Bluegrass Sod Webworms
The sod webworm can be one of the most destructive turf pests. Luckily it has not been serious in the Kansas City area for a number of years but does still pose a threat.
Sod webworms are the caterpillars of lawn moths. The moths are small about ½ inch long and whitish-gray. They clasp their wings close to their bodies and have mouthparts projecting forward from the head like a snout. The moths are usually noticed when flushed out by a mower or people walking. When the moths fly, they make a jerky zig zag movement and quickly return to the lawn. The moths fly over the lawn laying eggs which hatch in a few days and the young caterpillars start to feed.
Unlike white grubs, sod webworms feed above ground on the grass blades. The larvae clip off grass blades close to the soil surface exposing the crowns and roots to the hot sun, thus damaging the lawn. Normally damage of webworms appears as softball size dead areas in the lawn.
If moths are abundant, watch for signs of caterpillars feeding in about 7 to 14 days. An abundance of moths does not necessarily mean attack will occur. An indication of sod webworm activity may be noticed by a number of birds pecking holes in the lawn in search of caterpillars.
Before treating for sod webworms, check for their presence. Pull the turf apart and look for a silk- like case that houses the caterpillar. Caterpillars can also be driven out of the lawn by spraying a 4 square foot area with one tablespoon of laundry detergent such as Tide in one quart of water. Wait 10 minutes and then look for insects that crawl to the surface. Consider control if 2 to 4 caterpillars are found.
Another method is to treat about 7 to 10 days after a peak number of moths are spotted. Normally there are two generations per year, one in June and another in late July or August. Recommended controls include Bifenthrin and Cyfluthrin. Be sure to use enough water to thoroughly moisten the grass and thatch to move the chemical into the area where the caterpillars are feeding