The Study On The Control Of Henosepilachna Vigintioctomaculata Mots. By Entomogenous Fungus Metarhizium Flavoiride

A kind of fungi had been chosen which was easy to infect henosepilachna vigintioctomaculata from three entomogenous fungi: Beauveria bassiana, Metarhizium flavoiride, Paecilomyces farinosus. And its control efficiency, infectious approaches and pathogenic mechanism were also studied. The results were as follows:According to the result of choosing, a conclusion could be arrived that in the same concentration pathogenic effect of M. ahisopliae was the highest, and P. farinosus was lowest. Between l 106spore/ml and 1 108 spore/ml, the mortality was higher as concentration increased. So M. ahisopliae had a good control against H.vigintiocmaculata under the concentration of 1 108 spore/ml.According to the result of biological test methods, a reasonable conclusion could be arrived that Metarhizium flavoiride had a good control against H.vigintiocmaculata. The control effect was different under different temperature and humidity. Pathogenic effect could occur remarkably under the condition of above 25 and 95% relative humidity.A study on the effect of the same concentration against different instars indicated that the mortality increased with the decreasing instars. It was more powerful to younger larvae than elder larvae.The respiration of H.vigintiocmaculata infected by Metarhizium flavoiride had some change. After 48 hours, the metabolism of the treated larvae was interfered with and the respiratory metabolism level was decreased.The primary research about toxicological mechanism indicated that M. ahisopliae had variety effects on different enzymes. M. ahisopliae had strong effects on the activities of Protein's quantity and GSTs, yet had subtle effects on activities of ACHE and protease.The fungi infected insect body mainly through cuticle. Penetration process of M. ahisopliae include adherence, germination, appressoria and penetration. .Haphy in insect body no selection to host tissue. It grew in cutex, hemloymph lipoid and muscles, alimentary tract and malpighian tubule, etc. Pathologic change occurred on all tissue infected.