NEWS for North Dakotans
Agriculture Communication, North Dakota State University
7 Morrill Hall, Fargo, ND 58105-5665

July 1, 1999

NDSU Agricultural Engineer Offers Tips for Spraying Fungicide to Control Scab

This season's wet weather means scab will almost certainly be a problem in the region's wheat and barley fields. A North Dakota State University agricultural engineer says taking something other than a top-down approach to fungicide application will improve control of the disease.

"If you look at the crop from directly above, the heads make a pretty small target," says Vern Hofman of the NDSU Extension Service. "Providing some horizontal movement to the spray gives us much better coverage." NDSU research in greenhouses and plots the last two years has shown that fine tuning the angle of application, application rate and time of application can increase grain head coverage by two to three times.

For conventional sprayers, Hofman recommends using a double-swivel nozzle body equipped with two nozzles: one pointing to the front of the spray boom and the other pointing to the rear, and each angled downward by about 30 degrees. With this configuration, one side of the grain head is treated as the sprayer approaches and the other is treated just after the spray boom moves past, Hofman says.

An application rate of about 15 to 20 gallons per acre applied at 40 to 50 pounds of pressure per square inch will provide the best results. "Higher application pressures provide smaller spray droplets and better coverage, but as those droplets get smaller, the potential for drift increases," he notes.

In research, air-assist sprayers which direct the spray straight down have not provided any advantage over conventional sprayers. A prototype air-assist sprayer that directed air and spray horizontally did improve coverage. Researchers are looking to to develop an attachment for existing air-assist sprayers that may improve coverage.

Hofman, says up to 70 percent of the fungicide applied to control scab will likely be sprayed by aerial applicators because of wet fields and the amount of crop that will need applications in a timely fashion.

"Applying these sprays by aircraft requires some attention to detail if they are going to be effective," Hofman says. A rate of 5 to 7.5 gallons per acre is best and nozzles should be oriented at 90 degrees to the air stream to provide the best dispersion of the spray.

Spray should be applied from a height of 6 to 8 feet. Any lower than that and the spray may not be distributed well on the crop. Higher altitudes offer more potential for spray drift.

For more information ask for Extension Report No. 56, "Improved Fungicide Spraying for Wheat/Barley Head Scab Control," available at your county office of the NDSU Extension Service.

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Source: Vern Hofman (701) 231-7240

Editor: Tom Jirik (701) 231-9629