RALSTONIA ALERT By Stephen Carver (OFA) and Steve Nameth (OSU) This information is reprinted with permission from an OFA Hotline faxed to members last February Ralstonia solanacearum Race 3, Biovar 2, which causes Southern Bacterial Wilt (SBW) has been confirmed by USDA-APHIS on diseased geraniums in greenhouses from several states this winter. Here are answers to some key questions and directions for finding additional information as this episode progresses. Why is this pathogen such a concern? Ralstonia solanacearum Race 3, Biovar 2: Can be a significant problem of geraniums, especially in greenhouses that use recirculating irrigation systems, such as ebb and flow, and flood floor. The bacterium will move in the water from the root systems of infected cuttings to those of uninfected plants as the pots are "flooded." If sound sanitation procedures are not followed, the bacterium can also spread from plant to plant in sap while taking cuttings or thinning leaves, etc. Ralstonia is not airborne and splashing of overhead irrigation water typically does not contribute to its spread. Has been shown to be a pernicious pathogen of potatoes, causing serious losses in Europe in recent years. It will also attack other solanaceous crops such as tomato, pepper, tobacco (incuding ornamental nicotiana), and some weed species. Was not known to exist in the United States and is therefore regulated by Federal quarantine. It was first identified in the United States in 1999 on geraniums in greenhouses. The current reports are the first since that time. Is a soilborne bacterium, and will survive in temperate and subtropical climates in soil and host weed species. How will the USDA Animal and Plant Health Inspection Service (APHIS) respond? Because this organism is such a threat to potatoes and other food crops, and because of the fear that it could travel in infected plants from the greenhouse to the field, USDA has put R. solanacearum Race 3, Biovar 2 on its list of top hazardous pathogens to U.S. food and plant crops. APHIS has notified the states of the finding and has sent a draft action plan notification. In response, inspectors in a number of states have begun quarantining greenhouses where the pathogen is confirmed or suspected. APHIS is due to release its formal Action Plan as soon as today (2/26/03), which will spell out inspection, quarantine, disposal, and cleanup protocol. Quarantine: Who is at risk? According to several sources: Greenhouses that received rooted geranium cuttings from Glass Corner or Pleasant View greenhouses during a certain time window are potentially at risk. Ultimately, the answer depends on the aggressiveness of APHIS's management strategies, to be spelled out in the Action Plan. The current outbreak has been traced to a Goldsmith stock facility in Kenya. A small number of infected, but symptomless Americana ‘Dark Red' cuttings were supplied with healthy cuttings also from Kenyan and Guatemalan facilities to two of their U.S. greenhouse partners for rooting. Confirmed incidences of the pathogen, up to this point have been on rooted cuttings of several Americana cultivars shipped from Glass Corner. BUT NOTE THAT INCIDENCES OF RALSTONIA HAVE ONLY BEEN CONFIRMED ON GERANIUM CUTTINGS (NOT OTHER GENERA), AND ONLY ON THOSE GERANIUM CUTTINGS ORIGINATING FROM KENYA. Both Glass Corner and Pleasant View have been cleared by USDA-APHIS to continue shipping geraniums sourced from Guatemala. What are the symptoms of SBW? What should I do if I see suspect plants? Leaf yellowing and wilting of infected geraniums are typical symptoms. The wilting starts at the lower leaves and petioles and works its way up the entire plant, older leaves first and younger leaves last. These symptoms develop more rapidly under warmer daytime temperatures. Eventually the entire plant collapses onto the growing medium. The end is plant death. There are several other geranium diseases that will exhibit similar symptoms. Therefore, suspect plants need to be sent to a university or private lab. If your facility has already been quarantined, you must follow the quarantine directive to get samples analyzed. If you are not quarantined, contact your supplier for directions or ship a sample directly to a lab. Place plants in a sturdy, securely sealed double plastic bag that is stored in a refrigerator until shipping. It is important to minimize movement of suspect plants in the greenhouse, so bag the plants at the bench. Every greenhouse owner should be extremely concerned with this disease. It is very important that we do everything possible to contain and eradicate this disease. That means that everyone has a responsibility to help detect and destroy diseased plants following the exact protocol outlined in the USDA-APHIS Action Plan. DO NOT DISCARD ANY SICK GERANIUM BY SIMPLY PUTTING IT IN THE COMPOST PILE. If you have been quarantined, minimize movement of targeted plants and follow the directive in the APHIS Emergency Action Notice. Do not dump quarantined plants unless you have been cleared by USDA to do so. A USDA-APHIS official must be present to observe the dump. Containing and destroying this disease is possible if we all work together. We are still in the early stages of this episode, but with patience, diligence, and cooperation with USDA-APHIS, the industry will get through this challenge and minimize the ultimate economic impact on each of us. Additional information can be found on the following web sites including sites from which portions of this alert were drawn: Ralstonia information from Purdue www.ppdl.purdue.edu/ppdl/hot03/02-24.html Present Ralstonia outbreak information www.growertalks.com/ralstonia/ USDA Bans Geraniums From Kenya Due to Ralstonia www.aphis.usda.gov/oa/pubs/sa_phgeraniums.html Ralstonia on geraniums: information and photographs http://floriculture.osu.edu/archive/apr02/Bacterial.html www.state.me.us/agriculture/pi/pseudomonas.htm www.apsnet.org/pd/abstracts/2002/dse02ab.htm www.pestalert.org/Detail.CFM?recordID=70 Potato Diseases - Ralstonia www.aphis.usda.gov/ppq/ispm/potato/ralstonia/ www.aphis.usda.gov/ppq/ispm/potato/ralstonia/links.html