杨树细菌溃疡病自然病情观察试验

Observational Experiments on Poplar Bacterial Canker Disease in Natural Condition

观察试验表明：杨树细菌溃疡病自然病情增长很快，发病率和发病指数逐年明显提高；溃疡病斑大小逐年明显向四周蔓延，病级愈高蔓延愈快；蔓延发生在每年５月～８月，６月份蔓延速度最快；各级病木内、外部症状变化明显。

The disease of poplar bacterial canker in natural condition increased rapidly, and the incidence and index on disease raised significantly year by year. The speck of canker spreaded obviously on all sides year by year. The higher the class of disease was, the faster the speck spreaded. The spreading occurred from May to Augest each year, and the fastest spreading was in June. The inside and outside symptoms of trees in all disease classes changed obviously.