Historic and future modelling and mapping of early season temperature patterns and impacts for pome and stone fruit production

Growers are experiencing erratic and extreme weather conditions from dormancy until fruit set and early growth, possibly linked to climate change. The overall project objective is to investigate early season temperature patterns, during the historical and projected future periods, and their impacts on pome and stone fruit production.

A knowledge review informed discussions with experts and the Reference Group. Four phenological periods were used, with four generic fruit types representing early to late flowering cultivars in the Western Cape. Quantitative modelling and mapping was conducted for chilling, heat, Growing Degree Hours, cold, frost, temperature variance, leaf and fruit carbon balance. Six verified Global Circulation Models were used.

In future, chilling is reduced throughout. The risk of warm hours during dormancy increases, especially in warmer areas. GDHs are higher, and the difference grows over time. The risk of cold hours and frost during flowering decreases. Variability of daily maximum and minimum temperatures is unlikely to change.

Both negative and positive impacts are expected, often interacting with one another. The strength of impacts, and complex outcomes of interacting processes, especially in the transition from dormancy to flowering, will depend on cultivar (from ultra early to late flowering) and production area.

Climate change (warming) is projected to have significant impacts on processes that occur in fruit trees in the transition from dormancy to fruit set. Adaptive technologies and practices, and future-focused cultivar selections for different production regions, are needed for the continued sustainability and growth of the industry.