to 3/4 inch, brown to black adult weevils by their long snouts. Adult billbugs feed on grass stems. The small, white larvae look like a gooey piece of rice with an orangish-brown head. The larvae feed on plant roots. The larvae’s feeding is usually most destructive.
Look for the pest at the edges of dead spots. You also can see a frass (debris that looks similar to sawdust) near where the insects feed. If the dead grass pulls up easily, that’s another good sign you have billbugs.
Aerate the lawn and reseed with endophytic grass varieties. The botanical insecticide rotenone may provide some control. Several traditional insecticides, including diazinon, are labeled for controlling billbugs.
Chinch bugs: Chinch bugs are small, red (young) or black (mature) insects with a white spot or markings on their back.
You can often see chinch bugs by examining the grass near the soil surface. To be sure, push a bottomless metal can several inches into the ground in an area where the grass is just turning yellow. Fill the can with water, and the billbugs will float to the surface.
Eliminate thatch to improve water and fertilizer penetration and follow good cultural practices. You also may want to replant a chinch bug-resistant variety of St. Augustine grass called ‘Floratam’. Endophytic lawn varieties also resist chinch bugs. Insecticidal soaps effectively control chinch bugs, as do traditional insecticides such as chlorpyrifos and diazinon.
Greenbugs (aphids): Greenbugs, are aphids — small (1/16 inch), egg-shaped, long-legged, almost transparent insects that congregate on grass blades.
Greenbugs suck plant juices, turning the grass blades yellow to burnt orange and finally brown. These pests are particularly troublesome on Kentucky bluegrass lawns in the midwestern United States. Visual examination is the best way to confirm their presence — get down on your knees and look carefully in shaded areas during the hottest part of summer.
Most of the time, naturally occurring beneficial insects like ladybugs and lacewings keep greenbugs under control.
Sod webworm: Sod webworms are the larvae of a buff-colored, night-flying moth. You may notice the adult moth first. They flutter over the lawn at night, flying in a crazy zigzag pattern.
Examine the lawn at night with a flashlight. To confirm their presence, soak a small section of lawn (about 2 x 2 feet) with soapy water (2 tablespoons of dish soap in a gallon of water). The soap brings the worms to the surface in about 5 to 10 minutes.
Aerate the lawn to reduce thatch and improve water penetration. Bt is the preferred biological control of sod webworms. Predatory nematodes, insecticidal soaps, and pyrethrins are also effective.
White grubs: White grubs are the larvae of various types of scarab (or chafer) beetles. The type of grub that infests your lawn depends on where you live, but the grubs all look pretty much alike and do the same damage.
The grubs feed on grass roots, causing the lawn to turn brown in large, irregular patches. If dead sections of the grass pull up like a piece of carpet, you probably have grubs. Birds, moles, raccoons, and skunks like to feed on grubs, so if your lawn looks like a zoo, that can be another sign.
Predatory nematodes effectively control many types of grubs.