Strategies to overcome biennial bearing in apple – A review

Abstract

Biennial bearing has long been a challenge for perennial tree fruit production. Some cultivars are more susceptible and can have excessive bloom and fruit set in one year followed by insufficient bloom and fruit set in the next year. Although crop load management can be used to reduce biennial bearing, optimum crop loads in one year can still sometimes be followed by high variability in return bloom the next. Moreover, the fundamental mechanisms that drive this behavior are poorly understood. The two primary hypotheses of biennial bearing consider hormonal control and resource competition for carbohydrates and nutrients. Through reviewing the current literature and gaining a better understanding of carbohydrate and hormone cycling/signaling within trees, a framework for biennial bearing control can be developed. With an understanding of the physiological responses contributing to biennial bearing patterns, manipulation of carbohydrate and nutrient cycling within trees through management practices may influence flowering and fruit bud formation. Improved management practices of biennial bearing can be evaluated and adjusted to suit different planting systems and species.