Frances Gould | 11/16/2011 9:02:33 AM
LSU AgCenter researcher Dr. Roberto Barbosa is beginning tests on methods for measuring drift from ground and aerial applicators that could be easier for farmers to use to improve the efficiency of pesticide application.
Barbosa said the new drift measurement approaches being considered employ materials, such as PVC pipe, monofilament line and table tennis (pingpong) balls, that will be easier for farmers to obtain and methods they can more readily implement on their own.
"Upon reviewing the literature on tools and procedures commonly used for drift estimation, we concluded that most approaches are very difficult for a farmer to implement alone," Barbosa said. "Tools used for drift measurements usually are too expensive or too complicated, and laboratory procedures are not commonly available."
The LSU AgCenter researcher said farmers need access to simple tools that can help them estimate the amount of drift currently being produced by their equipment, and his new research that is being funded by the Louisiana Soybean and Grain Research and Promotion Board is looking to develop such methods.
"Reducing pesticide drift and involving the producer in the process of selecting drift-reducing techniques and equipment is a first step toward increasing the efficiency of pesticide application," he stressed.
Sampling drift-prone spray is different from sampling target-deposit spray, Barbosa explained, adding that usually when evaluating in-swath deposition, water-sensitive cards are a common tool to use. Such cards are produced by Syngenta and marketed through Teejet, and the cards contain bromophenol blue, a chemical component that changes color from yellow to blue in contact with water.
"Deposition on cards can be evaluated by comparison or by using available computer software," he said. "The problem with this approach is that drift-prone spray is usually made of droplets less than 50 micrometers in size. Those droplets do not have enough mass to make an imprint on the card, and therefore most drift-causing spray is not detected by this method."
Most drift measurements make use of either flat samplers, such as mylar cards or petri dishes, or cylindrical samplers (monofilament lines) or even air samplers. Quantification of spray is done by colorimetry, fluorometry or
any other detection method, according to Barbosa.
"We have selected two cylindrical samplers for comparisons that are very easy to find in any store, monofilament (fishing) line and table tennis balls," he explained. "Monofilament lines are exposed to drifting spray that is deposited on the line, and a mechanical action coupled with exposure to a solvent strips the tracer from the line."
Barbosa and his research team have designed a simple sampler made of PVC and capable of holding 70 millileters of water, which will be used as solvent.
"The idea is to extend approximately 30 meters of monofilament line in 3 heights – 20 inches, 40 inches and 60 inches," he said. "Once the lines have been exposed to the drifting spray, they are pulled through the sampler, exposed to the solvent and stripped of the tracer by a rubber stopper."
In addition, the table tennis balls are going to be mounted on a wood support and exposed to drifting spray. They will be collected using a resealable plastic bag and exposed to a solvent (water).
"Results of both samplers will be evaluated by comparison of solvent color and pure water and by fluorometry," Barbosa said.
The tracer chosen will be Rhodamine WT, and Barbosa said tests were beginning on schedule in late July and August. –Tom Merrill