ORONO – Two University of Maine researchers are recommending that farmers who raise organic corn take special precautions to ensure their crops are free from cross-pollination if genetically modified corn is grown in nearby fields.

The scientists recently completed a two-year study that confirmed that organic crops can be contaminated by wind drift of pollen from transgenic crops.

They are also cautioning organic farmers to be extremely careful about where they purchase seed, having discovered some of their own conventional seed to be contaminated with genetically modified seed.

“Farmers who plant within 100 feet of transgenic crops can expect some pollen transfer,” said Michael Vayda of the UMaine Department of Biochemistry, Microbiology and Molecular Biology.

Vayda, in partnership with John Jemison of Cooperative Extension, conducted a two-year study which confirmed Monday that genetically modified corn can cross-pollinate with conventional hybrid corn.

Jemison is an agronomist and water quality specialist for Cooperative Extension, and Vayda is a molecular biologist.

In August of 1999, anti-transgenic activists armed with machetes entered Jemison’s test plots and destroyed more than 1,000 corn plants. Although no one was ever charged in the incident, activists claimed the genetically engineered corn would drift onto organic crops when it bloomed.

While the survey results did not surprise the UMaine scientists, Vayda said the study was complicated by the presence of genetically modified seed in bags of conventional seed. In compiling the results, Jemison and Vayda found that their supply of conventional seed contained a low level of genetically modified seed.

Vayda said the seed had been commercially purchased. “The suggestion is that organic growers should be very sure of their seed source,” said Vayda. He would not identify the supplier of the seed.

Vayda said the drift issue is important because the presence of genetically modified components means that crops cannot be certified as organic under the standards of the U.S. Department of Agriculture or the Maine Organic Farmers and Gardeners Association. The researchers found that 0.16 percent of the seeds in a conventional hybrid batch was genetically modified.

“That is considered a very low level,” said Vayda. “The European Union sets 0.01 percent as their importation level and one-half of a percent is the level set by Japan and Switzerland. But the USDA sets zero percent.”

The purpose of trials conducted in 1999 and 2000 at the University of Maine’s Rogers Farm was to determine rates of cross-pollination between plots of conventional and genetically modified corn grown at varying distances from each other.

Vayda and Jemison grew plots of conventional hybrid corn to the south and east of plots of genetically modified corn known as Roundup Ready. In the 1999 trial, cross-pollination amounted to 1 percent or less in the conventional plots that were 100 to 130 feet east of the Roundup Ready plot. The rate of cross-pollination declined with distance.

Vayda said that was expected since prevailing winds during the summer blow from southwest to northeast. No cross-pollination was recorded in a conventional corn plot that was 1,150 feet to the southwest of the genetically modified plots.

In 2000, the results were complicated by the presence of a small amount of genetically modified seed in the conventional seed supplied for the research. As in 1999, the field trials showed about a 1 percent cross-pollination rate, but contrary to the previous year, the presence of the Roundup Ready gene increased slightly with increasing distance from the genetically modified plot.

It was also present in conventional plots planted to the south of the Roundup Ready plot. Roundup, also known by its chemical name, glyphosate, is an herbicide that works by blocking protein synthesis in plants and thus causes the plants to wither and die. Roundup Ready crops carry a gene that allows it to continue protein synthesis and thus resist glyphosate.

In the course of their studies, Jemison and Vayda harvested corn from the experimental plots and dried and shelled the ears to retrieve the seed. To test the conventional corn for cross-pollination with the genetically modified pollen, they grew the seeds in flats in a greenhouse. When the plants were about two inches high, they were sprayed with glyphosate. The plants that survived were assumed to have incorporated the Roundup Ready gene, and those plants were analyzed in a laboratory to confirm the presence of the gene.

As a result of the study, Jemison and Vayda suggested that organic farmers may need to take new steps to maintain their certification. They suggested keeping organic crops away from fields of genetically modified plants, not harvesting a few rows around the outside of their fields and purchasing supplies that are known to be free of genetically modified seeds.