Q: I have two river birch trees. Each year the leaves begin to pucker up like a Ruffles potato chip and they seem to have minute eggs. Is there anything I can do to get rid of this?
A: I’ll bet there are witchhazel shrubs somewhere in the neighborhood.
Witchhazel gall aphids cause conical protrusions on witchhazel leaves. Winged aphids develop inside the galls, then leave and fly to birch trees. There, they give birth to scale-like insects, which feed and induce the birch to form corrugated galls on the leaves. This “potato chip effect” is what you are seeing. This is mostly a cosmetic problem but if it really bothers you, spray the birch leaves with landscape insecticide just as the leaves open each spring. This might need to be repeated in fall if the population builds up again.
Another option is to apply imidacloprid (Bayer Tree & Shrub, Bonide Systemic Granules, etc) in March to control them.