ID

3009-1461

Authors as Published

Meredith E. Cassell, Entomology, Virginia Tech; Sue A. Tolin, Plant Pathology, Physiology, and Weed Science, Virginia Tech; Thomas P. Kuhar and Peter B. Schultz, Entomology, Virginia Tech

Bean pod mottle virus (BPMV) causes a disease of soybeans. The disease cycle in Virginia is still under investigation to find the primary source of the virus; however we do know that the virus is spread by the bean leaf beetle (Fig. 1). BPMV causes reduction in yields as well as reduced seed quality.

Image 1-1461
Figure 1. Bean Leaf Beetle

Symptoms

The visible symptoms of BPMV in soybeans are crinkled leaves with a mosaic of light and dark green regions (Fig.2). Seeds produced on infected plants often show a dark streaking, or “mottle” of the hilum. In areas where BPMV incidence is high, yield reductions between 10% and 40% have been reported. Earlier plant infection results in greater chance of yield loss.

 

Image 2-1461
Figure 2. BPMV Disease Cycle

 

The Midwest has a higher prevalence of BPMV than the Eastern US. This virus, however, seems to be reemerging in Virginia, Maryland and Delaware. In Virginia the disease is found mostly in the eastern part of the state (Fig. 3) with a high prevalence on the Eastern Shore and Northern Neck (Table 1). By investigating the possible sources of the virus, the disease may be managed to minimize impact on Virginia soybeans.

 

Image 3-1461
Figure 3. Locations where BPVM was sampled in 2009

 

 Table 1. 2009 BPVM Surveyed Counties
CountyPositive Fields/
Total Tested
ELISA-Positive
Beetles/Total Fields
Accomack9/2114/21
Northampton5/1710/17
Richmond5/55/5
Essex5/55/5
Middlesex0/2nt
Glouster1/1nt
Suffolk0/2nt
Worcester (MD)2/6nt

BPMV Prevalence on the Eastern Shore

Bean leaf beetles collected in 2008 and 2009 on the Eastern Shore of Virginia were tested for BPMV by ELISA (enzyme-linked immunosorbent assay). Assays in 2008 determined that over 80% of the beetles from the Eastern Shore AREC carried the virus on their mouthparts. In 2009 a total of 544 beetles from Accomack and Northampton counties were tested individually for BPMV by ELISA. Of these, 222 (41%) were positive for BPMV. Of 38 soybean fields tested in 2009, 24 fields had BPMV positive beetles and 14 had positive leaf tissue by TBIA (Fig.4) (Table 1). Accomack County had a higher percentage of infected leaf tissue and beetles than did Northampton County. In addition, fields from the Eastern Shore of Maryland as well as the Northern Neck of Virginia also had BPMV positive fields. Limited sampling in the Tidewater area of Virginia did not detect virus infected beetles and soybeans.

Beetle Processing for ELISA

Image beetle-1461
ELISA performed with Agdia BPMV alkaline phosphate conjugated antibody, and trapping antibody courtesy of M. Redinbaugh, OARDC.
1. Locate suspicious plant
Image 4a-1461
2. Roll and tear leaf
Image 4b-1461
3. Blot leaf sap on TGIA paper
Image 4c-1461
4. Develop membranes
Image 4d-1461
Reagents courtesy of Agdia, Inc. in collaboration with Legume ipmPIPE and research of S. Tolin and C. Sutula, Agdia
5. BPMV positive leaf sap is purple
Image 4e-1461
Figure 4. TBIA for Folage 

Possible Sources of the Virus

It is unlikely that the seed stage is responsible for being the viral source due to low disease prevelance in fields early in season. It is possible that winter annual, weedy legumes are the source. In the Midwest, the weed tick trefoil, or Tickerfoil has been shown to be an overwintering source for BPMV. The weed is not found in high abundance in Virginia. Tissue blot immunoassays (TBIA) have shown red sorrel and yellow wood sorrel to be positive for virus on the Eastern Shore of Virginia. Other legumes such as clover and vetch have not tested positive for virus, but need further evaluation.

Management Tactics

Breeding virus-resistant soybean varieties will likely be the best control tactic in the future. Other strategies that may reduce virus incidence include: 

  1. Controlling beetle-vector populations in the spring by using nicotinoid insecticide seed treatments or targeted sprays. (Our research has shown that bean seeds coated with nicotinoid insecticides can protect seedlings from beetle feeding until 3rd trifoliolate); 
  2. Adjusting planting date to avoid peak beetle populations when soybeans are young should decrease severity of disease (Fig. 5); 
  3. Eliminating virus-reservoir host plants (weeds) on the farm; and 
  4. Decreasing the incidence of seed-borne BPMV by only using clean seed, although incidence of transmission is quite low (< 1 in 1000 seeds). (Select varieties of soybeans that have less mottling). 
Image 5-1461
Figure 5. Seasonal biology of the bean leaf beetle in Virginia.

 

Funding for the production of this factsheet was provided by a grant from the Virginia Soybean Board.


Virginia Cooperative Extension materials are available for public use, reprint, or citation without further permission, provided the use includes credit to the author and to Virginia Cooperative Extension, Virginia Tech, and Virginia State University.

Issued in furtherance of Cooperative Extension work, Virginia Polytechnic Institute and State University, Virginia State University, and the U.S. Department of Agriculture cooperating. Edwin J. Jones, Director, Virginia Cooperative Extension, Virginia Tech, Blacksburg; M. Ray McKinnie, Administrator, 1890 Extension Program, Virginia State University, Petersburg.

Publication Date

September 9, 2010