Have you done everything you can to treat your yard for weeds and disease, but it still has dead spots? You might have lawn-damaging bugs. Use our handy insect identification guide below to find out what’s wrong with your grass.
White grubs are perennial pests of the cooler seasons and turf grasses. May and June beetles and Japanese beetles are found in all areas of Ohio and give birth to white grubs. The larvae eat organic matter including the roots of plants, and their damage first appears to be drought stress. Heavily infested turf first appears off color, grayish green, and wilts rapidly in the hotter weather.
Continued feeding from the grubs will cause the turf to die in large irregular patches. The tunneling of the larvae cause the turf to feel spongy under your feet and the turf can often be rolled back like a loose carpet. Smaller grub populations may not cause turf injury, but predatory mammals that feed on grubs such as skunks, raccoons, opossums and moles dig in the turf in search of a meal. This can cause a considerable amount of turf damage.
Sod Web Worms
Most sod webworm larvae are less than one inch in length and are characterized by having a series of dark spots down their bodies. Some species have these same spots just lighter in color. The most common lawn damaging sod webworms in Ohio are the bluegrass sod webworms. The larvae of this species feeds only in the late fall and early spring when the turf is actively growing. All the sod webworm larvae spend the winter as a partially grown larva buried several inches deep in the soil. At the approach of warm weather in the spring, the larvae move upward towards the surface and begin feeding on the lush spring growth of grass.
The sod webworm caterpillars live in tunnels constructed in turf thatch or extending to the soil under the turf. These tunnels are silk lined and the webbing causes the soil particles and the leaves to stick together. In thicker, greener turf, damage appears as small brown patches about the size of a quarter to three inches in diameter. When the majority of the larvae are present in mid-summer, the small brown patches run together and form large irregular, thin and brown areas.
Cutworms can be very destructive insects, particularly on golf courses and other highly maintained turf areas. Damage can occur any time from late May through the rest of the growing season. Damage is usually most obvious in June through August when temperatures are highest and cool season grasses are not growing as fast. Damaged spots look like smaller round dead areas and can persist for several weeks. Cutworms feed on several kinds of grass, most common are Kentucky Bluegrass and Bentgrass.
Adult southern chinch bugs are small and slender, 1/6 to 1/5 of an inch long. They have black bodies with white wings. Each wing bears a distinctive, triangular black mark. Chinch bug damage is usually first detected when irregular patches of turf begin to turn yellow then straw colored. The straw colored areas may be completely dead. These patches continue to become larger even if you consistently keep watering.
While the chinch bugs are feeding they block the conduction of water and food to the plant, which causes the vessels of grass stems to constrict. By the chinch bugs blocking the water, the leaves wither and food doesn’t get to the roots, resulting in dead turf. Damage generally occurs during the hotter, dryer weather from June into the month of September.
The Billbug adults are only 1/4- to 3/8-inch long and dark grey to black. The larvae are white with a brown head and look like legless white grubs. Billbug damage usually appears in late-June through August, when summer drought stress is common. Light infestations in lawns often produce small dead spots that look like the turf disease, dollar spot. Sometimes the damage looks like irregular dead spots or browning in the turf. Heavy infestations can result in complete destruction of the turf, usually by August.
The major problem with billbug damage is that it can be sometimes confused with a variety of other problems. Billbug damaged turf turns a whitish and can be straw colored. Soil under damaged turf is solid, not spongy as in white grub attacks. To confirm billbug damaged areas, grasp the dying turf and pull upward. If the stalks break easily at ground level and the stems are hollowed out or are full of packed sawdust looking material, billbugs are most likely the culprit.