Temperature Effects on Fruit Doubling and Bloom Prediction in Tart Cherry

Tart cherry (Prunus cerasus) is a key horticultural crop in Utah. Extreme summer heat and cold weather in late spring are challenges to tart cherry production causing economic losses. These problematic weather conditions are influenced by the local landscape and are exacerbated by changing climate. This research explores (1) the impact of summer heat stress on fruit deformities, and (2) the accuracy of temperature-based predictions of spring bud development. High temperatures and water stress after harvest are known to cause a deformity known as twin or double fruits, resulting in unmarketable fruit. This disorder has been studied in other orchard crops, but not in tart cherry. Large, portable structures were used to cover mature tart cherry trees in greenhouse plastic for short intervals post-harvest, to determine when heat stress causes doubling. The following year, double fruit number was observed both on the tree and in the machine-harvested product. Over two seasons, the highest doubling occurred when trees were stressed in the 5th week after harvest, indicating a target period for alleviating orchard heat stress. Yearly differences were seen in the total amount of double fruit. Models use local temperature data to predict spring flower bud development and guide management decisions in the event of a late spring frost. The widely known Utah Model was developed in the 1970s and other models have been developed since. We observed spring bud development in tart cherry orchards from 2020 to 2024. These field observations were used to test the validity of multiple existing models. We found that the Utah Model performed the best, but model performance varied by year and location showing the need for improvements. These studies lay a basis for future work in heat stress and bloom prediction in tart cherry as well as other fruit crops. By deepening our understanding of how temperature influences plant physiology, we can create better tools and management plans to combat the uncertainty of our changing climate.