Catalpa Worms: Tree Defoliators or Fisherman's Gold?

If your catalpa tree has been stripped of leaves by fat, striped caterpillars, you're hosting the catalpa sphinx moth (Ceratomia catalpae) larvae—commonly called catalpa or catawba worms.

Impact on Trees

Catalpa worms can completely defoliate a tree. Healthy catalpas usually refoliate quickly, but repeated severe defoliation over several years can cause branch dieback or tree death. Infestations are often sporadic and localized; some trees are hit yearly while nearby ones escape.

Natural Control

Parasitic wasps (especially Cotesia congregata) lay eggs in the caterpillars; the emerging wasp larvae kill the host. You'll often see white cocoons on the caterpillar's back—leave these parasitized worms alone to boost natural enemy populations. Birds and other predators also take a heavy toll.

Management Options

• Do nothing: Most trees recover; the worms are a temporary nuisance.
• Hand-pick: Collect caterpillars and give them to anglers—they are prized as top-tier catfish bait. Local bait shops may buy them.
• Bacillus thuringiensis (Bt): Apply this organic bacterial spray when caterpillars are small (early spring). It's safe for people, pets, and beneficials.
• Insecticides: Carbaryl (Sevin), permethrin, or other labeled products can be used for heavy infestations on valuable ornamental trees. Follow label directions.

A Matter of Perspective

For shade-tree owners, catalpa worms are pests. For anglers, they're a valuable resource. Many landowners plant catalpas specifically to cultivate worms for bait. Your approach depends on your priorities.