A little while back, RWC reader, Margie (from California), sent me an email sharing her experience with black soldier flies in her outdoor worm bins. I thought others might find the info helpful, so I asked Margie if it was ok to post it here. You can probably guess what she said.
(Thanks again, Margie!)
Below you will find her description, along with images of her outdoor bins
Hi! I have had four large plastic outdoor composting systems for several years. In the beginning, I used to have problems with black soldier flies (BSF’s), which look larger than your average fly and make a crazy and very loud rattling sound when flying. They like to lay eggs and have their larvae grow up in the supportive enviroment of a worm bin (where their larvae will quickly out-eat your wonderful red wigglers).
To deal with this situation, I make sure that my food stuff is “buried” well. After adding the food close to the bottom of the feeding side of the bin, I cover it with approx 5 inches (13 cm) of the more mature compost. Something that has really helped is that I’ve started to add a thick layer of cardboard or shredded paper to the top of my compost. With this technique, I haven’t seen the BSF’s for years now.
Sometimes I even leave the tops of my bins open with a simple large screen on top to promote air flow! Even with this easy access, I still don’t see any BSF’s! The layer of paper is also a great way to prevent fruit flies as well! I’ve never had swarms of them since I started to “buffer” my compost.
One tip for an easy source of shredded paper is to use the leftovers from your confidential paper shredder (if you have one). I know that people say the bleached paper irritates the worms, but if you have a large enough system it really doesn’t seem to bother them at all, especially if you work it into the compost slowly. As you may be able to see in the picture, the bottom layer of the shredded paper absorbs the moisture from the compost and starts to break down quickly. The worms seem to decompose the white paper just as happily as they do cardboard!
The reason I can leave my bin open with a screen on top is that I live in California, and we have a very defined rainy season. Our summer is very dry, with almost no chance of rain. I do get other visitors to my bin though, such as spiders, slugs and earwigs. They’ve never been a problem of excess, and I think of it as a happy habitat and balanced ecosystem.
Hope this helps!
-Margie in California