The projected increases in summer mean monthly maxima will affect the pome and stone fruit sector throughout the region, especially in areas that are already hot in summer. Impacts will be wide-ranging, from sunburn to increased irrigation water demand resulting from high evapotranspiration rates. The following approaches to adaptation can be considered by growers:
- Gradually shift to cultivars that are specifically bred or tested for heat tolerance;
- Gradually shift to cultivars that are specifically bred or tested for sunburn resistance;
- Plant early ripening cultivars in sites with intense summers, and later ripening cultivars in sites with cooler summers;
- Plant other fruit types or annual crops that are less sensitive to heat stress and sunburn;
- Seek cooler microsites on farms where summer maximum temperatures are milder;
- Investigate the feasibility of establishing orchards on available land at higher altitude or other areas where heat units were historically too low for pome and stone fruit production;
- Ensure that irrigation practices are optimal and water stress is avoided;
- Use mulches and cover crops to reduce evaporative water losses, build carbon-rich soil organic matter, and improve the water-holding capacity of the soil;
- Install protective netting to reduce the heat load and sunburn risk;
- Evaporative cooling of the canopy during intense heat is effective in reducing the risk of heat stress and sunburn, but is only recommended on farms with excellent water supply, and taking care not to waste water and possibly cause tree damage from soils that are too wet;
- Apply effective approaches to tree training and canopy management to reduce the heat load on the fruit;
- Expose the fruit to additional light during the final two to three weeks before harvest (through pruning of leaves and non-fruiting shoots) to enhance red colour development, especially in later ripening cultivars where this period is already cooler and sunburn is no longer a high risk;
- Enhance red colour development by using reflective mulch under the trees;
- Do not overcrop the trees since high crop load can negatively affect red colour development and other fruit quality traits, and this can be exacerbated in areas prone to heat stress;
- Shift to night-time harvesting where feasible to avoid heat stress in pickers.