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Home > Plants, Pests & Pest Control > Plant Diseases > Ralstonia solanacearum on Geraniums

Ralstonia solanacearum on Geraniums

Wilt symptoms from Ralstonia solanacearum, Biovar 3, race 2, develop under growing conditions where temperatures are maintained at 63F or higher.Ralstonia solanacearum (southern bacterial blight) is a bacterium that causes wilting and death of solanaceous plants like potato and tomato. The pathogen can be transmitted through soil, contaminated irrigation water, equipment or personnel. It also spreads very easily by transplanting infected plants and propagative materials. This bacterium is present in the United States, however R. solanacearum Race 3, biovar 2, is a newly detected, serious pathogen which could affect other important agricultural crops and is not known to occur in the United States. In addition to being a threat to important food crops, the wilting disease is lethal to geraniums.

Recently, detections of this exotic disease have been confirmed in several states and have been traced to shipments of infected geraniums from a large-scale production facility in Kenya.Typically a hot climate disease, this specific bacterium can survive more temperate, cooler temperatures thereby posing a serious threat to Minnesota agriculture, specifically the potato industry.

The MDA was notified that 20 Minnesota firms may have received potentially infected geranium plants from Kenya. MDA issued Stop Sale Orders to these firms. After considerable back checking of shipping records, 11 firms were determined to be of no risk and Release Orders were issued allowing the plants to be sold.

In February, MDA’s nursery inspection and invasive species staff, in cooperation with the Laboratory Services Division, coordinated activities to sample and test geranium samples from the high risk nurseries.

Testing at the state level can only detect R. solanacearum to the species level. If the bacterium is found in any sample it is forwarded to the USDA laboratory in Maryland where additional tests are conducted to determine if Race 3, biovar 2 is present. Initial testing has found five suspected firms free of R. solanacearum; while plants from four firms have been forwarded to the USDA for additional testing.

The geranium plants at all 9 remaining firms continue to be held “off sale” pending continued testing. Final disposition of these geraniums will be determined based on continued growth of the crop under prescribed temperature regimes that the USDA has developed. Destruction of suspect plants is also an option, however the USDA believes that testing in conjunction with the approved temperature regimes can detect and remove diseased geraniums, allowing the remaining crop to be safely sold in the marketplace.

Photo courtesy Caitlyn Allen, University of Wisconsin-Madison

MDA Contact:

Arrest The Pest Hotline.... 651-201-6684
Toll Free.... 888-545-6684
Invasive Species Program
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