Evaluation Of Chemical Pesticides Against Carya Cathayensis Root Rot Caused By Fusarium Oxysporum

Chinese hickory(Carya cathayensis),a species of the Juglandaceae family,is a precious unique nut tree in China.The C.cathayensis trees are mainly planting in Lin’an county,Zhejiang province.This plant produced the well-known nuts with high nutritional value and delicious test.The area of C.cathayensis in Lin’an county reached at 38000 ha and the nuts production reached at 15100 tons in 2019,which resulted in the economic value of 865 million RMB.However,in recent years,a root rot disease on C.cathayensis had been spreading in orchards,which caused the death of numerous plants and huge loss of nut production.This fungus Fusarium oxysporum had been reported as the pathogen of this disease.In this research,the investigation of this disease in field and application of the chemical fungicides were conducted for controlling this disease.The main obtained results are listed as following.1.The occurrence surveys of root rot disease of C.cathayensis had been carried out in three trials,including Shimashi Town,Heqiao Town and Tuankou Town,since 2017.The results showed that the average of incidence rate of this disease was 60%,which indicated that this disease is the current serious disease occurring on C.cathayensis.Moreover,the root rot disease mainly occurred in serious areas with low p H soil.2.The inhibitive rates of 4 selected chemical fungicides and 3 fungicide formulations were tested on the mycelial growth of Fusarium oxysporum on PDA plates.The selected fungicides included the 98% thiamethoxam,97% carbendazim,98% fumeidine and 97% quinoline copper.The fungicide formulations included 15% thiamethoxam SC,30% carbendazol·thiram WP and50% quinoline copper WP.The results showed that the fungicides thiamethoxam and carbendazim had the best inhibitory effects on the mycelial growth of F.oxysporum,resulting in0.09mg/L and 0.76 mg/L of the EC50,respectively.The inhibitory activities of 30%carbendazol·thiram WP and 15% Thiamethoxam SC were higher than 50% quinoline copper WP..The corresponding EC50 of both formulations were 1.02mg/L and 1.28mg/L,respectively.These results provided the candidate fungicides which could be applied to the prevention and treatment of the disease in field.3.After applied in the field,the control effects of the fungicides 30% Carbendazo· Thiram WP and 15% Thiamethoxam SC were tested.Both fungicides exhibited effective control against root rot disease of Chinese hickory in field.The relative control effect of 30% carbendazol·thiram WP and 15% Thiamethoxam SC was 90.0% and 77.77%,respectively.4.Moreover,the combination technology of fungicides and soil conditioner was tested on the control effect of root rot disease of Chinese hickory in field.The results showed that the root rot rate treated with the combination of fungicides and soil conditioners was 28.3%,lower than that of fungicide application alone.New roots germinated from the treated plants..In summary,the high incidence of Chinese hickory root rot disease indicated that this disease is epidemic and is causing huge loss currently.The fungicide 30% Carbendazo·Thiram WP showed high control efficiency against this disease in the field.The soil conditioner exhibited the synergistic effect on the disease control.The results presented in this study might contribute to the establishment of integrated management of this disease.