You may have recently purchased some beautiful houseplants, set them out in your home or office and got ready to sit back and enjoy them when suddenly you notice what seems like millions of gnats crawling out of the soil and flying everywhere. While you may want to recoil in horrified disgust and simply throw out your houseplants you will be relieved to know that you can avoid such dramatic actions. Almost everyone who grows houseplants has experienced these little black gnats. They are commonly called fungus gnats. They inhabit the fungus and decaying plant material that is found at the base of houseplants.
The Fungus gnat’s lifespan is as follows: Adult gnats will live about seven to ten days and deposit eggs on or in moist soil. The female gnat lays from 100 to 300 eggs in batches of two to thirty each in soil containing decaying organic matter. The eggs will hatch in four to six days and the larvae feed for twelve to fourteen days. The pupal stage is about five to six days before the adult gnat emerges.
While the adult gnats are an annoyance, they won’t hurt your plants. The larvae, however, can seriously damage the feeder roots and root hair causing a general loss of vigor to some plants. The best way to prevent fungus gnats is to use a sterile potting soil mix when you are re potting (one that is free of bark chips) and to make sure your pots have good drainage. These insects need a moist environment to feed and continue breeding, so if possible, it’s a good idea to let the surface of the soil dry out as much as you can (without injuring the plants) between watering. You can also set the plant in the sink and remove the drain tray to drain as much water as possible. Keep in mind that some plants require an inch of dry soil before needing to be watered again. This will also work well to kill the larvae.
These other methods may also help in removing gnats from your houseplants:
· Be sure that you practice good sanitation by removing any dead plant material and debris from the base of your new plants.
· Consider replacing the top few inches of soil with a sterilized potting mix.
· You may want to place yellow sticky traps near your plants to monitor the population and nab flying adults.
· You can use a fine peat moss on top of your potting soil to deter the gnats.
· Carefully place 1/2 inch slices of raw potato on the surface of the soil and discard (along with the larvae) after two days. Repeat this process until the larvae are completely gone.
· Pour red cooking wine or fruit juice in a glass and leave it out by your plants. The adult gnats will dive in and drown.
· Purchase a bag of horticultural charcoal and a bag of Perlite at your garden center. Then gently un-pot the plant and remove as much potting soil as possible without disturbing the roots. Gently mix the soil with the same amount of Perlite and add a handful of charcoal. Then carefully re pot the plant with the newly mixed soil. Your soil will now drain better and not attract fungus gnats in the future.
Using any of these methods will help rid your houseplants of gnats. The main thrust of this is make sure that you completely dry out your soil. For a temporary solution you can put some rubbing alcohol in a spray bottle and spray the surface of the soil with it. You will kill any fungus gnats that it hits on contact.