The cultivars tend to have a naturally heavy June drop. Fruit sets in clusters rather than singles. Fruit set in singles rather than in clusters. Bloom period is short and blossom-thinning sprays are used. Cultivars such as 'Golden Delicious' and heavy setting spur types are to be thinned.
High temperature is accompanied by high humidity before or after spraying.
When ideal fruit growth occurs before and after time of thinning. Blossoms and young leaves are injured by frost before or soon after spray application. Low humidity causes rapid drying of the spray and decreased absorption occurs before and after spraying. Foliage is conditioned for increased chemical absorption by prolonged cool periods. Cool periods follow bloom, without any tree stress.