Challenges to prune production in increasingly variable Californian weather conditions
There are approximately 20,000 ha of bearing prune trees in California but the industry is heavily reliant on one cultivar (Prunus domestica 'Improved French'). While, prior to a decade ago, the central valleys of California presented almost ideal conditions for growing prunes (winters cool enough to provide ample chilling, minimal risk of frost and moderate temperatures during and after bloom in the spring, a long, warm summer growing season and ample water available for irrigation) in the recent decade prune growers have experienced increasingly volatile winter and spring weather patterns and several years in which yields have been limited by environmental stresses. Interestingly, while California has experienced a number of low-chill winters in recent years this has had little apparent effect on prune crop production. The most important weather-related limitation to prune yields has been excessive temperatures that occur during bloom. In the past decade there have been 4 years in which crops yields appear to have been significantly reduced because of unusually warm temperatures during bloom and because statewide production is dependent on one cultivar in some years most of the trees bloom at nearly the same time. A second important weather related issue affecting cropping is the accumulated heat-units during the first 30 days after bloom. High heat accumulation after bloom shortens the period between bloom and harvest and can lead to smaller fruit sizes. The UC Davis prune breeding program is attempting to address these issues by developing new cultivars that present a broader range of bloom and harvest timings, have higher tolerance to high spring temperatures, while increasing fruit size and quality. Details of weather-related problems experienced in California and progress toward achieving our breeding goals will be discussed.
DeJong, T.M., Castro, S. and Niederholzer, F. (2017). Challenges to prune production in increasingly variable Californian weather conditions. Acta Hortic. 1175, 25-28
Prunus domestica, spring temperatures, dried plums, climate change, excessive heat, fruit set