Dealing with the fungus gnat.

Thanks to Jean for inspiring this post,

It is not my goal to eliminate all critters from the worm bin, nor would that be desirable. The goal here is to keep bins maintained in a fashion that prevents mass numbers of fruit flies and other such critters from forming. Most of the creatures is a bin are very beneficial, especially from a composting point of view.

Dealing with pest such as the pesky fungus gnat we must take their life cycle into account. Fungus gnats eggs incubate for about a week then they stay as larva for 2 weeks. During this time they remain in the bedding of the worm bin. After the two weeks they become an adult and live for a week, lay more eggs and die.

I call the following the "Shock-and-Awe" approach. What we must do is break the before mentioned cycle. To do this wage an all out war one day and kill as many of the adults as possible on that day. Then any more that hatch will not be laying till 7 days later. Whew! So we can now rest easy and relax knowing that those fungus gnats are laying potentially millions of eggs, no more nightmares of horror film sticky traps. But exactly 7 days later, no later, we must wage war again because those new hatchlings are going to start laying. So after doing this the second time in theory you should not have had any eggs laid for 14 days. Awesome, we are almost there since their life cycle is 4 weeks. Do this once more, not waiting for more than seven days, and you should have significantly reduced their numbers. After you get there numbers down you can provably keep them down and reasonable by keeping something on the surface to obstruct their access to the food supply. A thin layer of bedding works for this.

Now that leaves one unanswered question, how do we kill then without killing the worms. They are several things are effective that should not hurt the worms. A very mild soap solution sprayed lightly over the surface of the bin should be effective without hurting the worms. I suggest testing this out on a small sample from the bin first just to be sure. There is also some bacterias that will kill fungus gnats but I have no personal experience with it. I think it is sold under the trade name Gnatrol. What I use and personally know to be safe for me and the worms is diatomaceous earth. It is most effective when dry, but this is ok because we know we only need it to kill them on our one day.

Hope this helps out,

Matthew Wilson
Worms Etc