Apple carbohydrate thinning model this week (May 23) for Winchester

The weather network predicts a sunny and warm weather this week, and you might feel it’s the time to give thinning your best shot. So, let me remind you that thinning treatments take at least 7 days to show an effect if the weather was warm; and almost two weeks (if not more) if the weather was cold. With all the cold weather we had in the past two weeks, if you applied a thinning treatment two weeks ago, you should start seeing an effect on the tree now. However, if your last thinning treatment was a week ago, you should give it 4 more days (from today) to check your trees and see if more thinning is required.

If you will apply any thinning treatment tomorrow or Monday (May 24, 25), the carbohydrate model suggests increasing the rate of thinning materials by 30%. I, however, would recommend applying the standard rate. Temperatures are expected to be above 85 OF for several days by the end of this week, which may put the trees under stress, turning them oversensitive to thinning materials. This year, it’s normal to see on the same tree fruit that are 18-22 mm in diameter and others that range between 11-14 mm. Thinning treatments by 6-BA and NAA will only be effective on fruit that are less than 18 mm in diameter.

The carbohydrate thinning model for Gala apples in Winchester, VA. Green tip date= 3/16; Bloom date=4/20; Percent flowering spurs (51-75%).

Sherif M. Sherif, PhD
Assistant Professor
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.

Leave a Reply

Your email address will not be published. Required fields are marked *