In an annual weed resistance survey completed by BASF, three out of four growers surveyed suspect that glyphosate resistance is a cause of their tough to control weeds. As a result, BASF's survey found 76% of these growers have already changed their weed management program to address resistance.
In the survey, growers identified how they plan to change their programs in 2014. More than two-thirds of growers indicated that they would be applying a preemergence herbicide this season and more than half of growers are planning to add an additional herbicide to their existing program.
Additionally, 50% of growers plan to use more than one site of action and 47% said they plan on using overlapping residual herbicides to control resistant weeds. Only 11% of respondents do not plan on changing their weed control program.
The survey also highlighted the weeds that growers found the toughest to control in 2013. Nearly two-thirds of respondents said waterhemp was the most difficult to control, while 54% said that ragweed species were the toughest to control. Lambsquarter and marestail were also identified as difficult weeds.
Farmers were less concerned about morninglory species, kochia, palmer amaranth and prickly lettuce.
About 38% of farmers indicated that they experienced less than 5% reduced yield as a result of not effectively controlling resistant weeds, while 34% said they believed resistant weeds did not impact yield.
This story was updated to include graphics and expanded survey information on 12/17/2013.