This week, I got a note from Tristan Mueller (Iowa Soybean Association) seeing some corn leaf injury from redheaded flea beetle. The defoliation was noticeable and the farmer was considering a foliar insecticide. The fields did not have tasseled yet and he estimated 5-6 beetles per plant.
Redheaded flea beetles are a leaf beetle in the family Chrysomelidae and are distantly related to bean leaf beetle and corn rootworms. The adults are about 1/4-inch long with a shiny, dark body and black forewings. As the name suggests, they have a red head (funny how entomologists come up with common names!) and antennae about half the length of the body. Like most flea beetle adults, the hindlegs have large femurs that allow them to jump long distances.
This beetle feeds on a wide range of plants, including cabbage, soybean, corn, and alfalfa. They also are found on weeds (e.g., pigweed) and can be a nursery crop pest. Adults can feed on flowers and the upper or lower side of leaves, eventually creating skeletonized injury. Larvae develop in the soil, and feed on organic matter and roots.
If you notice redheaded flea beetle while scouting for insects and disease, try to estimate percent leaf defoliation. The adults are skittish and move easily if disturbed, therefore making density estimates difficult. If you are quick, you could collect the adults in a sweep net while sampling soybean to confirm the species. There are no treatment guidelines established for this insect, as it is considered a rare pest. However, if leaf defoliation exceeds 20% and plants are in the reproductive stages, it may be worth an insecticide application to protect yield.