油桐根腐病发生动态和预测研究

STUDIES ON THE EPIDEMIC AND FORECAST OF ROOT-ROT TUNG-OIL TREE

油桐根腐病是桐区历史性、毁灭性的病害,危害甚烈。病株须根和侧根皮层腐烂,生长停止,终致死亡。桐林年均病株率16.7％,年均株死亡率7.4—7.5％,3—5年将导致桐林毁败。各级病株同工酶谱较健株减少2—6条,活性减弱,反映出病株内部“生化症状”与外部衰亡程度的相关规律。桐林周年发病时期分为初期、初峰期、高峰期和末期。病情与桐区气候因素关系密切,通径植分析,其顺序地温>气温>相对湿度>降水量。经偏回归求算,建立的预测模式为: (?)=0.623+0.457x_1-0.391x_2-0.02x_3+0.005_4 X^2检验,X^2<P_(0.05),与实测值显著吻合。Ⅰ、Ⅱ、Ⅲ级病株周年峰期各为6月、7月和8月。桐株优势超过病菌时,出现2年病程型病株;反之,病株属于1年病程型。为此,改善寄主状况是控制病害的重要条件。林内中心病株呈团状分布,逐年扩展,阴坡病害高于阳坡3倍,土壤条件相对稳定,为病菌提供了适生环境而发生病害。因此,改变病菌的土壤生态适宜条件是控制病害的重要基础。

Root-rot of tung-oil tree caused by Fusarium solani f. sp aleuritidis Chen et xiao is a new root disease. The causative fungi mainly intrude into the root hairs and infect the lateral roots, thus causing root-rot and damaging the tree to death. The number of peroxidase isozymes decreased with the increase of severity of the disease, so that it can be taken as the intrinsic 'biochemical symptom' of the infected tree. Within a year, four developmental stages of the disease were observed. In order to forecast the epidemic trend of disease, a simulated model of partial ifferential regression equation has been assembled:Y=0.623+0.457x_1-0.391x_2-0.02x_3+0.005x_4A better result in application could be achieved when this model was used for forecasting.