Question
My daughter lives in NC and I believe it is this worm that defoliated her tree.  Will this kill the tree and what can she do about the worms next year?

Answer
THE CATALPA SPHINX1 is a common hawk or sphinx moth, (Photo 1) but it is the caterpillar stage,  that is most often encountered and best known.   The caterpillars, commonly called catalpa worms or "catawba" worms, feed on leaves of catalpa and often completely strip trees of foliage.   Loss of foliage may be serious, especially for shade and ornamental trees and nursery stock.   While the catalpa worm is well known as a tree pest, it may be as well or better known to some for its attractiveness to fish.   The caterpillars have long been valued for fish bait, and references to their collection by fishermen date back at least to the 1870's when the species was first described.

Infestations of the catalpa sphinx occur sporadically; they come and go and often seem to be highly localized.   Certain trees appear to be preferred and are attacked regularly while others of the same catalpa species seem to escape attack; the reason for this is unknown.   Caterpillars may be abundant for one, two, or three years, then scarce for several.   Natural enemies such as parasites and predators, take a heavy toll of eggs and larvae, and are largely responsible for maintaining populations at low levels.  

When caterpillars are numerous, infested trees may be completely defoliated.   Defoliated catalpas produce new leaves readily and trees usually refoliate promptly.   However, with multiple generations occurring, new foliage maybe consumed by subsequent broods.   Most trees survive but some dieback may occur.   Severe defoliation over several consecutive years can cause death of trees.   

The catalpa tree, with its broad, dense crown and showy flowers, is prized by many as a shade or ornamental tree.   Catalpa worms can essentially destroy this ornamental value.   In this circumstance, the catalpa sphinx is a destructive, unwanted pest.   However, there is another viewpoint.   As indicated previously, catalpa worms are prized for fish bait.   To many fishermen their presence is welcomed, even encouraged.   Catalpa foliage is the only food of the catalpa worms, and it is likely that many catalpa trees are planted and maintained as much or more for production of fish bait as for any other purpose.   Whether the catalpa sphinx is destructive or beneficial is a matter of point of view.

Generally the catalpa worms do not kill the tree. But make cause some branch die back. What I would do is check with some friends who fish and have them come over and collect the worms next year for their fishing trips. If you put out the word I am sure most fishermen would jump at the chance to get the worm. OR call a local bait shop and see if you can sell them or give them away.

Insecticides can be used one called Bt will work if sprayed early in the spring when the caterpillars are first seen. Too bad you are not closer to Alabama or I would take all you can grow.