Question
I have a lot of white moth's in my grass, can you tell me what is causing this?

Answer
Good Morning Jan:
From your description, I believe you have Sod Webworm. The adult moth is ?inch long, light tan or buff colored, and holds the wings close against the body in a tubelike fashion when at rest on a grass blade. When disturbed, the moth will fly in a dipping, zigzag pattern just a few feet above the turf. The caterpillar is gray or greenish, up to 1 inch long, slender, and covered with brown spots.  The caterpillar emerges at night from a silk-lined tunnel in the thatch and will eat grass blades down to the crown.
Attacked turf has irregular brown areas because the grass blades are gone, allowing the thatch to show. Green, 1/8 inch diameter feces are numerous at the base of attacked turf. Damage usually occurs during dry periods of the growing season.
Chemical insecticides are effective. Damaged turf usually recovers with irrigation (after the caterpillars are controlled) because the undamaged crowns and roots are able to grow new leaves.
Some web sites that can help you in control of the Sod Webworm are: (Copy and paste to your browser then hit "GO").

http://ohioline.osu.edu/hyg-fact/2000/2011.html
http://www.oznet.ksu.edu/dp_hfrr/extensn/problems/sodwebwm.htm
http://www.utextension.utk.edu/publications/spfiles/SP290-L.pdf
http://ipm.montana.edu/YardGarden/docs/sodwebworms-insect.htm

I hope I have helped. Have a good lawn!
Floyd McMahon