The full bloom dates for Pink Lady, Gala, and Honeycrisp in Winchester are 4/16, 4/18 and 4/18, respectively. In Central Virginia, bloom dates for these varieties are 7-10 days earlier. So, it’s about the time to think about chemical fruit thinning options and prepare our arsenal. The following are tables summarizing the materials, rates, and timing for chemical fruit thinning in apples. More details will be provided through our in-orchard meeting in Central Virginia and the In-Depth meeting in Winchester this week. Also, I will run the carbohydrate thinning model and provide weekly updates on model outputs and thinning recommendations based on three weather stations: Batesville-for Central Virginia; Gadino Cellar-for Rappahannock/Madison area and VT-AHS AREC for Frederick County/Shenandoah Valley.
Table 1: Common chemical thinners, tradenames, and manufacturers.
Table 2: Effective thinning sprays at petal fall to 5 mm fruit diameter.
Table 3: Effective thinning sprays at 6-15 mm fruit diameter.
Table 4: Effective thinning sprays at 16 mm-25 mm fruit diameter.
Note: Application rates are based upon a concentrate spray volume of 100 gallons per acre and product labels at the time of publication. When applying chemical thinners use the rates indicated on the labels of the products that you are using. Always follow the label when applying chemical thinners. The degree of thinning actions are listed according to the author’personal field experience. The degree of thinning action may vary from orchard to orchard and block to block.