Getting rid of these pests
While fungus gnats (or sciarid flies as they are also known) don’t pose a threat to humans, they can cause harm to plants. While this threat diminishes when seedlings get older, there is still a possibility that these 2mm little black flies can create problems. Their larvae attack the roots of plants, and adult flies can carry Pythium on their feet. Pythium is a pathogen that causes damping off in seedlings. If infestations are large enough, fungus gnats can stunt growth and even kill plants.
With all these dangers, and for the simple fact that fungus gnats are annoying, I have made it a priority to find ways to get rid of them in any way I can. I know it will be virtually impossible to eliminate them (as they breed very quickly), but I certainly believe it is possible to bring their numbers under control. Particularly now that I have started using some rather unconventional methods to attack the problem head on
The first of these methods (believe this or not) is to use a handheld vacuum cleaner to suck up the gnats as they crawl or hover around the plants. It might sound funny, but believe me, it works remarkably well. To do this, I water the plants from the top and suck the gnats into the vacuum cleaner. I can do this as they fly up after being disturbed by the water. When you consider that each adult fungus female fungus gnat fly can lay up to 200 eggs. Even if you only capture twenty flies in a single session, you will have removed the potential of another four thousand fungus gnats being born. That’s impressive