Gnat swarms #470099 - Ask Extension


Gnat swarms #470099

Asked July 13, 2018, 11:57 AM EDT

Hi, Not sure if this is the right place for this question, but here goes anyway. My backyard seems to be infested with gnats ( it's a typical suburban yard, no standing water or proximity to large bodies of water). I had read some material online that suggested spraying nematodes at certain times of the year to reduce the underground gnat egg numbers. Is that a viable solution? If so, what are the best times of the year to do so? Also, barring the elimination of standing water, anything else I can do to drive these annoyances from the yard?

Frederick County Maryland

Expert Response

We do not have research on nematodes to control gnats.  
If this is a chronic problem, something about your property provides an environment that encourages gnats. Most properties have fleeting occurrences of gnats.

Gnats like wet environments, so we recommend that you try to dry up any damp areas in the yard by filling in low areas where water sits (or make those areas into rain gardens so the plants will absorb the water) or changing the grade. Prune or clear up overgrown areas --especially non-native invasive plants--to encourage better air circulation and faster drying. 

Also, encourage a well-functioning ecosystem which will include lots of birds and predator insects to feed on the gnats. Hornets and wasps, for example, are big predators of flies and gnats. To do that, avoid all pesticides except those targeting a specific identified problem on a specific plant. Plant lots of berry and flowering trees, shrubs and herbaceous plants. 


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