| 摘 要： | 正Bleeding canker (BC) of pear trees,is a devastating disease in China.The disease was originally observed in Jiangsu Province and its causal agent was identified first as Erwinia sp.in the early 1970's and latter as a novel species,Dickeya fangzhongdai.BC is epidemically emerging prevalently from April to September annually in pear-growing regions in Zhejiang,Anhui and Shandong provinces,and threatening pear industry currently in China.To better control BC disease,it is crucial to know BC symptomatology,epidemics,etiology,and diagnostics first.The special topic of the three papers have well illustrated the points mentioned above.The first article by Chen et al.(2020b) described in detail the symptomatology,etiology and epidemiology of BC disease.BC mainly damages pear trunks and branches with no obvious symptoms early and bacterial rusty oozes mixed with tree saps exuded from died tissues later.The diseased portions display small soft and sap-filled brown spots or red streaks with strong smells likely of yeast fermentation.Importantly in this paper,the causal agent is identified as
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