Composition for preventing plant diseases

The invention discloses a composition for preventing plant diseases. The composition comprises, by weight, allicin, sterilizing agents, bacillus subtilis fermentation liquid, trichoderma pseudokoningii fermentation liquid, water-soluble chitin, monosodium glutamate residual liquid, fulvic acid potassium, boric acid, monopotassium phosphate, kasugamycin, methionine, thiamine, momordica grosvenori, polygonatum, astragalus, goldthread, asarum, honeysuckle, rosin, hot pepper and green Chinese onion. The allicin and the sterilizing agents serve as active components and are complexly combined, obvious synergistic interaction can be obtained, sterilizing and disease prevention capacities are improved, sterilizing spectrums are widened, the production of crops is improved, harmful bacteria is killed, diseases are restrained, residues are omitted, drug resistance is not easily generated, prevention and treatment of the plant diseases are improved, disease resistance of plants is improved, roots of the plants are lengthened and increased, stems of the plants are thickened, chlorophyll is increased, seeds of food crops are increased, grains of the food crops are plumped, ears and corners of the food crops are increased, fruits of fruit trees are increased and enlarged, and good quality and high production are obtained.