Researches On The Biological Characters And The Insecticidal Efficacy Of A Strain Of Metarhizium Anisopliae

Metarhizium anisopliae (Metschn.) Sorokin, which belongs to Deuteromycetes, Moniliales, Tuberculariaceae, Metarhizium, is a species of broad-spectrum insecticidal fungi. it can parasitize more than 200 kinds of insects belonging to 8 Orders, 30 Families, as well as mites and nematodes. This paper deals with the taxonomical identification and biological characters of a strain of Metarhizium anisopliae isolated from Spodoptera exigua Hübner larvae, an important agricultural pest. And the insecticidal effectiveness on Spodoptera exigua larvae, mole crickets, and white grubs was researched. The results are as follows:1. Isolation, culture, and identification of the pathogenic fungus strainThe pathogenic fungus strain was isolated and cultivated by PDA medium. The cultural characteristics of the strain, such as colony size and color, the formation of conidiospora stack, were described. Using light microscope, the morphological characters of mycelial, mature conidiospora, and conidiophore, including the shape, size, colors etc., were observed. By means of transmission electronic microscope, the morphological ultrastructure of mature conidiospora and conidiophore were also observed. According to these characters, the insect pathogenic fungus parasitizing Spodoptera exigua larvae was identified as a strain of Metarhizium.2. Some biological characteristics of the strain of Metarhizium anisopliaeThe pH ranges suitable for the growth of the strain was wide, the optimum pHs was 5～5.5. The temperature scope suitable for the strain's growth was also wide, ranging from 20℃to 30℃, the optimum one is 25℃.3. The screen of culture media of the strain fermentCompared with the first and third one, the second prescription made from distiller's grains was more suitable for the production of the spores, giving the highest yield.4. The insecticidal efficacy of the strain of Metarhizium anisopliaeThe pathogenic microorganism had good insecticidal efficacy to Spodoptera exigua larvae in lab. The correction death rates were 72.2% and 77.8% when the solutions of spores in the ferment liquids were 106 /mL and 107 /mL. But it was not effective to kill mole crickets and grubs.