Cereal leaf beetle, Oulema melanopus, is a leaf beetle in the family Chrysomelidae. These beetles are native to Europe and have been considered pests of small grains since 1737. In 1962, cereal leaf beetle was first detected in the United States in a Michigan grain field. Since the 1960s, this insect has spread throughout much of the United States and Canada; now at least 30 states have confirmed cereal leaf beetle populations.