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College of Food, Agricultural, and Environmental Sciences


New Weed Hurts Ohio Soybeans and Veggies

August 11, 2003

WOOSTER, Ohio-Vegetable gardens and soybean fields have been weeded out and targeted by an unfamiliar invasive plant and Ohio State University crop scientists are concerned. Apple of Peru, also known as shoo-fly, moved into Ohio about five years ago. The weed, first seen in a bell pepper field in Sandusky County, was mis-identified as groundcherry, said Joel Felix, an Ohio State horticulture and crop science research associate. Despite attempts to kill the weed with Command herbicide and hand-pulling, the problem escalated. "Apple of Peru is a highly competitive plant and if a few plants survive, we know there will be a reduction in yields," Felix said. "It's a major problem across the world, but we're just starting to see it here and we need to get it under control. One missed weed can leave thousands of seeds. As the adage goes, one year of seeding, seven years of weeding." Relatively little is known about apple of Peru because it is not a major problem in North America or Europe, said Felix, who works at OSU's Ohio Agricultural Research and Development Center in Wooster. In the United States, apple of Peru has been found in cotton fields in North Carolina and peanut fields in Georgia. The weed, however, is a major problem in soybean and sugarcane fields in Brazil and in other crops in Asia and parts of Africa, Felix said. In studies done in Japan and Australia, researchers showed more than a 30 percent yield reduction in corn. Apple of Peru is not as easy to spot in corn fields because of the crop's height, but in soybean and vegetable crop fields, the weed outgrows the crop and kills off competing plants, Felix said. "We saw apple of Peru in a soybean field in early July and it was about 2 inches below the soybean canopy. When soybean plants started to flower two to three weeks later, apple of Peru plants were 2 inches above the soybean canopy," Felix said. "When we went back two to three weeks later, the weeds had broken through the canopy and were 8 to 10 inches taller than the soybeans." While Roundup and Callisto herbicides kill apple of Peru, there are concerns that if it continues to spread, it may be as costly of a problem as velvetleaf in corn and soybean fields. Researchers have found that its seedlings tolerate herbicides including Command, Dual Magnum, Outlook, Basis and Permit. The biggest concern, however, lies with vegetable crops such as potatoes, tomatoes, bell peppers and other related produce. These crops are from the same family as apple of Peru, making it hard to find suitable herbicides that will kill only the weed, Felix said. The seeds, which grow in a cherry-looking fruit, are easily spread when the brittle fruit casing is burst. These seeds are dormant at harvest and therefore could build up quickly in soil seedbanks, Felix said. They also might collect in combine headers so that farmers sharing equipment are more apt to spread the weed. This year's rain also may have aided the spread of apple of Peru thanks to the constant movement of water in fields. Outside of fields, the weed is being spread by gardeners who are sharing and trading seeds for their "shoo-fly" ability, Felix said. The weed serves as an insect repellent and people have been growing the plant in their garden and rubbing it on their skin. In the era of West Nile virus, these gardeners could be major spreading agents. "Our concern is that we don't know the distribution or extent of apple of Peru in the area," Felix said. "From what we have seen, people are exchanging seeds and growing them in their garden. "If care is not taken to try to minimize and eliminate the weed at this stage, it could be a huge problem for soybean and vegetable crop growers," he said. The extent of the plant in Ohio is unknown because it is easily mistaken for other plants. At an early stage, apple of Peru looks similar to Eastern black nightshade, a weed common to vegetable crops. In its later stages, it looks like common groundcherry and bears similar fruits, the only difference being the brittle fruit of the weed verses the pliable fruit of the ground cherry. People might have the weed and not realize it because they have identified it wrong, Felix said. Farmers need to re-evaluate their weeds, watching closely for apple of Peru. During July and August it is easily identified by its light blue flowers and lantern-shaped berries. At this time researchers have estimated that infested fields in Sandusky and Seneca counties total about 2,000 acres. In order to better quantify and manage the weed, researchers are urging farmers to report all suspected apple of Peru plants to their local Ohio State University Extension agent.

Melissa Karcher
Joel Felix