Screening And Efficacy Evaluating For New Fungicides Controlling Rice Sheath Blight

Rice sheath blight caused by Rhizoctonia solani is one of the major diseases of rice, also known as moire disease, its common name is flower foot stalks. The disease can occur from rice seedling stage to heading stage, and the most serious stage is during the heading stage. It can infect sheath, leaves, stems, even spread to heads, which infect the the yield and quality of rice. Agricultural cultivation and application of Jinggangmycin were the main methord to control rice sheath blight in China for 30 years, which also got a good resul. However, with the popularization and application of high-yielding rice cultivation technology, sheath blight increasing year by year, the traditional control measures and methods have been difficult to meet the requirements of people on the prevention and control of sheath blight. Many new type fungicide and their combination which prevent from rice sheath blight were selected from recent modern efficient fungicide, not only to meet the needs of society, but also came possible.In this study, we adopt mycelial growth rate to measure the inhibition to rice sheath blight of six fungicide: strobilurin(QoIs) fungicide azoxystrobin; triazole fungicides hexaconazole, difenoconazole azole and propiconazole; succinate dehydrogenase inhibitor thifluzamide, and Jinggangmycin as the control agent. The test results show that under in vitro conditions, these six fungicides can strongly suppress Rhizoctonia solani mycelial growth, with an EC50 between 0.0051～1.2803 μg/mL. Among them, hexaconazole, thifluzamide and azoxystrobin have a higher virulence (EC50),azole difenoconazole is relatively poor, the next is propiconazole, the worst is Jinggangmycin. In fungicide composition, Jinggangmycin with propiconazole, difenoconazole with propiconazole, thifluzamide with azoxystrobin in different complex ratio, EC50 was 0.0459-0.2300 μg/mL,0.0748-0.1601 μg/mL,0.0235-0.0299 μg/mL respectively, and the SR values exhibited additive or synergistic effect, which can effectively reduce the amount of a single dose.We carried out the field measurement and yield-increasing test to 9 fungicide mentioned above with pesticides field efficacy trials prescribed method, and Jinggangmycin as a control agent, the results indicated that thifluzamide is the best, the control efficience after 22d was 91.20%, the next was thifluzamide-with azoxystrobin whose efficience was 90.23%; azoxystrobin, difenoconazole withpropiconazole, Jinggangmycin with propiconazole, propiconazole, hexaconazole were 88.23%, 75.78%,71.22%,67.54%,65.22% respectively, the worst is 49.59%.Single-agent thifluzamide, azoxystrobin and complex formulations thifluzamide-with azoxystrobin, azolewith propiconazole can significantly increased the yield, the output increased were 18.30%,15.05% and 16.20%,15.21%. Stimulation effect of hexaconazole and propiconazole was not significant, Jinggangmycin and Jinggangmycin-with propiconazole was the worst. The results also show that thifluzamide, azoxystrobin, thifluzamide with azoxystrobin and difenoconazole with-propiconazole have long-lasting effects to control rice sheath blight, and their function of treatment effect, insurance and increase productivity were significant effect. So we slected them as targets to carry out field efficacy of demonstration experiment. The results shows that the drug screening within the recommended dosage has no damage, is safe to rice and non-target organisms, they are environment friendly.In view of the characteristics of rice sheath blight development in this region and various factors, the proposed application dose of thifluzamide with-azoxystrobin is 300 g/L in the rice field, SC dose is 150 mL/hm2.Uusing secondary dilution method to spray at the late of tillering and heading stage is an effective methord to control rice sheath blight in horizontal and vertical expansion of the two peak periods, and there is a significant increase on rice production.This is the ideal chemical to control rice sheath blight. In addition, attention should be paid to the alternate use of different types of drugs, to suppress the generation of rice sheath blight.