We started a row of espaliered fruit trees four years ago, on the west border of our vegetable garden. Two are sour cherries; in between are three different apple cultivars grafted onto dwarf rootstock (all mail-ordered from Adams County Nursery in Pennsylvania). Last year was the first for the apples to flower, but the fruit was all dropped by the trees after early attack by plum curculio.
This season, we've tried Surround, an organic clay product that you start spraying onto the fruits just after petal fall and for a few weeks afterward, to control the plum curculios. Our apples are still on the trees and growing - much bigger than they got last year before dropping. At least for our rather petite and manageable orchard, Surround is working. My understanding is that for our application, it is a "protectant" rather than an "insecticide," which I think means the curculios don't like to touch/chomp it, but it doesn't kill them. We used one of those two-gallon pump-it-up green garden sprayers to apply.
This picture was taken mid-May, after fruit pruning, which encourages the trees to put energy into producing quality rather than quantity. The Surround is white and powdery when it dries. We ordered it from Seven Springs Farm in Virginia, and they shipped it super fast. Their price is good, and I think it got here the next day, which worked out very well for us, because we are real wait-till-the-last-desperate-moment types, and the plum curculios were practically breaking down the front door trying to get through the house and into the backyard... We made our first application just in the nick of time.