Worm composting and fruit flies

Asked January 22, 2015, 7:35 AM EST

Hi. I've had worm bins for a few years. I keep them inside in the winter. I have a terrible problem with fruit flies this year and would appreciate some guidance. Here's what I've done so far:

1) put new food scraps below the surface of processed worm "soil"
2) apply a thick layer of bedding above. I used shredded (in a shredder) office and newspaper avoiding colored inks
3) set home made traps - ACV in containers covered with perforated plastic wrap

And other suggestions? I wondered if there were cold temps the worms could survive, but the flies could not. I have two bins. They are kept in the basement. There are few other things they are attracted to (although they do occasionally find a wet tea bag or other organic attractions in the kitchen).

Thanks for your help!

Delaware County Pennsylvania

1 Response

Yes fruit flies are a problem. If you are going to vermicompost, from my discussions with sellers of worms, you may have to accept the reality of fruit flies. You are doing the right things but here are a few suggestions.

1. I think you are using fruit fly traps around your house already. Focus around your composting bin(s). Some of the commercial sellers have even recommended afixing a trap to the lid of the bin. You may have to use commercial ones as the apple cider vinegar may not work so well. Alternatively, try using an apple core for bait. Then, the flies will lay eggs in the apple core instead of the compost. Another possibility is yellow plastic discs with either mineral oil or honey (I'd recommend the honey) to attract a trap the flies.

2. Don't overfeed your bins! Since the flies and worms are competing for the same resources limit that resource to what the worms can digest quickly.

3.As you are doing . . place wet shredded newspaper over the top of any foodstuffs. One to two inches at least.

4. I don't know how you are storing your compostables before adding to the bin but you could try the following. Either refrigerate or freeze your compostables before adding to the bin. The cold will slow the developement of fruitflies and isolation in a sealed container will prevent flies from laying eggs. Also, some sources recommend heat treating your material to kill immature flies. In the winter this might prove tricky. Maybe the microwave or with a double boiler and steam? (I haven't tried heat methods as you might noticed) I have tried refrigeration, it helps but it is not a panacea.

5. With regard to your temperature question. I assume you are using red wigglers (Eisinia foetida)? The worms really should not get below 40 degrees. I would suggest the exact opposite of your idea based on my experience in my house. We had much slower digestion/production of compost when our bins were in our basement. Also occasional anerobic digestion and odors. Check your temperature near your bin. If it is cooler, you may find that a higher temperature boosts the worms activity, metabolism, and appetite so they can out compete the fruitflies more efficiently.

Hope that helps and keeps the wigglers wigglin' ! ! !