Fungal contamination of food products is a main problem in developing countries and it leads to a decline in quality and foodstuffs quantity. Some plant or spice extract can be used as food preservatives due to their strong antimicrobial activity. Avicennia marina (Forssk.) is commonly known as gray mangrove tree classified in the plant family Avicenniaceae. The aim of this study was to determine antifungal effect of the aqueous and ethanolic extracts of Avicennia marina (different concentrations) on Alternaria citri ” in vitro”. In this study, mangrove leaves were dried under suitable condition (in shadow), and then extraction was carried out with ethanol 96 degree and water. Antifungal effect of the extracts was evaluated by two methods, “Collins method” (spreading of the extract on medium surface) and “disk agar diffusion method” at 10, 20, 30 and 40 mg/ml. Minimum Inhibitory Concentration (MIC) and Minimum Fungicidal Concentration (MFC) was determined by incorporating various concentrations of extracts in Sabouraud Dextrose Agar (SDA) in tubes against Alternaria citri. Statistical analysis was carried out by analysis of variance (ANOVA). The results showed that the ethanol extract of mangrove leaf with “Collins method” in 2000 μg/ml inhibited the growth of Alternaria citri. In “disk agar diffusion test” the mentioned extract showed inhibition effect on pathogen molds growth. The results showed that MIC of Avicenna marina leaves of the aqueous and ethanolic extracts for Alternaria citri was 64 and 16 mg/ml respectively. The aqueous and ethanolic extracts MFC of Avicenna marina leaves for Alternaria citri was 128 and 32 mg/ml respectively. Results that showed Avicenna marina extract can be used as natural antimicrobial in food products.

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