Question
Mr. Hyland,  A friend of mine purchased a beautiful late 1800s industrial mansion in the piedmont of South Carolina approximately 5 years ago.  In July, when she closed on the property, the huge Catawba tree was covered in worms.
This continued until last summer and again this summer.  We have tried to find out why the worms quit  appearing on the tree.  It blooms beautiful in the spring, the "bean" appears, dries out and then most of them fall off.  Can you help us solve this dilemma and tell us how to bring back the caterpillars??  Also, how can we tell how old the tree is.  The grandson of the late Oliver M. Moore who built this beautiful home and helped to bring the railroad and the textile industry to this area is still living and in his 80's and remembers the tree as a child.
Thank you for your help.

Answer
THE CATALPA SPHINX is a common hawk or sphinx moth,  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.   One of the most common and important parasites is a small wasp that attacks the larva.   The female wasp deposits eggs through the skin of the caterpillar.   Wasp larvae feed and develop inside, then emerge to the outside and spin conspicuous white, silken cocooons on the caterpillar skin.   Parasitized catalpa worms do not survive to adulthood.

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.   

If early this spring, when the leaaves have filled out you do not see any small caltalpa caterpillars on the tree and if you know of a tree that has them, I would try moving some to this tree. I think is is just a down cycle in the population and they will come back. But adding some will speed this up. Make sure no insecticides are sprayed on these trees.