| Tetranychus cinnabarinus(Boisduval) is a kind of polyphagous agricultural pest mites which can cause huge damage. Insecticide resistance is on the rise for frequent use of chemical pesticide in daily prevention. The biological control can effectively avoid the drawbacks of chemical control which won’t cause insecticide resistance. However, there is no study on biocontrol methods to control the resistance problem of T. cinnabarinus. Therefore, based on the previous study of our laboratory, we used the Beauveria bassiana strain Bb025 infected the susceptible and resistant strains of T. cinnabarinus, the pathogenicity of strain Bb025 on different strains of T. cinnabarinus were tested, the impact of growth and development on abamectin-resistant(AR) strains of T. cinnabarinus were assessed. Also we discussed the difference of the major detoxification enzymes between the susceptible(S) and abamectin-resistant(AR) strains of T. cinnabarinus with the infection of strain Bb025. The main results obtained are as follows: 1. The virulence of Bb025 on three different strains of T. cinnabarinusIn order to explore the virulence of strain Bb025 on susceptible(S), abamectin-resistant(AR) and fenpropathrin-resistant(FR) strains of T. cinnabarinus and figure out whether Bb025 has preventive effect on the resistant mites, we tested the toxicity effect of Bb025 on three strains of T. cinnabarinus. The female adults of three different strains of T. cinnabarinus were infection with strain Bb025(1×108, 1×107, 1×106, 1×105, 1×105 conidia/mL), we recorded the mortality after seven days. The results showed that there were significant differences in lethal effect of three strains with Bb025. Toxicities of three strains shows that the LC50 value of the S, AR and FR strains of T. cinnabarinus were 2.91×105 conidia/mL 3.03×106 conidia/mL and 8.46×107 conidia/mL. So there were less difference between S and AR in virulence and we choose those two strains of T. cinnabarinus for further research. 2. The virulence differences of Bb025 on the egg and female adult of S and ARBased on the virulence and lethal effects of three strains of T. cinnabarinus, the differences in virulence of strain Bb025 on female adults and eggs of S and AR strains of T. cinnabarinus were tested in this part. The time-dose-mortality model was used to analyze the lethal effects of strain Bb025 on two different strains. We recorded the mortality and hatching rate day by day. The results showed that: the mortality of the S strain’s female adults and eggs were all higher than the AR strain. The death peak of two strains was no difference, when the the conidia concentration was 1×108conidia/mL, the LT50 value of female adults of the S and the AR strains were 3.31 d and 4.09 d. So there is no significant difference between two strains on the time from the infection to death. 3. The effect of fecundity and developmental duration of Bb025 on ARIn our study, we evaluated the effect of fecundity and developmental duration of AR strains of T. cinnabarinus treated with strain Bb025. The result showed strain Bb025 can decrease fecundity and longevity of female adult dramatically, but had no affect hatchability and developmental duration of the AR strains. The results of life table analysis showed after treated with strain Bb025, the generation duration of the AR strains became reduce and the fecundity and survival rate decreased. The net reproductive rate of 154.7 decreased to 125.2. 4. The effect of Bb025 on the detoxification enzyme activity of S and ARThe changes of three kinds of detoxification enzyme activity was tested between the S and AR strains after treated with strain Bb025. The enzyme activity test showed that: with the infection of Bb025, different strains of T. cinnabarinus had different changes in detoxifying enzymes activities. After the AR strain infected with strain Bb025, the activity of GSTs increased quickly, the activity of MFO first increased and then decreased, and the activity of CarE decreased all the time. But after the S strain treated with strain Bb025, the activity of GSTs had no significant change, the activity of MFO decreased all the time, and the activity of CarE first increased and then decreased. |
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