Biological Control Of Peach Shoot Blight

Peach shoot blight is an increasingly serious disease in southern China.In order to control the disease effectively,reduce the use of chemical pesticides,this paper studied the inhibition of Phomopsis amygdali by Bacillus licheniformis W10 and then screened the effective biopesticides and its synergistic effect with chemical fungicides as well as the control efficacy in the field.The results showed that the bacterial suspension and antifungal protein from W10 exhibited obvious inhibition on the mycelial growth,sporulation,conidial germination and germ-tube elongation of P.amygdali.The bacterial suspension of 2×109 cfu/mL and the antifungal protein with 3.064 mg/mL could completely inhibit the mycelial growth.The bacterial suspension of 5×109 cfu/mL and the antifungal protein with 7.660 mg/mL had 94.9%and 100%inhibiting rates on the sporulation,respectively.The bacterial suspension of 1×109 cfu/mL and the antifungal protein with 3.064 g/mL could completely inhibit the conidial germination and germ-tube elongation.Among them,the bacterial suspension of 5×108 cfu/mL and the antifungal protein with 1.625 mg/mL had above 80%inhibiting rate to the conidial germination and germ-tube elongation.Moreover,the bacterial suspension and antifungal protein were demonstrated to have a destructive effect on the hyphal shape and structure of the pathogen,with hyphal cell distortion,tumescence,protoplasm leakage,cell wall breakage,and hyphal rupture.Therefore,B.licheniformis W10 has a good biocontrol potential of peach shoot blight.When W10 bacterial suspension was mixed with prochloraz,carbendazim and diniconazole,respectively,the synergistic ratio(SR)values of W10 bacterial suspension and prochloraz with the mixed ratios of 1:1,1:2,were greater than 1.5,with increased toxicity effect,but the mixed ratio of 2:1 was the antagonistic effect.The W10 bacterial suspension and diniconazole with the mixed ratios of 1:1,1:2 and 2:1,also had a obvious synergistic effects.But when W10 bacterial suspension mixed with carbendazim,the mixtures showed the antagonistic or additive effect.The virulence of 10 biological fungicides against the pathogen was tested in the laboratory by the method of mycelial growth inhibition,and three biological fungicides with high virulence were selected to be used in the field control trials.Among these biological fungicides,zhongshengmycin had the strongest antibacterial ability,with EC50 value of 0.0419 ?g/mL,and shenqinmycin and tetramycin had better antimicrobial effects,with EC50 values of 0.2314 ?g/mL and 0.6554 ?g/mL,respectively.When shenqinmycin was mixed with chemical agents prochloraz,carbendazim and diniconazole respectively,in different proportion,the synergistic ratio(SR)values were all greater than 1.5,having increased toxicity effect.When mixed with the three fungicides,zhongshengmycin and tetramycin had mixed ratios,respectively,for synergistic or additive effects.Therefore,the mixtures of biopesticides and chemical fungicides can increase the virulence to the pathogen of peach shoot blight.The field trials showed that the W10 bacterial suspension had a good control effect in 2015 and 2016.The control efficacy of 108cfu/mL W10 was 38.33%.The mixture of 0.5 × 108 cfu/mL W10 and prochloraz 45%EW(4000-fold dilution),and the mixture control efficacy of synergism of 0.5 X 108cfu/mL W10 and diniconazole 50%SC all had the control efficacy of about 50%.Furthermore,the control efficacy of the mixture of zhongshengmycin 3%WP(1600-fold dilution)and prochloraz 45%EW(4000-fold dilution)was the best(50%).The control efficacy of the mixtures of shenqinmycin 3%EW(1000-fold dilution)and carbendazim 50%EW(2000-fold dilution)was 38.33%.The above results provide a basis for the effective prevention and biological control of peach shoot blight.The determination of physical and chemical properties showed that the surface tension and the contact angle of the some mixtures of biopesticides and chemical fungicides become smaller,and the foaming volumes of which were decreased,the stability of which was enhanced,compared with the single agent.These changed characteristics are good for improving the control effects of mixtures.This provides a theoretical basis for screening and field application of the mixture of biopesticides and chemical fungicides.