Retraction of netting near harvest: risks vs. rewards
Author: Lee Kalcsits
Published: 2024
Summary: Protective netting and evaporative cooling are commonly used in apple (Malus domestica Borkh.) orchards to protect apple fruit from sunburn in semi-arid environments like Central Washington. Sunburn is a physiological disorder caused by the combination of solar radiation and heat, which causes up to 10% or $100 million in yearly crop damages in Washington state. While protective netting and evaporative cooling can be effective for preventing apple sunburn, netting can also introduce new risks, especially the limitation of red color development on the apple peel. This study evaluated whether the retraction of netting before harvest improves red color development and/or changes sunburn risk compared to leaving netting in place until harvest. The first experiment compared six different treatments of ‘Honeycrisp’ apples in a research orchard consisting of combinations of netting either retracted ten days before harvest or not retracted and the presence or absence of evaporative cooling. The second experiment was performed on 'Honeycrisp' apples in a commercial orchard in Quincy, WA. Netting that had been in place during the growing season was removed fourteen days before harvest, seven days before harvest, or not at all. Fruit from both experiments were harvested and evaluated for sunburn incidence and external quality characteristics. Over the two years of experiments, netting reduced the levels of severe sunburn compared to the un-netted control. Meanwhile, the retraction of netting even up to 14 days before harvest did not increase sunburn risk in a younger orchard but in an older orchard with less vigor, sunburn was slightly greater when netting was retracted. Additionally, the retraction of netting before harvest increased the proportion of fruit with good and excellent red color. Overall, the use of retractable netting provided sunburn protection during the summer while avoiding red color penalties that come from netting deployed through harvest. Key words: Netting, sunburn, red color, retraction
