I don't know the answer, but will say root mealy is different that mealy bugs one sees on the plant; pls. do further research, I'm guessing spraying the roots w/ anything insecticidal will kill your plant.

While I've never grown Orbea, I grow other Stapeliads like Hoyas, Dischidias, Ceropegias and Huernias. I strongly advise against moving it up in size. If your Orbea behaves like Stapeliad which can largely be prone to rot from the start, doubling its pot size will greatly increase its chances of rot.

It is well grown out of its pot and is bursting through the sides of the pot. It has to be potted up. I pot up my stapelias all the time. The ones I have left, Because they grow so big. This is a huernia, or orbea, or any of a number of names, it is the variagata, very common one, The one most people start with.

I have found the only way to get rid of root mealies is to depot the plant, remove/rinse off all soil, spray with rubbing alcohol, wait a minute or so, and rinse well, examine the roots closely for any strays (remove with a toothpick) then pot up in a fresh pot and soil. I have done this to a number of cacti and succulents when I purchased an infected plant, and instead of isolating it, like I know I should, put it with some of my other plants and the mealies spread through the whole tray. After treating, all the plants are back to their healthy selves...and I learned that I should isolate new plants no matter what.

Kathy

I think I have run into a similar problem as you and am trying to find a solution as well. I have read in some places that something called Diamotaceous Earth and mixing it in with your soil will kill the bugs because it is sharp microscopically, yet not a chemical and is not harmful to the plant.

Bayer Tree and Shrub Insect Control concentrate diluted 1 ounce per gallon will cure your problem. Do not follow the directions on the bottle for trees/shrubs. Do not use other formulations with imidicloprid that contain fertilizers.

A 1 oz. (2 TBS) per gallon dilution will result in an imidicloprid concentration of 115 ppm, and can be used as a spray, or soil drench (what you need). Although expensive (around $20 per 32 oz), each container will make 32 gallons of soil drench, enough for lots and lots of meaiy outbreaks.