NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665
September 14, 2000
Using desiccants on oilseed and confection sunflower crops to speed drydown is not a common practice but can be useful when the crop is mature and an early harvest would be an advantage, according to Duane Berglund, extension agronomist at North Dakota State University.
Sunflower planted early last spring are starting to show signs of physiological maturity, and persistent rains in some areas have resulted in sclerotinia head rot, Berglund says. Early drydown of sunflower plants may slow or stop development of head rot and reduce sclerotia and destruction of seeds.
However, he says, reduction of head rot depends somewhat on weather following desiccation. Wet weather may actually increase the problem in desiccated sunflowers.
White mold does attack dead plant tissue, and, while little data is available, Berglund says grower experience indicates enhanced head rot when wet weather follows desiccation compared to green fields left untreated.
"Growers need to weigh the weather probabilities and the advantage of early harvest compared to the risk of wet weather following desiccation," he says.
There are other reasons desiccation might be desireable. "Bird pressure is always a concern for many sunflower producers. Applying a desiccant narrows the window of opportunity for those migrating birds that feed on a sunflower crop," says Berglund.
Reduced heat shattering is another factor favoring desiccation. "The quicker harvest time comes, the less time large sunflower heads will spend knocking against each other. Accelerating the harvest season will also prevent further deterioration of crops affected by disease," he says.
Using a desiccant to control weeds, especially large weeds like kochia and marshelder, will result in less dockage, less wear and tear on combines, and easier crop drying with reduced drying costs.
In North Dakota, Gramoxone (paraquat) and Drexel Defol (sodium chlorate) are labeled as sunflower desiccants. Both have a seven-day preharvest application interval.
Producers need to apply either desiccant after the backside of sunflower heads have turned yellow and the bracts are turning brown. Physiologically mature sunflower plants have a seed moisture content between 33 and 35 percent.
"Some of our sunflower hybrids now have a stay-green stalk characteristic, so go by the heads or seeds," Berglund says. "Another way to tell if physiological maturity has occurred is to rub the chaffy material on the front of a sunflower head. If it rubs off easily, the plant is physiologically mature."
Producers planning to apply a desiccant should check the herbicide label or consult the current edition of NDSU Extension Service publication W-253, 2000 North Dakota Weed Control Guide.
NDSU Agriculture Communication
Source: Duane Berglund, (701) 231-8135
Editor: Gary Moran, (701) 231-7865