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).