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Brazilians find electrostatic aerial spray system improves soybean rust control.


Houston, TX --- An aerial spray system made in the U.S. and patented by the U.S. government has provided Brazilian soybean growers with an effective new tool for control of soybean rust.

Brazilian aerial applicators who used the Spectrum electrostatic spray system the last two seasons report that it improved rust control by increasing fungicide deposition on upper and lower leaf surfaces; allowed them to spray 500 to 600 more hectares of soybeans per airplane per day; and reduced application costs for growers and applicators alike.

Developed and patented by the USDA-ARS and manufactured by Houston-based Spectrum Electrostatic Sprayers, Inc., the high-pressure, low volume electrostatic system applies fungicides, herbicides and insecticides at a rate of just one gallon of spray solution per acre (10 liters per hectare). Because the system applies an electrical charge to each droplet, spray droplets are attracted to and deposited on both the upper and lower leaf surfaces of the target vegetation.

Alan Poulsen, owner of Taim Aero Agricola Ltda. in the Brazilian State of Rio Grande do Sul, installed his first electrostatic spray system on an Ipanema aircraft four years ago. He now operates three Ipanemas equipped with the innovative spray system to spray nearly 50,000 hectares of rice, soybeans and cotton annually.

“The electrostatic system improves the spray deposition on both sides of the leaf, whether we’re applying fungicides or herbicides,” says Poulsen. “Aerial applicators in Mato Grosso who used the electrostatic system for soybean rust control last season said they got the same level of rust control with two 10-liter applications through the electrostatic system that they get with three 30-liter applications through a conventional spray system.”

Brazilian research shows small droplet size most effective

The electrostatic spray system produces small droplets averaging just 150 microns in size. This year, researchers at Brazil’s Sao Paulo State University conducted soybean rust control trials to compare the performance of the electrostatic system at 10 liters per hectare with other nozzle types at 10 and 20 liters per hectare. Those trials showed that the electrostatic system delivered 98.9 percent rust control at 71 percent humidity, and 99.6 percent rust control at 64 percent humidity.

Ulisses R. Antuniassi, Ph.D., professor of agricultural engineering at Sao Paulo State University, says his trials have shown that a small droplet size improves penetration of the soybean canopy compared to a large droplet size.

“Our tests have shown that fine to very fine droplet sizes of 100 to 200 microns are performing better on soybean rust than large droplet sizes,” he explains. “As a result, we are advising our soybean growers to use fine or very fine droplet sizes to increase canopy penetration and improve rust control when climatic conditions are right.”

Spraying 500 to 600 more hectares per day

Because the electrostatic system performs consistently under high temperatures and a range of humidity conditions, it allows applicators to spray several hundred more hectares per day … a critical advantage when soybean rust is spreading rapidly from one field to the next.

“We’ve found that when rust infections are high, you have to get it under control in the first two or three days or you lose control,” says Poulsen. “But when temperatures in the Mato Grosso reach 30 to 32 degrees Celsius, aerial applicators have to shut down for 5-1/2 to 6 hours until it cools back down. That’s because trials show we lose 40 to 50 percent of the material applied through a conventional high-volume system to evaporation when air temperatures exceed 30 degrees Celsius and humidity is 50 percent.

“But trials show the electrostatic system still achieves 89 percent deposition at 28 degrees Celsius and 38 percent humidity, allowing applicators to spray the entire day without shutting down. At an average rate of 100 hectares per plane per hour, that means they can spray an additional 500 to 600 hectares per day.”

Electrostatic system reduces application costs

Unlike other aerial spray systems, the Spectrum electrostatic system does not require the addition of crop oil to the spray solution. Poulsen says that represents a direct savings to growers of at least $1.50 per hectare. “If a soybean grower in the Mato Grosso has 10,000 hectares of soybeans, that means he saves $15,000 every time those fields are sprayed,” he points out.

The system also reduces costs for applicators. Since ag pilots using the electrostatic system can spray up to three times as many acres per trip compared with a high volume spray system, that means fewer refills, less time at the loading pad, and significantly less fuel consumption.

How can U.S. soybean growers use the electrostatic system?

Over the past six years, the Spectrum electrostatic aerial spray system has been successfully used on a variety of piston and turbine-powered fixed-wing aircraft to apply fungicides, insecticides and herbicides for cotton, rice, cereal grains, soybeans and other crops. The system is now in use in the United States, Australia, Africa and South America, and the first system was recently sold to China. An electrostatic system has also been installed on a Bell JetRanger helicopter to spray vegetable and cotton crops.

Ironically, while the U.S. government owns the patent on the electrostatic aerial spray system, federal regulations may prohibit U.S. soybean growers from using the same technology that is now being used in Brazil for soybean rust control. While the electrostatic system is engineered to work at one gallon of spray solution per acre, the labels of most fungicides approved for control of soybean rust in the U.S. presently require a minimum of 5 gallons of water in the spray solution.

“Chemical companies are now taking a close look at the electrostatic spray system,” says Blake Dobbins, president of Spectrum. “But if U.S. growers and aerial applicators want to use the electrostatic system this season, they’ll need to seek label exemptions from their state pesticide authorities, or ask the chemical companies to make label changes allowing them to apply fungicides at one gallon of solution per acre.”


For more information:

Spectrum Electrostatic Sprayers, Inc.

7500 San Felipe, Suite 860, Houston, TX 77063. Ph. 713-783-5771. Fax 713-783-5772.

Email technical@spectrumsprayer.com or visit the Spectrum web site at www.spectrumsprayer.com