Bean Pod Mottle Virus

Rugosity and mosaic symptoms on soybean due to BPMV infection. Photo credit: Iowa State University Click on image to view a larger version

The bean leaf beetle can transmit bean pod mottle virus when it feeds on soybean. Photo credit: University of Wisconsin

Bean pod mottle is a viral disease of soybean, snap bean and other legumes caused by the bean pod mottle virus (BPMV).

Like many plant viruses, BPMV is spread by an insect. In the North Central region, the most important insect vector is the bean leaf beetle, Cerotoma trifurcata. The bean leaf beetle feeds on soybeans or other legumes infected with the virus and transmits the virus particles to the next plant on which it feeds.

How the virus spreads

There are three potential sources of BPMV:

• virus in overwintered bean leaf beetles
• virus in perennial host species
• virus in infected seed

Although the level of virus transmission by overwintered beetles is low, beetle populations in the upper Midwest are at historically high levels, and thus even low rates of transmission through beetles may be important. In a recent 2-year study, bean leaf beetle population densities were linearly related to BPMV incidence in both years, indicating that BPMV epidemics were greatly influenced by bean leaf beetle

Similarly, the high beetle populations may make low rates of transmission through seed (less than 0.1%) important in the development of virus epidemics.

Finding out how BPMV spreads is an active area of research. It is possible that all three sources of the virus play important roles, depending on the specific location and environment.

References
Quantifying the Within-Field Temporal and Spatial Dynamics of Bean pod mottle virus in Soybean.
Byamukama, E., Robertson, A. E., and Nutter, F. W., Jr. 2011. Plant Disease 95:126-136 (pdf)