Whenever herbicide-resistant pigweed escapes, hand weeding is suggested, says Prostko.

“We know one female plant can produce at least 500,000 seed, so pulling out the few that may have escaped is a great way to battle this pest.”

Rotation with corn also is helpful in battling Palmer amaranth, he says. Broadleaf weeds that are not easily controlled in peanuts can be controlled by the herbicides used in corn production.

Researchers have come up with two herbicide programs for controlling herbicide-resistant Palmer amaranth, says Prostko.

The Valor-based program includes Prowl H20 3.8SC at 32 ounces per acre, and Valor 51WG at 3 ounces per acre pre-emergence. This is followed by Cadre 2AS at 4 ounces per acre with a 1-percent crop oil concentrate pre-emergence.

The Gramoxone-Dual-based program includes Prowl H20 at 34 ounces per acre two days after planting. This is followed by Gramoxone Inteon at 12 ounces per acre, Storm at 16 ounces per acre, and Dual Magnum at 16 ounces per acre 21 days after planting; along with Cadre at 4 ounces per acre plus Dual Magnum at 16 ounces per acre 37 days after planting.

Adding Dual to the Cadre helps provide longer residual control, says Prostko.

If a grower is looking to eliminate Cadre due to interactions with cotton, he suggests using Cobra or Blazer plus Dual instead.

A program that includes Cobra or Ultra Blazer plus 2,4-DB is a good option for farmers who are facing ALS-resistant pigweeds.

He recommends applying postemergence herbicides when pigweeds are 3 inches or less in height.

The future of peanut weed control is bleak at the moment, says Prostko. There are no new modes of action being developed for peanuts.

The herbicides Warrant, Fierce and Zidua are three new materials that are being tested for use on peanuts, and they may be effective on pigweed, but they do not represent new modes of action, and are not yet labeled for use on peanuts, he says.

“Non-selective applications should only be used in salvage treatments. We need to get at least 60 to 70 percent of the plant treated for those treatments to be effective.”

(An introduction to this series of keys to peanut profits can be found here. Keys No. 10 and No. 9 can be found here. No. 8 and No. 7 are here. Cost management, efficient water use two more keys to peanut profits came in at No. 6 and No. 5. Disease control ranked No. 4 and that information can be found here).