I worked for a commercial insectary for a few years and helped a friend control ear mites in his mouse cultures (the mite probably a Liponyssoides). I achieved some control of Pyemotes (straw mites) in the insect cultures at work--they are insect predators and also bite humans and are simply miserable to have. Pyemotes can destroy insect cultures in a very short time with simply exponential growth. More than one facility describes literal waves of thousands ( millions ) of the mites erupting out of rearing chambers when they have gotten out of control.
I used dusting sulfur in the cultures in both cases. The dusting sulfur didn't even have to be on the reared animals themselves. For instance, just a teaspoon of sulfur under the rodent bedding (in the standard plastic laboratory mouse container) did the trick. There is a paper concerning rearing cerambycids in dead wood where Pyemotes was a major problem, sulfur achieved complete control in a short time. I have no idea if sulfur would work for the mites in scrab beetle cultures, since it's a somewhat different situation from wood borers, but sulfur has generally low/no toxicity to insects. If I were to use it, I would obtain dusting sulfur from a garden center that is used to control--for instance--mildew on roses. Dusting sulfur has miscible agents added that allow it to mix with water and be applied as a fluid spray. I would sprinkle the dry dust on the very bottom of the containers before filling them with medium and the grubs. Let's say about a cc volume of dry dusting sulfur per quart of medium.
The cautions? Some mite species are totally unaffected by dusting sulfur. Control should happen within two weeks time. Wet medium with wet sulfur will be acidified as water and sulfur produces sulfuric acid under certain conditions. However, I never saw mortality in our cultures that could be ascribed to sulfur toxicity, wet or dry. And swampy, filthy conditions with anoxic decay must be avoided in any case, so I think you'd have a low probability of the super-acidic conditions that would be deadly to beetle grubs anyway.
As always, I would never try this on any untested species all at once. I would try a few individuals to see if they tolerate the treatment first--and to check if it works.
[DISCLAIMER: This message does not constitute a recommendation of the use of sulfur. Do not hold me responsible for any damage that may result from the use of sulfur. As always, read and follow the cautions and suggested uses, application rates and methods on the label of any regulated materials. ]
