Southern bacterial wilt of geraniums is caused by Ralstonia solanacearum. Ralstonia can be spread through soil, water, and propagation. However, it doesn't move through the air. Southern bacterial wilt symptoms are almost identical to those of bacterial blight, caused by Xanthomonas campestris pv. pelargonii, which is fairly common in the United States.
Ralstonia solanacearum occurs in the United States, but there's a strain of the bacterium called race 3 biovar 2 that was recently introduced, unintentionally, from a greenhouse in Kenya. Race 3 biovar 2 can cause serious disease problems on potatoes and other food crops.
The list of host plants for Ralstonia solanacearum race 3 biovar 2 is below.
|Cultivated Hosts||Weed Hosts|
|Geranium||Pelargonium spp.||Black nightshade||Solanum nigrum|
|Tomato||Lycopersicon esculentum||Climbing nightshade||Solanum dulcamara|
|Pepper||Capsicum spp.||Horsenettle||Solanum carolinense|
|Eggplant||Solanum melongena||Jimsonweed||Datura stramonium|
|Potato||Solanum tuberosum||Purslane||Portulaca oleracea|
|Bean||Phaseolus vulgaris||Mustard||Brassica spp.|
|Bittergourd||Momoridica charantia||Lambsquarters||Chenopodium album|
|Beet||Beta vulgaris||Bitterbourd||Momoridica charantia|
U.S. Department of Agriculture's (USDA) Animal and Plant Health Inspection Service (APHIS) is using a trail of paperwork to locate, evaluate, and destroy, if necessary, all infected plant material. State and Federal inspectors have visited all Iowa greenhouses that received shipments of geraniums from the Kenya facility. Suspect plants were collected and the Iowa State University Plant Disease Clinic has been conducting tests determine whether the plants are infected with Ralstonia. Once the bacterium is found, the plant is shipped to USDA, APHIS at Beltsville, Maryland, for genetic testing to determine whether the bacterium is race 3 biovar 2.
Please see the links below for more information.
- Present Ralstonia outbreak information
- Ralstonia on geraniums in Florida 2001
- Ralstonia on geraniums photographs
- Information on Ralstonia
- Potato Diseases - Ralstonia
- USDA Bans Geraniums From Kenya Due to Ralstonia
This article originally appeared in the March 7, 2003 issue, pp. 22-23.