Sod Webworms in Turf

Description

The moths are 12 to 34 inch long and 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. Their tiny, oblong eggs are white to pale yellow. Most sod webworms vary from pinkish to yellowish to light brown. They become 58 to 1 inch 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. The reddish-brown pupae are oblong and 38 to 12 inch long.

Biology

Many species of sod webworms occur in the United States. The actual species present in any given area, however, is variable. Sod webworms feed on lawns, golf course grasses, some clovers, corn, tobacco, bluegrass, timothy, as well as pasture and field grasses. They usually favor bluegrass and 'Tifdwarf' hybrid bermudagrass but attack most grasses. 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 two 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 two or three generations each year. About six 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 three or four 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.

Chemical Control

Recommendations for insecticides approved for control of these insects in home lawns can be found under sod webworms in the North Carolina Agricultural Chemicals Manual.

Recommendations for insecticides approved for use on sod farms, golf courses or other commercial sites can also be found in the North Carolina Agricultural Chemicals Manual.

Insecticide and Formulation

Amount per 1,000 sq ft

Precaution and Remarks

acephate* (Lesco-Fate, Orthene T, T&O) (Precise 4G) 0.5 to 1 oz 2.8 lb Home lawns only. Irrigate immediately.
azadirachtin* (Azatrol, Neemix, Turplex) 0.5 fl oz
Bacillus thuringiensis, various brands 1 to 2 lb/acre
bifenthrin* (Menace, Talstar, others) F, GC; G form also available 0.18 to 0.25 fl oz Use GC formulation for golf courses.
carbaryl* (Sevin) 80 WSP 2.5 to 3 oz
chlorantraniliprole (Acelepryn) 0.046 to 0.092 fl oz
chlorpyrifos* (Dursban) 4 E, 2 E, 5 G, Pro See label For use on golf courses; check new label.

clothianidin (Arena)

.5G

50 WDG

14 to 22 oz

0.15 to 0.22 oz

chlothianidin + bifenthrin (Aloft) See label
cyfluthrin* (Tempo 2, Tempo Ultra) 0.143 fl oz Irrigate immediately after application. Do not apply to newly seeded stands or bentgrass.
deltamethrin (Deltagard) G 2 to 3 lb
halofenozide (Mach 2) 2 SC 1.5 G 1.5 fl oz 1 lb Can be used two times per season at these rates.
imidacloprid + bifenthrin (Allectus, Atera) See label Rate varies with pest. Different formulations for different sites.
indoxacarb (Provaunt) SC 0.0625 to 0.25 fl oz Not labeled for use on sod farms.
lambda-cyhalothrin* (Cyonara, Scimitar, Battle) See label Do not make applications within 20 feet of any body of water. No reentry until spray has dried.
permethrin* (Astro) 0.4 to 0.8 fl oz
spinosad A and D (Conserve) SC 0.25 to 1.25 fl oz Rate varies with size and species.
trichlorfon* (Dylox, Proxol) 80 SP 1.5 to 3 oz
dinotefuran (Zylam) 20SG 1 oz per 1000 ft2

References

For assistance with a specific problem, contact your local Cooperative Extension Center