Heatwaves above 95 °F are showing up more often in citrus and avocado growing areas, pushing fruit surface temperatures to the point of damage along with damage to leaves and the canopy. Sunburn is no longer a rare problem: in avocado, for example, repeated hot, clear days can quickly lead to severe sunburn on exposed fruit and major losses at grading.
So, shade nets; overhead and undercanopy microsprinklers; sunburn suppressants, such as kaolin sprays (AlSiO3), talc (Mg SiO3), calcium-based products (PurShade, Screen Duo, Reflections, Eclipse, Diffusion, etc.), biobased coatings (Raynox, Parka); cover crops; pruning regime; and even paper bag wrapped fruit, all have shown promise keeping the orchard cooler and fruit free from sunburn. The challenge is finding the right mix of treatments that protects your yield without costing too much in installation, application, labor, or water. A wonderful discussion of different methods is found at a Washington State University webpage - severe sunburn correction methods. Across a wide variety of fruit crops, a scientific review on sunburn reports in depth on methods of preventing sunburn and heat damage to fruit and orchard.
All the available technologies are capable of reducing sunburn and orchard damage, but none alone will completely eliminate it. The sun burn tolerance cultivars of fruit crop must certainly be combined with other means of strategies to minimize sun burn in fruit crops. GEM and Lamb Hass carry their fruit in the canopy interior while many other varieties have more exposed fruit. Growers should identify which areas are more susceptible to sunburn, what control strategies can be employed in each area, and which areas have the best chance of achieving good returns on the additional investment.
And new technologies to apply materials