Ralstonia solanacearum Race 3
Geranium Southern Bacterial Wilt / Potato Brown Rot

Ralstonia solanacearum race 3 (biovar2) is a bacterial pathogen that causes several important plant diseases including southern bacterial wilt of geranium, brown rot of potato and bacterial wilt of tomato, pepper, eggplants and several other solanaceous plants. It is on the NAPPO list of A1 quarantine pests, as well as Canada's list of quarantine pests. There are five races of R. solanacearum varying in their host range and geographical distribution. Race 1 has a wide host range and is endemic to the Southern United States. Banana is the main host for Race 2 and is found in the Caribbean, Brazil, and Philippines. Race 3 is found worldwide except in Canada and the United States. Race 4 affects ginger in much of Asia, and Race 5 affects mulberries in China.

Early symptoms of wilting on geranium infected with Ralstonia solanacearum.  Photos courtesy of the Wisconsin Department of Agriculture.

On February 14, 2003 the Canadian Food Inspection Agency (CFIA) received notice from the USDA that R. solanacearum race 3 (biovar2) has been confirmed in geraniums in four commercial greenhouses in Illinois, Indiana, Michigan, and Wisconsin. Several Canadian greenhouses that may have received geranium stock from the infested US greenhouses were quarantined and tested for the presence of this disease. In the spring of 2003, infected geraniums were found in a total of four Canadian greenhouses and all associated plant materials were destroyed.

In June, 2003 the CFIA implemented an interim policy to prevent the introduction of R. solanacearum, Race 3 (biovar2) into Canada: Policy directive D-03-09: Import Requirements for Pelargonium spp. and Solanum spp. Propagative Material to Prevent the Entry of Ralstonia solanacearum, Race 3 (Biovar 2) into Canada.

The CFIA also established an action plan with eradication protocols, which will be used if the disease is detected. Previous outbreaks in Europe and the United States were controlled through good sanitation measures.

Further Information:

• Ralstonia solanacearum Action Plan - Canadian Food Inspection Agency
• Ralstonia solanacearum, race 3-biovar 2, Bacterial Wilt of Geraniums - Factsheet, Canadian Food Inspection Agency
• Pest Alert - Ralstonia solancearum race 3 biovar 2 - USDA, APHIS Plant Protection and Quarantine
• Outbreak of Ralstonia solanacearum race 3 biovar 2 on greenhouse geranium cuttings in the United States - NAPPO Phytosanitary Alert

General Information on Ralstonia solanacearum
(The following links describe symptoms of race 1.  Race 3 is similar but has a different host range and can cause more damage at lower temperatures, so the information should be used only as a guideline.)

• Diseases of Geranium - Connecticut Agricultural Experiment Station (includes a description of Ralstonia solanacearum race 1 (Southern Bacterial Wilt) symptoms on geranium and a comparison of key features of Bacterial Blight and Southern Bacterial Wilt)
• It Pays to Know the Difference - Floriculture Net, Ohio State University.  (includes pictures of Ralstonia solanacearum race 1 on geranium)

  Updated September 2006

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