Control of damping-off and root rot diseases of Acacia tree using some biological control agents and plant extracts

Abstract

The study included the isolation and diagnosis of the associated fungi to dampingoff and the root rot disease of the Acacia plants and evaluating the effectiveness of some biological agents in controlling the disease in vitro. The results of isolation and diagnosis from the infected roots of Acacia plant showed the presence of the two pathogenic fungi (Rhizoctonia solani and Fusarium solani), which appeared frequently in all samples brought from some nurseries in Babylon province. The isolates of two pathogenic fungi (R. solani and F. solani) affected the germination of Acacia seeds which led to occurring a significant excelling through raising the intensity of the infection with two pathogenic fungi (R. solani and F. solani) which amounted to 83.33 and 41.66%, respectively, compared to the control treatment, in which the intensity of the infection amounted to zero. The two fungi had also significantly reduced the dry and fresh weights of the total vegetative and root system. The results of the antagonistic potential test for the fungus (Trichoderma harzianum) showed high efficiency in inhibiting the two pathogenic fungi, which achieved an antagonistic potential on the PSA media. Azospirillum sp. bacteria showed high antagonistic potential in inhibiting the two pathogenic fungi (R. solani and F. solani) with a percentage of 64.1 and 61.1, respectively. The aqueous extract for the plants (fruits of castor, leaves, and flowers of Clerodendrum inerme, garlic oil) showed an effective effect in inhibiting the pathogenic fungi on the PSA. The extract of the castor fruit plant gave better efficiency than rest of the extracts where the percentage of inhibition to the two pathogenic fungi for the aqueous extract for the castor plant at a concentration of 15% amounted to 56.66 and 54.81%, respectively.