predatory mites v. earthworms
IÃ¢ÂÂve recently resumed composting, and with no outdoor garden space where I live in Thailand IÃ¢ÂÂm composting in plastic trash bins on a balcony. Layering well-aged cow manure, veg/fruit kitchen waste, and dry semi-decayed tree leaves, the process has worked well, with breakdown nearly complete in two weeks. The mix, which I turn regularly, is damp but not wet, except when I add a layer of kitchen waste topped with manure.
Hoping to enrich the almost-finished compost, I added a dozen earthworms and watched them burrow and eat, on or near the surface, although I placed some deeper. Within ten minutes they were attacked by what appear to be red mites. The worms convulsed and shriveled, drained of blood, and all died within an hour. The mites are about the size of a pinhead and a semi-glossy red-brown. Whatever their classification, these feed not only on decaying vegetable matter but on live worms.
To see if I could eliminate the mites and re-stock with worms I laid strips of papaya or mango skin on top of the compost. The skins quickly attracted dozens of mites, and I disposed of the lot, repeating the process several times over two weeks. But many mites remain. (A second bin, containing older and more advanced compost, has many fewer mites, but there were still enough to kill all the worms.)
I know that the mites and other invertebrates contribute to breaking down organic matter. But I had looked forward to the results of wormsÃ¢ÂÂ superior aerating and their castings. However, it seems I must choose: Mites or earthworms. I would rather not introduce more worms, only to have them killed by the parasitic mites.
Part of the problem may be that I am composting in plastic bins with no holes in sides or bottom, and at night in the monsoon season I must cover the bins with tight-fitting lids. In this somewhat sealed environment, neither mites nor worms have any place else to go. And despite my regular turning of the mix, perhaps it has remained damp enough to over-balance the mite population.
Should I just let the mites do their job and forget the earthworms? Or should I persist in trapping and clearing out the mites (assuming I could get them all)?
Last question: is there any downside to the mites, such as seeking living plants or humans as hosts? I am new to gardening in the tropics, and have no experience with predatory mites. I would be grateful for suggestions.