If you notice tiny gray or black flies wandering around your plant’s container or on the surface of the soil when you water, your plants are most likely infested with fungus gnats. These tiny insects can turn your pretty indoor garden into an eyesore in just a few weeks. They thrive in moist soil from your overwatered plants. Its larvae feed on the roots and burrow into the stem. Adults move from one plant to another, spreading diseases. It is good that there is an easy and cheap solution to prevent the fungus gnat:
Dilute the 35% hydrogen peroxide solution to a 3% solution by mixing one part with 11 parts distilled water. The storage container you will be using must be opaque to block light and must be able to hold a certain pressure.
When you have diluted the hydrogen peroxide to 3%, take one part and then mix it with four parts distilled water. Wait until your infected plant has dried out, then water it with the mixture until the water runs all over the pot. The larvae will die when they come in direct contact with the hydrogen peroxide. You will notice a bit of fizz, and this is normal. It will stop after a few minutes. After several more minutes of watering with this solution, it will break down into oxygen and water molecules. So it’s absolutely safe.
Use this solution for a mature plant, but it can be quite strong for seedlings. This initial treatment should kill the eggs in the compost. Adults live for about a week, but each female fungus gnat lays more than 100 eggs in that week. Adding 1/2 inch of sand to the soil surface should discourage adult mosquitoes from laying more eggs.
Using hydrogen peroxide is a simple fungus gnat prevention method that can also be used to solve other problems related to overwatering plants. If you frequently overwater your houseplants, you can start with one teaspoon and then add two and a half teaspoons of the 3% mix per gallon of water and use it each time to help prevent future problems.
The best advice for fungus gnat prevention is not to overwater plants. As mentioned above, fungus gnats love moist soil, so by simply watering properly, you can prevent these pesky insects from damaging your prized plants.
