| Summary: | In this study, for the environmental development, the antifungal, antibacterial, and antioxidant activities of a water extract of flowers from <i>Acacia saligna</i> (Labill.) H. L. Wendl. were evaluated. The extract concentrations were prepared by dissolving them in 10% DMSO. Wood samples of <i>Melia azedarach</i> were treated with water extract, and the antifungal activity was examined at concentrations of 0%, 1%, 2%, and 3% against three mold fungi; <i>Fusarium culmorum</i> MH352452, <i>Rhizoctonia solani</i> MH352450, and <i>Penicillium chrysogenum</i> MH352451 that cause root rot, cankers, and green fruit rot, respectively, isolated from infected <i>Citrus sinensis</i> L. Antibacterial evaluation of the extract was assayed against four phytopathogenic bacteria, including <i>Agrobacterium tumefaciens, Enterobacter cloacae, Erwinia amylovora,</i> and <i>Pectobacterium carotovorum subsp. carotovorum</i>, using the micro-dilution method to determine the minimum inhibitory concentrations (MICs). Further, the antioxidant capacity of the water extract was measured via 2,2′-diphenylpicrylhydrazyl (DPPH). Phenolic and flavonoid compounds in the water extract were analyzed using HPLC: benzoic acid, caffeine, and <i>o</i>-coumaric acid were the most abundant phenolic compounds; while the flavonoid compounds naringenin, quercetin, and kaempferol were identified compared with the standard flavonoid compounds. The antioxidant activity of the water extract in terms of IC<sub>50</sub> was considered weak (463.71 μg/mL) compared to the standard used, butylated hydroxytoluene (BHT) (6.26 μg/mL). The MIC values were 200, 300, 300, and 100 µg/mL against the growth of <i>A. tumefaciens</i>, <i>E. cloacae</i>, <i>E. amylovora</i>, and <i>P. carotovorum subsp. carotovorum</i>, respectively, which were lower than the positive control used (Tobramycin 10 μg/disc). By increasing the extract concentration, the percentage inhibition of fungal mycelial was significantly increased compared to the control treatment, especially against <i>P. chrysogenum</i>, suggesting that the use of <i>A. saligna</i> flower extract as an environmentally friendly wood bio-preservative inhibited the growth of molds that cause discoloration of wood and wood products.
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