Are Neem Cakes The Answer To Your Fungus Gnat Problem? Here's What We Know

If you're a houseplant lover or proud greenhouse gardener, you're likely desperately seeking a surefire way to keep pesky gnats away. Fungus gnats are the scourge of indoor growers. These tiny flies — rarely exceeding one-eighth of an inch long — thrive in a potted plant's damp, rich soil, feeding on decaying plant matter and fungi. And while they're more nuisance than nasty, having hundreds of fungus gnats buzzing around your living room is far from pleasant. Garden gurus and agricultural scientists alike seem to agree that neem cake, also called neem meal, is a helpful fungus gnat fighter. How can you use it in your garden? Well, you need to make it into a plant tea and apply it regularly.

Neem cake is leftover seed pulp, a by-product of extracting neem oil from the seeds of the neem tree (Azadirachta indica). It's cheaper and less concentrated than the oil but still contains azadirachtin, the active ingredient that makes neem an effective insecticide. Azadirachtin doesn't kill insects; it disrupts their lifecycle. Eggs don't hatch, and larvae metamorphosis is halted. Some experts claim neem, via this active ingredient, effectively controls fungus gnats, especially when used as a soil drench — when watering soil with neem-infused water. However, others argue it only works if you heavily soak the soil at least 3 inches down, and it's only useful for short-term control (you have to keep applying it in perpetuity).

Since science generally supports the use of neem cake, it's worth experimenting with it in your indoor garden. Neem cake comes in pellets or crumbs and can be easily found online in the U.S.A. Get a 44-pound bag of neem seed meal for $66.99 from Seven Springs Farm Supply, or order the same-sized bag of Ahimsa Organics neem cake pellets from Fedco Seeds for $110.00. Want something smaller? Buy a 2-pound bag of cold-pressed neem meal for $21.95 from Revival Gardening. Bonus: neem cake is a mild organic fertilizer similar to compost or manure, so you'll be feeding your plants, too.

Ready to get rid of bugs on indoor plants? Grab a large bucket, bottle, jar, or watering can. Follow the provided water-to-cake ratios if they're listed on the packet. If not, you'll have to test the different ratios experts recommend. Depending on how many plants you need to treat, mix 2.5 ounces (of meal) to 0.3 gallons (of water), 2 to 3 rounded tablespoons to 1 gallon, or 2 cups to 5 gallons. Give the mixture a good stir and leave it to aerate for a minimum of 2 and a maximum of 48 hours. You can strain the solution — through a cheesecloth, for example — or use it as is to water your plants, completely covering the surface of the soil when you do. Repeat every 3 or 4 days until the fungus gnats are gone.