Researchers strive to make spray application more profitable and sustainable for apple growers


AMES, Iowa – Spraying pesticides in apple orchards can be beneficial in controlling pests and harmful diseases. The question is, what is the best method and the best time to spray in order to have the most impact with the least negative consequences for the environment.

Mark Gleason, professor of plant pathology and microbiology, and his team of researchers at Iowa State University have partnered with researchers at Ohio State University and the USDA-Agricultural Research Service (ARS) to find ways reduce the amount of chemicals applied to an orchard while maintaining the health of the orchard. The progress of their three-year research project has recently been published in the scientific journal Scientia.

The first spray system the researchers are studying is an intelligent spray system, developed by Heping Zhu, a USDA-ARS agricultural engineer in Wooster, Ohio, and his team. This system uses a combination of laser beams and sensors mounted on an airblast sprayer to detect the location of apple tree foliage. Based on what lasers and sensors “see” as the tractor-drawn sprayer passes through the rows of trees, the spray nozzles open to specifically target areas of the foliage. This contrasts with traditional spraying methods, in which all spray nozzles actively spray throughout the passage along the treeline, resulting in excessive amounts of spray being spilled.

“We’re trying to see how far we can go with spray rates while still getting good application coverage and preventing pests and diseases,” Gleason said. “We don’t need trees dripping with pesticides, just enough cover to get the job done. “

So far, researchers have found that this targeted spraying method can reduce overall pesticide use by 30-70%. Gleason said less pesticides used benefit the environment and mean less back and forth to fill the sprayer, which saves time and fuel.

The other technology they are evaluating is a weather-based disease alert system, which measures the number of total hours the humidity level is 90% or more in an orchard. The warning system starts at the first cover stage of the season, just after the flower petals have fallen. After the system registers a total of 385 hours under such conditions, fungicide spraying resumes to prevent fungal disease. Using this method, as opposed to pre-programmed fungicide sprays every 10-14 days throughout the season, was found to result in an average of 2.3 fewer fungicide spray applications each year, a reduction of 25 %.

The researchers worked with six orchards across the two states, including those near Cambridge and Jefferson, Iowa, as well as the ISU Horticultural Research Station north of Ames, to conduct research and organize demonstration trials at the closed. Monthly meetings are held via Zoom to keep the entire team of researchers, students and orchard owners informed.

The team also got creative in sharing their research progress through a website, blog posts, podcasts and short videos.

One of the videos is a stop motion video created by Olivia Meyer, graduate student in horticulture and member of the Gleason research team, which explains how a fungal disease can impact apples. She breaks down what could be a complex subject into an easy-to-understand two-minute clip.

“We try to explain various aspects of our research in a fun way that helps communicate to producers what we’re doing,” Meyer said.

This aligns with the objectives of the research project, which includes educating growers on these more environmentally friendly methods of pesticide application. Wendong Zhang, associate professor of economics at Iowa State, and Nieyan Cheng, graduate student in economics, prepare an economic analysis that producers can use to determine whether either of these systems would save money. for their exploitation – another objective of the project.

“We are trying to interest producers in this. A lot of the learning will be in the hands of the producers, ”said Gleason.

The project is funded by the USDA Crop Protection and Pest Management Program.


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