Plant Health Initiative

Bean Leaf Beetle - Life Cycle

Overwintering adults feed on emerging seedlings. Their eggs become the first generation of bean leaf beetles. Photo credit: Kevin Black, University of Illinois.

Overwintering population

Adult beetles overwinter under leaf debris adjacent or near soybean fields. Once they become active in the spring they will feed on wild legumes, alfalfa and clovers. When soybeans emerge they quickly leave these alternate hosts and concentrate on soybean. They feed on emerging seedlings and deposit eggs in the soil near the plants. These overwintering adults generate the first generation of bean leaf beetles.

First and second generation

In addition to the overwintering adults, two generations of bean leaf beetles occur in the North Central region. The first adult generation usually peaks in the late vegetative or the early reproductive soybean stages, whereas the second generation peaks during the pod-fill stage. In mid- and southern parts of the region, this is usually mid-July for the first generation and late-August or early September for the second generation.

The adults eventually leave soybean and feed in alfalfa and other legume hosts before seeking overwintering sites under crop residue and leaf debris in fence rows and wood lots.