Starch iodine pattern as a maturity index for Granny Smith apples

The starch pattern index was used to examine differences in the patterns of change of the index in 3 districts which export Granny Smith apples. Average gradients for each district were 0.089, 0.071, and 0.046 units/day in Auckland, Hastings, and Nelson respectively. Starch conversion had occurred in Hastings and Nelson by mid March but not until the beginning of April in Auckland. However all districts reached an index of 3 units during the latter half of April. The commercial harvest periods in each district do not conform to consistent starch pattern indices at the opening and closing of harvest. A strict relationship of physiological maturity to the starch pattern index is uncertain because the respiratory climacteric is not closely related to commercial harvest dates. The incidence of superficial scald declined during the latter half of April, and ethrel sprays advanced the starch pattern index and reduced superficial scald. Yield of exportable fruit was higher in late April compared to early April.