Sod Webworm: A variety of “snout” moths including Crambus spp. and Bluegrass Sod Webworm, Parapediasia teterrella, Larger Sod Webworm, Pediasia trisecta, and Striped Sod Webworm, Fissicrambus mutabilis

IPM Steps to Reduce Sod Webworms

1. Sample for Pest

Confirm the presence of sod webworms before you treat.

Where to find it while inspecting: You may see adult moths on turf in summer. They hold their wings close to their body so they have a long slender appearance. Most notable is the long mouth parts that resemble a fluffy snout. Females lay eggs on turf at night. Larvae are active at night; during the day will stay in burrows in soil surface and if you suspect webworm damage, you may want to do a soap flush. Look for holes in grass blades or blades cut off near the crown. Damage is seen as small round brown patches (These are also clues for birds who will peck through the damaged grass) NOTE: FLOTATION METHOD OF SCOUTING. Soften the soil a little by pouring some water out of a watering can. Insert one end of the can into the ground at least two or three inches, leaving at least four inches above the ground. Fill the can with water from a garden hose (with moderate pressure) and wait about five minutes. Insects will float to the surface of the water, where you can count them.

2. Proper ID

Are they sod webworms?

Size and Appearance: The adult moths vary in colors and markings, generally dull grays and browns. The worms are generally brown to green with darker spots. Mature larvar up to 3/4".

3. Learn the Pest Biology

What is the life cycle of sod webworms?

Life Cycle: Sod webworms overwinter as mature larvae inside “silk-lined” tunnels or burrows. Larvae feed again in spring and pupate in late spring (May–June). Adults emerge in about two weeks and stay in sheltered areas during the day. Larvae feed from July through August and a second generation occurs before winter.

Preferred Food Sources: Adults do not cause damage. Larvae feed on turf, mostly at night, throughout July and August, choosing to chew off leaves just above the stem.

Preferred Habitat: Turfgrass and field grass. Some species specific to bluegrass and bentgrass.

4. Determine Threshold

How many sod webworms are too many?

Threshold: 5–15 larvae per square yard as determined by soil drench test

5. Choose Tactics

Creating a healthy soil condition and understanding turfgrass’s needs is the first step in reducing turf pests. What can I do to treat, reduce, or prevent sod webworms?

Best Management Practices: Dethatching at the time of infestation may reduce larvae. Applications of Bt (Bacillus thuringiensis ssp. Kurstaki) can be used but timing is essential (apply in cloudy weather when larvae are very small). Parasitic nematodes (Steinernema carpocapsae) are effective against webworm larvae as well as other larvae. The presence of natural enemies is often effective: earwig, rove beetle, robber fly, paper wasp, ant. While Bt and nematodes are low risk, organic options, they are still considered pesticide applications due to intent to kill, and require application by a certified pesticide applicator.

Treatment Methods: Insecticides are also an option: consult a certified pesticide applicator and the regulations in your state and district.

6. Evaluate

Was the tactic successful? Record the date pests were first noted, and the tactic you used, and its success. Use one of our RECORD KEEPING tools.

For More Information:

Penn State Entomology: Sod Webworms in Home Lawns

Remember:

When a pesticide application is necessary, all necessary and required precautions are taken to minimize risk to people and the environment and to minimize risk of pesticide resistance or pest resurgence. Pesticide use in your school may be prohibited or regulated by local policies or state and federal regulations. Risk reduction methods can include, but are not limited to, spot-treatment, the use of gel or paste bait formulations placed in inaccessible locations, injection into a crack or crevice, and other methods that reduce potential exposure.