一、霜冻的危害性我区无霜期短,多数地区在135天左右,晚霜结束期多在5月中旬,果树开花期也多在5月初到5月15日前后,因此花期正遇行霜季节。实践证明,果树冻花与霜冻时低温下降的幅度有直接关系。例如,苹果开花各时期的临界温度为:花蕾-2.8～-3.9℃;花-1.6～-2.2℃,很少耐到-4℃的;幼果-1.1 First, the dangers of frost My frost-free period is short, most areas in about 135 days, the end of the night frost and more in mid-May, the flowering of fruit trees are also mostly in early May to May 15 before and after, so the flowering season is encountered frost. Practice has proved that fruit frost and frost low temperature decline is directly related to the rate. For example, the critical temperature of apple blossoming at various periods is: buds -2.8 ~ -3.9 ℃; flowers -1.6 ~ -2.2 ℃, little resistance to -4 ℃; young fruit -1.1