Study On Synergism Of Biocontrol Agents Combined With Chemical Fungicides On Main Oil-tea Camellia Diseases

Camellia oleifera Abel is main tree of economic in south of China.Camellia oleifera anthracnose and Agariodochium camellia are major diseases in the major producing areas.In the prevention and treatment of Camellia oleifera anthracnose and Agaricodochium camellia,chemical control with food and environment safety,the onset of biological pesticides slow and limitation of agricultural control have become problems,which handicaps the development of the Camellia oleifera Abel industry.Strain R6 was bacillus subtilis,which was obtioned from oil-tea fruits through isolation and identification,possess better control effect to Camellia oleifera anthracnose and Agaricodochium camellia.This paper mainly studies the synergy between chemical fungicides and R6 wettable powerd for Camellia oleifera anthracnose and Agaricodochium camellia.The major research contains screening of chemical fungicides which have no inhibition on antagonistic bacterium R6,optimization of antagonistic bacterium R6 fermentation process antagonistic,development of the antagonistic bacterium R6 wettable powder and the synergy between chemical fungicides and R6 wettable powerd for Camellia oleifera anthracnose and Agaricodochium camellia.The main results were as followed:(1)Screening of chemical fungicides which have no inhibition on antagonistic bacterium R6.We screened out thiophanate-methyl by testing the inhibition to pathogenic bacteria and the effect to bacterias and spores of strain R6.It have a strong control effect Camellia oleifera anthracnose and Agaricodochium camellia,the EC50 were 2.425 mg/L,0.914 mg/L respectively.Under the selected concentration,the survival of bacterias and spores to different mass concentrations of thiophanate-methyl showed no significant difference.The antibacterial rate of Camellia oleifera anthracnose and Agaricodochium camellia ncreased by 9.99%～36.26%,6.67%～13.19%respectively,when we mixed different mass concentrations of thiophanate-methyl and fermentation broth of strain R6.(2)Optimization of antagonistic bacterium R6 fermentation process antagonistic.We optimizated antagonistic bacterium R6 fermentation medium at first,with cell concentration and antibacterial rate as main measures,the optimal carbon source is glucose,the optimal nitrogen source is yeast,the optimal mineral salt is magnesium sulfate by single-factor experiment.Then the effects of the fermentation conditions were studied by response surface,the best fermentation medium:glucose 5.02g/L,yeast 15.10g/L,magnesium sulfate 6.82g/L.The cell concentration,antibacterial rate for Colletotrichum gloeosporioides and Agaricodochium camellia were increased by 19.20%,13.65%,12.31%respectively compare to that before optimization.Optimize the fermentation conditions of strain R6 based on the optimal medium,three of the most significant influence factors were screened by the method of Plackett-Burman design as initial pH,rotating speed and cultural temperature.After response surface analysis was applied to establish the regression equation model.The optimal fermentation conditions were initial pH value 8.10,30.30℃ of culture temperature,171.00r/min of rotating speed,5%of inoculation,and 24h of culture time.Under the optimum conditions,the cell concentration and bacteriostatic rate for Colletotrichum gloeosporioides and Agaricodochium camellia were increased by 9.56%,12.24%,10.50%respectively compare to that before optimization.Combining with actural production need,the fermentation process were 5.02g/L of glucose,15.10g/L of yeast,6.82g/Lof magnesium sulfate,initial pH value 8.10,30.30℃ of culture temperature,171.00r/min of rotating speed,5%of inoculation,and 24h of culture time.(3)Development of the antagonistic bacterium R6 wettable powder.We made strain R6 into WP according to the biological of strain R6 and the characters of pesticide formulations.Screened the carrier and additives of WP with biological compatibility,wetting and dispersion as main measures.We confirmed the optimum formula of antagonistic bacterium R6 wettable powder were 70%of raw powder,7%of sodium lignin sulfonate,3%of sodium dodecyl benzene sulfonic acid,2%of sodium carboxy methyl cellulose,0.1%of ascorbic acid kaolin 100%as complement.Strain R6 wettable powder stored for 120 days at room temperature 25 ℃,the antibacterial rate of two pathogens.(4)Research on the synergy between chemical fungicides and R6 wettable powerd for Camellia oleifera anthracnose and Agaricodochium camellia.In 9 different proportions,When the weight ratio of strain R6 wettable powder to thiophanate-methyl at 7:1,compound bactericide F8 produced a synergism with Colletotrichum gloeospoioides,SR was 2.055.The weight ratio of strain R6 wettable powder to thiophanate-methyl at 9:1,compound bactericide F9 produced a synergism with Agaricodochium camellia,SR was 1.567.Pot experiment and control effect test showed that the antimicrobial effect of compound bactericide F8 and F9 500 times were more than 67%to Colletotrichum gloeosporioides and Agaricodochium camellia respectively,higher than the control effect of chiorothalonil.