MARSHALL LAMB

Initial data from a study to chemically terminate peanut flowering at 100 to 110 days after planting to prevent immature fruit “looks encouraging” for improving both quality and yield, says Marshall Lamb, director of the USDA/ARS National Peanut Research Laboratory at Dawson, Ga.

He emphasizes, however, that “at this point, this is research — and not recommendations for producers” — and that more study is needed. He spoke at the Mississippi Farm Bureau Federation’s summer peanut commodity meeting at Hattiesburg.

In explaining the program, he notes, “There’s a point in the season when these new fruit do absolutely no good. Rather, they’re taking energy away from peanuts that will actually mature and be harvested, and directing it to immature peanuts that will never be of benefit to you.”

The study was formulated two years ago, Lamb says, “to evaluate whether we can improve the maturity distribution and the flavor profiles of peanuts through chemical termination of flowering.

“If we can get the immature peanuts out of the system, will that help to achieve a more uniform flavor profile?”

Although it’s grown as an annual, the peanut plant is an indeterminate fruiting perennial, he notes. “Peanut plants have been kept growing for as much as three years. In a non-winter environment, they can live for many years if they have the nutrients and fungicides they need. They will continue to flower and put down new fruit as long as the plants are healthy.”

The problem in an annual production regime, Lamb says, is that “you get to a point late in the season when you’ve got peanuts ready to be harvested, but the plants are still putting down new fruit that will never mature and can result in off flavor when mixed with mature peanuts.”

Two compounds, generic glyphosate (Roundup) and BASF’s diflufenzopyr-sodium,were used at three different rates to terminate flowering. The study included about 184 plots, both irrigated and non-irrigated, located in Georgia, South Carolina, Mississippi, and Arkansas.

“We’d go out each day and count the flowers in each three feet of row,” Lamb says. “In untreated control plots, flowers were hand removed for comparison to the chemically treated plots.”

Untreated plots consistently maintained anywhere from 10 to 16 flowers per 3 feet of row during the period, he says, while in the glyphosate and diflufenzopyr-treated plots flowers had been reduced to only 2 to 3 per 3 feet of row.

“That’s the type of the result we were looking for,” he says.

After harvesting the plots, the hull scrape method was used to determine if maturity distribution had been improved.

“As peanuts mature,” Lamb notes, “the hulls change from white to yellow to orange to brown and ultimately, to black. The further the mesocarp is into black, the more mature the peanut is.  These are usually our largest, and always our most flavorful peanuts.

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“In the control group where no treatment was applied, we had an average of five pods in the far black column, which is common. But where applied treatments to interrupt flowering and fruit setting, we had from a three-fold to four-fold increase in the number of peanuts in the far black column.”

How did this translate into yield?

“On the irrigated plots, we had 4,680 pounds of yield in the control. Where we’d applied the treatments, yield increased to 5,545 pounds for the diflufenzopyr plots and 5,290 pounds for the glyphosate plots. On the non-irrigated plots, for the control we had roughly 3,200 pounds, while treated plots were as high as 3,600 pounds. Those are significant increases.

“We also had a 2.5 percent increase in sound mature kernels and sound splits, which was exciting. Kernels from the treated plots were denser, which means they were more mature, with higher oil content.”