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Cutting herbicide rates: False economy?

Cutting rates to reduce peanut weed control costs might save money. Then again, it might not.

At any rate, growers facing potential lower returns from next year's peanut crop because of changes in the peanut title of the farm bill owe it to themselves and their pocketbooks to do some arithmetic before slashing proven practices.

Eric Prostko, a University of Georgia Extension weed specialist, says a sound herbicide program offers little opportunity for cost cutting to begin with.

“Typically, farmers spend only about $35 per acre for weed control in peanuts,” he said during a recent production seminar, part of the fourth annual Southern Peanut Growers Conference in Panama City, Fla.

Trimming that expense may be difficult, but Prostko offers five other options for growers to consider as they wrestle with next year's budgets. Options include: reading (and following) the label, calibrating and measuring materials accurately, incorporation, timeliness and expert systems.

“Farmers often take pesticide labels for granted,” Prostko said. “But, that's the best place to go for information they need to avoid problems.

“For example, farmers who use paraquat (Gramoxone) on peanuts should understand that it clings to the soil and, as fieldwork stirs up dust, it coats peanut leaves and can cause injury. Consequently, growers should avoid applying Gramoxone in extremely dry conditions. That's on the label.”

Calibrating sprayers, he says, “is the only way to be certain you're applying the correct rate of herbicide. Applying too little means poor control; applying too much means wasted money. Accurate measurements also assure proper application rates.”

Incorporating pre-plant herbicides also makes a difference, and Prostko says an irrigation system may be more efficient than cultivation.

“Farmers can save from $2 to $7 per acre by incorporating herbicides with water. Mechanical incorporation remains a good option, but irrigation may be more consistent and less expensive.”

He says pre-plant materials remain an important tool in peanut weed control. “We still need them. They are inexpensive and play an important role in a weed control system. Use other soil-applied herbicides as needed, depending on the weed spectrum.”

Soil applied materials, he says, may reduce the need for over-the-top herbicides.

Timing, he says is especially important for those post emergence treatments. “Spray early, when weeds are smaller and easier to control. Early applications also mean weeds cause little or no yield loss.

“And lower rates may be adequate with earlier treatments. And remember, you don't need 100 percent control.”

Optimum timing for morningglory control is before it starts running. For pigweed, Prostko suggests Blazer applied when the weeds are from three to five inches high provides up to 99 percent control. At 7 to 8 inches, control drops to 57 percent and to 45 percent with weeds from 11 inches to 13 inches tall.

Prostko says farmers have programs available to help develop efficient weed control programs. “Expert Systems, including HERB and HADSS help farmers determine the most economical system to control weeds in peanuts,” he says. Scouting, to determine weed species and soil types is critical.

“So is accurate data entry,” he says.

He doesn't dismiss reduced herbicide rates as a cost cutter but insists it is “a gray area” and “not a guarantee to reduce expenses.”

Lower rates, he says, are not labeled but are not illegal. “With control failures, however, product manufacturers will not offer support. At best, reduced rate decisions must be part of a total program incorporating multiple strategies, including rotation.”

Prostko says growers interested in cutting herbicide rates should consider the following guidelines:

  • Calibrate application equipment regularly.

  • Have an irrigation system — or be able to predict rain.

  • Accomplish consistent weed control with full rates.

  • Understand the difference between two inches and four inches.

  • Be willing to scout fields regularly. Accept less than 100 percent control.

  • Don't be a lawyer or have a close family member who is.

“In some cases, reduced herbicide rates will work, depending on the weed species. With sicklepod, for instance, keep the rate up. Precise application timing is a key. Also, the weed must be susceptible and growing conditions must be good.

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