| ABSTRACT |
Fungicides are widely used in conventional agriculture to control plant diseases. Prolonged usage often poses health problems as the modern society is becoming more health-conscious because of their harmful residual effects. Penicillium digitatum , the causal agent of citrus green mold rot, is one of the important postharvest pathogens that cause serious losses annually. The disesase is currently managed with synthetic fungcides but there is, however a growing global interest on their replacement with other alternatives such as with enviroment-friendly biopersticides liker botanicals or biological control. Ethanol extracts (concentrations 500-5000 ppm) of neem, pong-pong, chili, lemon grass, and ginger were tested for their anti-fungal activity for citrus green mold and compared with the control fungicides (Guazatine,1000 ppm). The toxicity (IC50) of these extracts was determined by the BST test. Crude extraction from pong-pong and chili showed a complete fungal inhibition zone in PDA medium at 3000 ppm (100%) while neem, lemon grass and ginger recirded more the 70% fungus inhibition for the same consentration. In vivo, cocentration of 4000 and 5000 ppm from pong-pong, chili and neem prevented mycelium growth of Penicillium digitatum in storage for 21 days at 25oC+2. The LC50 values (Anon. 2004) of the plant extracts were: pong-pong was 5mg/ml (low); chili ¿ 20 mg/ml (low); lemon grass ¿ 473 mg/ml (safe); and ginger ¿ 495 mg/ml (safe). Ginger and lemon grass had better LC50 values when compared with LC50 value of 326 for Guazatine fungicide but showed high degree of infection (45-70% green mold) in storage. Besides having low LC50 values, chili and pong-pong showed the best results for the green mold inhibition in citrus. Hence, these extracts provide a good alternative to commercial fungcides in future plant disease management.
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