Stuff growing on birch tree leaves?

Question

My birch tree has tons of these little green (with a bit of red on top) balls growing all over the leaves. It seems to be taking over the leaves with these balls and killing them. Any ideas

Answer 1

I'd say what you're seeing is a type of gall - these are a place where some insect larvae or other irritant has caused the leaves to swell up around the source of irritation and it provides the insect with a source of food and/or protection:  http://ipm.ncsu.edu/photogallery/spwitch... , http://www.extension.umn.edu/yardandgard... (erineum gall) .  If you would cut some of these open with a knife, you'd probably see the larval insects inside if they haven't emerged yet.

If there's a high number of galls affecting the leaves, and you want to reduce further infection, you should remove and destroy any affected leaves before the larvae tramsform into breeding adults.

You could contact an county agricultural office or extension office, and they could probably give you more advice of the particular pest and how to control it.