WWII Tree Disease

WWII Tree Disease

Over the past few years, there has been a lot of debate over the unintended consequences of military invasions. A recent study demonstrated how an occupying army might even affect a region's natural environment.


An unintentional Allied offensive. I'm Bob Hirshon and this is Science Update.

Since the sixteenth century, the Italian forest estate of Castelporziano has been a walled oasis. But recently, its famous stone pine trees have been dying off.

Italian scientists asked forest pathologist Matteo Garbelotto of the University of California at Berkeley, to help figure out why. They were surprised to find that the culprit is a fungus from the eastern United States.


Because how can we explain the presence of an organism from the eastern United States in an estate that's been sealed off to the rest of the world since 1562? It just doesn't make any sense.

By combining historical and genetic research, they traced the infection to a brief encampment by American troops during World War II. Garbelotto says the fungus probably hitched a ride on infected supply crates.

He says this shows that any military invasion may spread diseases that could threaten local food crops and natural resources.


And when we talked to the military, we found out that there are prescriptions for cleaning up tools and troops when they go back into the United States, but there's none when the troops go into areas that they're invading.

He says a change in policy could help protect other nations' from unintended invaders. I'm Bob Hirshon for AAAS, the Science Society.

Making Sense of the Research

For nearly five hundred years, very few people set have foot in Castelporziano–except for a few Popes, wealthy hunters, and their guests. During that time, the natural ecology of Italy was forever changed by people who built houses, cleared forests, and planted non-native trees and crops. But inside the walls of Castelporziano, time stood still. If you want to look at the original landscape of the Mediterranean coast, Castelporziano is the place to do it. However, only a handful of people have ever been given that privilege.

In times of war, however, priorities change. And so for a very short time in 1944, this exclusive estate was lent to American forces for use as a temporary camp. Its walls protected the soldiers as they regrouped and planned for the next battle. Once the soldiers left, their presence there was all but forgotten.

Flash-forward to the present. For the past fifteen years, the estate's stone pines have been dying off in record numbers. When Garbelotto and his colleagues examined the trees, they couldn't believe what they found. The fungus they identified was common enough, but its genetic profile matched strains that are found only on the American East Coast, not Europe. How did the fungus get there?

Garbelotto knew that the fungus is a common problem in the lumber industry. And he discovered that untreated lumber was sometimes used in military supply crates. He believes that the fungus spread to just a few trees in Castelporziano at first, but over the next few decades, the fungus spread from one tree to the next through root-to-root contact and airborne spores. As a result, the disease radiated outward from the initial point of infection like ripples in a pond. This view is supported by the fact that although they are all descended from a North American strain, the fungus samples found on the estate today are somewhat different from each other genetically. This could only happen if the fungus had been mutating and reproducing over many years.

What can be done about this? Unfortunately, the answer isn't clear. By the time the disease can be seen, it's already too late, since the disease rots the tree from the inside out. The big concern now is that the airborne spores might spread beyond the walls of the estate, and threaten the entire Mediterranean coast's stone pine population.

Obviously, when you think of the possible consequences of war, the first thing that comes to your mind isn't the spread of plant diseases. But that's precisely why situations like these can happen. In this case, the occupying army was actually fighting on the same side as its host country, and still introduced a threat to its native plant life that may persist for centuries to come.

But it could have been worse. Imagine what would happen if an army accidentally introduced a disease that killed off an important food crop in a poor country. Or a crop that was essential to that country's economy, like coffee plants or rubber trees. In fact, many scientists believe that occupying armies have been doing just that for generations. This case is the first hard evidence that their suspicions may be correct.

Now try and answer these questions:

  1. How did the tree fungus get from North America to Castelporziano?
  2. Why did it take so long for the disease to spread? What evidence supports the belief that the disease started many decades ago?
  3. Why is it important to control the spread of plant diseases during military operations?
  4. What are some possible consequences of spreading plant diseases to remote parts of the world?
  5. Do you think military operations have also helped spread human diseases around the world? Why or why not?

For Educators

InvasiveSpecies.gov, a program of the National Agricultural Library, is a gateway to information about non-native plants and animals and their effects on an ecosystem.

Forest and Shade Tree Pathology contains information about diseases that affect trees.

Major Tree Diseases is a comprehensive database taken from USDA data.

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