Fungus Gnats in Greenhouse

Fungus gnats are troublemakers for almost every homeowner, especially for those who love gardening. Whether it’s adults or larva, these species are capable of damaging your precious plants.

Eliminating them becomes very important. To make this task easy, we are here with this article which is going to cover everything related to fungus gnats and greenhouses.

Let’s begin with how to identify fungus gnats.

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Identifying Fungus Gnats

Fungus Gnats in Greenhouse

We will begin with the larva of fungus gnats. The larva is legless and white with a length up to ¼ inches on maturing. The larva has a shiny black head.

Next comes the adult fungus gnat. The adult has a body similar to a mosquito. With a length of around ⅛ inches, adults have long legs, a pair of wings, and long antennae.

They are weak fliers and are mostly found resting in yards. 

Adult fungus gnats are sometimes confused with other dark-bodied flies called shore flies. Since they are similar in appearance, it is important to know the features of shore flies to make the identification of gnats easy.

Shore flies have antennae shorter than fungus gnats.  They are stronger and fly faster as compared to gnats. 

The most distinguishing feature is the presence of color spots on each of the dark wings of shore flies.

Life Cycle of Fungus Gnats

The female gnats can lay up to 300 eggs daily. All these eggs are laid in moist soil or surfaces rich in organic matter.

With this, the life cycle begins. It takes around 6 days for the eggs to hatch and turn into larva. The larva then takes around 10-14 days to get converted into a pupa. The pupa stage lasts for 4-5 days before becoming adults that live up to 10 days.

It takes around 4 weeks to get converted from an egg to an adult. The life cycle depends on the temperature, as the temperature rises, the development time decreases. 

Are Fungus Gnats Troublemakers?

Fungus Gnats in Greenhouse

It is the diet of fungus gnats that makes them troublemakers. Fungi is the most important part of their diet. The speed of their development increases when they are following a fungal diet. 

The problem arises when there is no fungus available. At this point, fungus gnats choose our healthy plants for nutrition. These are general feeders and can injure your flower crops grown in the greenhouse.

When it comes to damage, the larva outshines the adult fungus gnats. The larvae feed on plant roots, fungi, and decaying organic matter. They can even tunnel into the stem of the plants.

The damage caused due to feeding creates a way for pathogens to enter and kill the plants. The larva itself carries some soil-borne pathogens such as pythium, fusarium, etc.

A greenhouse with a high percentage of compost is likely to face the problems of fungus gnats. The larva present in soil or plants can lead to the emergence of adults.

How to Get Rid of Fungus Gnats?

As we have just got an idea about the damage that fungus gnats can cause to our greenhouses, it is important to take effective measures to ensure the safety of the greenhouse.

Below are the measures that should be followed to control the situation of fungus gnats.

  • As fungus gnats are attracted to decaying plant material, it is advised to remove the discarded plant material from the greenhouse.
  • Remove weeds from the pots. Make the environment of your greenhouse weed-free. The areas outside of the greenhouse should also be treated in the same way just like the inside areas.
  • Do not use too many organic fertilizers. Fertilizers with an excessive amount of manure, blood meal, or similar organic materials should be avoided.
  • As fungus gnats breed in algae, controlling the algae will help in getting rid of fungus gnats.
  • Always clean the standing water, check the irrigation system. This will control the amount of moisture present in your greenhouse. Gnats prefer abundant moisture, so it should be eliminated at any cost. 
  • You should stop overwatering the plants to control the amount of moisture.


A greenhouse is very important and it should be protected. Fungus gnats can kill the plants if present there for a longer time.

The damages can be avoided if appropriate measures are taken at the right time. Eliminating moisture and decaying materials is the most effective way to get rid of fungus gnats from your greenhouse.

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Daniel White
I'm Daniel White, and I live in Jacksonville, Florida. The warm and humid climate of Florida gives an ideal habitat for many different kinds of pests. So, if I had to live in Florida, I had to learn how to deal with these pests. Now, I have 7 years of experience in Pest Control.

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