Submitted to: Government Publication/Report
Publication Type: Government Publication
Publication Acceptance Date: 7/15/2009
Publication Date: 7/20/2009
Publication URL: http://www.ars.usda.gov/SP2UserFiles/Place/00000000/opmp/Soybean%20RLB%20FINAL%20July%202009.pdf
Citation: Hartman, G.L., Haudenshield, J.S., Smith, K.L., Tooley, P.W., Shelton, J., Bulluck, R., Engle, J., Magarey, R., Royer, M., Sutker, E., Cardwell, K., Herman, T., Datnoff, L. 2009. Recovery Plan for Red Leaf Blotch of Soybean Caused by Phoma glycinicola. Government Publication/Report. http://www.ars.usda.gov/SP2UserFiles/Place/00000000/opmp/Soybean%20RLB%20FINAL%20July%202009.pdf. pp. 4-21. Interpretive Summary:
Technical Abstract: Red leaf blotch (RLB) of soybean is caused by the fungal pathogen Phoma glycinicola, formerly known in the plant pathology literature as Pyrenochaeta glycines, Dactuliophora glycines, and Dactuliochaeata glycines. The disease presently occurs in only a few African countries on soybean and a wild legume, Neonotonia wightii. Yield losses of up to 50% in soybean were documented in Zambia and Zimbabwe in the 1980s. If the pathogen were introduced into the USA, losses could become substantial; although the pathogen may have limited ability to spread since it does not produce copious amounts of airborne spores like Phakopsora pachyrhizi, the causal fungus of soybean rust. Rain-splashed conidia would spread the pathogen causing red leaf blotch with additional dispersal caused by other abiotic factors such as wind, as a contaminant on various tools or clothing and by other biotic factors. The pathogen would most likely survive and overseason anywhere in the USA as sclerotia, or possibly pycnidia, in infected plant debris and/or in soil. Currently, there is no program monitoring for the introduction of P. glycinicola into the USA. Little expertise exists to detect the disease visually and no molecular assays are available. However, the National Plant Diagnostic Network, through its sampling of soybean rust sentinel plots, would be a likely first detector of the pathogen if professionals were trained on the diagnostic symptoms and were able to identify the pathogen. Toward this end, there is a need to develop, provide training materials, and train diagnosticians and growers who may encounter this disease on soybean leaves. If the pathogen were found in the USA, it probably has low potential for rapid spread and could be controlled, but may not be eradicated by fungicides. The most important components of this plan is to identify research needs and to promote education and training so that the disease/pathogen can be identified quickly soon after its arrival in the USA. Pathogen distribution at the time of detection would affect response recommendations, which may include a quarantine/eradication program at preventing further spread of the pathogen.