Digging Up the “Dirt” On Geraniums
Everything You Need to Know About the Ralstonia Outbreak
As the month of April came to a close the United States Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) confirmed the detection of Ralstonia solanacearum race 3 biovar 2 (R3bv2) in a greenhouse in Michigan. The infection was discovered in a species of geraniums identified as the Fantasia ‘Pink Flare’ variety.
It has been roughly sixteen years since this bacteria was last found on U.S. soil and since then has garnered itself the classification of a potential bioterrorism agent against the United State’s agriculture. In 2004, Florida’s tomato crops were threatened by the disease and led to the destruction of over 4 million plants to prevent its spread.
How It Can Impact the U.S.
This specific strain of Ralstonia solanacearum has the potential to impact several important agricultural crops. However, it is potatoes and tomatoes that are at the greatest risk from this disease. Both agricultural crops are common hosts of the disease and can wipe out the entire crop with infection before the symptoms can be identified.
The bacterial wilt made its way to the U.S, this time, through an infected shipment of plants from Guatemala. Since its discovery, the foreign greenhouse responsible for the infection has voluntarily ceased all incoming and planned shipments to the United States. With an additional 288 greenhouses in 39 states who also received cuttings from this grower, APHIS has been working tirelessly to prevent the spread of this infection.
Who & What They’re After
The plant is targeted for eradication is the Fantasia ‘Pink Flare’ geranium. As the USDA moves through greenhouses affected by this disease they will go through and sample, isolate and destroy any of the species. Due to the spread of the infection that can occur between host plants and non-host plants, the USDA will also target other geranium species in the suspected greenhouses for the same methods of control.
How Does This Happen?
While the majority of Ralstonia solanacearum strains infect tropical and subtropical climates, the host of the bacteria ranges into the hundreds and can be located in agricultural goods around the world. It is in colder tropical climates that R3bv2 develops. The development of this disease is majorly identified in the highland, cooler tropical, parts of Africa, South America, and Asia.
In an AmericanHort webinar, hosted for awareness of the disease, Professor Caitilyn Allen of Plant Pathology at the University of Wisconsin-Madison identified that the infectious tract for this disease is through the water-transporting xylem vessels. In a series of images she showed how, on a microscopic level, the bacteria infiltrates tomato stems and quickly takes over the healthy cells of the plant.
What To Look For
The most common symptom of this bacterial infection is stunting in plant growth. However, this disease can also be expressed by yellowing and wilting of the leaves, and eventually death of the plant. The University of Florida Institute of Food and Agricultural Sciences Extension states in their reporting of the bacteria that, “Symptom expression is favored by high temperatures (85°F-95°F). Symptoms of this disease may progress rapidly after infection, but plants may remain without symptoms for extended periods.”
The lack of symptoms that are in hosts makes the danger of this disease all the more pressing to the U.S. Agriculture. With the disease leading to a potato farmer’s nightmare, brown rot, it is truly a team effort of the industry to keep this disease from spreading.
It is additionally important to note that while there are symptoms that can help in identifying the disease, there are also a number of ornamental plants and Nightshade family weeds that can host the disease without symptoms.
Symptoms of Ralstonia solanacearum:
Here are a few ways to identify if your plants may possibly be infected:
- Upward rolling of the leaves, that eventually leads to their collapse
- When squeezing the stem of a suspected infected plant, a milky white ooze comes out
- Placing a suspected infected plant stem in a glass of water and after 15 minutes milky streaking of bacteria is coming out from the stem
How to Move Forward
While there are testing options available, they aren’t 100% accurate in many cases and can be quite expensive to carry out. Instead, the USDA is recommending that if you believe your plants to be infected by the disease, or that you have received a plant of the known infected variety to reach out to the contact facility or report the infection through the USDA State Plant Health Directors page. They will schedule a date to come out to the facility and inspect the plants, as well as obtain some first-hand information. Following their scheduling, they will issue their “Emergency Action Notification” document with a more detailed version of the following procedures.
It is asked that you hold all plants of the Fantastia ‘Pink Flare’ variety, as well as any other geraniums or known host plants of the disease. This qualifies towards any host plants that may have been shipped between 10/2019 until 04/2020. The USDA also asks that you hold any plant material that may have been exposed or come in contact with the suspected infectious plants or any materials exposed to it.
The suspected material will then be tested. If test results are negative, then the items are free to be moved again. However if the material is found to be contaminated, then the items will be destroyed and the area disinfected through means that have been outlined to be acceptable by the EAN procedures of the USDA.
The Ending Our Industry Deserves
While growers and inspectors seek out infestation to destroy this disease once again from U.S. soil, it is noteworthy to mention that 55 Canadian greenhouses have also been infected from this incident.
As we look to the future from this occurrence, many are wondering how they can protect their crops from something like this happening again? Our answer is simple, Plant Sentry™.
When infections like Ralstonia solanacearum are discovered, Plant Sentry™ works to immediately notify our clients of the potential risks their plants face. This communication is essential in helping to slow the spread of the disease from the grower to the vendor.
Early notification provided by Plant Sentry™ can reduce the potential exposure of the disease and may prevent the elimination of plants due to quarantine and destruction procedures by officials. We understand that every dollar spent should equal a dollar saved. At Plant Sentry™ we apply that mindset to protect your bottom line when a disease shows up to your nursery door. It is our responsibility as an industry to protect one another from the potential danger that a disease like this can cause. With Plant Sentry™ on your side, protection gets a whole lot easier!
To learn more about our efforts be sure to view our other blogs!
- Harmon, P. F., Harmon, C. L., Norman, D., & Momol, T. (2019, April 24). Southern Wilt of Geranium. Retrieved from https://edis.ifas.ufl.edu/pp131
- (2020, April 29). Retrieved May 29, 2020, from https://www.hriresearch.org/article/ralstonia-webinar-what-you-need-know
- Southern bacterial wilt now a problem in Louisiana vegetables. (2020, May 14). Retrieved from https://vegetablegrowersnews.com/news/southern-bacterial-wilt-now-a-problem-in-louisiana-vegetables/
- Sparks, B. D., Sparks, B. D., Sparks, B., Grassi, M. J., Ziner, R., & Greenhouse Grower. (2020, May 6). What You Need to Know About the Current Ralstonia Situation. Retrieved from https://www.greenhousegrower.com/production/what-you-need-to-know-about-the-current-ralstonia-situation/
- USDA Confirms Ralstonia solanacearum race 3 biovar 2 in Geranium Plants in Greenhouse. (n.d.). Retrieved from https://www.aphis.usda.gov/aphis/newsroom/stakeholder-info/SA_By_Date/SA-2020/SA-04/ralstonia-greenhouse-geraniums