Answer: What you describe sound like fungus gnats. They are living and breeding in decomposing organic matter at the soil surface. They thrive in moist places and when you walk on the lawn you disturb them and they fly up. They do not feed on the plant and they won't bite you. But, if they're bothersome, you can use an insecticide to kill them. The first step to control fungus gnats is to reduce the soil moisture. Change your watering schedule so plants receive sufficient moisture but the soil surface is allowed to dry. The only effective product for treating fungus gnat larvae in the soil is a bacterial insecticide, Bacillus thuringiensis var. israelensis, (e.g. Knock-Out Gnats). Also known as B.t. H-14, this insecticide is specific to fly larvae. However this product does not kill adult fungus gnats. There are insecticides that are effective against adult fungus gnats, such as pyrethrins. However, they are only a short-term solution. As long as there is a favorable site for the fungus gnat larvae to develop, adult flies will continue to be present despite treating the adults repeatedly.
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