Killing Soil Gnats Organically

Soil gnats are also called fungus gnats. The adults are actually harmless to the plant while the larva that lives in the soil is the damaging culprit. They love to live where there is moist soil and decaying organic matter. Damage is caused to the plant when these larva feed on the root system of the plant.

You will know you have a gnat problem when you find your plants wilting suddenly and showing poor growth or leaf yellowing.

It’s important to identify these flying insects first to know what you are dealing with. They are sometimes confused with other insects such as midges, mosquitoes, march flies and shore flies. Gnats have a darker color and are anywhere from 1/8 to 1/16 of an inch long. Their wings are clear to light gray.

To get rid of these innocuous and annoying pests, you will need to kill the larva for a start. But getting rid of the adults will help in that they can’t lay eggs for more larva when they are dead. 😉 It is also important to continue an ongoing treatment for a while as they multiply quickly into many generations at once.

Getting rid of the larva

1.      Dry out the soil between watering to a depth of one to two inches. This will discourage the gnat larvae and kill them as well as make the soil less attractive to the adults laying eggs there.

2.      Collect any dead and decaying plant material that is laying about on the soil. Do not add this to your compost pile.

3.      Press ¼-inch wedges of peeled potato into the soil around the plants. The gnats will burrow into them and feast. Then come back in two to three days and remove the potatoes and throw them into the trash barrel and not the compost bin. The gnats will be trapped in them and tossed out that way as well.
For plants growing in pots you can do this treatment as well. Make a solution ot 1-part hydrogen peroxide and 4-parts water. Pour this into the soil and let it drain out through the bottom of the pot


Getting rid of the adults

1.      You can buy sticky traps that you can lay around on top of the soil to attract the adults.

2.      Spray the adults directly with Mom’s Garden Secret Insect and Disease Control

3.      Make traps for the adults by pouring a half-inch of apple cider vinegar into a clear or
 semi-opaque plastic cup. Add a couple drops of liquid dish soap and stir well. Add a piece of fruit that is large enough to stick up above the liquid surface into the mixture. Banana or cantaloupe are good choices.
Use transparent tape to cover the top of the cup and leave a 1/8th inch opening in the center. Place several of these cups on the ground or (in the case of indoor plants) near the plants. To stabilize the ones on the ground, dig a small hole to set the cups in and leave an inch or two above the ground.