Bean leaf beetles returned to Iowa fields with revenge this year. Based on observations from agronomists across the state, this year Iowa seems to have the highest level of this insect pest since 2002.

The infestation also has resulted in a high incidence of bean pod mottle virus disease in Iowa fields. Infected plants are identified by the leaf symptoms, which show a yellow to green blotchy appearance, called leaf mottle. Sometimes the infected leaves have a raised or blistered appearance.

Not all soybean varieties show symptoms, which vary depending on the virus and the soybean variety, says John Hill, an Iowa State University plant pathologist. Presently, management of this disease is focused on controlling the main insect that spreads the virus – the bean leaf beetle.

What can you expect this fall?

Unfortunately, due to the high incidence this year, yield loss may approach 10% to 20% of yield potential for some susceptible varieties, says Hill. Also seed quality problems will be significant in seed harvested from infected fields. Typically, infected seed is characterized by seed staining or hilum bleeding.

Can farmers expect to have, in the future, a disease control strategy that is more effective? “Preliminary results from current research sponsored by the soybean checkoff provide information that allows us to be optimistic,” says Palle Pedersen, ISU soybean Extension agronomist.

“Results of studies that examine the potential for use of insecticide seed treatments are currently being analyzed,” he explains. “In addition, cooperative research between ISU and the University of Wisconsin has identified, for the first time, field tolerance to this disease. You can expect to read more about these results in the future.”