Toxicity Of Different Beauveria Bassiaua Strains To Lema Decempunctata Gebler And Subculture Degradation Control

The two strains of Beauveria bassiaua, SJ and LYS were isolated from H. hippophaecolus larva and E. Staudinger pupa respectively. The toxocity of the two strains to L. decempunctata Gebler larvae was assessed. The way to control the subculture degradation of the stains was tested. The results as following:1. During subculture, SJ conidia production declined from F1generation2.04×1010spore/mL to F5generation0.39x1010spore/mL; Also the LYS conidia production declined from F1generation8.96x1010spore/mL to F5generation2.39×1010spore/mL; Moreover, LYS strains each sporulation conidia production was higher than same sporulation of the SJ strains.2. The LC50of SJ and LYS conidia to L. decempunctata Gebler was5.17×106spore/mL and1.45×10spore/mL respectively. The LT50of SJ and LYS conidia to L. decempunctata Gebler was4.03d and5.88d respectively. The toxicity of LYS stains to L. decempunctata Gebler was higher than SJ, the optimal isolate was LYS.3.The conidia production of LYS strains on PDA-C2, PDA-C3, PDA-C4mediums which added silkworm power rose during subcultur-ring. The highest conidia production of them was the strain on PDA-C4, the conidia production declined from F6generation1.82×1010spore/mL to F10generation3.04×1010spore/mL. The strains rejuvenated as adding silkworm power to the medium between1%-4%. While added silkworm power to the medium8%, that was training on the PDA-C5, mycelium grown vigorous, but conidia production was very few. Excess nitrogen sources would lead to mycelium growing excessive and decline the conidia production. So it supported abundant conidia production by adding4%ilkworm power into PDA.