Chemical Fruit Thinning in Apple


I just wanted to share with you some of the slides and information I presented this past Tuesday via zoom in case you haven’t had a chance to attend the meeting. You may also consider reading my previous blog post on blossom thinning ( and the factsheet on the Virginia Cooperative Extension webpage ( if you want to get a better idea about the science and application of chemical thinners, e.g. 6-BA, NAA and ethephon.

Table 1: Chemicals and plant growth regulators labeled for fruit thinning in Virginia

Notes: Exilis 9.5 SC contains 9.51% of 6-BA, compared to 1.9% in Maxcel and 2% in Exilis Plus.
There are two forms of Refine, Refine 3.5 and Refine 6.25. The later contains a higher concentration of NAA.

Table 2: Thinning chemicals and rates recommended for petal fall-5 mm fruit diameter

Notes: NAD and NAA cause pygmy fruits when applied to Red Delicious and Fuji.
Carbaryl can be applied as a carbaryl only thinning spray between petal fall and 5 mm fruit diameter, but it will be less effective as fruits are getting bigger.

Table 3: Thinning chemicals and rates recommended for 6 mm-15 mm fruit diameter

Table 4: Chemicals and rates recommended for rescue thinning applications (at 16-25 mm fruit diameter)

Sherif M. Sherif, Assistant ProfessorVirginia 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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