Charging Ahead
Electrostatic Spraying Gaining Popularity
By Patrick Cavanaugh, PNP Editor
About a decade ago, when electrostatic spraying began making inroads into production agriculture, many growers asked: electro-what?
But today, most growers are firmly aware of the principles of electrostatic technology and many are utilizing the equipment in their orchards, not just for low volume concentrate spraying but dilute applications as well.
Joost De Moes, an almond grower in Delano, Calif., has been using an electrostatic sprayer for about three years and finds it fits all his spraying needs.
De Moes farms 400 acres of his own almonds as well as 320 acres for another person. "We find that the electrostatic really showers the whole tree and covers all the leaves, thus giving us excellent pest control," he said.
While he has used other types of sprayers before, De Moes enjoys the time and chemical savings found in his PTO-driven Spectrum 2010 electrostatic unit. "That’s important when we’re trying to treat an orchard as fast as possible," he said.
"I pull the 600 gallon sprayer with a 90 hp Massey-Ferguson tractor, which is plenty of power," said Jose Moreno, who is in charge of spraying for the De Moes farms. "We also have a 75 hp tractor that easily pulls the unit."
De Moes said he uses the Spectrum for his dormant, fungicide, worm, mite and hull-split sprays. For his mite and hull-split sprays, De Moes goes concentrate , applying only 50 gallons per acre which means he can spray a lot more acreage before a fill-up. "The electrostatic technology makes it an excellent concentrate spray," De Moes said.
The technology De Moes refers to is a charge that electrostatics put on the spray, attracting to the tree foliage and wood. In fact, of all the things surrounding electrostatic discussions, the "charge" is among the most mysterious. Yet, it’s really quite simple.
Apply a charge of static electricity to liquids, and they behave much like magnets. That is, they are attracted and adhere to trees and plants, like tiny magnets to metal. The key ingredients that make them behave this way are the negative and positive electric particles in atoms.
By charging liquid spray droplets with extra negative particles, they are attracted by electric forces to the positive particles inside trees and plants. The attraction of opposites is a very powerful force, particularly when electrostatic charges are applied to small droplets. Electric attraction will pull droplets up, down, and sideways to the nearest plant surface , even those away from the direction of spraying.
Air speeds at 200 mph shear water droplets to 50-60 microns as they exit the nozzles. There is only 20 pounds of pressure at the wind shear nozzles which have a 3/16-inch opening. "From there, the spray goes through the negative charge and out to the trees," said De Moes.
"Electrostatics have a simple, long-life centrifuge pump and it’s extremely easy to calibrate," said Kirby Wyllie, who uses Spectrums in his custom spray operation, Joaquin Inc., based in Tulare, Calif. "Once a grower knows the speed of the tractor, the calibration can be set in 15 seconds , or as fast as you can run a calculator," he said.
Nick Hill utilizes Wyllie’s services as well as his farm’s own electrostatic sprayers. Hill is the farm manager of Greenleaf Farms, Southern Division, Kingsburg, Calif. "We’ve been using electrostatic sprayers on nearly all spray applications for the past four years," he said. Greenleaf Farms consists of 1,000 acres of almonds and walnuts along with 50 acres of pistachios and 500 acres of citrus. "We use electrostatics for codling moth and blight control in our walnuts," said Hill. And for dormant and naval orangeworm sprays on almonds."
For fungicide sprays in almonds, Hill traditionally orders up the application by air.
Hill has turned to electrostatic technology specifically for its low volume concentrate spray advantage. "Our per-acre gallonages are between 50 and 100. And the coverage and controls at this rate have been as good as the big dilute rigs," he said.
But Hill, who also uses the services of Joaquin Inc., stressed that the secret of good coverage is slow speeds. "Some people like to go up to 5 mph with these units, but we slow it down to around 1-1.5 mph for best results," he said.
"My theory is that the big dilute rigs have a larger ‘slop’ factor in they are moving a large volume air, thus moving a lot of space," explained Hill. "The electrostatics move a small volume of air at a very high velocity. What we do by going slow is give time for the velocity of the air to move the leaves out of the way for better penetration."
Hill is especially impressed by the fuel savings offered by electrostatics. In fact, he purchased his sprayers a few years ago with the help of low interest loans offered by the California Energy Commission.
Part of the research surrounding the Energy Commission loans was to measure the fuel savings. Also looking into fuel savings and spray coverage was Jack Dibble, UC Extension entomologist, emeritus, based at UC’s Kearney Agricultural Center, Parlier.
"We see a big difference because in the PTO-driven low volume concentrate sprays you don’t need a sprayer with its own engine. And in most cases you can pull it with tractors above 70 hp," said Dibble.
"Whereas, with high volume sprayers, growers have to a load up every acre with water and they need a nurse rig. So you have three motors going, versus one," said Dibble. "Furthermore, you have more down time because you’re reloading every acre versus every 5-10 acres with the low volume, concentrate rigs. Another important consideration is when you have to load up less often, it also means workers are not exposed to chemicals as often."
Dibble said growers are seeing as much as 25-30 percent in chemical savings as well, simply because you don’t get the runoff that’s often associated with higher gallonages. Besides that, electrostatics often cost less than high volume sprays so the savings are compounded.
Generally, the average high-volume gallonages in California on deciduous trees is about 400 gallons. "So we’re comparing that with 100 gallons or less," noted Dibble. "And we see the control of short spots, but we see some short areas with the high volume as well."
While most growers with electrostatics use them for concentrate sprays, De Moes also uses the machine for semi-dilute sprays. "For our dormant sprays we go in with 200 gallons which works out well," said Moreno. "We have quarter mile runs in the orchards and with the 600 gallon tank we are able to make three rounds before re-filling," he said.
The coverage offered by the electrostatic sprayer paid off last season. While many growers throughout the state suffered as much as 10 percent or more of worm damage to both almonds and walnuts De Moes said his worm damage this year averaged only 1.78 percent. His younger 8-year-old Price and Nonpareil trees had less than 1 percent and his 16 year-old trees comprised of Nonpareil, Price and Carmel had about 3.5 percent. "It could have been much worse," said De Moes.
"The machine is very easy to set up and easy to calibrate," said Jose Moreno. "If you know your ground speed and the gallons per acre you want to apply, then you’re ready to go," he said.
"This year, with warm weather lasting deep into winter, there were a lot of leaves still on the trees during dormant sprays," noted Moreno. "But the sprayer’s wind shear action knocked most of the leaves off to help encourage dormancy," he said.