climate POMEWEST
Understanding
CLIMATE VULNERABILITY
A crucial step for pome growers in Western Australia
As climate change continues to impact agricultural practices worldwide, pome fruit growers in Western Australia face unique challenges. The Pome Strategic Plan aims to build resilience and promote environmental sustainability within the industry. Here’s a closer look at the key climate vulnerabilities and how growers can adapt to ensure a thriving future.
Words Susie Murphy White, Project Manager, Pomewest
Winter chill accumulation
APPLE and pear trees require a period of cold weather, known as winter chill accumulation, to break dormancy and resume normal growth. Breaking dormancy is a combination of two processes: winter chill followed by spring heat. Once the chill requirement has been met, internal metabolic inhibitors are no longer present and buds are ready to grow once temperatures increase. Insufficient chill accumulation can lead to sporadic bud break, poor fruit development, and reduced yields.
Recent data shows a concerning trend of reduced chill portions (CP) since 1995 looking forward to 2050 under medium global emissions scenario:
• Manjimup: Average chill portions reduced from 70–59CP.
• Donnybrook: Average chill portions reduced from 56–46CP.
• Bickley: Average chill portions reduced from 44–34CP.
Short-term management of low chill years includes the use of dormancy breakers or rest breaking agents. Rest breaking agents are designed to substitute part of the chill requirements and therefore have a greater effect in low chill years than in high chill years. Dormancy breakers may be ineffective in low chill years if too little chilling has accumulated prior to the time of application. This is because the buds are too physiologically immature to respond to the treatment.
Longer term adaptations for managing low chill will require the selection or breeding of cultivars that have good yields of high-quality fruit and are suited to the low chill environment.
Frost at flowering
Frost events during flowering can damage or kill apple flowers, leading to reduced fruit set and yield. While minimal changes have been observed in frost occurrences in Manjimup, Donnybrook, and Bickley, it remains a critical factor to monitor.
Sunburn at maturity
High temperatures during the fruit maturation period can cause sunburn damage, affecting fruit quality. The number of days with temperatures exceeding 34°C in the unnetted orchard is increasing since 1995 looking forward to 2050 under medium global emissions scenario:
• Manjimup: From 10–12 days.
• Donnybrook: From 21–25 days.
• Bickley: From 30–38 days.
Netting or protective cropping will be an essential adaptation for apple and pear production. The risk of browning will still be there when extreme heat goes over 37.9ºC in the netted orchard.
Chill calculations undertaken each year 1st March to 30th August using the chillR package of Luedeling et al. (2013) & Luedeling (2017)
Source: https://grf-smartfarm.daf.qld.gov.au/shiny/apps/chillcalculator/
High temperatures during the fruit maturation period can cause sunburn damage, affecting fruit quality.
Decreasing rainfall
Water availability is a growing concern, with decreasing rainfall patterns observed since 1995 looking forward to 2050 under medium global emissions scenario:
• Manjimup: Winter rainfall decreasing.
• Donnybrook: Spring rainfall decreasing by 18mm.
• Bickley: Winter rainfall decreasing by 78mm and spring rainfall by 50mm.
This highlights the need to improve water efficiency through changing irrigation practices, upgrading water
infrastructure or adopting new technologies.
Rising temperatures
Increases in both maximum and minimum temperatures are being recorded:
• Manjimup: Increase by 0.7–0.9°C.
• Donnybrook: Increase by 0.7–0.9°C.
• Bickley: Increase by 0.9–1°C.
The ideal temperature range during flowering in apples and pears is between 15–24°C ensuring successful pollination and optimal flower development. Outside this range can cause issues such as poor fruit set. While frost during flowering is reported to have a minimal impact temperatures above 24°C could become possible in the future and needs further investigation.
Potential evapotranspiration
While minimal changes have been noted in potential evapotranspiration, it remains an important factor for water management strategies.
Moving forward
Awareness of these climate vulnerabilities is crucial for pome growers in Western Australia. By understanding the specific impacts and adopting resilience measures, growers can mitigate risks and ensure the sustainability of their operations. The Pome Strategic Plan provides a framework to support growers in this endeavour, promoting a more resilient and environmentally sustainable future for the industry.
For more information on the predicted and past climate view the My Climate View.
What My Climate View offers horticulture growers:
1. Historical climate data (1964 to Present) Analyse past weather patterns to understand how your region’s climate has evolved and how it might affect crop yields and management practices.
2. Seasonal forecasts (1–3 months ahead) Plan your planting and irrigation schedules with up-to-date climate forecasts for the next few months, helping you manage risks like water shortages or heatwaves.
3. Future climate projections (2030s, 2050s, 2070s) Long-term climate projections allow you to adapt your farming practices for the coming decades, ensuring you stay ahead of shifts in temperature, rainfall, and extreme weather.
Key climate data available:
• Monthly rainfall: Understand seasonal rainfall trends and adjust your irrigation systems.
• Temperature extremes: Prepare for hotter days and longer growing seasons by modifying canopy structures or irrigation schedules and the use of protected cropping structures.
• Potential evapotranspiration: Monitor water demand for your crops to ensure efficient use of irrigation systems
Together, we can navigate the challenges of climate change and secure a prosperous future for pome fruit production in Western Australia.