On the All About Worms Facebook page, we were asked what causes Catawba worms to leave a Catalpa tree after many years. (We could have just as easily written “what causes Catalpa worms to leave Catawba trees,” as “Catalpa” and “Catawba” are interchangeable.) After many years of enjoying the leaves of a tree, why would Catawba worms simply leave? This is a difficult question to answer because there are various reasons why Catawba worms might leave any given Catalpa tree, and why they left our reader’s trees in particular is impossible for us to say without knowing anything about his circumstances. He merely asked “what will make” the worms leave. To a generic question we can only provide a generic answer, so we’ll explain some of the general reasons Catawba worms leave Catalpa trees.