Every thinning situation is unique. Blocks of trees are different, varieties are different and every year is different. The causes of variation in response to chemical thinners is not well understood. Some of the important factors to consider are presented in Table 1. Conditions affecting ease of fruit thinning with chemicals 1 .
Fruit spurs on the lower, shaded inside branches are low in vigor.
Moisture or nitrogen supply is inadequate. Trees are in good vigor with 12 to 18 inches of terminal growth with no mineral deficiencies. Root systems are weakened by disease or physical damage. Older trees in good vigor have a mature bearing habit. Bloom is heavy, especially after previous heavy crops.