| Bemisia tabaci(Gennadius)is an agricultural pest which has a wide host range and high fecundity,especially harmful to the greenhouse vegetable.The frequently used of chemical insecticides had resulted in increased resistance to B.tabaci and had adversely affect the safety of environment,humans and animals.So using entomogenous fungi against B.tabaci was the major emphasis of many experts and scholars.In this paper,two strains were screened from naturally diseased B.tabaci then the virulence of isolates against the nymphs of B.tabaci and impact on activity with subculturedmedia were studied to measure the potential for B.tabaci control.Furthermore,in this study,the compatibility of JMC-01 and Beauveria bassiana with 11 insecticides were tested and choosed highly insecticides mixed with JMC-01 and B.bassiana respectively to control whitfly in greenhouse.The main results were summarized as follow:1.Based on morphology and molecular methods,two strainswere identified to be Lecanicillium lecanii,named as JMC-01 and JMC-02.Compared growth of two strains in the three different media(PDA,SDAY and CAM media),the results showd the growth and sporulation of JMC-01 and JMC-02 were best in PDA medium,the best carbon source was sucrose and best nitrogen source was peptone.The sporulation,virulence and chitinaseactivity of JMC-01 and JMC-02 in the different subcultured media were measured,the results showed the three indicatorsof JMC-01 and JMC-02 in the PDA medium with cicada exuviae and the PDA medium with B.tabacic adaver powder were significantly higher than the PDA medium,the mortality of B.tabaci that infected with JMC-01 and JMC-02 could be reached 88.33%.2.The virulence of JMC-01 and JMC-02 against the nymphs of B.tabaci was measured by immersion method.The results showd all nymphs of B.tabaci could die after infection of two strains,the virulence was highest to 2nd instarlarvae and lowest to egg.The accumulative adjusted mortality of 2ndinstar larvae reached 82.22%and 81.11%after 7 days of treatment by 1 × 108 cfu/mL,respectively.The time-dose-mortality model was used to analyze the dose and time effects of JMC-01 and JMC-02 against B.tabaci that showed the best concentration was 1×108 cfu/mL and the control efficacy of two strains was better against 2nd instar larvae.3.Impact of 11 insecticides on spore germination,mycelial growth and sporulation of JMC-01 and B.bassiana were were tested to evaluate compatibility between the fungus and insecticides.The results showed neonicotinoid insecticides were lower compatibility with JMC-01 and B.bassiana,insect growth regulato and botanical insecticides showed higher compatibility with two strains and matrine was highest.The inhibition rate of spore germination,mycelial growth and sporulation were 6.43%,11.94%and 5.72%with JMC-01 in 10 fold dilution concentration,the inhibition rate of B.bassiana were 14.44%,12.63%and 10.17%,respectively.4.The joint virulence of JMC-01 and B.bassiana with matrine on the B.tabaci larvae was investigated,the results showed matrine mixed with JMC-01 and B.bassiana were obvious synergism and themixtures achieved the best efficacy when matrine mixed with strains with 4:1(v/v).The co-toxicity co-efficient(CTC)of matrine and JMC-01 was 304,that of matrine and B.bassiana was 293.Matrine with the concentration of 13.35mg/L mixed with the concentration of 1×108cfu/mL JMC-01 and B.bassiana to control B.tabaci with 4:1(v/v)that control effect of mixtures were higher than used single reagents.The highst control effect of matrine with JMC-01 was 71.11%after 7d of application and matrine with B.bassiana was 75.81%after 9d of application. |
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