Fungus gnats are tiny non-biting flies that swarm damp areas where mold, fungi, and rotting plant debris accumulate. They lay eggs in moist organic material, soon hatching larvae that feed on fungi and plant roots.
Though relatively harmless, their relentless swarming can drive even seasoned gardeners inside.
Like mosquitoes, as well as non-biting insects like fruit flies, fungus gnats easily find their way onto your property, flying in from nearby areas. Controlling them requires reducing breeding grounds and creating other deterrents.
Working for one of the biggest pest control companies in the United States, I was no stranger to fungus gnats. This guide covers ways to modify your landscaping to discourage these pesky invaders. I also suggest treatments, including introducing beneficial insects, to manage current infestations. Finally, I provide tips for repelling adult flies using natural ingredients.
Reduce Damp, Rotting Matter in Your Yard
Fungus gnat larvae need moist organic matter to survive. That means one of the best ways to get control of fungus gnats outdoors is by making your yard less hospitable to them.
Here are a few pointers for reducing the level of dampness and rot in your yard:
- Eliminating excess moisture and improving drainage. Remove standing water and aerate compacted areas. Allow the top few inches of soil to dry between waterings.
- Pruning dense vegetation and thinning overly shaded areas to increase airflow. Pay extra attention to compost piles, mulch beds, and other naturally damp environments.
- Raking or turning mulch and compost routinely to dry out soggy layers. Cover piles to keep rain from penetrating.
- Clearing fallen leaves, grass clippings, and garden debris where larvae feed. Use sodium vapor lights outdoors at night to deter adult flies.
- Applying a thin layer of sand to chronically moist garden beds. The gritty texture discourages gnats from laying eggs.
Treat Current Infestations
In addition to gnat-proofing your yard and property, you must treat any current gnat infestations you’re facing. Thankfully, with all the great products out there today, DIY pest control tactics are usually more than enough to successfully get control of fungus gnats outdoors.
Some of the best options for treating active fungus gnat populations include:
- BTi and nematodes: Applying Bacillus thuringiensis israelensis (BTi) or beneficial nematodes to damp areas kills larvae. This biological control provides ongoing protection.
- Traps: Sticky traps capture adults, while funnel traps draw them in to drown. The best gnat traps help reduce numbers but alone don’t provide long-term control.
- Sprays and foggers: Insecticide sprays treat larvae in soil. Foggers kill flying adults, but populations quickly rebound. Avoid harming beneficial insects like bees by using gnat repellent rather than harsh chemicals.
- Natural predators: Mites and other predatory insects you can introduce feed on gnat larvae. Once established, they provide natural gnat control.
You can find a variety of organic fungus gnat control products, including repellents and predatory insects, at your local garden center or at online retailers such as Planet Natural.
Repel Gnats Naturally
Whether you aren’t a fan of insecticides or want some additional methods to help prevent or repel gnats, these natural strategies for deterring fungus gnats are highly recommended by pest control experts:
- Fans circulate air, making covered porches and patios less inviting to hovering gnats.
- Repellent plants like lavender, mint, basil, and marigolds release smells that deter gnats. Crush leaves to activate oils.
- Citronella candles and torches offer a short-range repellent outdoors. Their scent overwhelms gnats’ sense of smell.
- Essential oils like eucalyptus, pine, and lemongrass make effective homemade repellents. Add them to carrier oils for diffusers. The ingredient vanillin also repels gnats.
- Dryer sheets rubbed on skin and clothing have a modest repellent effect. Their scent confuses gnats looking for a blood meal.
So, Is Controlling Fungus Gnats Outdoors Worth the Effort?
Getting rid of fungus gnats entirely may not be realistic, especially if conditions in surrounding yards remain ideal for them. However, implementing prevention techniques makes a significant difference in reducing their numbers to tolerable levels.
Traps and natural repellents provide additional control when paired with other control measures to discourage infestations. While not completely effort-free, these integrated pest management tactics are far less toxic than dousing your yard in insecticides. Approaching fungus gnats through prevention and exclusion brings longer-lasting and safer results.
Dealing with indoor gnats? You may find our article on testing out a DIY gnat trap helpful.
If you’re dealing with a particularly large and pesky gnat infestation, I recommend contacting one of the best pest control companies in your region.
FAQs About Controlling Fungus Gnats Outdoors
What attracts fungus gnats?
Moist organic matter attracts fungus gnats. Compost piles, overly damp soil, mulch, leaf litter, and decaying plant debris provide ideal breeding conditions. Stagnant water sources like birdbaths and clogged gutters also draw them.
Will vinegar kill fungus gnats?
Though vinegar kills larvae on contact, it doesn’t provide ongoing control. It may harm plants at horticultural strengths. For ongoing protection, use beneficial nematodes or BTi instead.
Do fungus gnats bite?
No, fungus gnats don’t bite humans or pets. At most, the larvae nibble on plant roots. It’s the annoying swarms of adults that make them a nuisance.
What kills fungus gnat larvae?
Treating damp soil with BTi, neem oil, or beneficial nematodes kills larvae. Let top layers of soil dry out between waterings. Remove excess debris and aerate compacted areas. Predatory insects and mites provide natural control.
Do ants kill fungus gnats?
Some ant species prey on fungus gnat larvae. But since ants also need moisture, minimizing damp conditions discourages both pests. Drying out problem areas deters larvae that ants eat.