Fungus Gnats

How to Get Rid of Fungus Gnats in Your Houseplants

Have you noticed little bugs flying around your houseplants? You probably have fungus gnats! We delve into what these pesty insects are, what they do to your plants, and how to get rid of them.

What Are Fungus Gnats?

Fungus gnats are insects that are about 1/8 inch long. They are black with a single pair of wings. Since they do not fly well, they generally stay close to the plants. They are not harmful to humans or animals and do not bite.

The life cycle of the gnat is relatively short, about 17 days. The female gnats lay between 100 to 300 eggs in the moist soil of plants. Once lain, the eggs hatch after three days. The larvae then develop into pupae after ten days. Adult fungus gnats emerge from the pupae four days later.

What Do Fungus Gnats Do To Your Plants?

Adult fungus gnats are not the problem. It is the larvae that do the damage to your plants. The larvae feed on root hairs and fungi found in the soil. This feeding results in the plant wilting, poor growth, yellowing of leaves, and leaf drop. Plants with root damage are also susceptible to root diseases.

How to Prevent Fungus Gnats?

Never having fungus gnats is always better than getting rid of fungus gnats.

Inspect

Always inspect plants before buying them. Look for signs of infestation, such as gnats hanging out on the soil or leaves. Also, look for overly moist soil, as this moisture is the ideal environment for larvae.

When you bring your plants in the house during the fall, inspect them for gnats. Infestations often occur when plants are outside for the summer.

Potting Soil

Do not use garden soil for houseplants. Use bagged, sterile potting soil. Using garden soil increases the risk of bringing in larvae and eggs.

Avoid using partially composted organic materials. These materials often contain gnat larvae.

Water

Avoid overwatering your plants. Overwatering leads to fungus, which in turn encourages gnats to your plants.

Poor drainage also encourages the growth of fungus. Ensure all plants have adequate drainage. Empty any saucers of standing water.

How to Get Rid of Fungus Gnats?

Sticky Traps

Reducing the number of adult gnats present minimizes the number of larvae that could develop. Using yellow sticky tape attached to skewers and placed in the pots traps the adults.

Potato Chunks

Place chunks of potato around the soil. The larvae love the moisture in the potatoes and gravitate to them. Once the larvae cover the potato, throw it away and replace it with a new one.

Let It Dry

Allow the plant with gnats to dry out completely before watering. Let it go without watering as long as the plant can without damaging the plant’s health. Drying out the soil kills the larvae, inhibiting the production of more gnats.

Repot the Plant

If the infestation is bad, repotting the plant may be necessary. Discard all the old soil and replace it with new, sterile potting soil.

Biological Control

The most common biological (natural) control for fungus gnats is Bacillus thuringiensis (Bti). This bacteria is toxic to the gnat larvae. Mix it with water and drench it in the soil. Always follow directions on the label.

Another natural control method is the use of a nematode, Steinernema feltiae. Nematodes are parasitic worms that search out hosts in the soil. These nematodes are also mixed with water and drenched into the soil. They reproduce over time and continue keeping the soil free of gnat larvae.

Chemical Control

Pyrethrins are insecticides used to control fungus gnats. If using pyrethrins, only spray the tops of the soil and not the flying gnats.

Pyrethrins are low in toxicity to people and plants. However, when applying any chemical product, read and follow all directions. It is best to spray the plant outside and wait for the chemical to dry before bringing it back into the house.

Fungus gnats are such a nuisance. They thrive in moist environments and love to chomp on the roots of your plants. Keeping them at bay is important to maintain healthy plants.

Other Related Articles

• Bringing Your Houseplants Indoors
• All About Plant Roots

How to Get Rid of Fungus Gnats in Your Houseplants