Study On Occurrence Regularity And Chemical Control Of Tobacco Black Shank In Zunyi City

Tobacco black shank is caused by Phytophthora nicotianae.It is one of the most devastating diseases in tobacco production.It severely restricts the yield and quality of tobacco.This kind of disease occurs in the main tobacco growing areas in my country,and it causes serious economic losses every year due to the disease.At present,the most effective way to control tobacco black shank is mainly based on chemical agents,but the unreasonable use of a single chemical agent can easily lead to resistance of pathogenic bacteria,and also cause environmental pollution and other problems.Therefore,in order to more effectively prevent and control tobacco black shank,the development of new drugs or compound drugs is imminent.An in-depth analysis of the law of disease occurrence is a premise for preventing and controlling disease effectively.In Zunyi City,Guizhou Province,China,due to the complex terrain and climate,the epidemic of tobacco black shank is also complicated and variable,which increases the difficulty of prevention and control.In order to effectively prevent and control tobacco black shank in Zunyi tobacco area.This article systematically investigated the occurrence and temperature,field humidity,rainfall,and field environment of black shank disease in five tobacco-growing areas in Zunyi City,Guizhou Province,and revealed the incidence of tobacco black shank and the epidemic factors of the disease.The mycelium growth rate method was used to screen and compound drugs.The method of Sun&Johnson was used to calculate the synergistic effect of the compound.According to the results of the indoor virulence test,single and compound agents were selected for tobacco Field trials of tobacco black shank were conducted.The specific research contents are as follows:1.Survey on epidemic factors of diseases:The epidemic survey of tobacco black shank in Zunyi found that the mature period of the lower leaves is the initial stage of tobacco black shank,and the average daily temperature and night average temperature are the main factors affecting the prevalence of tobacco black shank.It is the stage of the occurrence of tobacco black shank.The relative humidity in the field is the main factor for the prevalence oftobacco black shank,which determines the speed of the spread of black shank disease;The maturity of the upper leaves is the transition period of the occurrence and stagnation of tobacco black shank.Rainfall and average night temperature are the main factors affecting the prevalence of black shank disease,which determines the sooner or later the stagnation period of black shank disease.2.Research on chemical prevention of disease.The single-dose virulence test in the laboratory shows that enoylmorpholine,sclerotin,and difenoconazole have a better inhibitory effect on hyphae,with EC50 of 0.1153,0.2912,and 0.1908ug/mL.Secondly,oxyclofenac,fludioxonil,azoxystrobin,pyraclostrobin,trifluconate,propiconazole,carbendazim,carbendazim,EC50 at 1-15ug/mL;The results of indoor combined virulence test:the synergistic effect is the most obvious when the compound of difenoconazole and sclerotin is 3:1.The synergy of enoylmorpholine and sclerotium 2:1 is the most obvious,with a synergy coefficient of 1.7025;Field drug efficacy control test results:the control effect of the compound medicine is better than the single-agent,50%enoylmorpholine wettable powder and 40%sclerotium wettable powder 2:1 mixed solution,10%difenoconazole water dispersant and 40%sclerotium net wettable powder 3:1 compounding agent had better control effects,Control effect of 72.18%and 70.67%.In summary,this study clarified the epidemic factors of disease in different parts of tobacco during maturity,and at the same time,the screening and compounding of drugs obtained a better control effect,which has important significance for the prevention and control of tobacco black shank.