What to Know About Catalpa Trees and Their Worms

Catalpa trees, with two species native to the United States, are known for their beautiful and plentiful blooms, as well as for being the sole source of food for catalpa worms — a caterpillar that strips the tree of its foliage and eventually becomes the catalpa sphinx moth.

Though catalpa worms can completely defoliate a catalpa tree over the course of one summer, healthy trees typically recover the following year, and natural predators keep the worms from doing too much damage in the long term.

Because the worms are also native, they have ample natural predators, including various wasp and fly parasitoids. Worms from the catalpa tree have long been valued as fish bait, and some fishermen plant the trees just for this purpose. When fully grown, they’re around 2.5-3 inches long, and somewhat variable in color, though primarily either dark or pale with a black stripe or dots down the middle of the back.

Catalpa Worms and Braconid Wasps

The primary predator to catalpa worms is an endoparasitoid wasp, Cotesia congregata, from the Braconidae family. These wasps lay eggs along the back of the caterpillar; after they’ve hatched, they feed on the worm itself, eventually killing it. The wasps also inject venom into the caterpillars to control their development. These wasps are beneficial to the catalpa trees and the ecosystem overall, because they help stop the worms from killing the tree.

The Catalpa Tree

The two species of catalpa tree native to the United States — northern and southern catalpa, have a current distribution from New Hampshire and Nebraska in the northern United States, and across the South from Florida to Texas. Historically, the southern catalpa is native from northern Florida to Georgia, and west through southern Alabama and Mississippi. The northern catalpa’s natural range is along the confluence of the Mississippi and Ohio rivers from Southern Illinois and Indiana to northeastern Arkansas.

Like many places, plants, and rivers across the United States, the word catalpa originates from a Native American term, the Creek word catalpa, meaning “winged head,” and the Muskogee tribe used it to refer to trees. The tree’s name is also spelled catawba (which is how catalpa is pronounced). Some fishermen refer to the catalpa as the “fish bait tree,” and it has also been referred to as “cigar tree” or “bean tree,” because both the northern and southern species feature long, slender seed pods that look like a cigar or an unshelled long bean. The northern catalpa has pods that are slightly slimmer in diameter and up to two feet in length, while the southern catalpa usually has pods less than 12 inches in length. Both varieties produce large, white, erect flowers.

Catalpas are dual pollinators — bees pollinate the flowers in daytime, guided by the yellow and purple markings (nectar guides). Then, at night, increases in nectar and fragrance attract moths (including the catalpa sphinx) to continue the pollination process. They’re also tolerant of many different soil types, including compacted soil, and can grow near pavement. Despite their native range being largely confined to the southeastern United States, the trees can also flourish as far north as New Hampshire — meaning they’re fairly climate tolerant.

Historically, catalpa trees have served a variety of uses and have been extensively propagated for more than 200 years. European settlers used the wood for fence posts, and railroad companies used it to make track ties and fuel wood. Carpenters commonly used it for interior trim in houses, and craftsmen used it to make furniture. It has also been used as telephone or power line poles. The wood is lightweight, and the heartwood is resistant to deterioration when placed in the ground for several years.

The southern catalpa tree also has medicinal uses, and a tea made from the bark has been used as an antiseptic, snake bite antidote, laxative, sedative, and to remove parasitic worms. This tea was also used as a substitute for quinine in treating malaria. A tea made from the seeds was used in the treatment of asthma and bronchitis as well as a rinse on wounds. In addition to having a sedative effect, the plant also is reported to have a mild narcotic action, and used for the treatment of whooping cough, asthma and spasmodic coughs in children. Contemporary pharmaceutical research has shown catalpa trees have diuretic properties. Take care as the roots of the tree are poisonous and should not be handled or composted. Despite its many positive attributes and ability to attract pollinators, catalpa trees don't seem to be planted particularly often around the United States. Gardeners have attributed this to their distinctive odor, as well as the mess left behind as their seed pods drop to the ground in the spring. These pods can disperse widely, leading quickly to new catalpa sprouts.

Catfish Candy

Written references to catalpa worms as prized fishing bait date back to the late 1800s, and fishermen have likely planted the trees to have a steady source of bait since before then.

For sustenance fishing, a few catalpa trees could provide enough worms for a family. That said, not all trees produce worms. Historically, the practice was common in native environments where the worms typically appear, but they don’t always appear on trees outside of their native range.

Where they do appear, fishermen use them for bait to catch catfish, bream, perch, largemouth bass, and several other species. And for those who can’t find the caterpillars on an actual tree, frozen worms are now available to be thawed and used as bait through a company called Catawba Gold. There is currently an active US patent protecting a method of preserving live catalpa larva for use as fishing bait that has been on file since 2008, proof that people recognize the value in selling the catalpa worms.