Freeze Susceptibility to Fruit Buds of Selected Apple Cultivars in East-Central Ontario, 1986

Abstract

Freeze damage to apple fruit buds was assessed at the Smithfield Experimental Farm and in 14 commercial orchards in east-central Ontario following spring frosts in 1986, of −4.5°C at the 13 mm green stage and −4.0°C at the pink stage of bud development. Apple cultivars differed in bud hardiness during the two frosts. ‘Idared’ had the least amount of bud injury during the first frost but did not differ from ‘McIntosh’ during the second frost. ‘Delicious’ buds had more freeze injury than ‘McIntosh’ during the second frost but there was no difference in bud hardiness between the two cultivars during the first frost. Bud injury during both frosts was greater than expected based on previously reported critical temperature threshold values.