Pathogenicity Of Beauveria Bassiana BD01 To Ips Subelongatus And Its Formulation Development

Larix principis-rupprechtii is one of the important alpine tree species in the north China.It is the main component of pure forest and artificial forest,and has important ecological and economic value.As one of the main pests of L.principis-rupprechtii,the damage to Ips subelongatus is extremely serious.In this study,by isolating Beauveria bassiana from the body of the I.subelongatus collected from the field,the pathogenicity,insecticidal spectrum,biological characteristics,fermentation conditions and other indicators of the I.subelongatus were studied.Finally,a highly efficient,non-polluting wettable powder was developed to provide biocontrol strains and technical support for the biological control of I.subelongatus.The results are as follows:1.After the isolation of pathogenic fungus,morphological identification and ITS sequence analysis on the body of I.subelongatus collected from the forest,it was determined that the fungus isolated from the bark beetle was B.bassiana.2.The dipping method was used to determine the pathogenicity of different concentrations of spore suspensionsof B.bassiana BD01 to I.subelongatus.The results showed that the B.bassiana BD01 has strong pathogenicity to I.subelongatus,7d after inoculation,the cumulative corrected mortality rates of different concentrations of spore suspensions(1×108、1×107、1×106、1×105、1×104 cells/mL)treated with I.subelongatus were 98.19%,94.28%,85.34%,82.06%,68.08%.The LT50 of I.subelongatus treated at the concentration of 1×104～1×108 cells/mL was 6.92d,5.80d,5.66d,4.57d and 3.72d.The LC50 on days 3-7 were 4.50×108 cells/mL,3.71×107 cells/mL,1.21×106 cells/mL,4,86×104 cells/mL and 2.51×103 cells/mL.The insecticidal profiles of B.bassiana BD01 were determined by impregnation methodand spray method.The concentration of spore suspension was 1 × 104,1 ×105,1 × 106,and 1×107 cells/mL.The cumulative corrected mortality of each specimen inoculated with the highest concentration of 1×107cells/mL spores for 7d was Scolytus multistriatus(adult)89.25%,Cinara pinitabulaeformis(adult)69.12%,Hyphantria cunea(larva)63.74%,Dendrolimus superans(larva)57.45%,Semanotus bifasciatus(larva)73.86%,Anoplophora glabripennis(adult)10.26%.3.The cross method was used to determine the optimal growth conditions for the hyphae of B.bassiana BD01.The results showed that the optimal medium for the growth of the hyphae of this strain was PDA medium,the optimal growth temperature was 25℃,and the optimal light conditions were dark culture.The pH is 7.The optimum conditions for germination of the spores of B.bassiana BD01 were determined by the hanging drop method.The results showed that the optimum growth temperature for spore germination of this strain was 25 ℃,the optimum growth humidity was 100%,the optimum light conditions were dark culture,and the optimum pH The value is 7.4.The single factor analysis method was used to determine the major and minor effects of different pH values,culture temperature,shaker speed,initial inoculation concentration,and medium loading on the dryness of B.bassiana liquid fermentation hyphae.The main factors influencing the speed of the shaker,the initial inoculation concentration,and the amount of medium loading,were designed using L9(34)to design a three-factor orthogonal experiment.Finally,the optimal conditions for the liquid fermentation of B.bassiana BD01 strain were the initial inoculation concentration of 107/mL,the shaker speed is 150r/min,and the liquid sample volume is 80mL.Using the controlled variable method,the optimal culture conditions for solid-state fermentation were determined by changing the KNO3 concentration,the number of culture days,and the initial inoculum.The best conditions for solid-state fermentation of B.bassiana BD01 strain were the initial inoculation volume of 20%and the number of culture days for 20 days.The KNO3 concentration is 0.4%.5.The research and development of wettable powder was carried out by collecting the spore powder of B.bassiana BD01 obtained by liquid-solid two-phase fermentation.After mixing the spore yield,germination rate,wetting time and suspension rate of the sample,the formula of the wettable powder of B.bassiana BD01 was finally obtained as 30%of spore powder,5%of BX powder,5%of dispersant MF,and 60%of diatomaceous earth.