NEWS for North Dakotans
Agriculture Communication, North Dakota State
University
7 Morrill Hall, Fargo, ND 58105-5665
June 25, 1998
North Dakota State University researchers released new recommendations this week for spraying fungicides on small grains to protect them from scab.
"The fungicides available to protect the crop from Fusarium head blight, or scab, must be applied to the head for maximum effectiveness," notes Vern Hofman, an NDSU agricultural engineer. "Most spray research has focused on delivering spray to the leaves of plants. Consequently, most sprayers are designed to provide good coverage to horizontal leaves, not upright heads."
The researchers set up various sprayer configurations in the laboratory this spring to apply sprays to plants raised in the greenhouse. Their goal was to find a relatively low-cost way to improve the performance of sprayers producers and applicators were already using.
They found that the best spray coverage was delivered by creating an angled spray pattern. Best coverage was achieved with a double-swivel nozzle body equipped with two 8001 flat-fan nozzles applying 15 gallons per acre at 40 to 50 pounds per square inch (psi) of pressure and a ground speed of 4 miles per hour. The two nozzles are angled 60 degrees from vertical to the front and rear of the spray boom.
"This configuration provides coverage to the one side of the head as the sprayer approaches and to the other just after the sprayer passes over the head," Hofman explains.
Researchers also found that an 8002 twinjet sprayer nozzle gave good results.
The spray patterns should overlap. With a 20-inch spacing of the nozzles on the boom, the boom should be raised 18 inches above the crop for the twinjet nozzles and 9 inches above the crop for the double-swivel nozzle body.
When using the double-swivel body with 8002 flat fan nozzles or 8004 twinjet nozzles, increase the ground speed to 8 miles per hour. Those speeds should deliver about 15 to 18 gallons per acre, the recommended volume for applications of available fungicides.
NDSU Extension plant pathologist Marcia McMullen, NDSU Extension cropping systems specialist Terry Gregoire and University of Minnesota small grains specialist Jochum Wiersma cooperated on the project. They used a system developed by NDSU agricultural engineer Suranjan Panigrahi to evaluate spray coverage on the wheat heads in the trials.
The system uses digital video technology to evaluate spray coverage on plants. Traditionally, researchers and chemical applicators used moisture-sensitive paper clipped to plant leaves to evaluate coverage.
"The texture and position of heads makes that method unsatisfactory for evaluating spray coverage in this case," Hofman says. "This new technology allowed us to take a much more accurate look at how spray was collecting on those heads."
Despite the new recommendations, Hofman says producers will have to make difficult choices about spraying for scab.
"There is no reliable way to predict an epidemic yet," he notes. "And the cost of treating is significant."
Full recommendations from the research and a list of labeled fungicides are available from county offices of the NDSU extension service. Ask for AE 1148, "Application of Fungicides for Suppression of Fusarium Head Blight (Scab)."
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Source: Vern Hofman (701) 231-7240
Editor: Tom Jirik (701) 231-9629