Biological Control Of Apple Brown Spot

Apple marssonina blotch is a serious leaf disease which distributes widely in China. It is the reason for premature defoliation of apple, decreases the output and quality of apple, thus resulting in huge financial losses.With a view to obtain a high efficiency and without public hazard biological control method towards apple marssonina blotch, the present study was undertaken in antagonistic bacterial strains screening, identification, colonization ability, laboratory experiments and field trials.82 bacterial strains were isolated from apple root soil and leaves, antagonistic strains BS-6 and LQ-13 were isolated from primary and further screening; The results of inhibitory effect of antagonistic bacteria against Marssonina coronaria in vitro leaves showed that the strains BS-6 and LQ-13 have excellent biocontrol potential.Based on the results of morphology, physiological and biochemical character, the strain BS-6 was possibly identified as Bacillus, the strain LQ-13 was possibly identified as pseudomonas.The strains BS-6 and LQ-13 were induced to be resistant to 200μg/mL rifampicin and used to research colonization ability on the surface of leaves. The results showed that the strains BS-6 and LQ-13 had colonized well on the surface of leaves, the strains can be detected after 15 days, it offers precondition for biocontrol.The strains BS-6 and LQ-13 can culture in one plate, didn't have antagonistic activities to each other; the laboratory experiments showed that control efficacy of the compound fermentation broth of strains BS-6 and LQ-13 reached 85.8%, it had significantly higher than the control efficacy of fermentation broth of strain BS-6 and LQ-13 respectively.Field trials showed that all of the treatments with the compound fermentation broth had meaningful control efficacy against marssonina blotch. The control efficacy of the treatment with the compound fermentation broth, BFA salt fertilizer and leaf fertilizer reached 93.51%, it had significantly higher than the control efficacy of chemical bactericide.The compound fermentation broth was beneficial to the growth of trees. The treatments with the compound fermentation broth had significantly higher than the treatment with chemical bactericide in leaves weight, commodity fruit rate, fruit coloration, etc.