By Raymond Cloyd, K-State extension horticultural and plant protection entomologist.
The catalpa caterpillar or catalpa sphinx, Ceratomia catalpae, is an insect pest native to the eastern USA that only feeds on catalpa trees, including Catalpa bignonioides and C. speciosa. This article describes the biology, damage, and management of the catalpa caterpillar.
Biology
Adults are brown (Figure 1) and have a 2.5 to 3.7 inch (6.3 to 9.3 centimeter) wingspan. Adults are present from spring through fall. After mating, females lay clusters of up to 1,000 eggs on the underside of leaves. Young catalpa caterpillars that emerge (eclose) from eggs are white with black spots on the body (Figure 2). Older caterpillars are approximately 3.0 inches (7.6 centimeters) long, with a black head and black stripe that extends the length of the back (Figure 3).
There are also yellow stripes, with black vertical bands, that extend along both sides of the body (Figure 4). Some caterpillars will have a row of black spots along the back but will not have a black stripe. There are five instars (stages between each molt). Caterpillars are present from spring to late fall. Caterpillars eventually move to the base of a catalpa tree and enter the soil to pupate. They overwinter as pupae in the soil at a depth of 2 to 3 inches (5.0 to 7.6 centimeters). There may be up to three generations per year in Kansas.
Catalpa trees contain iridoid glycosides, which are compounds that serve as antifeedants for generalist insect species or attractants for specialist insect species. The presence of iridoid glycosides, also called catalposides, may be why the catalpa caterpillar only feeds on catalpa trees. The iridoid glycosides, which are stored in the hemolymph, are sequestered by catalpa caterpillars, resulting in their being unpalatable to predators.
Damage
Young caterpillars feed initially in groups and then disperse among a tree. Caterpillars remove leaf tissue, except for the main veins. Extensive populations of older caterpillars can completely defoliate a catalpa tree (Figures 5 and 6).
Management
- Remove leaves with eggs and caterpillars from trees and place them into a bucket with soapy water.
- Ensure that catalpa trees are properly watered and fertilized so they can withstand feeding by catalpa caterpillars and produce new leaves later in the growing season.
- Apply a contact or stomach poison insecticide when young caterpillars are present in the spring.
- Replace young catalpa trees that are completely defoliated with a different type of tree.
Caterpillars are susceptible to attack by a parasitoid, Cotesia congregata. A catalpa caterpillar that has been attacked by the parasitoid will be covered with white cocoons (Figure 7).
