Ralstonia Solanacearum Race 3 Biovar 2

Last Modified: March 04, 2024
Geranium plant with wilted, yellowing leaves.

Ralstonia solanacearum is a bacterium that destroys the vascular system of plants, causing them to succumb to wilt disease. A soil-borne pathogen, R. solanacearum can harm more than 200 crop species, including tomatoes, potatoes, and eggplant.

There are five known races of R. solanacearum, but only race 1 is endemic to the United States. USDA considers R. solanacearum race 3 biovar 2 to be a select agent because the pathogen has the potential to pose a severe threat to plant health. It causes diseases such as brown rot of potato, bacterial wilt of tomato and eggplant, and southern wilt of geranium.

The following symptoms can typically be found on plants infected with R. solanacearum race 3 biovar 2:


  • Yellow leaves
    • A lack of chlorophyll, the green pigment that gives plants their color, is indicated by yellow, wedge-shaped areas on leaves.
  • Wilting
    • The plant is limp, appearing dry and droopy. The disease develops rapidly as wilting moves upward from older to younger leaves. Geraniums may appear to recover in cooler night temperatures.
  • Dead tissue
    • Usually, issues begin in a localized area of a plant — such as the tips of leaves or the ends of roots — and spread. Dead cells can turn parts of a plant brown or black.
  • Stem collapse
    • This can occur during later stages of disease. Stems, particularly where the below ground and above ground parts of a tree meet, and roots have vascular discoloration, which can blacken and eventually die.

Tomatoes and Potatoes

  • Wilting
    • Early symptoms occur on the youngest leaves during the hottest time of the day. Wilting may be limited to the top portion of the plant on just one side of a leaflet or an individual branch. Plants may appear to recover following rain or when temperatures cool down at night.
    • Infected tomato plants often develop unusual roots on the lower stem and can die within 4–7 days after the first appearance of wilting.
  • Leaves
    • Leaves can wither, but dried leaves remain green.
  • Stems
    • When disease develops very rapidly, ooze may appear on the surface of intact stems.
    • Infected stems may collapse, revealing brown tissue displayed as narrow, dark brown streaks with grey-white bacterial ooze.
  • Color
    • In symptomatic potatoes, the vascular ring turns a grey-brown color that may extend into the pith or cortex as the infection progresses.
    • When infected potatoes are cut open, they ooze a milky-white sticky fluid. Visible threads may form from the ooze when the two sides of a cut potato are pressed together and then pulled apart. This ooze may also cause dirt to adhere to potatoes.
  • Bacterial streaming
    • A common diagnostic sign is bacterial streaming, which occurs when freshly cut stems from infected plants are placed in water. Fine, milky white strands of a thick, sticky white slime containing bacteria often run from the cut end of the stem within 15 minutes.

View photos of symptoms on geraniums, tomato and potato plants, potato tubers, and wild plants in our gallery.

Prevention is critical, as there is no effective chemical control for R. solanacearum race 3 biovar 2. Geranium growers should purchase clean cuttings, label, and separate geranium varieties, and avoid using subirrigation systems in greenhouses. Greenhouse workers should wear gloves or wash hands as they handle different geraniums and use footbath stations as they move from greenhouse to greenhouse. Potato growers should start with certified seed potatoes to avoid R. solanacearum race 3 biovar 2.

Growers should not attempt to treat R. solanacearum race 3 biovar 2 on their own. If you suspect your plants are infected, immediately contact the nearest APHIS office or your State department agriculture. They will provide plant handling and treatment instructions.

Report Plant Pests and Diseases

Have you seen this pest or signs of pest damage? Immediately report your findings. Diagnostic labs that detect R. solanacearum must follow USDA Select Agent reporting regulations.
Find your State plant regulatory official
Find your State plant health director

Controlling R. solanacearum race 3 biovar 2

R. solanacearum is a Select Agent. Diagnostic labs that detect R. solanacearum must follow USDA Select Agent regulations.

New Pest Response Guidelines

Minimum Sanitation Protocols for Offshore Geranium Cutting Production 
In 2007, APHIS implemented a certification program for geraniums imported to the United States. The program requires specific clean-culture practices and regular testing in offshore greenhouses. Shipments must also be accompanied by a phytosanitary certificate with an additional declaration attesting that the geraniums have been tested and are free of R. solanacearum race 3 biovar 2.

See also USDA Select Agent regulations

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Lynn Evans-Goldner

National Policy Manager