sealPurdue News

December 10, 2002

Purdue professor responds to accusations of U.S. agroterrorism

WEST LAFAYETTE, Ind. – Scientific research doesn't support a recent Serbian newspaper article accusing the United States of agroterrorism by introducing the western corn rootworm beetle into Yugoslavia during the early 1990s, said a Purdue University expert.

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C. Richard Edwards, a professor of entomology, said it's more likely that the pest was accidentally introduced through passenger or cargo air travel. Historically other pests have been accidentally introduced to many countries by cars, boats, planes and trains, he said.

"I don't really believe that someone planted the insect there," Edwards said. "It is highly likely that the insects hitched a ride on an airplane into Yugoslavia in the mid-1980s, and they weren't observed until 1992 when plant damage was first noticed."

A Serbian official quoted in the article said the western corn rootworm was introduced in the early 1990s. Edwards said a few beetles couldn't cause the type of damage reported in one or two years. It usually takes five to seven years for a rootworm population to build up to damaging levels.

A representative of the U.S. Department of Agriculture's Animal and Plant Health Inspection Service asked Edwards to respond to the accusations because of his expertise on the western corn rootworm beetle, Diabrotica virgifera virgifera. Edwards is a leading researcher of corn rootworms, also known as diabrotica, and has been actively following the situation in Europe since 1994.

He chairs a subcommittee on diabrotica for the International Working Group on Ostrinia and other Maize Pests, is a United Nations Food and Agriculture Organization diabrotica network expert, and a member and adviser of the European Union's diabrotica project. He traveled to Belgrade, Yugoslavia, five times in the past seven years to research the insect and assist local entomologists.

In addition to his international work in western corn rootworm, Edwards is a Purdue Cooperative Extension field crops specialist who specializes in pests of corn, soybeans, small grains and alfalfa.

The western corn rootworm beetle and its damage were found near the Belgrade International Airport in 1992. Since then the insect has spread quickly throughout Central and Eastern Europe. The beetle is now found in Bosnia-Herzegovina, Romania, Hungary, Croatia, Bulgaria, the Slovak Republic, the Czech Republic and the Trans-Carpathian region of the Ukraine. It's also been found in Western Europe in northern Italy, southern Switzerland, near Paris and in eastern Austria.

Edwards said he thinks females carrying fertilized eggs were the first of the species to make the long voyage. He said they likely hitched a ride on an airplane from the Midwest – perhaps from Chicago's O'Hare International Airport, which had flights to Belgrade during the 1980s.

Once they landed in Belgrade, the beetles found conditions very similar to their native environment. Most importantly, they found cornfields less than 500 yards from the airport, Edwards said. Mature beetles feast on corn pollen, silks and leaves. In the United States, females lay their eggs in the soil from early July through August. Those eggs hatch in the spring and the larvae begin eating the roots of corn seedlings.

Typical corn rootworm larvae damage includes extensive root pruning that can cause lodged or goosenecked plants. Adult corn rootworms also can decrease pollination rates by feeding on corn silks. Yield losses of 10 to 15 bushels per acre are common, but losses greater than 50 percent can occur. A traditional corn to soybean crop rotation is the main means of controlling rootworm infestations in most of the United States, but a population of the pest has developed a tolerance to rotation. Those females lay their eggs in soybeans or other crops, taking the chance that corn will be planted there the following spring.

Edwards said the beetles in Belgrade are being genetically analyzed to determine if they're rotation resistant. If they are, then crop rotation may not be a viable control method.

"We are assessing the situation to determine the best course of action in either case." Edwards said.

The Serbian newspaper article, published Nov. 17 in Glas Javnosti, quotes Slavoljub Markovic, the former chief of the Yugoslavian Plant Protection Agency. He said that the beetle could not survive on an ordinary passenger plane or ship due to the long distance. Markovic did not address how he believes the insects were brought into the country.

Edwards disagreed. He said that it takes 10 to 12 hours for people or goods to be transported to many areas of the world, including from the Midwest to Belgrade. Researchers in his laboratory and others have noted that many insect species survive under challenging conditions, including less than ideal temperatures, food deprivation and other extremes.

"In my laboratory we have completed experiments that removed food and controlled temperature, environment, light and fresh air, and days later some test insects were still alive," he said.

The corn rootworm beetle, which is indigenous to the United States, normally spreads up to 50 miles per year, depending on the time of movement. There is no way to predict which direction or when the insects will spread without following the weather, Edwards said.

"The Western corn rootworm isn't a likely choice for agroterrorism because of its unpredictability. When it first arrived in Yugoslavia, more than likely in the 1980s, there was no way to know what effect it would have, or even if it would have an impact," he said.

Writer: Kay Hostetler, (765) 494-6682,

Source: C. Richard Edwards, (765) 494-4562,

Ag Communications: (765) 494-2722; Beth Forbes,;

Related Web sites:
Corn rootworm life cycle animation

Purdue entomology professor C. Richard Edwards demonstrates the difference between a healthy corn plant's root structure (left) and one that has been ravaged by corn rootworms. (Agricultural Communications photo/Tom Campbell)

A publication-quality photograph is available at


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