The study was carried out at Dien Chau district, Nghe An province from 3/2011 to 10/2011 (in Spring-Summer and Summer-Autumn crop, 2011). There are 16 species pest and 7 diseases and 15 natural enemies on the watermelon field. Among them, Spodoptera litura, Diaphania indica and Thrips palmi Kamy is one of the most serious pests. The Anthracnose, caused by the fungus Colletotrichum agenarium is one of the most serious disease of watermelon. In each watermelon season, Spodoptera litura, Diaphania indica have 2 generation. There are 3 peaks of Thrips palmi Karny on the watermelon field in each season. On the watermelon field, Spodoptera litura, Diaphania indica and Thrips palmi Karny serious damaged at flowering and fruit emerge stages. The anthracnose (Colletotrichum agenarium) disease has been damaged from flowering stage to fruit development. Some insecticides have high efficiency in controling to Spodoptera litura, Diaphania indica, Thrips palmi Karny such as Proclaim 1.9 EC, Starrimec 5 WDG, Actara 25 WG
Confidor 100SL. Fungicides such as Bavistin 50 FL, Carbedazim 50 EC and Score 25 EC have high efficiency in controling to anthracnose Col/etotrichum agenarium disease on the watermelon field.