According to the results of previous experiments, several treatments which played the most significant role on the experiments above were chosen as the treatments in this experiment. They were as follows: 1) sterile distilled water with no additives (control); 2) sterile distilled water to which 1% acetic acid had been added; 3) sterile distilled water to which 0.1% (w/v) chitosan and 1% acetic acid had been added; 4) was sterile distilled water to which 500 ml/l methyl jasmonate, 0.1% (w/v) chitosan and 1% acetic acid had been added; 5) sterile distilled water to which 500 ml/l methyl jasmonate had been added. After 20 ml of liquid of each treatment was pipetted into each wound of the tomato fruit, 10 ml of conidial suspension of A. alternata (1 107/ml) was pipetted into each wound. Then the treated tomatoes were placed in plastic boxes sealed to maintain high humidity (approximately 95%) and incubated at 20 C. The diameter of each lesion was measured and recorded every 24 h until all of the fruits in the control went decayed, and the percentage of decayed fruits in each treatment were recorded then. Each treatment was replicated three times with 20 fruits per replicate and the entire experiment was repeated twice.