Identification And Pathogenicitic Characrerization Of Entomopathogenic Fungi Isolated From Cephalcia Chuxiongica Xiao(hymenoptera: Pamphiliidae)

Cephalcia chuxiongica is a new defoliator pest of coniferous forest in Yunnan province. It has become one of the most dangerous for restricting the sustainable development of local forestry because of the heavy damage, fast diffusion, and difficult control. Up to date, there is no efficient way used for controlling this pset. Entomopathogenic fungus is a key factor for keeping pest natural population, and important resource used for pest biological control. Using of entomopathogenic fungi for pest control has been a dominated mean way in integrated pest management. In order to provide entomopathogenic fungi resource for controlling this pest, this study carried out the investigation of isolation, identification and screening of highly pathogenic fungi. The main achieveed results are as follows:(1) Identification of entomopathogenic fungi. The 5 entomogenous fungi isolated from naturally diseased Cephalcia chuxiongica, collected from Xundian county of Yunnan province in the Southwest of China. Named as SWYH01, SWYH02, SWYH06, SWYH07 and SWYH09. They were identified to be Beauveria brongniartii(Sacc.) Petch, Paecilomyces lilacinus(Thom) Samson, Bionectria ochroleuca(Schwein) Schroers & Samuels, Isaria farinose(Holmsk.) Fr. and Beauveria bassiana(Balsamo) Vuillemin by morphology and molecular methods.(2) Screening of highly pathogenic strains. Following Koch’s postulate validation, the pathogenic ability of the 5 strains at the level of 108 conidia/m L was measured. To observation the infection sites, the strain SWYH06 infects primarily through the spiracles, while body wall, integument fold, head or tail are the sites infected by other four strains. After 16 d, The result showed the death rate and corrected death rate of strain SWYH06 both reachs 100%, and the infected larvae rate of this strain is 91.65%. The most low pathogenic one is the strain SWYH02, of which just reached less than a half in the death rate and corrected death rate are below 50%, and its infected rate is 25%.(3) Biological characteristics of strain SWYH06. After environmental and nutritional conditions screening, PPDA was recognized as the best solid medium for mycelial growth and spore production of strain SWYH06. There is no effect of carbon source on mycelial growth. The optimum nitrogen source and mineral salt for mycelial growth are yeast extract powder and Mg SO4.The optimum carbon source, nitrogen source and mineral salt for spore production are dextrose, NH4NO3 and carbamide, Zn SO4 and Mg SO4, respectively. The optimum temperature is 25℃ for mycelial growth, spore production and spore germination.The relative humidity over 90% is satiable for spore germination. Although the effect of the amount of light was not obvious to mycelial growth and spore germination, it can promote spore production.(4) Measurement of virulence of strain SWYH06 to the larvae of C. Chuxiongica and Tenebrio molitor. Under different concentration, the death rate increases with the spore suspension concentration, indicating they are with a positive correlation. By infecting with conidial suspension of 1.5/g108conidia/m L, the death rate peak occurs respectively during 4to 6 d and 2-4 d for C. Chuxiongica and T. molitor. The death rate and infected rate of C. Chuxiongica are 98.35% and 96.65%, of which of T. molitor are 93.33% and 96.65%.(5) Biological control assessment to C. Chuxiongica in lab. Strain SWYH06 is fermented on the solid medium contained 40% cottonseed hull, 40% mill feed, 8% saw powder, 1% glucose and 1% calcium carbonate. It can grow and spores well on this culture medium. After 10 to 15 d, the hypha can grow fully of the culture bottle. At 20 d, the spores were ranged from 4.5×108/g to 6.7×108/g. Next,we infected in different spraying condition to C. Chuxiongica sprayed with strain SWYH06 by three different ways, the death rate are 74.08±7.64% and 63.33±12.58% by using the fungus powder mixed with soil and spilling the them on the surface of soil before the larvae get ting into the soil, respectively. It suggests taht strain SWYH06 has a good potential utilization for biological control of C. Chuxiongica.