Apricot (Prunus armeniaca L.) trees are highly susceptible to late frost injury during blooming period. Frost is a serious problem for apricots in Northern China, and it causes considerable yield losses to growers. For many years, the extent of frost injury has been associated with the intensity and duration of low temperatures and the resistance of different cultivars to frost. However, the discovery that ice nucleation-active (INA) bacteria can severely damage plants due to inducing ice nucleation at -2--5℃, has provided a new field for further researches on the prevention of frost injury. In recent years, the relationship between INA bacteria and frost damage has been paid a great attention in apricot. Two strains of INA bacteria, isolated from apricot, were identified as Pseudomonas syringae pv.syringae Van Hall 1920 and Erwina uredovora Dye 1963. Relevant studies have showed that INA bacteria could increase supercooling points of apricot floral organs by about 2℃. The INA bacteria have become an important factor stimulating and aggravating frost damage to apricot.
In order to alleviate the frost damage to apricot by controlling INA bacteria, five out of nine bactericides，labeled as No.1, No.2, No.3, No.5, and No.7, were selected for eradicating INA bacteria and destroying ice nucleating protein by means of vali and culture on medium containing INA bacteria. The effects of selected bactericides were investigated on preventing frost damage in solar greenhouse and field. The results indicated that when frost occurred at -4℃ in solar greenhouse, both No.3 and No.7 were most effective among the five bactericides with frost-controlling efficacy being 4705%-67.74% and 49.44%-69.33%, respectively, and No.3 and No.7 increased percentage of fruit set by 1225%-14.83% and 4.69%-11.36%, respectively, as compared with control. In filed experiment, the frost-controlling efficacy of No.3 was 21.80% at -6.5℃, and it significantly increased the percentage of fruit set by 9.17%.