This weed can be resistant to a variety of herbicides
By Kaitlynn Anderson
Staff Writer
Farms.com
As August arrives, farmers may want to continue looking for waterhemp in their fields.
This weed, which produces many small seeds, can germinate throughout the growing season, Johanna Lindeboom, a sales agronomist at Clark Agri Service, told Farms.com today.
“Once you have this weed in your field, it’s very difficult to get rid of,” said Lindeboom, who has found waterhemp in fields in both Haldimand and Hamilton-Wentworth counties.
While waterhemp looks similar to pigweed, growers can look for distinguishing features to identify it.
“Waterhemp is virtually hairless, unlike most other pigweed species,” she said. “It also tends to have longer, narrower leaves with a waxier appearance when compared to redroot pigweed.”
Right now, farmers may find this weed is most noticeable in soybean fields.
Since soybeans are less competitive with waterhemp than other crops and farmers have fewer options to control the weed in-season, “it’s very important to apply a residual herbicide upfront,” she said.
Growers may find these weeds more easily as soybean fields begin to mature.
“As beans start to dry down, any weeds that are growing above the crop become extremely visible,” Lindeboom said.
Even if farmers applied herbicides earlier in the season, they may have to make additional passes with their sprayers.
“You may have to come in and spray again, because waterhemp will germinate all season long in a wide range of temperatures,” she said. “Toward the middle of August, residual herbicides may start to break down and you might get some weed escapes.”
If farmers find this weed in their fields, they may want to contact researchers at the University of Guelph’s Ridgetown campus. These individuals can collect plants and test them for herbicide resistance back at the lab.
This research may help growers manage waterhemp more effectively in the future, she said.
“It can shed light on how and why the weed is spreading,” she said. “By studying the methods of herbicide resistance within plants, as well as (plant) responses to different herbicides, (farmers) can determine the best way to manage (these weed) populations on farm.”
Producers can contact Lauren Benoit, a graduate student working on the research project at the University of Guelph, at benoitl@uoguelph.ca.
For more information on waterhemp, check out the Farms.com Field Guide.
hauged/iStock/Getty Images Plus photo