Mr. Houser in Bulletin 194 of this Station says: "During the early summer, the tender growing tips of the catalpa become swollen and in time blacken at the point of injury. During the early part of the season the injury is usually found three or four inches below the tip, and at a lesser distance during late summer when the tree is growing less rapidly. The tip above the injury dies. Following the death of the tip in early summer, the next node below develops one or more branches, and frequently a cluster of leaves, giving the tree a bushy growth. The ultimate result, after continued topping, is a stunted, crooked, forked growth."

[Gossard seems to have identified this with Cecidomyia catalpae [syn: Contarinia catalpae], but Gagné (1989) lists this damage separately, assigning it to an undescribed midge.]

Catalpa
...
Larva in bud...cecidomyiid

In early summer new shoots become swollen and contain gregarious larvae. Full-grown larvae drop to the ground, after which the shoots turn brown and die. Host: C. bignonioides. Distr.: Ohio