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Foster, Jessica A.

Plant and Soil Science

2021

M.S.

Fermented cider production has rapidly increased in the US over the last decade with an annualized growth rate of 50% between 2009 and 2014, and revenues totaling $ 2.2 billion in 2018 (Becot et al., 2016; Miles et al., 2020). Cider producers seek juice with high sugar, high acid, and phenolics that enhance "mouth feel" to make unique, high-quality cider. Specialty cider cultivars are selected for their juice qualities, not for their yield or ease of production. Growers have found many cider cultivars are challenging to grow due to disease susceptibility, biennial bearing, premature fruit drop, and excessive vegetative growth. Cider cultivars of European origin respond poorly to traditional crop load thinning methods, leading to fluctuating crop yields from year-to-year. Controlling the year-to-year crop variation or biennial bearing of cider cultivars is important to the overall profitability of an orchard. Growers are in need of new methods and information to understand how to maintain adequate crop yields and improve return bloom. The objective of this project has been to explore the use of hedge pruning and summer applied plant growth regulators as methods to improve return bloom. Chapter 2: In this study, tall spindle trained cider apples 'Somerset Redstreak' and 'Harry Masters Jersey' and traditional dessert apples 'McIntosh' and 'Empire' trained to a tall spindle system were hedged during the summer to evaluate their response of return bloom, yield, tree growth, and juice quality. Treatments consisted of 1) normal winter dormant pruning with hand tools as a control; 2) mechanical winter dormant pruning with a hedger; 3) mechanical pruning at pink (prebloom) bud stage with a hedger, and; 4) mechanical pruning at the 12-14 leaf stage, in mid-June. 'Harry Master Jersey' exhibited a strong biennial tendency, with no return bloom in 2020. There was a noteworthy difference in canopy size for all cultivars the first season, with most hedging treatments being reduced nearly by half. Juice quality was unaffected by hedging treatment for soluble solid content, pH, titratable acidity, and total phenolics. Chapter 3: Three plant growth regulators were evaluated alone and in combination for their effects on return bloom and fruit and juice quality on hard cider trees when applied at different times throughout the growing season. Plant growth regulators evaluated included: Carbaryl 4L at 0.58 L ha-1, naphthalene acetic acid (NAA) at 210 g ha-1, and Ethephon at 0.29 L ha-1. Growth regulator treatments did not have a consistent effect across cultivars. 'Somerset Redstreak' adequately flowered and cropped in 2020 with no differences seen between treatments. 'Kingston Black' and 'Harry Masters Jersey' had little to no return bloom in 2020. In 2019, Kingston Black' treated with NAA had higher yields than those treated with ethephon. Ethephon caused increased fruit softening in both 'Kingston Black' and 'Somerset Redstreak' in 2019. Juice from 'Somerset Redstreak' treated with ethephon had higher pH at harvest. Naphthaleneacetic acid or ethephon treatments during the bloom year of a biennial bearing cycle did not promote return bloom for two out of three hard cider cultivars tested.