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Fungus Gnats

How does one get rid of gnats in houseplant soil? I have also heard these gnats called fungus gnats. They are over running my house! PLEASE help me!

I can sympathize with your situation. I recently moved a potted plant into my office and have been dealing with fungus gnats ever since! It is a common problem during the winter when houseplants are moved indoors.

To combat the fungus gnat it is good to know a little about them. The adult gnat lives for about 1 week, mates and reproduces. Outdoors they can be found in compost bins, around rotting wood, and in leaf piles. They thrive on decaying organic materials and fungi. Indoors they are attracted to similar conditions found in moist potting soils that have a high organic content.

The females will lay her eggs on top of the soil. The hatched larvae feed on plant roots and root hairs in the top inch of the soil. They also feed on fungi on the surface of containers and potting benches.

Fungus gnats only eat during the larvae stage of their life cycle. To eradicate the problem, you must eliminate them at this stage.

First, isolate the plant or plants where the gnats are living. Next, cut back on water to make the soil less attractive to the adult female gnat. You don’t need to stop watering completely, just allow the soil to dry out between watering.

If you catch the problem early enough, cutting back on water may be all you have to do. However, if the problem is more severe you should take the additional step of removing the top 1 to 2 inches of the soil. This can be done with a fork or a spoon. Do this gently to prevent damaging the surface roots of your plant. Now, just add a new layer of soil. It is important to buy new, sterile potting soil for this.

Now, if you change the soil and you still have a problem, I suggest applying an organic pest control containing Bacillus thuringiensis, or BT. You should be able to find a product at your local garden center. Select one that is water-soluble and drench the soil with the mixture. To work, BT must be consumed by the gnat larvae. So apply your mixture to any containers you suspect may be harboring the pest.