Butterflies in my lawn? No it’s Sod Webworms the Pest.
Sod webworms are caterpillars of small brown to dull gray moths. Webworms grow to a length of nearly ¾ inch. Depending on the species they range in color from pinkish white to yellowish brown with a dark brown or black head. The caterpillars are somewhat transparent except for a green line showing the digestive tract. The moths have a wing span of about ¾ inch. They fold their wigs closely about their bodies when they rest and have a prominent forward projection on the head. The moths hide in shrubbery or other sheltered spots during the day. They, like the caterpillar are active in the evening however the moth will fly over the lawn as you walk through it during the day. Mowing equipment or walking in the grass will scare up the month. The female scatters eggs over the lawns as she flies. There are only two stages, the moth and the worm. You will notice the web in the early morning as the dew has settled on your grass.
Sod webworms caterpillars sleep during the day, and are curled up in a c shape as they sleep and they feed at night (sounds like our kids) leaving large circular patches as they feed on the leaves and stems of the sod. It appears the next morning as though some large animal has fed at night on your grass. It happens that quick. They move fast as they feed. If you look closely, you will see the blades of grass are serrated at the edges where the sod webworm has fed. If you will look closer at the edge of the pattern of feeding you will find them sleeping just above the soil, full of grass. Next to them will be their excretion in little green pellets called fecal fraff. The webworm looks like slime green about the size of the lead in your pencil. A heavy feeding can destroy a lawn in only a few days. The most severe damage generally occurs from June through August in conjunction with higher webworm numbers and hot, dry weather conditions.
Products containing either Bacillus thuringiensis, or Sevin are suggestions for treatment for the caterpillars. Talk to your licensed commercial applicator or your local retail outlet rep for suggestions of what can be done.
Lastly, remember what they did to your lawn last year and get them under control before they reach the adult stages. It will be easier to control in the beginning. Take care of the problem before it gets out of hand. With the Turf under stress from mother nature we need to give it all the help we can and maintain a thick, strong, healthy turf.