I'm in mid-eastern PA near NJ, zone 6.
I have a Burkwook Viburnum that is six years old and well on it's way as an angling 3 or 4 stemmed tree at over 12 feet. Every year I have thinned out the foilage after bloom to reduce rubbing and also to clear out curling, malformed leaves. It's always been a problem only at the beginning of the growing season and seems to go away by heat of summer and after I've pruned it out. This year it seems worse and some of the leaves are also showing a thinness and transparency with yellow discoloration. I don't know if the two symptoms are related. I don't see any aphips on this tree? What's causing the curling leaves, that seemingly grow malformed this way?