Targeting application technology helps cut pesticide waste and drift in orchards

By Renee Stern

Contributing Editor

Nut and tree-fruit growers can simultaneously reduce pesticide application waste and lessen environmental impacts with tree-targeting technology.

Sensors and computer controls that open and close sprayer nozzles direct pesticides at their intended target: the tree canopy. The technology is available on new machines, or growers can retrofit older sprayers.

Durand-Wayland Inc.'s SmartSpray sees its targets with the help of waterproof ultrasonic sensors, emitting sound waves and measuring reflected signals to build a picture of tree rows as the tractor drives between them, says Rick Cordero, sales director at the LaGrange, Ga., company. Researchers also are exploring laser and infrared sensors.

"The more you spray and the more expensive your spray materials are, the quicker you earn (the equipment investment) back," says Franz Niederholzer, University of California Cooperative Extension farm advisor for Yuba and Sutter counties.

Cutting the amount of material sprayed doesn't change overall results, Niederholzer says. Sprayers deposit the required amount where it's most effective, reducing waste.

Savings versus costs

Chemical savings vary, depending on how uniform the targeted blocks are.

Storm damage had left holes in his apple orchard when Mike Wittenbach, co-owner of Wittenbach Orchard of Belding, Mich., first tried targeted sprayers. He used 25 percent less pesticide that year, but as replacement trees have grown, those savings now average 10 percent.

Wittenbach runs two targeted sprayers on 225 acres of apples. "I spend $100,000 a year on foliar applications," he says. "Ten percent is a two-year payoff."

Durand-Wayland's basic six-sensor SmartSpray system--three sensors per side--costs $14,000 to $16,000, Cordero says. A 10-sensor model is available for tower or oscillator sprayers.

Young orchards offer even greater savings potential, says Steven Mendonca, chief financial officer at Mendonca Orchards Inc. of Chico, Calif. Small trees that haven't filled out their 15-foot spacing require much less spray coverage, saving as much as 90 percent.

Tightly planted orchards with no missing trees, on the other hand, may produce only a 5 percent reduction. Mendonca's operation, with 500 acres of almonds and 40 acres of walnuts, averages 25 percent savings with two sprayers.

More than cutting pesticide costs

Reduced pesticide costs are the main draw, but both Mendonca and Wittenbach say they also gain time and labor efficiency from making each spray load go further.

Focused sprays help cut pesticide drift and ground and water contamination as concern grows over farm neighbors and waterway buffer zones.

"The first step in reducing drift is targeting the tree," Niederholzer says.

Keeping pesticides on target also aids worker safety, he says.

Building a better targeted sprayer

Researchers are focusing on ways to make targeted sprayers even more efficient. Current sensing technology determines the presence or absence of a tree canopy and opens and closes spray nozzles accordingly. An improvement over continuous spraying, it's still a rough measure, says Masoud Salyani, professor of agricultural and biological engineering at the University of

Florida's Citrus Research and Education Center in Lake Alfred.

Because orchards and groves contain a wide range of canopy structures, customizing spray patterns to individual trees would create still more gains, Salyani says.

Ultrasonic signals fan out with distance, reducing precision at the far edges. Laser sensors emit nonspreading signals that travel faster and generate plenty of data for more precise calculations of tree characteristics, he says.

Salyani and his colleagues are developing a laser-based system that will detect not only canopy presence and size, but also density. A thick, tight canopy intercepts more spray material than a loose or dead canopy, with noticeable differences in drift.

Cordero says Durand-Wayland is switching to tracking sprayer locations with global positioning system units, which could lead to pinpointing spray treatments for specific problems to individual trees. The company's SmartSpray equipment currently uses radar tracking.

Other improvements in development would alter application rates for canopy density or growth stage during the season, he says.

Targeting technology does have limitations, particularly speed, Salyani says. The faster the sprayer runs through the block, the greater the savings, but driving too fast can create spotty coverage from outrunning sensor processing and bouncing over uneven terrain. About 3 miles per hour is the limit of current technology, he says.

Regularly calibrate sprayer for best results

SmartSpray sensors are placed in line with spray nozzles for tight tracking, Cordero says.

Regular calibration will help avoid unintended discharges or shutdowns, Salyani says. He recommends calibrating at least once per season, but especially after such system adjustments as replacing nozzles or switching between light and dense spray materials.

Field conditions, such as muddy ground during dormant applications, sometimes hinder operations, Niederholzer says.

"You're using high tech in a low-tech situation, but it's not the fault of the technology," he says.

Wittenbach agrees: "Any time you put a computer in a farm environment, stuff happens.”

If sensors or controllers malfunction, the machine reverts to manual broadcast spraying.

Growers should have someone within their operation who's comfortable with technology—and work with a dealer who provides speedy service when needed, Wittenbach and Mendonca say.

"Don't be afraid to work with it," Cordero says. "It's a tool and can be refined or adjusted to local conditions."