After years of farmers spraying the same types of herbicides, several varieties of wild plants have developed a resistance to the stuff meant to kill them off.
U.S. farming annually produces $100 billion worth of crops, but estimated yield losses due to weeds left uncontrolled exceed $8 billion a year, according to a report this year from Ohio State University and Purdue University.
The weeds have outsmarted the chemistry, said Bill Hitchcock, manager of Ag Plus, a faming products company in Woodburn. Theyve built up an immune system to them. Its been going on for years.
That topic and others will be addressed during the 12th annual Tri-State Conservation Farming Expo in Auburn on Friday. The St. Joseph River Watershed Initiative is hosting the event.
Jennifer Thum, program manager of the group, said participants will learn about wild plant control from an expert.
She agrees that weeds are becoming more of a problem, which is why expo organizers invited Bryan Young, a professor of weed science from Southern Illinois University, to speak.
Allen County Farm Bureau President Roger Hadley said the wild plants are being transported from Southern states.
Manure used for fertilizer is the main source, he said.
Weve been on a pretty high alert for the past three or four years, Hadley said. Some folks refused to think it was an issue, but it is.
Mick Lomont farms about 1,600 acres of corn and soybeans in Allen County. You dont have to tell him when something isnt working.
These things develop a resistance, Lomont said. If somethings not working, try something else.
The situation isnt hopeless, Hadley said. Farmers can use another family of herbicides that existing weeds havent adapted to, he said.
Mark Loux is a professor in the Department of Horticulture and Crop Science at Ohio State. He helped write the report on weeds. Loux said, since 2005, farmers have annually loss about 5 percent of their yields due to the rogue plants.
He admitted that farmers losses are probably offset by higher commodity prices. But a loss is a loss, Loux added.
The Ohio State and Purdue researchers said crop rotation is one of the most effective ways for improving long-term weed control. Sometimes, however, farmers are their own worst enemies – not the weeds.
Some folks are just from Missouri , and until they see it for themselves, they dont want to believe its a problem, Hadley said, so, they just keep right on using the same old herbicides.
Loux, who specializes in weed management, said mares-tail, giant ragweed, water hemp and Palmer amaranth are some of the most common weeds finding their way onto northeast Indiana fields.
The university report listed some of the best practices to combat weeds.
Narrow row spacing for soybeans
Proper planting date and seeding rate
Insect and disease control
Adequate soil fertility and drainage.
Soybeans are most vulnerable to attacks from weeds because there are fewer herbicide options, Loux said.
Wiping out weeds takes perseverance, not skepticism, he said.
There is a segment of farmers out there who dont do anything different until they have a yield loss high enough, Loux said. Most, though, arent like that and are willing to do what it takes.