Apple Carbohydrate Thinning Model-Winchester-May 20, 2020

If you plan to put any thinning treatments tomorrow or Friday, the model suggests increasing the chemical thinning rate by 30%. I would recommend postponing thinning treatments until Saturday or any day next week for three reasons: a) 6-BA and NAA treatments will be more effective as average daily temps. are predicted to be above 70 oF. b) only apple clusters from late bloom will be responsive to your thinning treatments whereas those resulted from early bloom and that represents the primary crop would be less affected by thinning next week; and c) Fruits affected by past frost events would be more likely fallen by that time, allowing you to make a better assessment of your crop load and the need for any further thinning.

Sherif M. Sherif, Assistant Professor of Horticulture, Virginia Tech, School of Plant and Environmental Sciences, AHS Jr. Agricultural Research and Extension Center, 595 Laurel Grove Road, Winchester, VA 22602 Tel. 540-232-6035 , Email:

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