Sumac leaf die-off
We have two smooth sumac trees in our back yard, planted three seasons ago. The first season, growth was vigorous and both plants appeared healthy. Last season, all went well until later (we think) in the summer, when leaves seemed to be wilted. We found, on the underside of the leaves, heavy infestations of what appeared to be short, thin, black threads. We washed the leaves with a diluted solution of dish-washing soap and water. The leaves, nonetheless, died and fell off prematurely, and we feared for the plants. This year, one plant has recovered nicely, even though there are a number of leafless branches. The other has one branch which has grown vigorously and there is vigorous growth of new plants at the base of the plant. This plant has numerous barren branches. What is alarming is that on this second plant, we are seeing a return of the infestation which did so much damage. We need to know: 1. What is this infestation; 2. What can we do to control/eradicate it, if anything; or 3. Do we give up and find another tree/shrub for these areas? Thank you for your attention.
Hennepin County Minnesota