PURPOSE: An acetogenin material isolated from Annona squamosa seeds and a composition containing the same are provided to prevent plant diseases without environmental pollution. CONSTITUTION: A composition for preventing plant diseases contains acetogenin compound of chemical formulas 1-5, plant extract containing the compound, or mixture thereof. The plant diseases are caused by Meoidogyne spp., Puccinia spp., Phytophthora spp., Magnaporthe spp. or Colletrichum spp. The plant extract is isolated from Annona plant. An active ingredient is squamocin, squamocin-G, squamocin-H, squamocin-L, squamocin-M, squamocin-I, squamocin-K, squamocin A, annoteomoyin A, and solamin.