2004 Risk of Low-Temperature Disorders in Apples

CIPRA is a computer-based program used to predict disease and pests of several horticultural crops, based on weather data (Bourgeois et al., AAFC, Québec). More recently, CIPRA has been expanded to predict the risk susceptibility of apples to certain storage disorders (Bourgeois, DeEll, and Plouffe). These models not only consider the weather data, but also fruit maturity at harvest. CIPRA is presently being used commercially in Quebec, while it is currently being evaluated and adapted for Ontario (Bourgeois, DeEll, and Nichols).

Low-temperature disorders develop in storage following cool and wet conditions during the months of July and August. As CA storage temperatures drop below the critical level of 3^oC, the incidence and severity of these disorders increase. A risk model has been developed based on weather data observed during those months. The figure below shows the results from 1985 to 2004 using weather data from Simcoe and Delhi in Ontario.

In July 2004, degree-days and days with rainfall were close to normal. However, in August, degree-days were lower than normal and days with rainfall were higher than normal, which contributed to increase risks of low-temperature disorders in storage. According to results from the risk model, the 2004 season ranks 5^th in the last 20 years for the Simcoe area. The 1992 season had the highest risk, followed by 1985, 1997 and 2000.