银杏叶枯病发生规律的探讨

于1998年～2000年在桂林市雁山区、灵川县、兴安县、全州县等银杏种植区，自始见病斑起，用对角线法随机取点，每点标定4株银杏结果树，每树确定一个树枝，按病情分级标准，每月15日左右观察和统计标定树枝上不同级别的叶片数，然后算出树上标定枝叶的病情指数，分析银杏叶枯发生规律；根据银杏品种、树龄、雌雄株，以及施肥状况、坡向、叶面追肥等不同进行调查；探讨它们与叶枯病发生的关系。结果是银杏叶枯病在桂北产区，始发期在4月中下旬，较明显的2次发病高峰分别在6月15日前和8月15日前。银杏的特枯病在桂北产区，但温度和降雨量是决定叶枯病发生和消长的主要因素。培育良种壮苗、选择立地条件良好的地块建园，加强水肥管理可有效抑制病害的发生。

Investigation on Occurring Patterns of Gingko Leaf Blight

The investigation of occuring patterns of gingko leaf blight was conducted in gingko orchards of Yanshan of Guilin, Lingshun, Xin'an, Quanzhou in the north of Guangxi in 1998 to 2000.Sampling spots were randomly selected by the diagonal. Four trees were chose for each spot, and one branch of each tree was observed. The diseased leaves were classified and counted to determined the disease index of the selected branch and occurring pattern on the 15th of each month.Gingko leaf blight disease first occurs in the middle and ten days in April in the north of Guangxi. There are two highest disease incidences in one year which happen respectively before June 15th and before August 15th. Many factors influence the incidence of leaf blight disease such as characters of gingko including varieties, tree years, gender, etc., orchard location including slope direction, soil condition etc. and cultivation measures including water and fertilizer management ,pruning and clearing etc. and climatic factors including temperature, rainfall etc.. Among them temperature and rainfall are main factors affecting the leaf blight disease's happening and development. Cultivating improved varieties and fit stocks , choosing favorable orchard location and enhancing management of water and fertilizer are effective ways to control the happening of the disease. Chemicals are necessary to controll the developing of the disease.