They look like mosquitoes, but actually aren’t parasites. Gnats in houseplants are fungus gnats, small flies about 1/8-inch long compelled to feed on decaying plant material at the base of indoor plants.
Gnats are prevalent on houseplants that have too much moisture, which is why you should avoid overwatering in the first place. However, what do you do when the damage is already done? How do you deal with a swarm of pesky flies around your plant? Here we explain the best methods for eliminating gnats in house plants.
How to identify gnats in indoor plants
Look for fungus gnat eggs. These eggs hatch into larvae that feed on fungi found in potting soil. Fungus gnat larvae are about 1/4-inch long and shiny black, with transparent bodies.
It may also choose to eat roots or seedlings and leave a slimy trail behind like slugs and snails do. If you see a slime trail, there is a chance there are gnats in your plants.
Light entices gnats, so you may see them on your windows, especially if there are houseplants nearby.
Fruit flies often get confused with fungus gnats, but they are completely different insects. Fruit flies will stay around fruit and look like oval, inimic miniature house flies, unlike fungus gnats, which are white in colour.
Identifying Fungus Gnats
A fungus gnat is a miniature flying insect very similar to a mosquito. They can be found all year, but tend to be more prevalent during the fall and winter. A female gnat can lay more than one generation of larvae in a season because it doesn’t sift her eggs when she lays them.
Usually, fungus gnats don’t stray far from the plant. However, they can infest nearby plants, as they are attracted to light. You may see them buzzing around light bulbs or in windows and on walls near your plants.
How to Get Rid of Soil Gnats
Most plants need deep watering to kill fungus gnats. Allow the top two inches (5 cm.) of potting mix to dry completely between waterings.
A dry environment is less conducive to the survival of fungus gnats in houseplant soil. Use clean pots with drainage holes and always empty water from the bottom into a drainage saucer.
Bright yellow sticky traps, which resemble index cards in size, are usually effective in reducing the numbers of pests and preventing fungus gnat damage. Remove the sticky parts of the traps, then attach them to the wooden or plastic stick and place the traps into the potting soil. Re-supply the sticky traps when they are covered with gnats. These sticky traps are available at most garden centers.
Several days before planting, lay a chunk of raw potatoes on the surface of the soil and check it every two days. Discard gnat-infested potatoes and replace them with new ones.
Get rid of gnats in 3 easy steps
It is important to eliminate gnats immediately when you observe gnat signs.
There are a few ways to get rid of adult gnats fairly quickly. You could buy a few carnivorous house plants as a long-term solution but there are plenty of shorter-term solutions that will work just as well or better.
1. Make a homemade gnat trap using vinegar
- Put a tablespoon of sugar in a bowl.
- Mix together 2-3 drops of dish soap with a cup of white vinegar in the same bowl. Cover the bowl with a cling wrap.
- Put the cling wrap over the house plant. Put the bowl in a position where it catches flies overnight.
2. Use sticky fly traps
A sticky gnat trap is another option if the smell of vinegar puts you off creating your own DIY gnat trap. You can hang these traps from the branches of the plants, or install them directly in the soil, so that all unwanted critters are caught. By reducing the adult population, you will reduce the number of eggs laid in the soil of your plants.
Renew the sticky paper traps once they are covered with gnats and dont touch the leaves of the plants.
Check out non-toxic traps that are double-sided to maximize your effectiveness.
3. Fly catcher for indoors
If it is not your first time fighting gnats in your house plants, then you might want to invest in an indoor fly catching device.
LED lights and fans are used in conjunction with these devices, along with USB power, to attract and suck flies into the trap.
Keeping gnats away from indoor plants
While getting rid of adult gnats is an important first step, it’s often only a short-term fix. More adults are likely to emerge from the larvae in the soil. In order to keep gnats from laying eggs in the moist soil around plants, it is better to allow the soil to dry out prior to their larval stage. This will enable plants to be protected from gnats for good.
- Do not overwater – Allow your plant’s soil to dry between waterings. The eggs and larvae usually die in dry soil.
- Drain your saucers of excess water – Keep your soil and plants healthy by choosing a pot with good drainage. This will also prevent the plant from succumbing to common problems such as root rot.
Additional Fungus Gnat Control
Toxic chemicals should never be used at home and insecticides are usually unnecessary. Non-toxic control methods are always the best choice for home use. If nothing else works, however, very low-toxicity insecticides such as those with pyrethroids or Bacillus thuringiensis israelensis may work. Products have to be reapplied regularly, because they don’t provide long-term control. Reapply products as directed on the label. Store products away from children and pets.
Repotting the plant in gnat free soil is the best option if all else fails; remove the plant from the infected soil and wash off all of the soil from the roots of the plant. Remove the soil gnats from the infected plant, repot it in fresh soil, and allow it to dry out in between waterings. By doing this you will kill any eggs or larvae still in the pot.
Repotting the plant in gnat-free soil is the best option if all else fails; remove the plant from the infected soil and wash off all of the soil from the roots of the plant. Remove the soil gnats from the infected plant, repot it in fresh soil, and allow it to dry out in between waterings. By doing this you will kill any eggs or larvae still in the pot.
Other ways to avoid fungus gnats
Many fungus gnats are more noticeable in autumn. They might have hitched rides on plants that have been brought inside at the end of summer.
Check plants before bringing them inside to make sure they are free of insects. When buying new plants, check them for insect infestations. Use a sterile potting mix when planting or re-potting.
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