United States Department of Agriculture

Animal and Plant Health Inspection Service Pest Alert Plant Protection and Quarantine

Ralstonia solanacearum race 3 biovar 2

Ralstonia solanacearum race 3 biovar 2 is a bacterial pathogen that infects certain vegetables and ornamental crops, causing brown rot of potato, bacterial wilt of tomato and eggplant, and southern wilt of geranium. The pathogen is not harmful to humans or animals. It is not known to occur in the United States.

In April 2020, the U.S. Department of Agriculture’s (USDA) Animal and Plant Health Inspection Service (APHIS) confirmed the detection of Symptoms of bacterial wilt of tomato caused by Ralstonia solanacearum race 3 biovar 2. R. solanacearum race 3 biovar 2 in a Photo courtesy of C. Allen, University of Wisconsin. U.S. greenhouse that had purchased brown rot (also known as bacterial in lower areas of the plant where geranium cuttings from an offshore wilt). Symptoms include wilting, moisture accumulates. Infected production facility. This is the first stunting, yellowing, upward curling tomato plants may also have pale confirmed detection of this pathogen of the leaves, and eventually death. or yellow leaves. Glistening beads in a U.S. greenhouse since 2004. Symptoms may occur at any stage of of dark gray, slimy ooze may appear APHIS has successfully eradicated potato growth. Wilting may be severe at cross sections of the stem. When all previous detections of this in young plants of highly susceptible stems are cut and placed in water, pathogen in U.S. greenhouses. varieties. In the early stages of the fine, milky white strands will be Symptoms disease, only one leaf or branch of visible to the naked eye. Infected a plant may show wilting. But as plants may not show any symptoms In geraniums, R. solanacearum race the disease develops rapidly, all for long periods of time. 3 biovar 2 causes a disease called branches may wilt quickly. Young southern wilt. Look for upwardly potato plants may develop dark Transmission curling leaves, often beginning near narrow streaks on the stem. R. solanacearum race 3 biovar the bottom of the plant. Affected 2 is transmitted mainly through leaves will become limp, wilted, and Brown rot symptoms may be visible contaminated water, including yellowed. In advanced stages of the in potato tubers in the later stages shared water systems. It can also disease, the lower stem may become of the disease. A cross section of an be spread through contaminated discolored and browning of roots infected potato may show a gray- soil and equipment or inadvertently can occur. Symptoms of southern brown ring that extends into the by people. For example, people can wilt may appear similar to those of center of the tuber. Infected potatoes spread it by propagating infected bacterial blight, which is caused may ooze a milky-white substance. plants, taking cuttings without by Xanthomonas campestris pv. Symptoms in potatoes can be disinfecting tools between plants, pelargonii; however, bacterial blight confused with bacterial ring rot. and pinching buds of infected causes leaf spots that are not typical In eggplant and tomato, plants without sanitizing hands. The of R. solanacearum. R. solanacearum race 3 biovar 2 pathogen is not readily spread from In potatoes, R. solanacearum causes bacterial wilt. Look for severe plant-to-plant contact or aerially. race 3 biovar 2 causes potato rapid wilting of leaves, particularly Symptoms of brown rot of potato caused by Symptoms of southern wilt of geranium caused by Ralstonia solanacearum race 3 biovar 2. Ralstonia solanacearum race 3 biovar 2. Photo courtesy of the Wisconsin Department of Agriculture, Trade and Consumer Protection. Photo courtesy of P. Champoiseau, University of Florida.

Guidance for Homeowners and Gardeners

Homeowners and gardeners who recently purchased geraniums Management from a retail store, nursery, or greenhouse should monitor the plants There is no effective chemical for signs of disease and place any dead or wilting plants, along with control for R. solanacearum race their pots and soil, in a sturdy garbage bag. Do not discard diseased 3 biovar 2. Prevention is critical. or dying geraniums or contaminated potting soil in a compost pile. Geranium growers should start by Instead, place the bagged plants, pots, and soil in a trash can with purchasing clean cuttings. They refuse that will ultimately end up in a landfill. should label and separate geranium varieties and avoid using sub- irrigation systems in greenhouses. Greenhouse workers should wear FOR MORE INFORMATION gloves or wash hands between handlings of different varieties and If you suspect R. solanacearum in geranium, potato, tomato, use footbaths between houses. pepper, or eggplant, contact your nearest APHIS office or State department of agriculture immediately for further instructions. For Potato growers should start with a list of APHIS offices, go towww.aphis.usda.gov/planthealth/sphd. certified seed potatoes to avoid A directory of State Plant Regulatory Officials is available on the R. solanacearum race 3 biovar 2. National Plant Board website at www.nationalplantboard.org/ membership.

APHIS 81-35-036 Issued May 2020 USDA is an equal opportunity provider, employer, and lender.