IPM meets laser tag

In part I (December 2013, page 30) the authors covered how growers have successfully used IPM. In part II, they demonstrate intelligent sprayers, a novel approach to include in any IPM program.

When pest population levels are unacceptable and other techniques don’t work, it’s time to bring in the big guns — laser tag style. Air-blast sprayers are typically used to apply pesticides to field-grown nursery crops. However, they have very low spray application efficiency — less than 30 percent of pesticide applications are typically intercepted by the target plants. That means 70 percent of pesticide expense per application is wasted when spray lands on the ground, non-target plants in the nursery, or is lost as drift that can land on soil or water, ultimately contaminating natural ecosystems.

In collaboration with researchers at the University of Tennessee, The Ohio State University and Oregon State University, Heping Zhu and his team at the USDA-ARS Application Technology Research Unit in Wooster, Ohio, recently developed two novel “intelligent” sprayers to increase spray application efficiency: a vertical boom hydraulic sprayer and an air-assisted sprayer. Currently, we are testing pest control efficiency, reliability and durability of these revolutionary sprayers in commercial nurseries in Tennessee, Oregon and Ohio. Diana Cochran and Amy Fulcher from the University of Tennessee are evaluating how the intelligent sprayer performs at Walker Nursery in McMinnville, Tenn. In Oregon, evaluations are being performed by Robin Rosetta and Derek Wells of Oregon State University at Hans Nelson & Sons Nursery and Sam Doane at J. Frank Schmidt & Son Co. In Ohio, evaluations are conducted by Randy Zondag and Luis Cañas from The Ohio State University, and Mike Reding, Chris Ranger, Charles Krause and Heping Zhu of USDA-ARS at Willoway Nurseries and Sunleaf Nursery.
 

High-tech helpers

Intelligent sprayers have several high-tech features. The air-assisted sprayer uses a high-speed laser scanning sensor and the vertical boom sprayer uses an ultrasonic sensor. The sensors are the eyes of the sprayers: they detect the plant, its canopy structure and foliage density, and tractor speed, while controllers manipulate nozzles independently to produce variable-rate spray outputs based on plant characteristics in real time. No plants? No problem. The sprayer detects the absence of a plant within a row and turns off nozzles until a plant is detected.
 

Air-assisted sprayer performance

Growers often don’t adjust spray application rates as the season progresses, yet plants generally grow throughout the season. This is another way the intelligent sprayer can increase spray efficiency. Pesticide use between the intelligent sprayer and the intelligent sprayer without its sensor/controller system, as well as a conventional air-assisted sprayer were compared at three growth stages (in April, May and June) in Ohio. Pesticide use was dramatically reduced with the variable-rate intelligent sprayer. The intelligent sprayer reduced the spray volume by 52-70 percent and achieved a uniform 40 percent coverage. The intelligent sprayer without the controller and the conventional air-assisted sprayer over-saturated the foliage with 45-90 percent coverage.
 

Hydraulic boom sprayer performance

The boom type intelligent sprayer was compared to a conventional nursery boom sprayer on six tree species (Red Sunset red maple, European hornbeam, Sargent’s crabapple, purple-leaf sand cherry, Autumn Blaze Freeman maple and Japanese maple) with a range of plant height and width and overall plant shape (0.8 to 8.2 feet high and 0.2 to 2.0 inch caliper). The variable-rate intelligent sprayer provided consistent spray deposition uniformity inside tree canopies at different travel speeds. Most importantly, it reduced spray volume by 86 percent compared to a constant 100 gpa and by 71 percent compared to tree-row volume estimated applications.
 

Hydraulic boom and air-assisted sprayer pest control

So we know that the two intelligent sprayers reduce pesticide consumption and provide more even, consistent coverage, but is that fraction of the coverage enough to control pests?

In Tennessee, the variable-rate intelligent sprayer was compared with a conventional air-assisted sprayer to control powdery mildew of dogwood, one of Tennessee’s more serious diseases. This experiment really put the variable-rate intelligent sprayer to the test — we had nine rows of dogwoods in a block. Dogwoods were scouted weekly between fungicide applications. We are still crunching the numbers, but the disease levels associated with the first fungicide application are in. For three of the four weeks following the initial fungicide application, there was no difference due to sprayer type. We anticipated that the interior rows might have greater infection, but that was not the case. Stay tuned as more results become available.

In Oregon, Norway maple liners were scouted to monitor powdery mildew and to compare control by a conventional boom sprayer and the intelligent variable-rate boom sprayer. Prior to fungicide applications, powdery mildew infection was not different on one date and lower for the intelligent sprayer plot on the other. This difference, 0.15, was not considered biologically relevant or likely to bias the trial. Once fungicide applications commenced, powdery mildew ratings were not different or infection was lower for plants sprayed with the intelligent sprayer on all dates but one. Trials controlling aphids with the intelligent boom-type sprayer were also successful. Aphid populations were either no different or better with the intelligent sprayer.

Both variable-rate intelligent sprayers continually matched canopy characteristics and controlled spray output in real time. This high level of spray application efficiency reduced off-target losses and has the potential to drastically decrease pesticide use and associated costs, increase environmental quality, and enhance worker safety. The reduced spray coverage from the intelligent sprayers controlled powdery mildew and aphids at comparable levels with conventional sprayers.

Think about it — these types of sprayers could cut pesticide costs in half or more every year. While these are prototypes, we anticipate that they will lead to a commercial product that will help nursery growers save money and reduce pesticide use while effectively controlling pests. The material cost to build a sprayer prototype for research use is about $21,000. This cost can be significantly reduced for commercial sprayer manufacturers. For more information please see www.oardc.osu.edu/scri/ or contact Amy Fulcher at afulcher@utk.edu or Heping Zhu at heping.zhu@ars.usda.gov.

The authors acknowledge the USDA SCRI award “Intelligent Spray Systems for Floral and Ornamental Nursery Crops.”

Amy Fulcher is assistant professor for sustainable ornamental plant production and landscape management, Department of Plant Sciences, University of Tennessee; Diana Cochran is postdoctoral research associate, University of Tennessee; Robin Rosetta is associate professor and extension entomologist, Oregon State University; Randy Zondag is assistant professor and extension educator at Ohio State University Extension; and Heping Zhu is agricultural engineer at USDA-ARS Application Technology Research Unit.