How to get Rid of Fungus Gnats

Fungus gnats: little black bugs that fly around and make their homes in your houseplants. Dangerous? No. Annoying? Absolutely. In this post we’ll be talking about fungus gnats: what they are, what they do, and how to get rid of them.

Fungus gnats are tiny, non-seasonal insects that love house plants as much as you do. They're especially attracted to damp and well-lit environments. The adults’ hobbies include flying around and being annoying, but they won’t do any actual damage to your plants. The larvae, on the other hand, love to snack on plant roots. In great enough numbers they can really mess up your plant growth. “The key is to catch them early”, says Sam, our resident horticulturalist. “As long as you stay on top of your plant maintenance they shouldn’t be too much of an issue”. 

The life cycle of the fungus gnat is very quick: only up to twenty-eight days. About four to six days after an egg is laid, the larvae will emerge. After munching on organic plant matter for about two weeks, the larvae grow into pupae, and three to four days later they’ll emerge from the soil as adults, ready to start laying eggs again.

Because of this rapid reproduction, many stages of the life cycle may be present at any given time. Not only do you need to get rid of the adult gnats, but you’ll need to deal with the larvae too.

How can you deal with fungus gnats? 

Sticky traps work best for catching the adults. Since one adult can lay up to 300 eggs, this helps to slow population growth. Simply place the traps in your affected plants to catch the adults as they buzz by. You can pick up sticky traps from any local garden store.

For the larvae it’s a little different. We recommend using what is commonly known as 'The Potato Method'. Since potatoes are starchy roots, the larvae will find them just as delicious as they find your plants. Cut off a few small chunks of potato and bury them in the soil around the affected plant’s roots. The larvae will attach themselves to to the potato chunks. After four to eight hours simply dig them up, throw them away, and repeat until no larvae are left. 

This is very effective if your gnat infestation is mid to low level. If you have a lot of gnats in your pod, you can also try working with hydrogen peroxide. Remove your pod from the base and leave it somewhere sunny until the top layer of coir is totally dry. 

Mix 1 part 3% hydrogen peroxide with 4 parts water, then drench the dry coir with this solution. After fizzing for about 30 seconds, the solution will break down into hydrogen and water — both of which are harmless to your plants. This will effectively kill off most, if not all larvae. It’s a good idea to use the potato hack after this to catch any larvae that might be left over. For an alternative to hydrogen peroxide, this same method can be used with neem oil as a substitute.