Jumping in here -- I had trouble with mealy bugs that looked just like that. And they did seem to carry around some sort of mold. A friend's suggestion worked for me: Fill a spray bottle with Listerine (brand name only) and spray the plant every day. Since I use that now as a daily prophylactic, I can keep many more plants together indoors without worrying about the bugs, mold etc. that used to plague them. The only thing it hasn't completely gotten rid of are the gnats, but I only have an occasional one -- not the huge hatch-outs I used to have. If I suspect that, I spray the soil surface well.
But I don't know if extreme heat will affect that -- if you want to try it, I'd suggest using it in the evening... MR
