Isolation, indentification, bioassay and distribution of ice nucleation active(INA) bacteria were done on branch rot of mulberry which was severely developed after harvest of mulberry branches in autumn. Twelve isolates and two isolates out of thirty-six isolates had ice nucleation activity from -5$^{circ}C$ to -1$0^{circ}C$, and over -5$^{circ}C$, respercively. Isolates which formed ice nucleation from -5$^{circ}C$ to -1$0^{circ}C$ were not inclined to injure tomato and corn seedlings. However, Two isolates, SE9316 and SE9338 which formed ice nucleation over -5$^{circ}C$ injured mulberry, tomato and corn seedlings. SE9316 and SE9338 were identified as Pseudomonas syringae based on the morphological, cultural and biochemical characteristics. Populations of ice nucleation active bacteria, fluorecent pseudomonads, were higer in February and April, but they decreased in May. Populations decreased as they become distant from the center of the symptom. The bacterial populations of all sampling times and sites were higer than 105 cfu/g which was enough to induce frost injury.