Degree Days as a Method to Estimate the Optimal Harvest Date of ‘Conference’ Pears

Abstract

The European pear is a climacteric fruit species characterised by high storability. The ‘Conference’ pear can be stored in a CA (controlled atmosphere) room without major losses for half a year. However, for ‘Conference’ storage to be successful, the fruit must be harvested when fully developed before it enters the climatic maturation phase. Among the various methods used to determine the optimal harvest date, the degree-day method, which relies on the sum of active temperatures, seems to be relatively accurate and easy to apply. During 11 years of study, pears were harvested on four dates (every 4–5 days) chosen based on measurements and observations, and then, after a six-month storage period, the optimal harvest date was determined. During the growing season, the temperature was measured using an automatic weather station to calculate the sum of active temperatures from full bloom to the optimal harvest date. Measurements made after storage were analysed, and the sum of active temperatures needed for the proper development of the ‘Conference’ pear was calculated to be 2469 degree days. The calculations are very accurate because the dispersion calculated using the standard deviation was only 20°. The base temperature with the smallest error was 0 °C. This study shows that this method can be recommended as useful for determining the optimal harvest date.