Questions and

Answers on Ralstonia

solanacearum Race 3

Biovar 2

General

Q. What is Ralstonia?

A. Ralstonia solanacearum race 3 biovar 2 is a bacterial pathogen that infects numerous plants. Various

races of Ralstonia affect different crops around the

world including tomato, potato, eggplant, and banana.

While race 1 is endemic to the Southeastern United

States where it affects tomato crops, Ralstonia

solanacearum race 3 biovar 2 is not known to occur

in the United States and is considered of quarantine

importance.

Q. What are the horticultural and agricultural

risks of Ralstonia?

A. Ralstonia solanacearum race 3 biovar 2 is known

to infect ornamental plants (e.g., geraniums) and several important agricultural crops (e.g., potatoes,

tomatoes, eggplants, and peppers). In potatoes,

Ralstonia solanacearum race 3 biovar 2 causes

brown rot, or bacterial wilt, which renders the potatoes unmarketable. Global damage estimates on

bacterial wilt of potatoes currently exceed $950 million per year.

Q. How is Ralstonia transmitted between plants?

A. Ralstonia solanacearum race 3 biovar 2 can be

transmitted through irrigation water, contaminated

soil, equipment, or people. For example, it may be

spread by propagating infected plants, taking cuttings

without disinfecting cutting implements between

plants, pinching buds of plants without sanitizing

hands, and especially by shared water irrigation systems.

Q. Does Ralstonia pose a threat to human

health?

A. Ralstonia solanacearum race 3 biovar 2 does not

cause disease in humans or animals.

Scope of Recent Ralstonia Infestation

Q. How many geranium plants have tested positive in the United States?

A. Ralstonia solanacearum race 3 biovar 2 was

found in two varieties of geraniums—Americana

Coral and Americana Bright Red in a greenhouse in

New York in December 2003. A third variety,

American Cherry Red II, is implicated because it was

produced in the same greenhouse in Guatemala as

the two varieties that tested positive.

Q. How many greenhouses are thought to be

affected?

A. Approximately 450 facilities in 41 States have

received suspect geraniums from the infected

Guatemalan facility.

Q. How were greenhouse owners notified that

they may have received potentially infected

plants?

A. Based on records provided by the plant importer,

U.S. Department of Agriculture’s (USDA) Animal and

Plant Health Inspection Service’s (APHIS) Plant

Protection and Quarantine (PPQ) officials compiled a

confidential list of potentially affected nursery facilities. This list was then provided to the corresponding

State Department of Agriculture, who in cooperation

with Federal officials, contacted the affected nurseries to schedule an investigation. During this investigation, PPQ or State inspectors collected invoices

and shipping lists and recorded the location and

number of suspect plants. The purpose of the investigation was to assess the extent of potential contamination of other plants in addition to the three geranium varieties of concern, and whether wilt was present in other geranium varieties as well.

Q. Has any sampling been performed in the

country of origin to establish a link between the

positive plants in New York and the host country?

A. PPQ scientists have inspected the implicated

Guatemalan facility and have confirmed Ralstonia

solanacearum race 3 biovar 2 in 5 Americana Bright

Red samples collected from 2 greenhouses in

Guatemala. The positive test results were confirmed

by a University of Wisconsin researcher. Some of the

positive samples and the New York–positive plants

were collected from the same Guatemalan greenhouse. The basis for APHIS’ control program is the

positive test samples in New York. Confirmatory testing in Guatemala was not necessary for APHIS to initiate control actions.

Factsheet

Plant Protection and Quarantine April 2004

APHIS
APHIS Control Actions

Q. Is there an available treatment for infected

geraniums?

A. No. There is no available treatment for plants

infected with Ralstonia solanacearum race 3 biovar 2.

Potentially infected geraniums must be destroyed to

prevent the spread of the disease.

Q. Can greenhouse owners sell infected geraniums?

A. No. Greenhouses that have received suspect

geraniums will be issued a “hold order,” which prohibits the movement of suspect geraniums and other

potentially infected plants from the property until further evaluations can be made or control actions taken.

Q. Will potentially infected geraniums be

destroyed?

A. Yes. USDA has ordered the destruction of all

Americana Bright Red, Coral, and Cherry Rose II,

also marketed as Cherry Rose, shipped from a geranium producer in Guatemala between August 2003

and January 2004. Additional plants may be potentially infected based on watering and sanitary practices at the nursery. Destruction of potentially infected

geraniums should be witnessed, supervised, and documented by a PPQ or State official.

Q. Is APHIS testing plants prior to destruction?

A. No tests are available for the large–scale nondestructive sampling necessary to reliably determine if

stock is free of Ralstonia solanacearum race 3 

biovar 2. Available immunological tests require the

destruction of tested plants and can only identify the

Ralstonia solanacearum bacterial group, not the targeted race and biovar. Based on the lack of available

testing methods and more precise data from the geranium producer on potentially infected plants, APHIS

must conclude that all Americana Bright Red, Coral,

and Cherry Rose II cuttings produced in Guatemala

between August 2003 and January 2004 are potentially infected and should be destroyed.

Q. Are asymptomatic (i.e., wilt–free) geraniums

necessarily free of Ralstonia solanacearum race 3

biovar 2?

A. No. Geraniums that appear healthy and do not

exhibit symptoms of wilt may in fact be infected with

Ralstonia solanacearum race 3 biovar 2. The only

way to ensure a plant is not infected with Ralstonia

solanacearum race 3 biovar 2 is to destroy the plant

and perform laboratory testing. The number of

asymptomatic plants that would be required for testing

to assure a group of plants is free of the pathogen is

not currently known.

Q. What are the major differences between the

2003 and 2004 Ralstonia solanacearum race 3 

biovar 2 action plans?

A. The February 2003 action plan developed to manage last year’s Ralstonia introduction is not to be used

to manage the current introduction. The major

changes from the 2003 action plan are:

• Definition of the basic unit of control. In the 

February 2003 version, the shipment was the 

basic level of control. In the current situation, 

three geranium varieties (Americana Bright Red, 

Americana Coral, and Americana Cherry Rose II 

[also marketed as Americana Cherry Rose]) are 

the basic unit of control. These plants, and other 

potentially infected plants as defined in the action 

plan, are targeted for destruction.

• Elimination of the destruction of all plants within 

1–meter of an infected shipment. There is little or 

no risk of Ralstonia solanacearum race 3 biovar 2

transmission through leaf contact or splashing of 

water from leaf–to–leaf.

• Elimination of the time/temperature model for 

holding plants. The model was an attempt to 

predict when infected plants express wilt 

symptoms. USDA based this on the idea that 

uninfected plants would not express wilt while 

infected plants would wilt if subjected to high 

enough temperatures for a long enough duration.

USDA has since learned through research that 

this model is unreliable and cannot be used to 

accurately and consistently identify infected 

plants. Studies indicate that some plants continue

to have latent infections, not showing wilt, even 

when high temperatures are maintained for long 

periods of time.

Compensation

Q. Will greenhouse owners be compensated for

destroyed stock?

A. USDA is not compensating owners for destroyed

stock. For additional information or guidance, growers

may consult the USDA Crop Disease Assistance services (i.e. Farm Service Agency, Risk Management

Agency) at http://disaster.usda.gov/crop_jump.htm, as

well as private insurers for crop insurance.
United States Department of Agriculture • Animal and Plant Health Inspection Service • Safeguarding American Agriculture

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