NEWS for North Dakotans
Agriculture Communication, North Dakota State
University
7 Morrill Hall, Fargo, ND 58105-5665
May 21, 1998
Dead weeds and bugs have always been sure signs of good spray jobs. But with escalating spray costs and environmental concerns, those signs aren't good enough.
Researchers at North Dakota State University are using computerized "eyes" to fine-tune pesticide spraying techniques. The goal is to kill more weeds, disease organisms and insects with less pesticide.
Agricultural engineer Suranjan Panigrahi, (SUR-in-jin pani-GRA-he) head of NDSU's Bio-imaging and Sensing Facility, is leading the effort. He's using computerized video equipment to detect spray coverage on plant material.
A specially designed camera takes a photo of a sprayed plant leaf or head. The spray is laced with a compound that shows up under the camera's ultraviolet lighting. The photo is digitized and put into a computer where software calculates the amount of spray coverage. The software must be modified for each kind of plant. So far, researchers have worked with sugar beets, potatoes and wheat. Research assistants Dan Gu and Ron Marsh are helping fine-tine the technology and computer programs.
"We have good chemicals to use under many different conditions," Panigrahi says. "But without a good measurement tool to assess how much of the spray is reaching plants, we're not going to be very effective."
The tool that's been used for decades is simply a slip of moisture-sensitive paper clipped to a plant leaf. Chemical applicators look at the paper to determine how much spray is reaching the plant. Panigrahi notes the flaws in the system: the clip and paper can flex or change plant leaves, the surface characteristics of the paper and of a plant leaf are different, dew, perspiration and other moisture can give false readings, and some spray droplets are so small that they may not be detected at all. Those factors all lead to inconsistent and inaccurate evaluations which can lead to reduced effectiveness, increased costs and wasted pesticides. In addition, using cards is tedious and labor-intensive. And the cards are sometimes difficult to locate in a heavy plant canopy.
"If you can look at spray coverage on the plant surface it has to be better than some artificial means of gathering that same information. And you also remove some of the human element," Panigrahi says.
But the clip and paper method does have one significant advantage: it's cheap and portable. But Panigrahi's making inroads there too.
At first, plant material had to be brought to the laboratory for evaluation. Now the system travels from field to field in the back seat of a car. But Panigrahi plans more improvements. He envisions a hand-held device that can be used without removing leaves from plants. Eventually the system might be mounted on the sprayer to give the operator information for on-the-go adjustments.
"We're making steady progress toward something that's cost-effective and practical for field use." he says.
The economic and environmental impact of the system could be significant. In 1997, N.D. farmers grew 125,000 acres of potatoes, one of the crops the system was initially tested on. Most of those acres received up to five or more applications of fungicide. Researchers commonly see differences in spray coverage analysis of 10 percent or more between the video system and the traditional paper and clip method.
Researchers are already putting the technology to use.
Agricultural engineer Vern Hofman, plant pathologist Gary Secor and potato specialist Duane Preston used the system to evaluate more than two dozen sprayers, including spray planes, conventional sprayers and air-assist sprayers. With support from the Red River Sugarbeet Growers Association, the Red River Valley Potato Growers Association and the North Dakota Aerial Applicators Association, they looked at spray patterns and coverage on various potato and sugar beet crops under various environmental conditions. Results of that study are being widely used by producers and commercial chemical applicators.
Now Hofman and plant pathologist Marcia McMullen will be using the system to look for better ways to control scab, a fungal disease that has devastated wheat and barley crops in the Dakotas and Minnesota. Using small-scale sprayers in the laboratory, Hofman is spraying wheat plants and using the system to evaluate spray coverage. Delivering a good dose of fungicides to all sides of grain heads is a key to controlling the disease. Until now, most sprayer research has focused on leaf coverage.
"We haven't had any method of determining percent of coverage on grain heads before," he says. Hofman and McMullen are looking at various nozzles, nozzle angles, spray volumes, spray pressures and other modifications that can be made to existing sprayers. Their goal is to develop affordable recommendations that producers and commercial applicators can use this growing season.
Additional research will focus on how spray interacts with dew on plant leaves and heads. The researchers say there's been no research on how spray might migrate toward or away from critical areas of the plant with condensation. The video imaging system gives them the ability to track that movement. "This system gives us insight we've never had before," Hofman says.
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Sources: Suranjan Panigrahi (701) 231-7270 & Vern Hofman (701) 231-7240
Editor: Tom Jirik (701) 231-9629