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Animal and Plant Health Inspection Service
U.S. Department of Agriculture
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APHIS Modifies Testing Protocol for Ralstonia solanacearum to Detect Race 3 Biovar 2 at Plant Inspection Stations

The United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) began testing randomly selected imported Pelargonium (geranium) plant material on September 27, 2021, for the bacterial pathogen Ralstonia solanacearum at Plant Protection and Quarantine’s Plant Inspection Stations located at major ports of entry. On September 26, 2022, APHIS will further refine the Pelargonium testing program by using a commercially available test for Ralstonia solanacearum, race 3, biovar 2.

Because plants and cuttings infected with Ralstonia solanacearum can remain asymptomatic for some time, visual inspection could miss infected plants. The technology used for this new testing is sensitive enough to detect Ralstonia solanacearum, race 3 biovar 2, in symptomatic and asymptomatic plants. The testing will add a powerful safeguarding measure to our rigorous offshore certification programs, which are designed to minimize a commodity’s plant pest risk before it ships. It will also provide enhanced protection to the U.S. greenhouse industry and to several important agricultural crops, such as potatoes, tomatoes, and eggplant, against this pathogen.

When a shipment is randomly selected for testing, plant samples will be secured during the visual phytosanitary inspection. Testing will commence the same day if time allows or be scheduled to start at the beginning of the following business day. The testing may increase the shipment’s time on hold by approximately 8 to 24 hours. The delay can be minimized if shipments arriving early in the morning are able to be locally scheduled for same day testing. Plant Inspections Stations and brokers will communicate and work locally for scheduling purposes. The number of plants that APHIS tests will depend on the shipment’s size. APHIS will not test more than 298 cuttings in a shipment. Pelargonium cuttings that are tested will be destroyed.

Regulatory action will be taken on an entire Pelargonium shipment in the event that at least one plant cutting tests positive for Ralstonia solanacearum, race 3 biovar 2.

USDA considers Ralstonia solanacearum, race 3 biovar 2, a plant pathogen of quarantine concern because of its potential to cause serious harm to U.S. agriculture. It causes plant diseases such as brown rot of potato, bacterial wilt of tomato and eggplant, and southern wilt of geranium. It can be transmitted through contaminated water, soil, and equipment, or by people’s inadvertent actions. Fortunately, it is not harmful to people or animals.

Using advanced technology to detect harmful pathogens is the latest effort taken by APHIS to ensure that the U.S. horticultural and potato industries are protected from potential invasive and economically devastating plant pests.
For more information about the Ralstonia program, please visit USDA APHIS | Ralstonia

For additional information regarding Ralstonia solanacearum testing, please email

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