SOD WEBWORMS, Crambus and Pediasia species, Pyralidae, LEPIDOPTERA
Adult-The moths are 1/2 to 3/4 in. long. They have a prominent snout. The forewings are brown or dull ash gray with a whitish streak from the base to the margin; the hind wings are brownish. When at rest, the moths fold their wings closely.
Egg-The tiny, oblong eggs are white to pale yellow.
Larva-Most sod webworms vary from pinkish to yellowish to light brown. They become 5/8 to 1 in. long with thick bodies, coarse hairs and spots on each segment. The head is yellowish brown to black. Individual caterpillars often assume a C-shape.
Pupa-The reddish-brown pupae are oblong and 3/8 to 1/2
Larvae cut off grass blades just above the thatch line, pull them into their tunnels and eat them. The injury appears as small brown patches of closely cropped grass. Where many larvae are present, patches merge into large, irregular brown patches.
Webworms overwinter as young larvae in silk-lined tubes a few centimeters below the soil line among the roots of weeds and grasses. During early spring, larvae feed on the upper root systems, stems and blades of grass. They build protective silken webs, usually on steep slopes and in sunny areas, where they feed and develop. In early May, they pupate in underground cocoons made of silk, bits of plants and soil. About 2 weeks later, adults emerge. Beginning in May, moth flights may occur until October. The moths, erratic and weak fliers, live only a few days and feed solely on dew. Active at dusk, moths rest near the ground in the grass by day. Presence of moths indicates a possible infestation of larvae. The eggs are laid indiscriminately over the grass and hatch in 7 to 10 days. Young larvae immediately begin to feed (mostly at night) and construct silken tunnels. The most severe damage occurs in July and August.
Most sod webworms complete 2 or 3 generations each year. About 6 weeks elapse between egg deposition and adult emergence. Infestations in lawns can be detected by applying 1 tablespoon of pyrethrin insecticide or 1 ounce of soap in 1 gallon of water per square yard. Sod webworms will surface among the blades within a few minutes at the border between living and dead areas of turf. If 3 or 4 webworms are found in a square foot, control is recommended. Because birds and other predators are not reliable in giving acceptable control, it is sometimes necessary to use chemicals to protect fine turf from further damage. Apply one of the suggested chemicals to the lawn but do not water it in. Use 6 gallons of spray mix per 1000 square feet except where noted. It is best to treat in the late afternoon as sod webworms feed in the evening.
Recommendations for insecticides approved for control of these insects in home
lawns can be found under Sod Webworms in Insect
Control in Home Lawns in the NC Agricultural Chemicals Manual.
Recommendations for insecticides approved for use on sod farms, golf courses or other commercial sites can be found in Commercial Turf Insect Control in the NC AgriculturalChemicals Manual.
Recommendations for the use of chemicals are included in this publication as a convenience to the reader. The use of brand names and any mention or listing of commercial products or services in this publication does not imply endorsement by the North Carolina Cooperative Extension Service nor discrimination against similar products or services not mentioned. Individuals who use chemicals are responsible for ensuring that the intended use complies with current regulations and conforms to the product label. Be sure to obtain current information about usage and examine a current product label before applying any chemical. For assistance, contact an agent of the North Carolina Cooperative Extension Service in your county.
Ohio Fact Sheet
© 2001 NC Cooperative Extension Service
June 1994, Revised April 2002
Note lasted reviewed January, 2011 by the webperson