Heat protection is not a one-size-fits-all decision. Two orchards in the same valley can experience very different heat loads, depending on slope, canopy density, irrigation method and market requirements. Before investing in nets, reflective coatings or cooling systems, it pays to understand how much orchard cooling your crop actually requires, and where your current setup might already be doing part of the job.
Why fruit temperature matters more than air temperature
When air temperatures pass 35 °C, fruit surfaces can climb 10–15 °C higher in full sun. At a fruit temperature of 40–45 °C, cell membranes start breaking down, which triggers mild to moderate sunburn browning. Above 50 °C, tissue collapse becomes irreversible, a point reached in minutes under clear midday sun.
Washington State University research shows that every 1–2 °C of surface cooling can lower sunburn losses considerably across crops. The goal is therefore not cooling for comfort. It is to keep surface temperatures below the critical 40 °C threshold during extreme heat events. Here is where to start.
Step 1: Map your orchard’s heat load
Start by identifying where heat builds fastest:
- West-facing rows and upper slopes receive the harshest afternoon radiation.
- Blocks with light, sandy soil heat up quicker and reflect less moisture.
- Sparse canopies after pruning expose fruit directly to sunlight.
- Rows next to reflective water surfaces, such as ponds or canals, can experience mirrored heat intensity.
A thermal or infrared thermometer lets you measure fruit and leaf surface temperatures during peak heat. If your readings routinely exceed 40 °C on clear days, your cooling deficit is around 4–6 °C. Most reflective coatings or nets can cover a gap of this size when correctly timed.
Step 2: Estimate your protection gap
Studies in California and Spain show that:
- Shade nets lower canopy temperature by 5–10 °C, depending on colour and mesh density. Black nets absorb more heat but soften light, while white nets reflect more.
- Reflective mineral sprays typically reduce fruit temperature by 3–6 °C, depending on coverage and evaporation rate.
- Evaporative cooling systems can deliver the strongest temperature reduction, typically lowering fruit surface temperatures by 8–12 °C. However, they need a reliable water supply and responsive infrastructure to work well. In regions facing water scarcity or drought, these systems are often not feasible or widely adopted.
Compare these ranges with your measured gap. This shows whether you need structural or seasonal protection, or only a temporary spray programme during critical weeks.
Step 3: Ask the right questions before you choose
What is the average UV index in your orchard region?
Heat alone does not cause sunburn. Excessive UV radiation increases stress on fruit and speeds up skin damage, especially when it combines with high surface temperatures. The UV Index (UVI) measures how intense UV radiation is. Values above 6 are already high, and values above 11 are considered extreme, where direct exposure can rapidly increase crop stress.
Regions such as Chile, Australia, New Zealand, Bolivia and Peru regularly experience very high UV levels. If your orchard operates under high UV and heat conditions, fruit surfaces will reach risky temperature thresholds faster and more often. That makes it essential to evaluate protection strategies carefully. Before investing in any system, ask practical questions that directly affect your packout and margin.
What fruit surface temperature is risky for your crop?
For many crops, fruit temperatures above 40 °C increase risk. On clear days at 32–35 °C, exposed fruit can run 10–18 °C hotter than the air. Your protection strategy should consistently keep fruit below risky levels, even during multi-day heatwaves. Also consider UV sensitivity. Some varieties are more prone to photo-oxidative sunburn, especially when fruit suddenly shifts from shade to direct sunlight after pruning or leaf drop.
How consistent is the cooling effect?
Ask suppliers for leaf and fruit temperature data from multiple seasons, not just a single trial. Look for temperature curves that show stable cooling across different humidity levels, canopy densities and repeated heat events. Consistency across seasons is what protects your margin.
How does it affect daily operations and long-term cost?
Shade nets may complicate spraying or mechanical pruning. Reflective coatings may influence packhouse washing. Make sure the solution fits your existing workflow and does not create hidden labour or efficiency costs.
Calculate the real seasonal cost per hectare, including labour, water and application. For example, a reflective coating that costs $300–400 per hectare but saves 5 tonnes of premium fruit can outperform a net that costs $10,000 per hectare, especially if you lease land or rotate varieties. Evaluate the return over at least three seasons, not just one.
Does it align with your export requirements?
Confirm compliance and sustainability standards before you commit. Export markets increasingly emphasise environmentally responsible inputs and clear regulatory classifications. New-generation biobased reflective coatings offer a biodegradable alternative that reduces heat stress and aligns with evolving sustainability requirements. Choosing a compliant solution today helps secure long-term market access and reduces the risk of future regulatory limits.
Step 4: Control the timing, not just the tools
Protection succeeds because of timing, not quantity. Research from CSIRO Australia found that applying reflective sprays 2–4 days ahead of forecast heatwaves prevents surface heat build-up, whereas spraying after symptoms appear has little value. In the same way, partial net closure or irrigation bursts scheduled by canopy temperature sensors make the system far more efficient.
The bottom line
You do not need to chase every degree of cooling. You need enough reduction to keep fruit below critical damage thresholds during peak heat. Start by identifying your temperature gap. How far do exposed fruit surface temperatures rise above safe levels in your orchard? From there, choose tools based on both performance and practicality.
For many export-focused orchards, combining targeted reflective coatings with strategic netting offers a balanced approach. It delivers cooling where it matters most, while keeping flexibility, cost control and long-term sustainability, rather than relying on a single method.
The key is to plan ahead of the season. Once visible sunburn appears, the margin is already lost. Protection works when it keeps fruit below risk thresholds before damage begins.
