Question
How do I get rid of them?  I have 4 very large Catalpa trees and the Ceratomia catalpae has killed 1 of the trees.  I want to save the other 3.  What can I do?

Answer
First I would not think the caterpillar will kill the tree. It will eat all the leaves and make the tree look dead. But hardwood have the capability of leafing out again and one defoliation will not kill them. Defoliation over several years may cause the limbs to die back.

The catalpa sphinx caterpillar occurs primarily in the southeastern United States but can be found as far west as Colorado and as far north as Michigan. Apparently its only host plant is the catalpa tree. Since the early 1800s, fishing partisans often have used these larvae as bait and have cultivated the catalpa for no other purpose than to attract the insect.

Biology
Adults are brownish-gray and have irregular dark and light colored lines across the forewings; wing expanse is up to 3 inches. The adult is a type of "hawk moth" and resembles the adult moth of the tobacco and tomato hornworm.

In the spring, the adults emerge from the soil where they overwintered as pupae. Eggs can be laid in masses of several hundred on the underside of leaves or in smaller masses on twigs and branches.

Younger larvae are pale yellow. The group feeding behavior of the larvae continues until the later instar stages, when they feed singly before moving to the ground seeking a pupation site.

Full-grown larvae are about 2 to 3 inches long and possess a stout black horn near the rear of the body. They vary in color from pale yellow with green markings to black with yellow markings. In Missouri, the common color pattern of mature larvae is a black head; the top portion of the body black; sides of the body yellow with small black markings; and a black line running the length of the body, separating the yellow sides from the light-colored underside. Depending on the geographic location, there can be up to four generations of catalpa sphinx each year.

Control
On small trees, the best nonchemical control for these gregarious caterpillar species is to search the foliage for egg masses and tips of branches for colonies of larvae, then prune and destroy the infested leaves or twigs. This should be done early in the summer when populations are usually low since the initial infestations are found primarily on the lower branches.

A control technique that may be helpful is to till the ground thoroughly (if appropriate) in the immediate vicinity of the trunk in the fall. This will destroy some of the overwintering pupae.

The walnut and yellownecked caterpillars and the catalpa sphinx are all attacked by a number of invertebrate and vertebrate natural enemies, reportedly providing a fairly high level of natural control under most circumstances. This natural mortality coupled with an early-season examination of the trees usually provides sufficient control.

For larger trees where it is impractical to search the foliage, chemical control may be required. Chemical applications should be made as soon as groups of larvae appear. Some insecticides that can provide control for these colony feeders are certain formulations of carbaryl, cyfluthrin, acephate, neem and Bacillus thuringiensis (Bt). The insecticides except Bt can be sprayed on the trunk as the caterpillars are moving down the trunk to the soil and this will kill them.

IF you have friends who fish call them and they should want the caterpillars for bait. They are excellent fish bait and even some of the bait stores near you may want them.

Some catalpa trees are never attacked. So if the other three do not have caterpillars on them now chances are they will not. It is not really under stood why this happen but it is thought to be genetic of the different trees.