Mossquito dunks work really well. When you use high-powered broad-spectrum sprays you wipe out the various beneficials that can help keep the skeeter population in check. I have a good gardening friend who has martin houses on all four sides of her yard and she has no mosquitos. Bats are very helpful, tho' the bathouse I put up didn't attract any. Plant things that attract hummingbirds--hummers eat a lot of mosquitos. Fish in a pond will eat the wigglers and a fountain or dribbler will keep them from laying, but of course that wouldn't help in a culvert.

Thanks, i saw those at Lowe's yesterday, but was not sure how well they really work. i guess i can pick up a pack to try. if they work good, then i will get more to keep them in the culverts.

This probably won't work, but it's an interesting tidbit. I have a recipe for a bat garden. I know that bats consume up to 500 insects an hour, including mosquitoes, although mosquitoes only make up about 10 percent of their diet.

Bat Garden:
Salvia, Silene, Phlox, Stock (and Evening Stock), Cornflower (Bachelor's Buttons) and spearmint.

Don't remember where I got this "recipe" and don't know why I have it, but there it is.