Jeffrey Hahn, Asst. Extension Entomologist
An interesting caterpillar has been found apparently for the first time in Minnesota in several areas of the state. A genista broom moth caterpillar, Uresiphita reversalis, is about one inch long when fully grown. It's a pretty insect with a black head with white markings and a slender yellowish green or mustard colored body. There is a series of black and white colored tubercles (raised spots) running down its body with white hairs coming out of them.
When gardeners have discovered this insect in Minnesota, it has been feeding on false indigo, Baptisia. According to BugGuide this caterpillar has also been reported to feed on Acacia, Genista, Lupinus, Texas Mountain Laurel (Sophora secundiflora) and other pea family shrubs as well as Crapemyrtle (Lagerstroemia indica) and honeysuckle (Lonicera spp.).
The adult has a conspicuous snout and holds it wings in a delta shape when at rest. The forewings are light to medium brown with several small dark spots and marking while the hind wings are yellow or orange (see the Moth Photographers Group for images and the known distribution in the U.S.).
Genista broom moths are generally distributed throughout much of the southern U.S. It has been found as close to Minnesota as Iowa and Wisconsin (which are also seeing somewhat higher than normal numbers of this moth this summer). The appearance here of this insect is likely the result of migrant moths moving into Minnesota, possibly with the help of weather patterns. A perusal of the University of Minnesota's Insect Museum emphasizes that lack of genista broom moths found in Minnesota; only nine adult moths were found in the collection and none of them are from Minnesota.
We appear to be near the end of their feeding now as larvae look like they are getting ready to pupate. If you find these caterpillars in your garden and they are about one inch long, you can ignore them as they are essentially done with their feeding. If they are smaller, you have a few options. Probably the easiest thing you can do is to handpick them. It they are numerous, consider a low impact insecticide, such as insecticidal soap, spinosad, or Bacillus thuringiensis.
It is unclear whether genista broom moths will survive winters in Minnesota. If you have discovered this caterpillar in your garden, please contact the author (firstname.lastname@example.org) and report it. We are trying to establish where these insects have been discovered and whether they are found in the same sites next summer.