Abstract: Five crystal destruxins were purified from the fermentation broth of Metarhizium anisopliae var. anisopliae strain MaQ10 via preparative HPLC and re-crystalization, which were classified to destruxin A, B, C, E and A₂, respectively. Contact toxicities of destruxins A and B against the grubs Exolontha serrulata (Gyllenhall) and Holotrichia ovata Chang were bioassayed by immersing the insects in aqueous dilutions. The results indicated that at 96 and 120 h after treatment, the LC₅₀s of destruxins A and B were estimated as 78.1571 mg/L and 88.7562 mg/L towards E. serrulata and 66.5308 mg/L and 79.4309 mg/L towards H. ovata, respectively. At the concentration of 300 mg/L, the LT₅₀s of destruxins A and B were 13.4159 h and 10.5331 h towards E. serrulata, and 13.6399 h and 9.9451 h towards H. ovata, respectively.

Key words: Metarhizium anisopliae destruxins, purification, toxicity, Exolontha serrulata, Holotrichia ovata