Gnats are small insects that are attracted to moisture, rotting food and light. These pests come out in the warmer months, starting in the spring. Gnats are not dangerous to humans, but they can spread germs and bacteria by landing on your food or in your drinks. Screen doors designed to keep pests out of your home are not always the best defense at preventing a gnat invasion. Because of their small size, gnats can easily fit through the mesh holes of a screen door or window screen.
Remove mulch piles or anything that traps and stores water near your screen. A majority of your gnat problem could be from conditions providing too much moisture near your home. Turning mulch piles will also help, as this allows your mulch to dry out faster.
Wash your dishes after every meal, and make sure that there are no dirty dishes on tables in any rooms. Gnats are attracted to dried and rotting food and will slide through screens to get to their next meal. Keeping food unavailable to the gnat will cause it to go elsewhere for dinner.
Place a small cup of apple cider vinegar by your screen door. The vinegar will attract the gnats but will also prove fatal. The acidity in apple cider vinegar is too much for gnats and will kill them in a matter of seconds, once they land in the cup to drink.
Ensure that your screen has no tears, rips or missing weather stripping. These small areas allow gnats to slip-in unseen. Repair any damage that you find. Tighter meshes are also available for installation to help reduce indoor gnat populations.
Turn off lights that are near your screen, during the day or anytime you have your windows or doors open. Gnats are attracted to light like moths and other insects. By limiting light sources, gnats will be drawn away from your home by street lights.