Sciarid flies, also known as fungus gnats, are small dark-winged insects that are attracted to moist organic matter. They are common pests of houseplants and mushrooms, where they lay their eggs in the soil or compost. The larvae feed on decaying plant material and sometimes on plant roots, causing damage to seedlings and cuttings.

If you have sciarid flies in your home or greenhouse, you may notice them flying around your plants or running over the soil surface. They can be annoying and unsightly, but they are not harmful to humans or animals. However, they can reduce the quality and yield of your plants and mushrooms, especially if the infestation is severe.

Fortunately, there are some effective ways to control sciarid flies and prevent them from damaging your plants and mushrooms. Here are some tips to help you get rid of these pesky pests:

• Reduce watering. Sciarid flies thrive in damp conditions, so avoid overwatering your plants and mushrooms. Let the soil or compost dry out slightly between waterings, and use well-drained pots and trays. This will reduce the moisture and organic matter that the flies need to breed and feed.
• Improve ventilation. Sciarid flies prefer warm and humid environments, so increase the air circulation around your plants and mushrooms. Open windows and doors, use fans or vents, and remove any dead or diseased plant material. This will lower the temperature and humidity and discourage the flies from settling.
• Use yellow sticky traps. Sciarid flies are attracted to yellow color, so you can use yellow sticky traps to trap and kill them. Place the traps near your plants and mushrooms, especially near the soil surface where the flies emerge. Check and replace the traps regularly, and dispose of them safely.
• Apply biological control. Sciarid flies have natural enemies that can help you control them organically. One of them is a beneficial nematode called Steinernema feltiae, which parasitizes and kills the larvae in the soil or compost. You can buy these nematodes online or from garden centers, and apply them according to the instructions. Another option is a predatory mite called Hypoaspis miles, which feeds on the eggs and young larvae of sciarid flies. You can also buy these mites online or from garden centers, and sprinkle them on the soil or compost surface.
• Use insecticides. If none of the above methods work, you can resort to using insecticides to kill sciarid flies. However, be careful when choosing and applying insecticides, as some of them may be harmful to your plants, mushrooms, or beneficial insects. Always read the label and follow the directions carefully, and wear protective clothing and gloves when handling insecticides. Some of the insecticides that are effective against sciarid flies are pyrethrin-based sprays, neem oil, or diatomaceous earth.

By following these tips, you can control sciarid flies in your houseplants and mushrooms, and enjoy healthy and beautiful plants without any annoying pests.