UNIVERSITY PARK, Pa. — Apple production contributes billions to the U.S. economy; however, the apple industry faces challenges related to a labor shortage and application of excess fertilizer and chemicals, according to the U.S. Department of Agriculture (USDA). One of the most traditionally time-consuming, labor-intensive processes of apple production is blossom thinning, which involves manually pruning flowers so that remaining blooms can reclaim the plant’s resources to grow better fruit. More recently, the process has shifted to broad chemical spraying, which can have harmful environmental impacts. To assist producers and mitigate environmental harm, the USDA has awarded a three-year, $601,125 grant to a team of Penn State researchers for the development of a robotic precision spraying system.

“During the blossom period, apple trees generally produce a large number of flowers, which later can be pollinated to set fruit,” said team leader Long He, associate professor of agricultural and biological engineering in the College of Agricultural Sciences. “Each flower requires resource allocation from the tree to grow properly and turn into an apple fruit. However, when the number of flowers is too high, an abundance of small, low-quality apples can result that may be unworthy for sale. Therefore, it is very important to adjust the number of flowers to set fruits.”

Traditionally, blossoms were selectively thinned or removed manually to adjust flower numbers in each flower cluster, but that process is not practical for large orchards. Chemical blossom thinning has proven to be one of the most effective methods to improve apple quality, size and color, He noted. It can achieve large-scale blossom thinning at a fast speed.

“However, using conventional orchard sprayers that apply a noticeable amount of chemicals without precision control results in huge chemical wastes and environmental impact,” He said. “It is critical to find a more effective method for chemical blossom thinning.”

The researchers plan to develop an autonomous system capable of traversing orchards to precisely manage crops at the flower stage. It will consist of a novel, advanced machine vision component to estimate crop yield, as well as artificial intelligence decision support to precisely manage the crop load at the flower stage. It will also include a precision sprayer system that can apply chemical thinner targeted at the flower clusters in tree canopies.

“The expected outcome of this project will be a precision crop load management strategy with an integrated spraying system that can conduct chemical blossom thinning with high precision and significant chemical-usage reduction,” He said. “Attainment and adoption of such a system will have a significant positive impact on crop management and improving the long-term economic and environmental sustainability of the U.S. tree fruit industry.”

Other research team members at Penn State include Shirin Ghatrehsamani, assistant professor of agricultural and biological engineering; Paul Heinemann, professor of agricultural and biological engineering; and James Schupp, professor of pomology.