by John Hartman
Kentucky Pest News

Bacterial wilt, caused by Ralstonia solanacearum race 3, biovar 2 (Ralstonia), has been found recently in greenhouse-grown geraniums throughout the U.S., including Kentucky. Readers may be aware that this bacterium, which poses a threat to many U.S. crops, was introduced last year from foreign sources into the greenhouse trade. For more details about this disease and the threat it poses, consult Kentucky Pest News (issue 977, March 10, 2003) and appropriate USDA web sites.

Why the concern with Ralstonia?

Ralstonia solancearum race 1 already exists in the U.S., but race 3, biovar 2 does not. This new Ralstonia can attack several crops in the field so finding it in the greenhouse before it is accidentally moved to the field is a serious matter. This pathogen is cited on the USDA Agricultural Bioterrorism Act of 2002 Select Agents and Toxins List, as a serious pathogen of potatoes, tomatoes, and other solanaceous plants. The present entry seems to have been an unintentional introduction of the pathogen during the routine and normal importation of geranium cuttings by a US company.

Where does the Ralstonia on geraniums come from?

U.S. suppliers of geranium cuttings and rooted cuttings have obtained them from contaminated suppliers abroad. This year, the contaminated geraniums came from Guatemala and last year from Kenya. This year's introduction involves the geranium varieties 'Americana Coral,' 'Americana Bright Red,' and 'Americana Cherry Rose II' (also marketed as 'Americana Cherry Rose') with origins at Goldsmith's Guatemala facility. The U.S. Department of Agriculture's Animal and Plant Health Inspection Service (USDA-APHIS) investigative team determined that the new Ralstonia was present at the Goldsmith, Guatemala facility where these three varieties were produced. Thus, all shipments from this facility would be considered contaminated; apparently, 14 Kentucky growers obtained contaminated plants and their greenhouses were placed under quarantine.

Now that it is here, what is being done?

USDA-APHIS has ordered the destruction of all geraniums of the varieties indicated originating from the contaminated Guatemala facility. Each state has already been provided with a list of establishments that were sent these suspect varieties from Goldsmith, Guatemala. In Kentucky, this crop destruction is already underway. In addition, USDA-APHIS will trace forwards to determine if there has been movement of the varieties to retail outlets. All of the plants that have been moved to alternate locations must also be destroyed. In some cases, where watering systems or plant placement compromised other plants in the greenhouse, these exposed plants may also be destroyed. Once the suspect varieties have been destroyed and the greenhouse facilities sanitized, the greenhouse may be released from the quarantine.