Pennsylvania Stories
Bumping up Biosecurity
May 2004
Plum pox virus isn't the only recent invader with the potential to do serious damage to the U.S. economy. In 1984, the citrus canker invaded the Florida's citrus industry and efforts are still underway to eradicate it. In the southwest, karnal bunt, a fungal disease of wheat, is a major concern. In Maine, potato mop-top virus was discovered just last year.
Within the last century, such pathogens have had occasion to be devastating. Wheat rust epidemics during the 1920s and '30s spread from Texas into Canada within two months, devastating millions of acres of wheat. In 1970, Southern corn leaf blight nearly destroyed the entire corn crop in many states: Losses were estimated at $1 billion.
These naturally occurring epidemics are bad enough. But what if such a pathogen were deliberately released?
Last August, Penn State plant pathologist Fred Gildow testified before the Pennsylvania legislature's Emergency Preparedness committee in a hearing on agroterrorism. "Most people outside of agriculture," he said, "are probably not aware of the potential for plant-infecting microbes to be used as bioterror weapons." As Gildow adds now, "Plant-disease-causing microbes could be used not only to reduce potential food supplies, but more importantly to disrupt trade in agricultural commodities that would impact national economies."
It wouldn't exactly be easy to do. To start an epidemic, a terrorist would need what Gildow calls "the disease triangle—a virulent pathogen, a susceptible host, and the right environment. You need all three," he says, and the last is particularly tricky. "These outbreaks are highly dependent on the weather."
Still, Gildow reminded the panel, a 2002 National Research Council report concluded that U.S. agriculture is "very vulnerable" to attack. With increased importation and relaxed trade barriers, it has become more and more difficult to maintain border security. "With over 400 million acres of crop lands in the U.S., absolute security is impossible."
He outlined some major new initiatives aimed at emergency preparedness. The Agricultural Bioterrorism Protection Act of 2002 established a Select Agents List of eleven pathogens "most likely to enter into the U.S. in the near future and to have a devastating economic effect once established." Plum pox virus is on that list, as are Ralstonia (a bacterium that wilts potatoes, geraniums, and other crops), and the fungus that causes soybean rust.
The Department of Homeland Security has established a National Biodefense Analysis and Countermeasures Center to develop interdisciplinary responses to animal, human, and plant pathogens. There are also plans to create a national network of five regional diagnostic laboratories, each linked to similar labs at corresponding land-grant universities.
At Penn State, Gildow reported, his own department of plant pathology has submitted a proposal to the USDA to develop an Integrated Plant Health Security System focused on better pathogen detection, surveillance, response protocols, and education. In addition, a number of faculty in the College of Agricultural Sciences are working on biological and genetic studies of invasive pathogens on the select agents list, as well as on other plant and animal pests. ("Studying invasive species is one of our strengths," says Bruce McPheron, associate dean for research.)
Gildow stressed the need to learn from experience in order to improve biosecurity protocols. For Pennsylvania, he told the committee, there's no better model than the coordinated, multi-agency response that nipped plum pox in the bud.