Studies On Occurrence Rules And Chemical Control Of Rot Disease Of Apple Tree In Shannxi

Rot disease of apple tree is a worldwide fungal disease. It becomes very popular and serious in Shannxi province and results in a great loss in apple production. In order to control this disease effectively, we performed the studies on pathogenic types, occurrence rules and control methods of rot diseases of apple tree. Results showed as follows:1. According to isolation and identification results, we concluded the pathogen of rot disease of apple tree was Cytospora mandshurica Miura and C.carphosperma Fr. Two pathogens could result in rot disease of apple tree and the mortality is 100% by cytospora sp. inoculated , 87% by C.carphosperma Fr. inoculated and 100% by both of them.2. The occurrence rules of this disease was this disease occurred during March to October every year and its occurrence fastigium was in May and September. The influencing factors including the cultural density, apple varieties, apple age, soil types, the physiognomy of orchard and management of apple orchard could influence the occurrence and development of this disease. Especially, the cultural density, apple age and the physiognomy of orchard indirectly influenced disease occurrence and development by apple tree size.3. Through the toxicology assay, fungicide Subaoli could efficiently prevent and control the rot disease of apple and its effect was better than Fumeishen. The results show that Subaoli has apparent restraint to Valsa mali, and the effects were well to Fumeishen .The ED50 are 15.41 ppm,The toxicant effect of 12.5% Subaoli is 1.12 multiples to 40% Fumeishen.Effective middle dosage were 15.41ppm and 17.21ppm respectively. Toxic effect of 12.5% Subaoli WP was 12 times of 40% Fumeishen, which showed that Subaoli could inhibit pathogen development effectively.4. According to field assays, some new fungicides displayed certain effect on preventing and control rot disease of apple tree but Changxiaoji is the best fungicide. In addition, effect of cutting spot adding Changxiaoji was better than cutting streak and directly laying on fungicides.