Abstract：【Objective】In order to screen out effective fungicide for controlling kiwifruit brown spot disease. 【Methods】The toxicity of nine primary chemical fungicides against C. cassiicola were measured by mycelial growth rate and conidial germination inhibition methods. Compound fungicides were selected according to the toxicity of different fungicides，which applied to determination of the toxicity to mycelia and field control efficacy. 【Results】The results indicate that the toxicity of tebuconazole, pyraclostrobin and difenoconazole to the mycelial growth of C. cassiicola was the highest, and their EC50 values were 10.81, 11.69 and 12.48 µg/mL, respectively. But carbendazim and pyraclostrobin have low toxicity to mycelial growth, and their EC50 values were 35.19 and 41.85 µg/mL, respectively. The toxicity of tebuconazole and trifloxystrobin to conidial germination was the highest, and their EC50 values were 8.33 and 8.50 µg/mL, respectively. The toxicity of difenoconazole, azoxystrobin and pyraclostrobin is middle, with EC50 values of 12.69, 14.60, and 15.89 µg/mL, respectively. But the toxicity of carbendazim and boscalid is lower, with EC50 values of 33.65 and 40.35 µg/mL, respectively. Based on the results of these primary chemical fugicides, as well as the field investigation on fungicides using, we selected some primary fugicides with better inhibitory effects on C. cassiicola in the laboratory, and chose the compound fungicides containing these primary fugicides as the test agents. Among the eight compound fungicides, the toxicity of fluzoxammide-pyraclostrobin to the mycelial growth of C. cassiicola was the highest. When the concentration was 1 µg/mL, fluzoxammide-pyraclostrobin had the best inhibitory effect, but only reached 63.45%, and the others were all lower than 50%. When the concentration was 10 µg/mL, the inhibitory effect of fluzoxammide-pyraclostrobin on mycelium was still the best, and the inhibitory rate can reach 88.59%. The inhibitory effects of difenoconazole-trifloxystrobin and fluriramide-trifloxystrobin were the second, with inhibition rates of 77.30% and 73.08%, respectively. The inhibitory effect of tebuconazole·trifloxystrobin was the worst, and the inhibitory rate was only 39.44%. Fluzoxammide-pyraclostrobin can completely inhibit mycelium growth when the inhibition rate of fluriramide-trifloxystrobin was 85.85%, but the inhibitory effect of tebuconazole·trifloxystrobin was the worst, and the inhibitory rate was 46.93% at the concentration of 20 µg/mL. When the concentration was 50 µg/mL, the inhibitory effect of fluriramide-trifloxystrobin and propiconazole·azoxystrobin was 96.08% and 91.46%, respectively, while fluzoxammide-pyraclostrobin can completely inhibit mycelium growth. In addition, the inhibitory effect of difenoconazole-trifloxystrobin reached 89.55%; The inhibitory effect of tebuconazole·trifloxystrobin was still the worst, and the inhibitory rate was only 51.92%. Fluriramide-trifloxystrobin can completely inhibit mycelium growth at the concentration of 100 µg/mL. And the inhibition rates of propiconazole-azoxystrobin, difenoconazole-trifloxystrobin, difenoconazole-azoxystrobin, clofiurfenazole-pyraclostrobin and tebuconazole-trifloxystrobin to the mycelial growth were 99.46%, 95.04%, 89.04%, 60.03% and 57.18%, respectively. According to the inhibition effects of 7 compound fungicides on mycelium growth of C. cassiicola and their field effects, 6 agents of fluzoxammide-pyraclostrobin, fluriramide-trifloxystrobin, difenoconazole-trifloxystrobin, difenoconazole-azoxystrobin, clofiurfenazole-pyraclostrobin and tebuconazole-trifloxystrobin were selected for field efficacycontrol tests. In the field efficacy test, after 7 days of the first application, the control effect of each compound fungicide on kiwifruit brown spot disease was different. Among them, the control effect of fluzoxammide-pyraclostrobin was up to 76.17%, and the control effects of difenoconazole-azoxystrobin, clofiurfenazole-pyraclostrobin were over 60%. But the control effects of tebuconazole-trifloxystrobin and difenoconazole-trifloxystrobin were 58.60% and 53.50%, respectively. 7 days after the third application, the control effect of fluzoxammide-pyraclostrobin was up to 85.69%, and the control effects of fluriramide-trifloxystrobin and difenoconazole-azoxystrobin were up to 83.25% and 81.33%, respectively. And the control effects of the other three compound fungicides all did not exceed 80%. Among them, the control effect of difenoconazole-trifloxystrobin was only 70.19%. According to the control effects 7 days after the first application and 7 days after the third application, fluzoxammide-pyraclostrobin had the best effect, followed by fluriramide-trifloxystrobin. According to the field efficacy test, two kinds of compouond fungicides, fluzoxammide-pyraclostrobin and fluriramide-trifloxystrobin, were promoted to used for controlling kiwifruit brown spot disease in Dujiangyan and other planting areas in Sichuan Province. From 2019 to 2021, the control effect of the two compound fungicides on kiwifruit brown spot in different planting areas could reach more than 80.00%. In 2019, the control effect of orchards in 5 planting areas, including Lushan and Dujiangyan, was 81.45%-89.25%, and the incidence rate in the treatment group was basically controlled within 50%, among which the incidence rate in Mianzhu and Lushan was only 8.86% and 12.40% respectively. In 2020, the disease control effect of orchards in Anzhou, Lushan and Dujiangyan planting areas reached 86.79%, 86.61% and 84.87%, respectively. The disease control effect of Anzhou and Dujiangyan orchards in 2021 was 81.03% and 81.16%, respectively. According to the disease index and incidence of the disease in different planting areas from 2019 to 2021, the disease has a trend of increasing year by year. But the control effect of the set of fungicides application scheme for the disease can still remain above 80.00%.【Conclusion】Fluriramide-trifloxystrobin and difenoconazole-azoxystrobin are recommended for the prevention and control of kiwifruit brown spot disease.
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