STUDIES ON THE PHYTOTOXIC ACTIVITIES OF LA-Ⅰ AND LA-Ⅱ PRODUCING BY BROWN SPOT NEEDLE BLIGHT FUNGUS (LECANOSTICTA ACICOLA) Primary Research on the Pathogenic Mechanisms of Lecanosticta acicola, the Causal Agent of Brown Spot Needle Blight States and Advances of Resistant Studies on Slash Pine to Brown Spot Needle Blight in China Separation and Purification, Structure of LA-I Toxin Produced by Brown Spot Needle Blight Fungus (Lecanosticta acicola)