The genista caterpillar, Uresiphita reversalis, also called sophora worm, is the larva of the genista broom moth, Lepidoprera pyralidae. Its native range is Nova Scotia to Florida, California, Texas, Colorado, Nebraska, Iowa and parts of Mexico. It is a tenting caterpillar that uses silk to spin a tent-like form in the plants and trees where it feeds. In large numbers, genistas can defoliate a tree or plant in favorable conditions. Small numbers of them don’t cause trees any permanent damage.
Genista caterpillars hatch in the fall from clusters of tiny, cream-colored eggs laid on underside of leaves by the female broom moths. They feed during the fall and early winter season, and spend the winter in the pupal stage. They hatch into adult moths in the spring, who feed and mate during the summer. The caterpillars and moths produce more than one generation in a season.
Genista is the common name for the broom plant, and genista caterpillars are commonly found on those plants. They also feed on mountain laurel and other bushes and trees in favorable environmental conditions. The caterpillars eat new foliage, buds, shoots and new leaves. The tents and bags they spin serve as shelter while they feed.
Adult genista moths are triangular, light brown, and only about an 1/2-inch long. Some have light striping or black dots on the outer edges of their wings. The genista caterpillar has a light brown or green body with raised black and white spots and white hairs. The head is black with white dots. The caterpillar is about the same size as a mature moth.
Controls for the genista caterpillar include high-pressure water sprays with a hose and broad-spectrum insecticidal sprays. Infested branches need to pruned, and feeding worms can be stopped with Bacillus thuringiensis. Water sprays and pruning are effective against small populations of genistas. More aggressive applications are required for larger infestations. The best prevention method is to eliminate any cream-colored eggs from plants before the caterpillars hatch. Look for them on the undersides of leaves of valuable landscape plants in late summer and early fall.