From the Fields
Bean pod mottle virus (BPMV) was first reported in Illinois in 1975 and now appears to be the states most common soybean virus. Yield losses can be insignificant to major, and the virus can have a negative effect on bean quality. Interest in this disease has increased since BPMV is transmitted by leaf-feeding beetles such as the bean leaf beetle.
According to Dean Malvick, University of Illinois Extension plant pathologist, symptoms of BPMV are green to yellow mottling on young leaves. In severe cases, leaves may become distorted and puckered. Laboratory diagnosis is needed to confirm whether plants or seeds are infected with BPMV.
BPMV infection is associated with seed coat mottling and green stem syndrome, in which plants retain green stems, and sometimes leaves, after pods and most nearby plants have matured. But it is often not a cause-and-effect relationship between BPMV and green stem syndrome.
BPMV is transmitted by bean leaf beetles and western corn rootworm. Rate of transmission by seed is very low. According to Malvick, the bean leaf beetle can harbor the virus over the winter or acquire it by feeding on infected soybean or other host plants (common bean, some clovers, and perennial weeds) in the spring. Even though the transmission efficiency of BPMV is lower for the western corn rootworm than for the bean leaf beetle, the western corn rootworm beetle has greater mobility and could result in increased spread of BPMV.
Management of BPMV is a challenge. At this time, the use of insecticides (either foliar or seed treatments) in Illinois to control BPMV cannot be justified based on available data. Some possible exceptions might be in areas where BPMV has been verified, and near woods, alfalfa fields, and other areas where large numbers of bean leaf beetles have been observed. Commercial soybean varieties resistant to BPMV are not available. However, there appears to be differences in susceptibility and expression of symptoms among some varieties.
Research is under way at the University of Illinois to develop answers to critical questions regarding BPMV.
Jim Morrison can be reached at the University of Illinois Extension office at 815-397-7714; FAX 815-397-8620; or e-mail at Morrisonja@mail.aces.uiuc.edu.