The Temporal-Spatial Dynamics Of Beauveria Bassiana And Metarrhizium Sorokin In The Soil Of Baoding And The Screened Of Surporier Beauveria Bassiana Strains Against Plutella Xylostella (L.)

In this paper,resource of Beauveria bassiana and Metarrhizium Sorokin in the surroundings of Baoding is investigated from March to October.The research use method was isolated Beauveria bassiana and Metarrhizium Sorokin from soil with Tenebrio molitor larvae.389 soil species were isolated Beauveria bassiana and Metarrhizium Sorokin from 699 soil species.We obtained 389 strains Beauveria bassiana and Metarrhizium Sorokin.The isolate rate of Beauveria bassiana and Metarrhizium Sorokin from soil samples is 55.7%.The results showing that Tenebrio molitor larvae easily reared under laboratory conditions were used as bait to islate Beauveria bassiana and Metarrhizium Sorokin from soil samples.Statistical comparisions of the Beauveria bassiana and Metarrhizium Sorokin in the soil which from different vegetations of the surroundings Baoding.These strains have apparently distribution characteristics.In terms of total isolate rate of soil under different vegetation,the rank order is fruit trees＞vegetables＞corps＞trees.In terms of total isolate rate of every month,isolate rate of July is the highest,which is 72.0%.In terms of vegetation,total isolate rate of the cypresses is the highest in trees,which is 66.7%.The results showing that Beauveria bassiana and Metarrhizium Sorokin species of the surroundings Baoding is plentiful,and intenstivly distribution in different habitats.Distribution and diversity of the Beauveria bassiana and Metarrhizium Sorokin are influenced by many factors,such as climate vegetation and season.From 33 strains,8 high pathogenicity strains were screened by bioassay which objection was the larve of Plutella xylostella(L.)that a serious vegetable pest.In order to estimate the pathogenicity of insects and the potential of application,pathogenicity of 8 strains Beauveria bassiana to larve of insects were tested in laboratory.Toxity of 8 strains Beauveria bassiana to the larve of Plutella xylostella(L.)were tested in laboratory.The results show a general consistency infection mortality to Plutella xylostella(L.).But a significant difference among the 8 strains Beauveria bassiana.LC₅₀ of 8 strains was 4.75×10⁴ conidia/mL～1.33×10⁷ conidia/mL,The LC₅₀rank order of the isolates is BD-B001＞BD-B008＞BD-B007＞BD-B021＞BD-B017＞BD-B029＞BD-B010＞BD-B026.LT₅₀of 8 strains of 10⁸ conidia/mL was 1.57d～5.54d.On the whole,the LT₅₀rank order of the isolates is BD-B008＞BD-B001＞BD-B007＞BD-B021＞BD-B017＞BD-B010＞BD-B029＞BD-B026.The results showing BD-B026,BD-B010 and BD-B029 could be used for controlling Plutella xylostella(L.) in field.The pathogenicity of Beauveria bassiana were tested on difference insects.The results of pathogenicity indicated that Beauveria bassiana was effective to the insects of Coleoptera,Lepidoptera,Homoptera and Hemiptera.Among the four orders,the effect to Homoptera was the best,and the effect to the Lepidoptera was the second,following is Coleoptera and Hemiptera.The order of controlling effection is adults of Callosobruchus chinensis Linnaeus,Sitobion avenae Fabricius,Bombyx mori Linnaeus,Leucanur separate Walker,Eurydema dominulus Scopol,Eurydema dominulus Scopoli,Leis axyridis Pallas.A comprehensively comparative study of 8 Beauveria bassiana strains were conducted in terms of biological characteristics,including desication tolerant ability, ultaviolet-resistant,heat-resistant,cold hardiness and colony diameter.BD-B017, BD-B010 and BD-B029 are superior in comprehensively evaluate.The toxicities of BD-B017 to the larvae of Plutella xylostella(L.)was lowest compared with strain BD-B010 and BD-B029.Judging from their biological characteristics and toxicities to insect.Results showed that BD-B026 and BD-B010 strains are superior to others.So the two strains may serve as a potential source of biocontrol agents for Plutella xylostella (L.).