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Pest Type
Plants Affected
Do you have little flies on your houseplants? They may be fungus gnats! Often considered only a minor houseplant pest, fungus gnats can quickly becomea significant issue (and annoyance) if an infestation gets out of hand. Here’s how toidentify, eliminate, and prevent fungus gnatinfestations in yourplants.
What are FungusGnats?
Fungus gnats are a fruit fly–sized insect pestthat primarily affects indoor houseplants. Attracted to the moisture ofpottingsoil, adult gnatslay their eggs (up to about 200) on organic matter near the soil surface. After about three days, the eggs hatch into larvae, which burrow into the soil tofeed on fungi and decaying plant material. Adult gnats emerge from the soil two weeks later to repeat the process. Adults live for about oneweek.
Fungus gnats are utterly harmless to humans since they can’t bite and don’t spread diseases. They can be a problem for houseplants; however, their larvae feed on plants’ thin roots when their population explodes. Fungus gnats may also spread Pythium, a group of plant pathogens that causes“damping off” inseedlings.
Once you have a fungus gnat infestation, consistent management and prevention techniquesare the key to ending it. Further down on this page, we’ve listed a few of the best ways to get rid of adult gnats and prevent new gnats fromemerging.
Identification
How to Identify a FungusGnat
- Size: Adult fungus gnats are tiny. Their size ranges from about 1/16 to 1/8 of an inch in length (1.5 to 3mm), which is about the same size as afruit fly. Fungus gnat larvae may be up to 1/8 of an inch inlength.
- Appearance:Adult fungus gnats are grayish-black and havegray or see-through wings. Their long legs and long antennae give them a mosquito-like appearance, though they are much smaller.Compared to a fruit fly, fungus gnats have a thinner body with longer legs and antennae.
Larvae have a small, black head and a thin, white, or see-throughbody. - Activity: Fungus gnats tend to spend most of their time on the soil surface of potted plants, but they may be seen flying around the outeredge of the pot or near drainage holes as well. They are not strong fliers, so they walk along the soil and fly only in short bursts. Their flight is erratic and much slower than fruit flies, acting more like mosquitoes while flying.
Annoyingly, fungus gnatstend to fly into people’s faces and drinks, though they are completely harmless, and a few well-placed swats will show them what’swhat.
Fungus GnatDamage
In small numbers, fungus gnats are more of an annoyance than anything. In fact, adult gnats don’t actively harm plants or people.However, if their population gets out of hand, thelarvae may start feeding on plant roots, causing notable damage. This is especially bad for young plants, such as seedlings with only a few delicate roots. Fungus gnats can also spread the plant pathogen that causes damping offand the eventual death ofseedlings.
Fungus gnat damage will appear similar to any other root-related issue, such as root rot. Lower leaves may turn yellow and drop, and the plant’s growth may slow down or stop altogether. In particularly bad cases, wilting of the entire plant couldoccur, followed by the death of the plant if the roots are extremelydamaged.
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