Resistance detection of tobacco black shank and bacterial wilt
[Objective]Long-term and continuous application of chemical pesticides to control tobacco root and stem diseases resulted in different degrees of resistance of pathogenic bacteria.In order to clarify the level of resistance of pathogenic bacteria,the effective,low toxicity and low residue fungicides were screened for tobacco K326 black shank and bacterial wilt according to the key factors of their occurrence and prevalence,and the precision application technology was established.[Method]The pathogenic bacteria of black shank and bacterial wilt were isolated by the tissue separation method.EC50 of different fungicides against pathogenic bacteria was measured by the growth rate method,and then the resistance index was calculated.[Result]A total of 185 strains of tobacco black shank and 79 strains of tobacco bacterial wilt were isolated in Guangxi.Among them,50%dimethomorph wettable powder had the best inhibition effect on tobacco black shank,with EC50 only 1.96 μg/mL.The inhibitory effect of 66.5%propamocarb hydrochloride aqueous solution was the worst,with EC508863.03 μg/mL.The pathogen had developed high resistance to metalaxyl mancozeb,azoxystrobin,methyl,carbendazim and propamocarb hydrochloride.52%chloruria copper sulfate soluble powder had the best inhibitory effect on tobacco bacterial wilt,with EC50 reaching 97.55 μg/mL.The inhibitory effect of 20%thiodiazole-copper suspension was the worst,with EC50 reaching 198.25 μg/mL.More than 90%of the bacterial wilt were sensitive to the 6 agents and did not develop obvious resistance.[Conclusion]In Guangxi tobacco-growing area,dimethomorph and Flumorph+Fosetyl-aluminum can still be used in the production and control.For 5 other agents,all the isolates were highly resistant strains,and the resistance frequency reached 100%.These 5 agents have been ineffective in the prevention and control of tobacco black shank in Guangxi,and have no practical value.For tobacco bacterial wilt,the sensitive strains of thiasene copper,chloruria copper sulfate,mesocin,Zn thiazole,coppernonylphensulfonate and thiodiazole-copper were the dominant groups,accounting for 94.94%.Two strains showed high resistance in Jingxi and two strains showed medium resistance in Fuchuan,accounting for only 5.06%of the total number of strains.The above six agents can still be used to control tobacco bacterial wilt in the main tobacco-growing areas in Baise and Hezhou.
Guangxi tobacco-growing areatobacco black shanktobacco bacterial wiltresistance
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