After spring flooding this year, Morris Heitman of Mound City, Mo., says he will need to invest more time and money to control resistant weeds.
The U.S. hosts 138 herbicide-resistant weed species—and the time to control them is now
When it comes to confronting herbicide-resistant weeds, farmers have two choices: pay now to prevent them or pay later to remove them.
Weed control experts say that this harsh reality exists because it’s not a matter of if a farmer will face the scourge of resistant weeds but when.
In roughly the past decade, the U.S. has gone from having a handful of resistant weed problems to hosting 138 different resistant species in 45 states, according to the International Survey of Herbicide Resistant Weeds, a collaborative effort between weed scientists in more than 80 countries. That’s about two-and-a-half times more resistant weeds than Australia, which has the next highest population, with 57 resistant weed species.
While some of the factors contributing to the spread of resistant weed infestations can be avoided, others are beyond even the most diligent farmer’s control, says Ken Ferrie, Farm Journal Field Agronomist.
"The reality is you can’t control what comes across your farm in water, and it could be resistant-weed seed," he says.
Ferrie references the historic Mississippi River flood this past spring as an example of a factor beyond farmers’ control. The river, along with its tributaries, washed dirt, debris and weed seed onto thousands of crop acres from Missouri south to the Louisiana Gulf Coast. Farmers in other parts of the country had similar experiences.
Floodwaters washed away 400 acres of Morris Heitman’s corn and soybean crops near Mound City, Mo., this past spring when the Army Corps of Engineers released water from reservoirs on the upper Missouri River in the Dakotas and Montana.
Portions of the same acreage also flooded in 1993. That year, the receding water left behind willow and cottonwood seed.
"We ended up using a moldboard plow to get rid of the seedlings that fall," Heitman says.
Richard Zollinger, Extension weed specialist, North Dakota State University, explains that weeds will readily germinate and thrive where the crop has not developed a canopy and covered the soil.
Fewer options. This time around, Heitman is worried about johnsongrass. "I know it’s up and down the river; I don’t have any at the present time and don’t want any either," he says.
The same goes for resistant weed species. So far, Heitman’s weed control program has kept them at bay.
"We stay away from continuous glyphosate and include other chemistries in corn and beans," he says.
- November 2011