Plants as weapons: Be aware, not alarmed

WOOSTER, Ohio – The likelihood of a plant pathogen being “weaponized” – cultured in the lab or the field, collected, transported, and somehow introduced – in the United States, it very small.

Anti-crop bioterrorism is a threat to the United States but not a “gigantic” one, said Larry Madden, an Ohio State University plant-disease specialist.

Madden, a plant pathologist at the university’s Ohio Agricultural Research and Development Center in Wooster, is an international expert on plant epidemiology, the growth and spread of plant pathogens. He serves on a National Research Council committee investigating biological threats to livestock and crops.

Not insurmountable. “There is some threat of biological terrorism to U.S. agriculture. It’s not a zero threat,” he said. “But it’s not the kind of threat that if it happens it will be unsolvable or can’t be dealt with. It can be dealt with.

“There’s concern about anti-crop bioterrorism,” he said, “but it’s not a gigantic concern compared to other things to be concerned about in life.”

Many variables. One reason that an introduced plant pathogen might not wipe out a crop is, simply, the weather, Madden said.

Unlike human and animal pathogens, plant pathogens are very much influenced by weather. If the temperature, humidity, wind and other conditions aren’t right, a plant pathogen won’t survive, let alone spread.

Furthermore, because U.S. agriculture is widely dispersed, with many different crops in many different places, it would be difficult to cause an industry-wide epidemic, Madden said. A crop or a region could be quarantined; other crops from other regions would still be OK.

Won’t starve. And even if a crop were hit, Americans wouldn’t go hungry, he said.

“There’s zero chance that people in this country would starve to death even under the most successful of attacks,” he said. “You can’t affect the whole food supply. Even if there’s a large yield loss of corn or soybeans, we could buy what we need from other countries. The consequences would be economic.”

And that, perhaps, is the biggest concern – to farmers and the country as a whole, Madden said. If a crop were harmed, farmers would lose income, food prices would rise, and trade may be lost with other countries.

Recent example. For instance, when karnal bunt, a minor wheat disease, appeared (naturally or accidentally) in Arizona in 1996, it threatened the export of all U.S. wheat. Reason: While many countries have karnal bunt, many don’t, and they won’t accept wheat from countries that do.

In response, the USDA’s Animal and Plant Health Inspection Service quarantined wheat from Arizona, six adjacent counties in New Mexico and Texas, and later two counties in southern California. A plan was developed to test U.S. wheat to screen for the presence of karnal bunt spores.

Almost all of the countries that bought U.S. wheat agreed to keep doing so providing it was certified to come from areas where karnal bunt wasn’t present.

“Even though it was an inconsequential outbreak, there was great danger that we’d lose many billions of dollars of international trade,” Madden said. “Those are big consequences and very real concerns.”

Questions in Iraq. Fortunately, there have been no known cases of anti-crop bioterrorism in the United States, Madden said.

Worldwide, however, it’s not as clear. There’s evidence that countries such as Iraq have or had programs in agricultural bioterrorism. A rare wheat disease outbreak in Iraq a few years ago raised eyebrows, although Madden said it’s merely speculation that the disease escaped from a terrorist lab.

The committee that Madden serves on, the Committee on Biological Threats to Agricultural Plants and Animals, was formed in part because of these concerns. Its mission: “to evaluate the ability of the United States to deter, prevent, detect, thwart, respond to and recover from intentional biological attacks on the U.S. food and fiber supply.”

For now it’s focusing on response and detection. Its report to USDA is due in 2002. Until then Madden can’t give details.

The committee was created last year, he said, not in response to Sept. 11.

Farmers on front line. The challenges? Early detection – by farmers, field scouts, Extension agents and plant pathologists – is always important. So is knowing what to do if something is detected. The NRC committee is developing such a protocol.

“No one has come up with a scenario where someone has engineered a plant pathogen that’s virtually unnoticed or invisible,” Madden said. “Such a thing doesn’t exist as far as I know.”

Meanwhile, farmers can’t do much about the risk other than what they already do: keep an eye on their fields.

“I don’t think growers should change anything in their procedures,” Madden said. “But they should know that scientists are monitoring the situation. The government is aware of it, too; there’s no ignoring agriculture. For now, we’re evaluating how vulnerable we are and how to respond.”