What Time of the Year Do Catalpa Worms Appear?
The broadleaved catalpa, or cigar tree, is a caterpillar's playground. Its large, dinner-plate size leaves provide food for the catalpa sphinx moth caterpillar, sometimes called the catalpa worm. While considered a pest in some areas, in others, according to Texas A&M University Extension, it is collected and used for fish bait.
Catalpa sphinx moth caterpillars have a distinctive black horn at the last body segment. When fully grown, caterpillars have a black head and black stripe running down their backs. The rest of the caterpillar is white to pale yellow with a black spot or vertical stripe on each segment. The black stripe on the back can sometimes be broken up into individual spots.
Life Cycle and Emergence
Pupae are found under the soil at about 2 to 3 inches. They remain in the soil all winter long and emerge as adults in the spring, around May. When new caterpillars appear depends on when females lay their eggs. Usually it is as soon as they emerge. They can lay up to 1,000 eggs and the eggs hatch in 10 to 14 days. Caterpillars can actually emerge all summer. Depending on where you live, the catalpa sphinx moth caterpillar can have as many as five generations a year. The number of generations depends on how long your summer is.
Given the large numbers of these caterpillars that can appear during the summer, defoliation of a host catalpa is a possibility. According to Virginia State University trees on high ground and in poor soil may never host an infestation. They also state that infestations don't always occur in consecutive years due to parasite activity. Because they only appear sporadically, not year after year, catalpa worms rarely kill trees.
Because they cause only cosmetic damage and do not seriously harm the tree, control of catalpa worms is not usually necessary. Defoliated trees will re-leaf and and be just fine. Caterpillars can be harvested by hand from trees and used fresh or frozen as fish bait. If you do feel chemical control is necessary, both Texas A&M and Virginia State University suggest contacting your local extension agent for insecticide recommendations approved for their control in your state.