If you're a plant collector like I am, you can expect to have a fungus gnat problem at one point or another. First off, keep calm and don’t throw the whole plant away! I got you, Boo. This is my method for controlling fungus gnats in my house plants. I am pretty aggressive in my approach with my house plants because I grow also organic cannabis. I need to nip pest problems on my house plants before they can make it to my cannabis plants.
"Know Thy Enemy"
The fungus gnat is a small dark fly from the order Diptera, or “true flies”. This pesky little fly also multiplies rapidly, so a few annoying gnats can quickly get out of hand. Although the adults can be quite a nuisance, the larvae feed on plant roots and can cause significant damage below the soil.
Four Stages of Fungus Gnat Development:
Egg - One adult female can lay between 30-200 eggs.
Larvae - The larvae feed under the soil for about two weeks.
Pupae - The pupal stage lasts about 3-6 days.
Adult - Adults can live up to 10 days.
You can control and eliminate your fungus gnat problem, but you need to be diligent in repeat treatments, taking the 28-day life cycle of the insect into account. This means you're going to treat your plants weekly for at least four weeks.
Fungus gnats lay their eggs in the presence of fungus, so having overly wet soil or wet saucers is the perfect breeding ground. Avoid over-watering your plants, and make sure your pots have adequate drainage. Keep a clean environment. Pests require a suitable environment to thrive.
Here's what you'll need to launch all-out warfare:
Yellow sticky traps - to catch the adults. These are available in any garden centre or online. I also like to keep a few sticky traps up as a monitoring tool. It lets me know I have pests before I otherwise would.
Diatomaceous earth - Think of this as microscopic shards of glass that cut the crap out of soft-bodied insects. To humans, it’s just a soft powder. I mix this into my potting soil before I pot my plants.
Neem oil and soap spray - Add a couple of drops of neem oil and a couple of drops of dishwashing soap to a spray bottle mixed with water and use this as a weekly foliar spray for your plants. Neem is a natural insecticide. The dish soap covers the insects, effectively suffocating them.
Insecticide spray containing pyrethrin. Pyrethrins are pesticides found naturally in some chrysanthemum flowers. They are a mixture of six chemicals that are toxic to insects. Pyrethrins are commonly used to control mosquitoes, fleas, flies, moths, ants, and many other pests. I sprayed my plants every couple of days the first week, then weekly for four weeks. Be sure to spray your plant saucers to catch any bugs that may be hiding out.
If you follow these steps you will catch all the life cycles of the fungus gnat and control your pest problem.