Northern Plains Integrated Pest Management GuideIPM

Authors: Buyung Hadi, Jeff Bradshaw, Loren Giesler, Dean Malvick and Lawrence Osborne

Causal Organism

Bean pod mottle virus (BPMV) is a member of the genus Comovirus in the family Secoviridae. In 1958, a report from Arkansas announced the first incidence of BPMV on soybean in the United States. BPMV is commonly found in soybean growing regions in the south and southeastern U.S. Lately, BPMV incidences in soybean fields throughout North Central region of the U.S. have been reported with increasing frequency.

Symptoms and Signs

Symptoms range from leaf yellowing and crinkling, severe mosaic to leaf distortion and death. Symptoms are clearly shown in plants infected early in the season. Cool weather also promotes symptom development. Hot weather may mask the symptoms, so even though BPMV may be present in the field, it is not immediately evident. BPMV infection has also been associated with a soybean disorder called “green stem”. As the name implies, the stems of plants with this condition remain green even as the plant mature. The green stems are difficult to cut during harvesting. Yet, the relationship between BPMV infection and green stem has not been fully investigated and the precise causal agent of green stem remains unknown.

Crinkled leaves, a common symptom of BPMV infection

Yellowing mottled leaves due to BPMV infection

Disease Impacts

Depending on the cultivar and time of infection, yield loss due to BPMV infection range from 3-52%. Early infection causes the highest yield loss. Seeds produced by BPMV-infected soybean also show mottled seed coat, reducing the seed quality. Seed transmission is very rare.

Healthy (A) compared to mottled seeds (B) produced by BPMV-infected soybean

Life Cycle and Epidemiology

BPMV infection is facilitated by leaf feeding beetles. Beetles feeding on infected plants acquire the virus for a limited time and are able to infect the next healthy plants they feed on. Bean leaf beetle is an extremely efficient vector of BPMV. Other beetles that potentially vector BPMV include grape colaspis, banded cucumber beetle, spotted cucumber beetle and striped blister beetle. During winter, BPMV survives on leguminous weeds such as tick trefoil. In the spring, overwintering beetles start to feed on the infected weeds before they move to soybean, carrying the virus to the crops. The subsequent generations of leaf feeding beetles continue to distribute the virus in and among soybean fields.

Bean leaf beetle, a vector of BPMV

Management Approaches

Cultural Methods

Delayed soybean planting date has been suggested to manage BPMV. Delayed planting is supposed to help soybean escape the migration period of beetle vectors of the virus. However, a three year field data from Iowa showed that delayed planting does not consistently result in BPMV field incidence.

Host Plant Resistance

Soybean cultivars with feeding deterrents against bean leaf beetle may not be sufficient to reduce BPMV incidence in the field. No resistant cultivar against BPMV is commercially available.

Chemical Control

Since infection in early stages of soybean development causes the highest yield loss, control of bean leaf beetles in early season may be necessary in fields with history of BPMV infection. Insecticide seed treatment using neonicotinoid insecticides or foliar pyrethroid insecticides between emergence and first trifoliolate reduces total BPMV incidence. Additional applications of foliar insecticides around blooming may further suppress virus incidence.