small black insect rapidly defoliating trees
A friend of mine purchased a number of trees this year from our local water authority (ashes, dogwoods, poplars, etc.) She noticed recently that all the trees they purchased are being quickly defoliated by very small black insect. They look like beetle larvae to me (not unlike ladybug larvae in appearance except for their size and coloration) and are small and totally black. They skeletonize the leaves leaving nothing but the fine veins behind and are rapidly destroying all the leaves on the small trees (the trees are a foot tall to slightly taller). The trees are planted in a shady area by a creek in their backyard. No other trees (all trees around them are mature trees) appear to be affected.
All attempts to reach the nursery that supplied the trees have been unsuccessful, and my friend suspects that the trees may not survive much past this weekend if they can't find a way to bring the infestation under control. Does anyone have any ideas as to what pest might be attacking the trees and how to control them? For that matter, has anyone else experienced a similar infestation (enough trees were sold by the water authority from a nursery in Rochester, NY that we can't help wondering if others have had the same problem). Handpicking appears to be ineffective because there are so many of them (the leaves and stems are completely covered & others quickly take the place of those removed).