Tuesday, May 7: Another Chance For Thinning Applications

If you are not done yet with your thinning sprays and feel that another application is needed, tomorrow, Tuesday-May 7, is another good chance for thinning. Fruit sizes for Gala, Pink Lady and Honeycrisp in Winchester are 12, 12.5 and 10.5 mm which are still within the recommended range for thinning with 6-BA/carbaryl or NAA/carbaryl mixes. Temperatures will drop to 65F this Wednesday making thinning with 6-BA and NAA a bit challenging. The addition of 1 pt/100 gal of oil (e.g. 70-sec superior, JMS Stylet oil) can help increase the response to thinning sprays. However, the addition of oil may cause russeting on some cultivars. Also, Captan should be avoided within 7 days of oil applications, as it may lead to sever russeting. As per the carbohydrate thinning model, the rates of chemical thinners should be increased by 15% for Wednesday applications to compensate for the potential increment in the tree carbohydrate level.

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About S. Sherif

Dr. Sherif M. Sherif is an Associate Professor of Horticulture at the School of Plant and Environmental Sciences at Virginia Tech, USA. He received both his bachelor's and master's degrees in horticulture from Alexandria University, Egypt, and his doctorate in plant agriculture from the University of Guelph, Canada. Dr. Sherif's broad research experience in molecular biology, plant development, and tree physiology has led him to lead several research projects focusing on the biotic and abiotic factors affecting fruit trees' production, sustainability, and competitiveness. Sherif's current research program at Virginia Tech focuses on frost mitigation strategies, precision crop load management, high-density production systems, molecular regulation of critical horticultural traits, and germplasm development.