Application Evaluation And Screening Of Beauveria Bassiana Strains For Biocontrol Of Bemisia Tabaci

Bemisia tabaci is one of the most serious pests in agriculture and forestry.As a sucking pest,it has a wide range of food and high levels of fecundity.In this article,the author screened a Beauveria bassiana strains which had high pathogenicity to B.tabaci at first and then studied a set of further research about this high pathogenic strains,such as the stability,the rejuvenation,the optimization process condition of liquid-solid biphasic fermentation,insecticidal spectrum measurement and controlling effects.The main results of this study are as follows:1.Screening a strain which had the highest pathogenicity to the B.tabaci from five strains of B.bassiana.The order of cumulative corrected mortality from high to low is Bb03>Bb781>Bb11>Bb07>Bb06.Therefore,Bb03 is the best one and its cumulative corrected mortality is 97.3%,LT₅₀ is 4.5d and LD₅₀ is 2.29×10⁵conidia/m L.2.There were three aspect in successively subculture.From the aspect of morphology,the area of aerial mycelium became more and more wide.From the aspect of spore production,the number of spore production decreased to 1.01×10⁷ conidia/cm² in the twelfth generation from 5.85×10⁷ conidia/cm²,the first generation.From the aspect of cumulative corrected mortality,the number of cumulative corrected mortality decrease to83.5%in the twelfth generation from 98%,the first generation.3.There were two different measures to rejuvenate the Bb03 strains.On the one hand, the result of different rejuvenation culture medium showed that the rejuvenation method of adding 4g insect powder of Galleria mellonella had the best effect.After rejuvenation,the spore production was increased to 1.29×10⁸ conidia/m L,the growth rate was 3.9mm/d,the cumulative corrected mortality was 93.0%and the LT₅₀was 5.6d.On the other hand,the way of increasing the time of rejuvenation did not achieve a better effect than the first generation.But it become more stable in spore production and cumulative corrected mortality with the increased times of rejuvenation.4.In the optimizing experiment of liquid fermentation,the results showed that mycelial dry weight reached a high level than the control group after adding the insect powder.The insect powder of G.mellonella had the best effect,and the mycelial dry weight reached a higher value at 68h which was 3.1 times higher than the control group.What’s more,the mycelial dry weight of added the insect powder of G.mellonella reached a higher level nearly advanced 72 hours and it was no downward trend until 167h.In the optimizing experiment of the solid fermentation conditions,the results showed that optimal combination was A₁J₃F₃I₁H₂D₂E₂B₂G₁C₃ which the spore production was 3.17×10⁸conidia/g.5.The insecticidal spectrum of Bb03 included at least five different orders consist of hemiptera,lepidoptera,acarina,homoptera and coleoptera.Bb03 had high pathogenicity to Tetranychus cinnabarinus,Jacobiasca formosana,B.tabaci,Plagiodera versicolora,Popillia mutans,Galleria mellonella and Bombyx mori,and the range of cumulative infection mortality is from 80.0%to 98.8%.General pathogenicity to Spodoptera exigua,Hyalopterus arundimis fabricius,Ectropis obliqua hypulina wehrli,Epilachna vigintioctopunctata and Plutella xylostella and the range of cumulative infection mortality is from 40.0%to 60.5%.it has no control effect on Hyphantria cunea,Spodoptera litura,Pyrausta nubilalis,Diaphania perspectalis,Pseudococcus comstocki kuwana and Frankliniella occidentalis.6.The optimal time of moisturizing when infecting the B.tabaci is 36h.The results of the infection test of Bb03 strains in a greenhouse showed that the corrected mortality of1×10⁸ conidia/m L was 73.3%and control effect was 72.7%.