Turfgrass - Sod Webworms

sod webworm moth sod webworm larva sod webworm damage



The sod webworm complex (Family Pyralidae) is a large group of insects consisting of over 20 species that infest turfgrasses in the United States. Among the more important turfgrass-infesting species are those belonging to the genus Crambus.

Adult sod webworms, sometimes referred to as "lawn moths" are buff-colored, about 1/2 to 3/4 inches long with snout-like projections extending forward from the head. At rest, they fold their wings around the body, giving them a cylindrical or cigar-shaped appearance. Sod webworm larvae (caterpillars) are gray to tan with small dark spots on the body and brown heads. They reach 3/4 to 1 inch when fully grown.

Life History

Sod webworms overwinter as partially grown larvae in silk-lined tunnels in the thatch and soil. In most years, larval activity resumes in April or early May. Webworms complete development, pupate and emerge as adults from mid-May to mid-June. Adult sod webworms rest in the turf and on shrubbery during the day and randomly scatter their eggs into the grass in the late afternoon and early evening while flying in a zigzag fashion just above the turf surface. Eggs hatch in about one week, and first-generation larvae feed until mid-summer. A second and partial third generation occurs during the remainder of the season. Frequently, generations overlap with all stages present by late summer.

General Symptoms of Sod Webworm Damage to Turfgrass

Sod webworm moths do not damage turf. Larvae feed at night on grass leaves and stems near the soil surface, and hide during the day within burrows lined with silk webbing (hence the name "webworms") which penetrate through the thatch layer and into the soil. Sod webworms feed on most turfgrasses including bluegrass, bentgrass, tall and fine-leafed fescues, zoysiagrass and buffalograss.

One of the first signs of webworm infestation is small, ragged brown spots in the turf. Upon closer inspection, these areas will have a grazed or scalped appearance. As webworms continue growth and feed, the injured areas enlarge and coalesce. Under heavy sod webworm pressure, large areas of turf can be defoliated and even killed during periods of summer heat and drought. While sod webworm larvae are active from early spring through fall, the most serious turfgrass injury usually occurs in mid to late summer.

Sampling Techniques

An early sign of potential infestation is sod webworm moths zig-zagging over the turf at dusk. If a sod webworm infestation is suspected, closely examine the turf for evidence of insect activity. Small patches of grass will be chewed off at ground level. Fresh clippings and green fecal pellets are also usually present. Examine the thatch layer and top inch of soil for larvae, silken tubes and webbing.

To confirm the presence of webworms, mix 1 tablespoon of 1% pyrethrins or 1/4 cup of household detergent with 2 gallons of water. Mark off several one square yard sections of the turf suspected of having a webworm infestation, and apply one gallon of the solution to each section. The solution irritates the caterpillars, causing them to move to the surface within 5 to 10 minutes where they can be counted and a management decision made.

Management Strategies

Sound cultural practices, especially proper irrigation, will usually allow turf to outgrow light to moderate webworm injury. However, if 15 or more webworm larvae are present per square yard in reasonably healthy turf, an insecticide application may be justified. Fewer larvae can cause significant damage to stressed or less vigorous turf.

Insecticidal Control

If insecticides are used, the turf should be mowed and the clippings removed before treatment to enhance insecticide movement into the turf canopy. A thorough irrigation (1/2 to 3/4 inch) prior to application will move webworms closer to the surface. For best results, apply insecticides in the late afternoon or early evening when larvae are active. Following application, the treated area should be lightly irrigated (1/8 inch), but delay heavy watering for 24 to 48 hours unless irrigation is indicated on the insecticide label. Granule applications also should be lightly irrigated immediately after application to wash granules off grass blades and activate the insecticide.




Entomology News at Nebraska

Breaking Entomological News...

  • Samantha DanielGraduate student Samantha Daniel did an awesome job being interviewed  by KODY radio about overwintering insects!!  http://www.huskeradio.com/mugs-in-the-morning/.  Samantha is a master's student mentored by Dr. Julie Peterson.
  • Dr. John RubersonDr. Tom WeisslingCongrats to John Ruberson and Tom Weissling who were honored at the University of Nebraska-Lincoln's Family and Friends Recognition Awards. These awards are nominations by parents for faculty and staff who have a made a significant difference in the students’  lives. Tom has now been recognized twice with this award! Congratulations! And a big thank you to the thoughtful students and parents.
  • Dr. Jeff BradshawDr. Jeff Bradshaw was chosen as president-elect of the North Central Branch of the Entomology Society of America. Bradshaw is an associate professor of Entomology, extension specialist, and interim director of the Panhandle Research and Extension Center in Scottsbluff. 
  • Entomology Alumna Jennifer Weisbrod was recently selected as the new Pesticide Safety Education Program coordinator in the Department of Agronomy and Horticulture. Weisbrod graduated with her master's degree in Entomology in 2020 and is taking the reins from her predecessor Clyde Ogg, emeritus extension educator.
  • Dr. Sylvana Paula-MoraesCongratulations to departmental alumna Dr. Silvana Paula-Moraes who was recently named the recipient of the 2021 Department of Entomology Alumni Recognition Award. She presented a online seminar in connection with the award on Monday, March 1, 2021.
  • 7 seal awardThe UNL Department of Entomology has been awarded the Seven Seals Award by the Employer Support of the Guard and Reserve (ESGR). The Seven Seals Award is presented in recognition of significant individual or organizational achievement, initiative, or support that promotes and supports the ESGR mission, to include the efforts of the more than 4,500 volunteers who carry out ESGR’s mission across the nation on a daily basis. The Entomology Department is fortunate to support Courtney Brummel and Sheldon Brummel in their service to the nation. Thanks for the nomination, Courtney and Sheldon!