Study On Chemical Control Technology Of Diaporthe Citri

In order to obtain the best control agents and their proportions for Diaporthe citri,the research on the occurrence regularity,condition and control technology of Diaporthe citri was carried out in Mayang County,Shimen County and Jiangyong County,which are the main citrus producing areas in Hunan Province.The main results are as follows:(1)The regularity and condition of Diaporthe citri.The pathogen began to infect leaves in April and fruits in May.There was a peak in June-August.The damage process of the pathogen lasted until October.The occurrence degree of the disease is positively correlated with the local rainfall,and the more rainfall,the more serious the disease.Pathogens on branches and leaves are the main primary source of infection.Application of 33% glyphosate and 20% glyphosate in orange orchards aggravated the occurrence of Diaporthe citri,and application of 33% glyphosate affected the root growth of citrus fruit trees.There was no correlation between citrus varieties and age of citrus trees and occurrence of Diaporthe citri.(2)Screening of indoor medicines.The indoor toxicity of 26 fungicides to Citrus psammophthora was compared by growth rate method.Among therapeutic fungicides,250g/L pyrazole ether ester EC50 was 0.200 1 mg/L,and 80% mancozeb wettable powder was the most virulent,EC50 was 3.394 6 mg/L.The results of toxicity test and evaluation showed that the mixture of pyrazole ether ester and mancozeb had the strongest inhibitory effect on the growth of Citrus psammophthora with EC50 of 0.0842 mg/L and synergistic coefficient of 7.6295.(3)Field efficacy control.The control effect of 43% manganese zinc suspension 300 times solution + 50% pyrazole ether ester water dispersible granule 3000 times solution +Wynut 1000 solution was 98.68%,and that of 80% manganese zinc wettable powder 300 times solution + 19% acetoxy propiconazole suspension 1000 times solution + Wynut 1000 times solution was 99.21%.The two groups of fungicide formulations could be used alternately in the field.Four times of field application had the highest control effect on Diaporthe citri.The application period was 2/3 of Citrus flowering loss,the size of broad bean,the size of table tennis ball and mid-July.In addition,planting orchards in the orchards,applying organic manure and compound fertilizers,pruning in the winter or spring,spraying before spraying and adding spray assistants in the medicament will improve the control effect.