Measuring the impact of leaf removal on spur and tree health
Author: Lee Kalcsits
Published: 2025
Summary: Leaf removal before harvest can be useful for enhancing red color for bicolor apple cultivars. Red color increases the appeal to consumers. Despite the potential benefits of leaf removal for enhancing red color, there may also be risks to fruit quality. Removing leaves increases sun exposure, which can lead to sunburn damage, reducing the percentage of marketable, non-sunburned fruit and affecting overall fruit quality. It is important to maximize fruit coloration but minimize risks to both the current and subsequent seasons' crops. In the industry, leaf removal has been used to enhance red color but has not thoroughly addressed the impact on tree health and productivity in subsequent years. Here, two experiments were conducted to research the impact of leaf removal on fruit quality. In one experiment, five different leaf removal levels were applied (0%, 25%, 50%, 75%, and 100% of the leaf canopy) 14 days before harvest (N=5) to assess their effects on fruit coloration, sunburn, return yields, and shoot vigor in ‘Honeycrisp’ and ‘WA 38’ apples. In the second experiment, red color development and sunburn was evaluated for leaf removal treatments either 7 or 14 days before harvest compared to an untreated control. As the percentage of leaf removal increased, the percentage of marketable, non-sunburned fruit decreased, indicating that sunburn increased as leaf removal increased for both cultivars but to a lower extent for ‘WA 38’. Red color coverage increased with an increase in leaf removal, with 100% removal resulting in the highest percentage of red color coverage in both ‘Honeycrisp’ and ‘WA 38’. When leaf removal severity was greater than 50%, the yields the following year were lower but shoot vigor was unaffected. Leaf removal at either 7 or 14 days before harvest improved red color compared to the control, but there were no differences between these two treatments, indicating that the window for leaf removal can be as little as 7 days before harvest. ‘WA 38’ was easier to color than ‘Honeycrisp,’ and deleafing in a poor color year was good for both cultivars but in a good color year like 2023, deleafing was only useful for hard to color cultivars like ‘Honeycrisp’
