I'm having severe problems with spider mites on three plum trees which
I'm maintaining in pots until I have a place to put them in the
ground. Nothing I have tried seems to help. Insecticidal soap kills
the beasties off; but three or four days later, they're back. Then I
spray them again, and the cycle repeats. With malathion, things are
much the same.

Since the trees are not fruiting this year, I tried a systemic poison
(disulfaton); after two months of application, it seems to have had no
effect at all.

So far this year two of the three trees have been completely denuded
of leaves, and have grown back a new set. Now they're losing the
second set. I don't know how much more of this they can take.

I'm looking desperately for ideas on how to control this plague!