7 tips for preventing sunburn in your apple crop

7 tips for preventing sunburn in your apple crop

Apple growers are acutely aware of the damage sunburn can cause on their crop. This physiological disorder caused by excessive sun and high temperatures results in severe crop loss every year. With an expected increase in frequency and severity of extreme heat events, higher rates of sunburn damage may be expected in orchards in the future.

While we can’t change the weather, taking an integrated approach that includes orchard management practices and protective strategies can help reduce the chance of sunburn damage in the orchard. Below are seven tips to prevent sunburn in your apple orchards: 

1. Design new orchard layout to maximize shade protection

The location and design of orchards has an influence on the potential to create protective shade to keep fruit temperatures below critical levels that induce sunburn. For new plantings, it’s recommended to develop a layout that maximizes shade protection from the tree’s foliage at times when afternoon temperatures are highest. Orient tree rows to avoid exposing fruit to extensive periods of direct solar radiation.

2. Protect the fruit cuticle

Once sunburn occurs in your apple crop, the damage cannot be undone. The cuticle is the fruit’s first layer of defense against environmental stressors and plays a key role in maintaining the protective barrier function on the plants surface. Growers can take a proactive approach to sunburn prevention by protecting plant cuticle with a foliar applied cuticle supplement early in the growing season.

Too much solar radiation and heat can impact apple tree health and production. By supplementing the cuticle of the fruit and leaf, you can provide sunburn protection and improve overall fruit quality. Cuticle supplements allow the plant to use excess light energy for growth, rather than damaging the photosynthetically active tissue.

3. Improve air movement through fruit blocks

Encourage air movement down rows of trees. Adequate air circulation in the orchard is important to move hot air around the fruit to remove some of the heat to equalize the temperature of fruit and air. When there is no air movement less heat is lost from fruit, increasing sunburn rate.

4. Schedule irrigations

Water stress during the summer can increase the risk of sunburn. Healthy, fully irrigated trees gain the maximum cooling benefit from transpiration. Pay close attention to weather forecasts to anticipate heat waves and make irrigation scheduling adjustments before the trees are stressed and damage is done. Plan to use irrigation just before or during heat waves to avoid tree stress and sunburn

5. Train fruit tree canopy

Apple sunburn is associated with thin, exposed canopies or with the sudden exposure to sunlight when branches move under the weight of the crop. Train young trees with less fruit developing at the ends of branches with scaffold branches that can support the fruit load to avoid branch movement. Developing good leaf cover in the canopy to shade the fruit can be effective in reducing heat-build up and sunburn in apples.

6. Avoid early summer pruning and leaf thinning

Adjust summer pruning to local conditions and combine with other cultural practices to avoid sunburn. Plan to perform summer pruning and leaf thinning on cool overcast days when cloudy weather is likely to follow to allow time for antioxidants and beneficial heat-shock proteins to accumulate prior to exposure to full sun.  Avoid limb movement and sudden exposure of fruit to direct sunlight, especially during hot weather.

7. Protect harvested fruit from direct sunlight

Even short periods of exposure to intense direct sunlight can cause significant damage to picked fruit in bins. Place recently harvested fruit in bins under cover as soon as possible in shade or out of direct sunlight.

Managing fruit quality and minimizing damage is an integrated approach. Watching the weather and tree developments while making timely management interventions and protecting the cuticle is critical to good quality fruit at packout. These preventive measures give fruit growers the orchard management tools to cope with the changing climates. Talk to your Cultiva representative today to learn more about essential strategies to maximize your marketable yield today.