Diverse Compost Ecosystem – Protection From Fruit Flies?

Large Worm Bin Mite

As mentioned in another post, I recently brought in a fair amount of material (containing worms) from my big outdoor worm bin. Not long after doing so, I started noticing large fruit flies flying around in my worm room. One bin in particular seems to have developed a pretty bad infestation. What’s interesting is the fact that I am now exclusively using open tub systems, and I am feeding the worms food waste paste (aka “homemade manure“) – in other words, my systems should be prime targets for serious fruit fly invasions – yet, for whatever reason, most of my bins seem to be staying free of fruit flies. The one bin that developed the bad infestation contains material collected from one of my garden worm beds (aka ‘garbage gardens‘) and a lot of partially decayed straw from my bin – not all that much actual compost material.

I have a sneaking suspicion that the reason most of my bins are fending off the fruit flies is that they contain a very diverse ecosystem, with plenty of predators. I find that aged manure in particular seems to contain a lot of different critters, with quite a few different predator species. Some of them, like the big vicious-looking beetle larvae and wolf spiders, are pretty obvious, while others fly under the radar a bit more easily due to their smaller size. Mites are one such group that I suspect play an important predatory role in manure heaps without being too obvious about it.

I once purchased predatory mites (Hypoaspis miles) to help me deal with a bad fungus gnat infestation. In comparison to the typical ‘worm bin mites’ I was used to, this species was incredibly fast moving – which makes logical sense given the fact that they need to capture their prey. Interestingly enough, I’ve noticed that manure seems to contain an incredible abundance of mites that looks exactly like Hypoaspis sp. I’m no mite taxonomist, and I’m relying on naked-eye observations – not the use of a high-powered dissection microscope – so my observations are meant to be taken as gospel. This is just a hunch.

There are of course some other potential explanations. One in particular relates to the use of the blended food waste. As I’ve written elsewhere, I suspect that the use of this material may actually help to reduce the impact of a fruit fly invasion since the worms can consume it much more quickly and easily. Chunks of food waste on the other hand, can act like little protective habitat (and food source) for zillions of fruit fly larvae – which of course quickly hatch out into the clouds of annoying adults most of us are all to familiar with.

Anyway, I’ve always been fascinated with natural ecosystems and little critters, so I definitely plan to spend more time exploring the possibility that various organisms are playing a protective role. I will certainly keep everyone posted!

[tags]mites, ecosystem, compost, compost heap, compost pile, wolf spider, larvae, predators, worms, red worms, vermicomposting, worm composting, fruit flies[/tags]

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  1. It’s funny you bring up your diverse ecosystem to prevent infestation. I use vermicompost for amending soil in the garden. I use Subculture B by General Hydroponics to bacterially amend the castings before introducing into soil. It breaks down nutrients in high salt environments to be made available to plants. I haven’t had any fruit fly infestations since using it.

    • Adam Nelson
    • November 30, 2008

    I have just ordered my first batch of worms and am waiting for them to arrive to their freshly made (slightly rotten) home. In the mean time I have been reading up on all the worm issues, and one theme that I am picking up is that whether it be fruit flies, gnats, biting flies, or some other type of pest there is going to be a certain bit of just dealing with it (necessary evil). Am I wrong or are these just horror cases. I have been planning on keeping my bin in the basement and my wife definitely is not a big fan of that. Please let me know if this a norm or something that can be managed to avoid angry wife syndrome.

    • Sherry
    • December 1, 2008

    I have 4 working bins in the spare bedroom of my apartment. My greatest fear is having a massive fruit fly problem. Hubby is fine with my worms, “as long as he doesn’t see one” but a fruit fly infestation will definitely cause him to throw the bins over the balcony.

    I’ve had these bins for several months, and have never had fruit flies, or fungas gnats. (Kocking on my head for luck). My sincere advice to you is to freeze all your food first. This kills any fruit fly eggs on the food. Thaw and drain for a few days to get it nice and palatable for the worms. I use the food processor to mince my food and freeze in plastic bags. They gobble this up very quickly, in fact I have to feed them more often than I am. I’m currently feeding them 2 large ice cream containers per week and I have to feed more.

  2. Adam – I keep my bin in the basement and have no real problems with fruit flies or any other insects or smells. Like Sherry, I freeze all my scraps, which I think kills the fruit fly eggs. Unlike Sherry, I do not thaw them first. I just put the frozen scraps in the bin, assuming the worms will move out of the way and not come back until the food is thawed and ready to go. My bin is very active and very productive so I have to assume my hypothesis is correct. Sure beats having thawing food scraps on the counter! I mostly just dice my scraps small and do not run them through the food processor. Another benefit of freezing the scraps is that they break down more quickly. Good luck!

    • Bentley
    • December 1, 2008

    Adam – your comment definitely made me smile!
    Keep in mind that I #1) am a walking disaster zone, #2) run a vermicomposting business out of my home (so lots of bins etc), and #3) am a vermicomposting educator, so I almost encourage these infestations from time to time just so people can learn from my mistakes!
    Listen to Sherry and Mary – they are clearly masters of the ‘an ounce of prevention is worth a pound of cure’ school of thought. (something I agree with wholeheartedly, by the way).

    That being said, I’d be surprised if there is anyone who has vermicomposted for numerous years without ANY sort of invasion from at least SOME type of undesirable critter.

    Don’t sweat it Adam. ‘Angry Wife Syndrome’ (or ‘AWS’ among us experts) is usually a temporary condition, often cured with chocolate and flowers.

    • Rich A.
    • December 1, 2008

    I have both fruit flies and fungus gnats. The fruit fly problem I seem to have solved by stopping new feeding for a week, and thereafter freezing all scraps first.

    The fungus gnat problem has been tougher. I use fly paper, insecticidal soap, and most recently ScanMask predatory nematodes. These three methods and some colder temperatures in the garage have kept the problem manageable.

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