Effects of Spring Frosts on Four Apple Cultivars

Abstract

The effects of two successive frosts on pistil mortality and on young apples were studied on the cultivars ‘Lobo,’ ‘Melba,’ ‘Cortland’ and ‘McIntosh’ in two apple orchards located at high and low elevation sites at Frelighsburg, Que. The first frost occurred at bloom stage on May 2, 3 and 4th and the second frost was experienced on June 3rd, 1986. The low elevation orchard was colder and its trees were more seriously affected by the frosts than the trees of the high elevation orchard. ‘Cortland’ flowers exhibited a certain degree of cold tolerance but the young apples were very sensitive to low temperatures. The last frost killed drastically more young fruit of ‘Melba’ in the low elevation orchard. After ‘Melba,’ ‘Lobo’ had the highest number of fruit survival after the second frost. It is suggested that its higher fruit set may be attributable to its extreme cold hardiness. In both orchards, the reduction in the number of viable fruit of ‘McIntosh’ and ‘Cortland’ was pronounced after the second frost. During bloom and early fruit formation, no difference in cold resistance could be observed among the cultivars.