Alfalfa producers need to stay ahead of troublesome weeds

Growers have watched herbicide-resistant weeds crop up in corn, soybeans and sorghum fields and they are not alone.

Dwight Scholl, manager at Tri Rotor Crop Services LLC, Lakin, Kansas, said alfalfa growers are facing pigweed and Palmer amaranth and those weeds are difficult to control.

The grower has to look closely at each field and not assume he does not have those weeds, Scholl said, even if the cutting schedule is on a 28-day interval.

The best herbicide is Mother Nature, he said, as he talked about cutting the crop too close to the ground. “Keep the ground covered. Keep it shaded as much as possible.”

Growers still have some good herbicides to work with, but they need to stay with a regiment.

“Keeping ahead of the little weeds is worth it,” said Scholl, who has been an aerial applicator with Tri Rotor Crop Services since 1999.

Unfortunately, Palmer amaranth is becoming more difficult. “I’m running out of ammunition.”

One of his strategies growers should look at is doing a pre-treatment at least three weeks ahead each of the first three cuttings at rate of 3 pints per acre of Prowl H2O or Warrant. He went through some of his go-to herbicides and stressed the importance of working with crop consultants.

They include hexazione, flumioxazin, diuron, metribuzin and BASF’s Sharpen on established stands before green up. Raptor and Pursuit work well on new alfalfa once they get to the third trifoliate.

Growers should review their herbicide strategies. Scholl likes to rotate herbicides through the growing season, to lessen the opportunity for herbicide resistance. Like corn and soybean growers, alfalfa producers know herbicides are too expensive to not have results. Glyphosate was once a reasonable choice but the cost of $20 a gallon heading into 2021 is now over $60 a gallon and that makes it less practical, he said.

Prior to swathing applying a dose of Prowl and Warrant have also been effective, he said.

Scholl started in the fertilizer business in 1973 by operating a dry fertilizer floater. He started with Tri Rotor Crop services in April 1999 as their first branch manager. Tri Rotor Crop Services, LLC now operates out of nine locations in Kansas, and fly for several retailers throughout the western United States.

“Every field is different,” he said, which is why he recommends regular scouting.

Although growers might be enticed to believe that Roundup Ready alfalfa is the answer, he has seen some growers experience frustration with weed pressure as a result of resistance. “The No. 1 problem is Palmer amaranth.”

Limitations on how much herbicide can be applied also have to be taken into account, which was why he liked the applications 21 to 28 days before the first three cuttings.

His strategy is to keep the weeds as from ever germinating so the alfalfa plant can maximize its growth and hopefully keep the weeds at bay.

Maintaining alfalfa production requires a focus on weeds, non-beneficial insects, diseases and fertility.

Insect pressure

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Scholl is often asked about control of grasshoppers, which are difficult, but there are baits that have been very effective. Chemical not labeled for alfalfa can sometimes be used around the perimeters of the field to stop the hoppers from ever getting into the field.

Weevils are also a difficult pest because the grower needs to make sure that beneficial insects are also not killed, he said.

Lorsban has been effective in killing aphids, but the Environmental Protection Agency has halted the use of chlorpyrifos on food crops. This indicates to him that Lorsban (chlorpyrifos) has a limited life in the market.

Scholl has heeded the advice of a southwest Kansas grower who told Scholl he applied a sugar-water mix because aphids can’t process sugar and it kills them. Scholl said the producer was right. Scholl recommends 2 pounds of sugar for each gallon of water and apply at a rate of 4 pounds of sugar per acre, he said.

Growers can source granulated sugar from big box stores. Tri Rotor has found that 5 quarts of molasses contains 4 pounds plus of sugar and is easier to handle. Molasses, along with humic acid, and humates have helped with fertility issues also.

The bottom line for growers is they need to make sure they are regularly testing the soil and alfalfa quality and should be ready to act because healthy soil means a quality crop and is the best defense against pests, he said.

Dave Bergmeier can be reached at 620-227-1822 or [email protected].