Cool periods follow bloom, without any tree stress. Rain occurs before or after spray application. Endogenous ethylene production is low. Prolonged cloudy periods reduce photosynthesis before or after application of chemicals. 1 From Williams and Edgerton, 1981.
Table lists the chemicals currently labeled for use as apple thinners.
Fruit thinning chemicals for apple. Monitoring Response Careful monitoring before and during the thinning season is essential to a successful program. Before a thinning application is made the grower should be aware of the orchard conditions as well as the factors affecting chemical thinning response. Thinning results are affected by fruit set, climate, weather, tree age and vigor, and orchard management practices. A few trees in each treatment should remain unsprayed to use as a comparison against sprayed trees.