I believe this is the ideal time to schedule your thinning applications for Gala and other cultivars with a green tip date around March 12 and a full bloom date of April 12. In some areas, Honeycrisp and Fuji reached full bloom a week after Gala. Therefore, make sure to check the Carbohydrate Thinning Model on the NEWA website (https://newa.cornell.edu/apple-carbohydrate-thinning) and input the exact dates for your cultivars. Using the weather station data from Roseland and Gala’s phenology data, I ran the model and here are the outputs: three positive indicators for good thinning conditions. First, the accumulated degree days are expected to reach the optimal range of 200-250 DD by this Sunday, April 28. Second, the 6-D weighted average of tree carbohydrate balance is showing a promising decline as we approach April 28. Third, the current weather forecast predicts next week’s temperatures will exceed 80°F, which is ideal for the effectiveness of 6-BA and NAA treatments, with partially cloudy days contributing to the carbohydrate deficiency needed for effective thinning. If this is your first thinning treatment for Gala this year, aim for Sunday, April 28 through Tuesday, April 30. However, if you have already applied a thinning treatment at petal fall, delay your next treatment until the end of next week, around May 2 and May 3, to observe the effects of the initial application.

Also, for detailed guidelines on thinning practices during petal fall and the 6-18 mm window for Gala, Honeycrisp, Fuji and other cultivars, please refer to my previous post (https://blogs.ext.vt.edu/tree-fruit-horticulture/2024/04/18/apple-fruit-thinning-general-notes-and-specific-recommendations-for-central-virginia/).