WOOSTER, Ohio – Researchers at Iowa State University and The Ohio State University have teamed up with the USDA-Agricultural Research Service to find ways to decrease the amount of chemicals applied to an apple orchard, while maintaining the orchard’s health.

The researchers’ progress on their three-year research project was recently published in the scientific journal, Scientia. The first spraying system the researchers are studying is what they refer to as an intelligent spraying system, developed by Heping Zhu, USDA- Agricultural Research Service agricultural engineer in Wooster, Ohio, and his team.

The intelligent sprayer system was first put on the market in spring 2019, but since then it has been upgraded.

“A standard sprayer releases pesticide constantly down a row, so a lot of extra pesticide goes into the air, and onto the ground,” said Zhu, who led the team that created the sprayer in collaboration with the USDA and other universities.

Funded by the USDA’s Crop Protection and Pest Management Program, this system uses a combination of laser beams and sensors mounted on an air blast sprayer to detect where the apple trees’ foliage is located. Based on what the lasers and sensors ‘see’ as the tractor-pulled sprayer passes through the rows of trees, spray nozzles open to specifically target sectors of the foliage.

Mark Gleason, Iowa State University professor of plant pathology and microbiology, and his team of researchers, said this contrasts with traditional spraying methods, during which all spray nozzles are actively spraying during the entire pass along the tree line, resulting in excess amounts of spray being discharged.

“We’re trying to see how low we can go with spray flow rates, while still getting good application coverage, and preventing pests and diseases,” he said. “We don’t need trees dripping with pesticide; just enough coverage to do the job.”

So far, the researchers said they have found this targeted spraying method can reduce the overall pesticide use by 30-70 percent. Gleason said less pesticide means fewer trips back and forth to refill the sprayer, saving time and fuel.

The other technology researchers said they are evaluating is a weather-based disease warning system, which measures how many total hours the humidity level is 90 percent or higher in an orchard.

The warning system starts at the first-cover stage of the season, just after the flower petals fall off. Once the system logs a total of 385 hours under such conditions, fungicide spraying resumes in order to prevent fungal diseases.

The researchers said using this method – as opposed to pre-scheduling fungicide sprays every 10 to 14 days all season – has been shown to result in an average of 2.3 fewer fungicide spray applications each year, which results in a 25 percent reduction.

The researchers have been working with six orchards among Iowa and Ohio.

The team has also been sharing their research progress through a website, blog posts, podcasts and short videos: https://wwwsmartapplespray.plantpath.iastate.edu/project-videos.

One of the them is a stop motion video created by Olivia Meyer, an Iowa State University graduate student in horticulture and member of Gleason’s research team, that explains how a fungal disease can impact apples.

“We’re trying to explain various aspects of our research in fun ways that help communicate to growers what we’re doing,” Meyer said.

Wendong Zhang, Iowa State University associate professor of economics, and Nieyan Cheng, economics graduate student, are putting together an economic analysis apple growers can use to determine if either of these systems would offer cost-savings to their operations – another project goal.

Gleason said, “We’re trying to get growers interested in this. A lot of the learning will happen in the hands of the growers.”