Abstract:

In Heilongj iang,Jilin and Liaoning Provinces,the distributions of Ice Nucleation Active (INA)bacteria on poplar trees were universal.The bacteria produced INA under-4℃~-6℃temperature. They belonged to 3 genera and 5 species or varieties:Pantoea ananas Serrabo; Erwinia uredovora(pon et al.)Dye; Pseudomonas syringae pv.syringae Van Hall; P.Syringae pv.lachrymans(Smith & Bryan) Dye and P.Syringae pvs..In nature,freezing inj ury of poplar trees can be increased by INA bacteria. The duration produced freezing injury by INA bacteria was the early stage of poplar tree buds sprouting in spring.Most of INA bacteria strains were isolated from large lesion cankers caused by Dothiorella gregaria Sacc..Lowest of INA bacteria strains were isolated from blister lesion cankers caused by the same fungus. After inoculation of INA bacteia and freezing at -6℃temperature 6 h,the incidence infected by D. Gregaria was increased and large lesion cankers were formed.It proved that,the freezing injury and otherwounds are the major reasons to form the large lesion cankers caused by D.Gregaria.It is suggested that integrated control are necessary to the freezing inj ury caused by INA bacteria and canker caused by D. Gregaria on poplar trees.

Key words: Poplar trees, INA bacteria, Freezing injury, Fungous canker