The increase in winter mean monthly minima holds both positives and negatives. Less frost damage could be one outcome. However, dormancy could be disrupted, with trees beginning to flower earlier, which may even increase the risk of frost damage during the early season. Insufficient accumulated chilling would have significant impacts on pome (and some stone) fruit production in already warmer production regions. Many pests and diseases would be able to over-winter in the warmer conditions, thus changing the timing and severity of early season impacts on orchards. The following approaches to adaptation can be considered by growers:
- For current sensitive (high- to medium-chill) cultivars, seek new, cooler microsites on farms where chill unit thresholds are still met i.e. establish such cultivars in cooler drainage lines, south-facing slopes, higher altitudes, and other terrain features that are cooler; this requires a very good understanding (preferably backed up by monitoring data) of the microclimate of the land in question;
- Optimise or introduce the application of chemical rest-breaking agents, including on fruit species that are not currently sprayed;
- Gradually adopt lower chill cultivars within each fruit type to replace the higher chill ones, and gradually plant or increase the plantings of lower chill fruit species;
- In areas where frost risk is not eliminated, especially where early and late frost can still strike and phenologies are responding to warming, use early warning systems for local frost warnings and implement a frost mitigation system. Avoid planting lower chill, early flowering cultivars in such areas.
- Monitoring-based pest control measures will be the most important response to potentially increased pest risks under a future climate;
- In some areas and in some years, the deployment of traps may need to be adjusted;
- Moth control i.e. the optimal timing and frequency of insecticide applications, can be undertaken scientifically using degree-day models. When based on measured temperatures on-farm or nearby (weather stations), this will automatically adjust to a shifting climate over time.