I subsequently added a touch of soap and got a bit better luck -
still only spots on the plums, but something at least.
I have been using Surround on my apples, peaches, apricots, and plums
this year for control of curculio and for moths. I started spraying
a bit too late but I ended up losing very few complete apple clusters
to curculio. I do have quite a few apples with small curc "bites"
which I would have preferred to avoid but at least they did not ruin
it all. I did less well on the plums, partly I think due to the lack
of coverage on the fruit (also again I started the regimen too
late). I probably lost 3/4 of the plums, but on the plus side did
not need to thin what started as a significant overset. I lost very
few peaches; only the nectarines had damage. Overall I am reasonably
happy with how it worked. I concentrated the spray on and around the
fruit itself to try to save on product (and on the number of refills
of my backpack sprayer). Maybe I should have covered a greater
portion of the tree to add to the general annoyance factor for the curc.
I have now been adding spinosad try to improve the effectiveness of
Surround against moths. So far it seems to be working well on the
early generations, but the story is not over yet. I wonder if the
powder of the Surround helps to distribute the spinosad onto the
moths by covering them with powdered spinosad. It certainly works on
me as I brush past my trees!