Studies in Precision Crop Load Management of Apple

T.L. Robinson, L. Gonzalez, L. Cheng, Y. Ziang, G. Peck, B. Arnoldson, M. Gomez, M. Guerra, Mario Miranda Sazo, C. Kahlke, T. Einhorn, A. Wallis, S. Musacchi, S. Serra, K. Lewis, T. Schmidt, P. Heinemann, L. He, T. Kon, S. Sherif10, J. Clements1, and C. Layer

IHC 2022, 31st International Horticultural Congress, 14-20 August, 2022, Angers, France.

“We are conducting a USA national SCRI project to develop precision crop load management strategies and machines to manage the number of fruits per tree to exactly the economic optimum. We have done physiological experiments to define the biological potential of yield and fruit size of ‘Gala’ and ‘Honeycrisp’ apple cultivars in four climates (West, Mid-West, North-East and South-East USA) to estimate the economic optimum number of fruits per tree. Our results show that the dry, high light climate of WA generally can support a higher crop load than the eastern USA growing regions. Our multi-location experiments have shown that leaving too many flower buds during pruning results in lower crop value than the optimum flower bud number. Optimum flower bud number in our studies of ‘Gala’ and ‘Honeycrisp’ was between 1.5-2.0 flower buds per final target fruit number. To achieve the optimum fruit number per tree we
employ: 1) precision pruning to remove flower buds to a pre determined flower bud load; 2) precision chemical thinning through sequential chemical thinning sprays guided by the use of computer models to adjust the dose and timing of chemical
application and to assess the effect of the chemical sprays shortly after application to inform re-application; and 3) precision hand thinning to guide human workers to leave an exact number of fruits per tree. We are developing computer vision to streamline the counting of buds, lowers and fruitlets. The information from each tree is georeferenced and is uploaded to the cloud and then can be communicated to human workers to guide their work in reducing crop load to the optimum level.”