Released: January 26, 2004

‘Invader’ Geranium Disease Testing Diagnostic Network

MANHATTAN, Kan. – A bacterial disease in imported geraniums could be devastating for the U.S. greenhouse and nursery industries, as well as the nation’s tomato, potato, pepper and eggplant growers.

The only good thing about the situation may be that a nationwide team of experts already is on the job, watching out for U.S. nursery plants and field crops. In fact, their new National Plant Diagnostic Network has been training to prepare for a possible outbreak, figuring the bacterium could be their first wide-ranging test.

The plant-killing import’s name is Ralstonia solanacearum Race 3 Biovar 2.

It’s related to bacteria that already are established in the United States, according to Ned Tisserat, plant pathologist with Kansas State University Research and Extension. But the imported strain can withstand colder temperatures. So, it can survive in a much wider geographic area.

Plus, it causes two separate, fatal plant diseases: southern wilt and brown rot.

“This race of R. solanacearum probably originated in Peru,” Tisserat said. “It’s now spread to Asia, Australia, Central America, Europe and other countries in South America.”

The bacterium was first detected in the United States in geraniums shipped from Kenya last January. As a result, the U.S. Department of Agriculture’s Animal and Plant Health Inspection Service (APHIS) had to put 921 greenhouses in 47 states on hold.

By May, almost 2 million plants had been destroyed and their 127 greenhouse homes disinfected. So, the year’s remaining geraniums could go on sale.

“Sadly, the pathogen was reintroduced this fall on geranium cuttings from Guatemala,” Tisserat said. “To date, it’s only been found at one location in New York state. But cuttings from the same contaminated lot had already been shipped to locations throughout the United States.”

Fortunately, the new plant surveillance and diagnostic network includes not only USDA but also the U.S. state and territory departments of agriculture. It includes the widespread land-grant university system, known for its county Extension agents and its Research and Extension functions in every state.

The network also is working to involve the surveillance capabilities of industry and consultants.

“Many people can recognize when something looks weird or unusual, but the diagnosis can be specialized. With an invasive species, often just a few U.S. scientists know it well enough to be able to identify it,” Tisserat said.

That’s why the network is building an arsenal of Internet and other information-sharing abilities. Via Web-based videoconferencing, they can attend impromptu, wide-reaching meetings from their own office. They even look at microscopic images in real time over someone’s shoulder in a far-distant lab. Their network extends from Guam to Alaska to Puerto Rico. It simply ignores “turf” lines.

“I don’t think you can exaggerate how important this is. Invasive insect, weed and disease species already cost the United States $100 billion every year,” Tisserat explained. “New plant problems can have a big impact on our international balance of trade. They can have an impact on the very foundation of our personal survival: the nation’s food and fiber supply.”

During last year’s first R. solanacearum outbreak, the network was just beginning to test its abilities. Even so, team members started watching for local cases of geranium disease, too. The network’s five regional hubs also organized training on how to handle suspect plants and how to identify the new geranium diseases in the lab.

“An unfamiliar pathogen can be a challenge. This one is particularly difficult because in geraniums, it causes symptoms that look like those of other diseases – the kind we see every year. It also may vary from host to host,” said Tisserat, who is associate director of diagnostics for K-State’s regional center, the Great Plains Diagnostic Network.

Jim Stack, a wheat pathologist, is the GPDN’s interim director. The regional network includes not only an array of testing and diagnosis experts at K-State and in Topeka but also their counterparts in Colorado, Montana, Nebraska, North Dakota, Oklahoma, South Dakota, north Texas and Wyoming.

On the national front, USDA-APHIS confirmed the second R. solanacearum outbreak as 2003 ended and 2004 began. Since then, APHIS has traced the contaminated plant materials to the Guatemala facilities of Goldsmith Plants, Inc. Goldsmith has voluntarily quarantined the contaminated greenhouses there and suspended shipments until those facilities pass a USDA inspection.

“USDA is working with state agriculture officials to notify the greenhouses that may have received a contaminated shipment,” Tisserat said. “We’re all advising greenhouse growers to be vigilant, but not to take cuttings or plants from suspect lots until state regulatory personnel inspect them. With luck, we’ll be able to stop this pathogen once again before home gardeners start shopping for their year’s geraniums.”

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K-State Research and Extension is a short name for the Kansas State University Agricultural Experiment Station and Cooperative Extension Service, a program designed to generate and distribute useful knowledge for the well-being of Kansans. Supported by county, state, federal and private funds, the program has county Extension offices, experiment fields, area Extension offices and regional research centers statewide. Its headquarters is on the K-State campus, Manhattan.

Story by:
Kathleen Ward, Communications Specialist
kward@oznet.ksu.edu
K-State Research& Extension News