For a natural way to get rid of gnats in outdoor spaces, adjust the environment in which they thrive, suggests Amie Taylor of SFGate. Cool temperatures and copious water sources encourage the birth and flourishing of gnats.
Let lawns and garden beds dry thoroughly between watering to cut down on the moisture-rich environment favored by gnats, suggests Taylor. Eliminate decaying organic matter such as grass clippings, dead plants and leaves, which are a common place for gnats to lay their eggs. Avoid using peat moss beds, since they are a favorite of gnats.
More tips for keeping unnecessary moisture at a minimum in an outdoor space include raking and overturning mulch from time to time to allow moldy or wet layers to dry, watering in the morning to avoid overnight fungus growth, and checking gutters and drainage areas for standing water, states Julie Day of Today's Homeowner. To keep gnats from swarming faces and necks, Day suggests dabbing vanilla on the brim of a hat.
For a biological way to keep gnats from infesting outside, consider using one of its natural predators such as beneficial nematodes. Steinernema feltiae and Steinernema carpocapsae are two such nematodes that are effective in reducing populations of fungus gnats, relates Taylor.