Bean Leaf Beetle

Entomologists in the North Central region recommend including bean leaf beetle in the early season scouting schedule. Injury due to the beetle is easily recognized. See the article Recognizing bean leaf beetle injury in the Iowa Integrated Crop Management newsletter.

Researchers at Iowa State University have constructed a flowchart to help growers with early-season management decisions. The flowchart is a dynamic, two-pronged decision guide based on field history, View flowchart (pdf)» View the entire article at: Bean leaf beetle and bean pod mottle virus management: An integrated approach (2005) Iowa State University - Integrated Crop Management

The bean leaf beetle (Cerotoma trifurcata) is a common soybean pest that can damage soybean by feeding on cotyledons, leaves and pods. Populations of bean leaf beetles have been increasing in the North Central region. Back-to-back mild winters have favored the survival of overwintering adults.

Overwintered bean leaf beetles feed on alfalfa and other legumes, without causing apparant damage, in the early spring before soybeans emerge. As soybeans emerge, the beetles move from legumes to soybeans to continue feeding and lay eggs in the soil. The insect also feeds on peas, snap beans, and dry beans. Feeding injury is recognized by small round or oval holes in the middle of young leaves or on the leaf edge.

Two more generations of beetles emerge in early and late soybean reproductive stages

Overwintered beetles feed on soybean during May and June in this region. Females from the overwintered population lay eggs that develop into first-generation beetles that emerge in July. This first- generation population usually peaks in the early reproductive stages. Feeding by the over-wintering population or the first-generation beetles does not usually cause yield loss.

However, a second population of beetles peaks during the pod-fill stages, and feeding by this population can cause extensive damage to pods, seed yield, and seed quality. Damaged pods are also more susceptible to rotting and discoloration.

Bean leaf beetles can transmit viruses

In addition to the physical injury to the plant, bean leaf beetles are now known to transmit the Bean pod mottle virus (BPMV) from plant to plant as it feeds. The increasing numbers of bean leaf beetles in the region is thought to be the cause of a higher incidence in BPMV observed in recent years.

Information on these pages is from the cooperative effort of researchers throughout the North Central states. Information from this site can be copied and distributed for educational use. Please credit the source with our name and URL: NCSRP Plant Health Initiative at www.planthealth.info. Please do not use copyrighted photos without permission.