I found plum leaves in North Dakota with odd growths on them. The growths appear as though they are some sort of cocoon but are actually deformed growth caused by the tree’s reaction to gall mites feeding on the leaves. I have seen this to a lesser degree in my own yard in Washington.
Great visual image, WD.
I think a lot of people have no idea what is affecting their trees until they see a clear picture like this one.
I thought the pear rust structure was nasty. That looks really disturbing. I might have to cut that all off and burn it just for peace of mind.
I found galls on Lombardy poplar leaf stems in Puyallup. Apparently caused by aphids. The gall is a spiral with small chamber where the aphids live. When you tug on the stem the gall uncoils.
Excellent visual explanation, WD.