Influence of CPPU on Fruit Quality and Storage Potential of 'McIntosh' Apples

N-(2-chloro-4-pyridyl)-Ni-phenylurea (CPPU) was applied to mature McIntosh apple trees at 0, 7.5, or 15 mg 1−1 at either late bloom or 19 days later when fruit size was 8 to 9 mm. It caused a small amount of thinning at both times of application but it did not influence return bloom. CPPU increased fruit weight by more than 25%. Flesh firmness at harvest was increased only when it was applied at the 8 to 9 mm fruit size stage, but this firmness increase was not sustained following regular air storage for 20 weeks. The fruit length-to-diameter ratio (L/D) ratio was increased when CPPU was applied during bloom, but it was decreased when applied later. Seed number was reduced and the reduction was more severe when CPPU was applied at the later timing. All treatments increased the number of irregularly shaped fruit. CPPU increased the number of fruit developing senescent breakdown following 20 weeks of air storage. Stored fruit that received an early application of CPPU developed less superficial scald than untreated fruit, whereas fruit that was treated 19 days later developed more scald.