Evaluation of ACC and AVG Combination as a New Tool for Managing Pre-Harvest Fruit Drop and Improving Red Color in ‘Honeycrisp’ Apples

Abstract

Pre-harvest fruit drop (PFD) poses a major challenge in apple production, often leading to significant yield losses. This phenomenon is closely associated with the fruit’s ripening process, during which the phytohormone ethylene plays a critical role by promoting cell wall breakdown, ultimately leading to fruit detachment (Tipu and Sherif, 2024). At the same time, achieving adequate red peel coloration— primarily due to anthocyanin accumulation— is essential for marketability, especially in bi-colored cultivars like ‘Honeycrisp’. Ethylene also plays a central role in regulating this color development. This dual role creates a fundamental dilemma: while ethylene is essential for desirable coloration, it simultaneously increases the risk of fruit drop (Tipu et al., 2025). To combat PFD, growers often apply aminoethoxyvinylglycine (AVG), commercially known as “ReTain” (Valent BioSciences), which effectively reduces drop by inhibiting ethylene biosynthesis (Liu et al., 2022). However, the major drawback of using AVG is that by reducing ethylene, it also hinders the development of red color (Miah and Farcuh, 2024), resulting in fruit that may stay on the tree but fail to meet market color standards, creating a difficult trade-off between preventing yield loss and achieving desired quality. Addressing this challenge requires alternative strategies that can balance drop control with optimal coloration. This publication highlights the potential benefits of combining AVG with 1-aminocyclopropane-1-carboxylic acid (ACC), the immediate precursor of ethylene. Emerging evidence suggests that ACC may have signaling functions independent of its conversion to ethylene (Polko and Kieber, 2019). The core concept— that an AVG-ACC combination can help reduce pre-harvest fruit drop without compromising color— was detailed with physiological, biochemical, and molecular evidence in a peer-reviewed article by Tipu et al. (2025). This current report presents a grower-focused summary, distilling the key messages from that work and offering a practical solution to the ongoing challenge of balancing fruit retention and coloration.