Pathogen Identification And Screening Of Control Pesticides For Scab Of Zanthoxylum Bungeanum

Zanthoxyhum bungeanum is an important economic tree in our country.Z.bungeanum industry has become the pillar industry of rural economic revitalization.With the growing of Z.bungeanum planting area,Z.bungeanum disease is becoming more and more serious,which hindered the development of Chinese Z.bungeanum industry.Z.bungeanum scab is a new disease found in the early investigation of Z.bungeanum disease in Shaanxi.In order to effectively control the occurrence and spread of Z.bungeanum scab,this study investigated the regularity of field occurrence of Z.bungeanum scab,identified the pathogen causing Z.bungeanum scab,and studied the biological characteristics of Z.bungeanum scab,studied the biological characteristics of Z.bungeanum scab,measured the indoor virulence activities of different fungicides against Z.bungeanum scab,and carried out field control experiments of three fungicides against Z.bungeanum scab.The following research results were obtained:（1）When prickly Z.bungeanum scab occured,there were grayish white striped pebbly spots on the surface of the leaves.The spots were convex on the periphery,sunken or split in the middle,and the leaves margin were curled.At the later stage,there were yellow brown raised patches on the back of the leaves.Fengxian Dahongpao was more susceptible to disease than Hancheng Dahongpao.The disease began to occur in mid to late July when there was a small temperature drop,continuous rainfall and high humidity,and the disease was common from August to September.（2）Six fungi strains were isolated from the disease samples by pathogenic agents,and the results of pathogenicity verification showed that strain Zb-SD1 was pathogenic.The Conidia peduncle of strain Zb-SD1 were erect or curved,with compartments.Its conidial were in the shape of inverted stick or nearly oval,with diaphragm,part of the longitudinal（oblique）diaphragm.Alternaria alternata was identified by morphological identification and molecular identification based on ITS,RPBR2 and TEF-1αsequences.（3）The optimal medium for the growth of pathogen of Z.bungeanum scab was oatmeal agar medium and carrot ager medium,the optimal temperature was 25℃,the optimal p H was8.0～9.0,the optimal condition the optimum condition was 24 hours continuous light,and the optimal carbon source and nitrogen source were maltose and yeast powder,respectively.The optimum medium for sporulation of Z.bungeanum scab was potato ager medium,the optimum temperature was 30℃,the optimal p H was 9.0,the optimal condition was 24 hours continuous darkness,and the optimal carbon source and nitrogen source were starch and yeast powder,respectively.（4）The inhibition effect of 16 fungicides on the colony growth of Z.bungeanum scab showed that 96%Fluopyramide had the best inhibition effect(EC₅₀ was 0.0061 mg/L).97%Prochloraz,96%Difenoconazole and 95.4%Hexaconazole followed(EC₅₀ was 0.0155 mg/L,0.0273 mg/L and 0.0374 mg/L,respectively),and 10%Matrine had weakest effect(EC₅₀ was1 603.7760 mg/L).The top 8 fungicides with good effect were selected to further test their inhibitory effects on spore germination of Z.bungeanum scab.The results showed that,99%Pyraclostrobine ether ester had the best inhibition effect(EC₅₀ was 0.3966 mg/L).The effect of 97%Chlorothalonil and 98%Boscalid followed(EC₅₀ was 0.4662 mg/L and 5.8649 mg/L,respectively),and 95.4%Hexaconazole had weakest effect(EC₅₀ was 102.8463 mg/L).（5）The spray method was used to control Z.bungeanum scab in the field.The results of the field prevention tests of three commercial pesticides showed that 75%Chlorothalonil（WP）had the best effect,and the prevention effect of 28 days after the third spray was 87.92%,followed by 45%Prochloraz（EW）（76.88%）and 30%Hexaconazole（SC）（49.95%）.The results of the field treatment trial showed that 45%Prochloraz（EW）had the best effect,and the effect of 7 days after the third spray was 59.46%,followed by 75%Chlorothalonil（WP）（41.63%）and 30%Hexaconazole（SC）（37.03%）.In conclusion,Chlorothalonil could be used as a preventive pesticide in field,and Prochloraz could be used as a preventive and therapeutic pesticide in field control of Z.bungeanum scab.This study clarified the regularity of field occurrence of Z.bungeanum scab,the pathogen of Z.bungeanum scab was identified for the first time as A.alternata,clarified the biological characteristics of Z.bungeanum scab,screened out the pesticides to prevent and control the Z.bungeanum scab,and provided a theoretical basis for the scientific prevention and control of Z.bungeanum scab.