Tools for climate resilience in tree fruit II: a calcium carbonate-based foliar spray showed potential for protecting fruit quality during an unprecedented heat event

Abstract In 2021, an unprecedented heat event caused widespread damage to tree fruit crops across western North America. In a preliminary trial conducted that summer in an apple (var. “Fuji”) orchard in the Okanagan Valley, British Columbia, a calcium carbonate-based foliar protectant reduced severe sunburn by 9% and fruit asymmetry by 17% but had no other effects on fruit quality, water stress, or leaf gas exchange. With climate change, extreme heat events are projected to become more frequent and extreme. Foliar protectants show potential for preserving fruit quality, but further research is urgently required to optimize their use in Canada.