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!
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