Grant no mercy to suspected herbicide-resistant weeds. If it’s alive after harvest or remains green in-season following prescribed herbicide applications, do whatever is necessary to remove the offensive pest from the field.

It’s a numbers game, says Jason Bond, Mississippi State University weed scientist out of the Delta Research and Extension Center in Stoneville. If an average of 1.5 female Palmer amaranth plants escape control in a field (in a non-competitive environment), they can produce up to 2 million seed in the first year. In year two, if a producer accomplishes 99.9 percent weed control, as many as 1,000 plants may survive. If just 400 of those are female, they may produce as many as 160 million seed.

“We can’t count the number of seed that could survive in year three,” he said.

Bond, who has had ample experience with glyphosate-resistant weeds, especially Palmer amaranth or pigweed, in Mississippi cotton and soybeans fields, told a group of Texas farmers that if they let the weeds get a head start they’ll soon see more weed in their fields than crop.

“Herbicides do not create resistant weeds,” Bond said at the annual Ag Technology Conference in Commerce, Texas. “We create resistant weeds through selection pressure.”

Using the same herbicide or the same mode of action over and over allows weeds that are resistant to that product to survive while the weeds susceptible to the material die. In several years, a field is infested with weeds that can no longer be controlled by a particular herbicide.

“The resistance is already present in the weed population,” Bond said. “Abusing the chemistry may create significant problems within three years.”