Because mealy bugs have that waxy coating they are most likely not affected by diotamaceous earth. DE does not hurt plants, I actually add diatomite to my potting mixes instead of perlite.
I would recommend using a systemic insecticide. I lost over half my Stapeliad collection to root mealies and after trying every other control method I managed to save some plants when I broke down and got some Bayer Advance systemic. I tried neem drenches, soapy water drenches, insecticidal soap etc but none of them worked at all.

Mike

I know we've had this conversation...guess I'll have to give it a try with the BATS. Maybe it will make its way through. The little %$#@ers are on Mathilde, which I dearly love. Likely on others as well. I loathe mealybugs. Thanks for the help with my other query btw. (pity about the Neem - it's being touted as the cure-all for so much, but not apparently, root mealies)

Kelly in Victoria

Kelly there is one thing you can try if it's only a couple of plants that has a good chance of working. Take a sink or bucket and fill with warm soapy water, completly immerse the pot and potting mix plus the plant if it fits and leave sit for a couple of hours. The soapy water will decrease the surface tension of the water which will not allow air bubble to stick to the mealies and they will drown. I could not use this method when I had the problem with root mealies because my Stapeliads were dormant/dry and they would have rotted. Dunking a Hoya for a few hours would not hurt it a bit as long as it drys out afterwards. I think this would be best done when the plant is dryish because the potting mix is going to end up very wet for a few days.

Good luck.

Mike

Will do. I'll use liquid Ivory. Condolences on your stapeliads...

Thanks M