The Study Of Efficacy Of 687.5 G/L Fluopicolide·Propamocarb Hydrochloride Suspension Concentrate For Management Of Black Shank On Tobacco

Tobacco black shank,caused by oomycete pathogen Phytophthora nicotianae?syn.Phytophthora parasitica var.nicotianae?,was one of the main diseases in tobacco production.This disease occurs annually in the major tobacco production areas in China,causing serious losses in yield and affecting the quality.The application of fungicides is the primary approach in managing tobacco black shank.However,the use of a single fungicide for a long period of time might makes field isolates of Phytophthora spp.had diverse degrees in insensitivity to fungicides.Therefore,screening novel and environmental friendly fungicide is desirable for enhancing the control efficacy and flue-cured tobacco yield of tobacco black shank and reducing selection pressure for fungicide resistance development.In order to screen out potential fungicides,The inhibitory effect of six fungicides on P.nicotianae was evaluated by the method of mycelial growth rate in the laboratory toxicity test.Then the greenhouse and field trials were conducted to to evaluate the control efficacy of the combination of fluopicolide and propamocab hydrochloride?propamocarb-HCl?on tobacco black shank and its effect on tobacco plant growth in.The results are as follows:?1?The results of laboratory toxicity showed that the metalaxyl,dimethomorph,mefenoxam,fluopicolide,propamocarb-HCl alone and the combination of fluopicolide and propamocarb-HCl inhibited P.nicotianae which representative tobacco black shank strains screened in various regions with EC₅₀ value of 10.22,2.02,0.70,0.20,3.30,0.06 mg/L,respectively.The results indicated that inhibition was greatly increased when combined use two technical materials fluopicolide and propamocarb-HCl in very low concentrations,which better than others siple dosage.The results proved that the combination of fluopicolide and propamocarb propamocarb-HCl had the potential to control tobacco black shank.?2?The results of the safety tests of fungicides on three varieties of tobacco plants showed that different doses of the combination of the combination of fluopicolide and propamocarb-HCl were safe to tobacco plants.The combination of fluopicolide and propamocarb-HCl had a good effect on promoting the growth of tobacco plants.?3?In the greenhouse experiment,the combination of fluopicolide and propamocarb-HCl could significantly reduce tobacco black shank severity and exhibited remarkable control effect against the disease,and displayed the best effect on the plant growth.The combination of fluopicolide and propamocarb-HCl control efficacy of tobacco black shank was kept above70%,and the maximum control value of the combination of fluopicolide and propamocarb-HCl was 81.50%.The combination of fluopicolide and propamocarb-HCl showed protective effect on black shank better than that of dimethomorph?67.83%?.Treatment of metalaxyl could inhibit the disease to a certain extent,with control efficacy of55.75%.Furthermore,the combination of fluopicolide and propamocarb-HCl was able to improve tobacco height,stem diameter and leaf area compare with untreated control,and the combination of fluopicolide and propamocarb-HCl displayed the best effect on the plant growth.?4?Field trials conducted in Weifang and Tai'an demonstrated that all of the fungicides applications in tobacco seedlings significantly reduced the disease incidence of black shank and exhibited remarkable control efficiency.The combination of fluopicolide and propamocarb-HCl at 773.4 g a.i./ha had control effect on tobacco black shank with 93.50%.In addition,the combination of fluopicolide and propamocarb-HCl improved tobacco plant height,leaf number,stem diameter,the maximum leaf length and the maximum leaf width of the tobacco compared with the untreated controls.The combination of fluopicolide and propamocarb-HCl increased the agronomic traits of tobacco leaves.As for flue-cured tobacco production,seedlings treatments with the combination of fluopicolide and propamocarb-HCl could remarkably improve tobacco yields and quality,and the maximum yield came up to2648.7 kg/ha,far exceeding the untreated control yield?1723.3 kg/ha?by 53.70%,and increased by 18.09%over the metalaxyl yield?2243.00 kg/ha?.On the other hand,the quality of flue-cured tobacco is quite different.The proportion of superior tobacco treated with the combination of fluopicolide and propamocarb-HCl-386.7 was up to 46.29%.The upward trend with the rising concentrations of the combination of fluopicolide and propamocarb-HCl,the combination fungicide at dose of 773.4 g a.i./ha could remarkably improve the proportion of superior tobacco to a maximum of 48.29%.The values of the proportion of superior tobacco by the combination were significantly better than that of metalaxyl?25.75%?and dimethomorph?39.61%?.