Getting rid of Sciarid flies

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

Other methods

Bug Zapper

Something else that I have found affective is a bug zapper. A bug zapper is an electrical-discharge or electronic insect control system. It works by luring flying insects with fluorescent light into a deadly electrical current. The gnats get attracted to a bright light, and they get fried. It is pretty satisfying hearing the intermittent crackling sound that happens when fungus gnats fly into the device . Each crackling sound says goodbye to the potential of another two hundred fungus gnats. What’s more, no effort is needed. You simply keep the device on, and it will quite happily continue destroying the little pests.

Another thing I am trying is to sprinkle to tops of the potting soil my seedlings are planted in with worm castings. This apparently acts as a deterrent to the fungus gnats laying their eggs. It acts as a barrier over the top of the potting and makes it difficult for the adult flies to lay eggs. No eggs mean no larvae, which ultimately should lead to the cycle being broken.

On the larvae front, I have had reasonable success with mosquito bits containing Bacillus Thuringiensis Israelenis but they only seem to work for a while. After a week to ten days of using them, the fungus gnats seem to reappear in their hundreds. Before long they seem to be around in such numbers that they don’t seem to have gone away in the first place. The packet however does state the bits will only kill any larvae present in the soil at the time of application.  It means adults can lay eggs directly after the application of the mosquito bits, which in turn will lead to more larvae

Similarly, hydrogen peroxide (3 %) seems to work well. However, once again, it only seems to work for a week or so.  It is necessary to use it weekly for it to be effective. Up to now I have used the H202 at every alternate week, but recently learned that for the mosquito bits to be totally effective, they need to be applied weekly for three to four weeks in a row. It is certainly something I am in the process of testing

Over and above these methods, I am also using sticky yellow fly paper to put the final nail in the coffin of the gnats. The fly paper from previous experience works well. It captures the odd fly that escapes all the other measures mentioned.

Final thought

As mentioned in my previous post, it has become obvious (that a fungus gnat infestation needs to be attacked from multiple angles). Not only do the larvae need to be destroyed, but it is also essential to eliminate the adult flies at the same time. This is the only way the continuous cycle of these pests can be broken once and for all

While it has only been a couple of days since I have combined all of these methods the initial results seem quite impressive. The numbers of gnats have decreased significantly. So much so, I am really hoping that just maybe I will be able to get rid of this problem once and for all. Here’s hoping anyway!

Image credits

Katja Schulz / CC BY-NC 2.0/ via Flickr

Ian Jacobs /CC BY-NC 2.0/ via Flickr

Maja DumatCC BY 2.0 // via Flickr

One thought on “Getting rid of Sciarid flies

  • 25th May 2022 at 2:32 am

    thank you. That was a clear and concise. I have tries several methods to try and rid my plants of these fungus gnats. seeing each one captures i will now think maybe it was actually 201 and that makes me continue the quest to eliminate the unwelcome uninvited midges.
    Thank you


Leave a Reply

Your email address will not be published. Required fields are marked *