| The carmine spider mite, Tetranychus cinnabarinus (Boisduval), one of the most important pests on cotton, vegetables and other crops, is widely distributed in China. Because of its high fecundity and short generation time, the mite can form rapidly population of a certain number of stocks in a short period of time, develop resistance easily and thus it is difficult to prevent and control this mite.In the current thesis, the differences of y-aminobutyric acid (GABA) content and the activities of the enzymes about GABA synthesis and metabolic from T. cinnabarinus of SS and AbR strains were comparatively analyzed. Subsequently, the biochemistry resistance mechanism of T. cinnabarinus to abamectin and the relationship with. synthesis and metabolic about the GABA was discussed. The aim is to reveal another mechanism of the abamectin-resistant strains, prolong the service life of abamectin, and to provide a theoretical basis for the management to the abamectin-resistant strains. This main results were as follows:1. The bioassay about laboratory maintained susceptible (SS) and abamectin-selected strains (AbR) of T. cinnabarinus was conducted applying the modified residual contact vial (RCV) method. The results showed that abamectin-selected strain of T. cinnabarinus has developed a 38.9-fold resistance to the SS (34.8 times for slide dip method). No interaction resistance existed between ivermectin and abamectin. So did between abamectin and fipronil at low concentrations. However, about 2.5-fold interactive resistance appeared between fipronil and abamectin in high concentrations. The synergist of DEM, TPP, PPO can inhibit AbR strains of T. cinnabarinus about 34.2,21.7 and 21.6 times of resistance and the mixure of the compounds can inhibit AbR strains of T. cinnabarinus about 24.8-33.7 times of resistance.2. The contents of GABAfrom T. cinnabarinus of different strains and mite stages were comparatively measured by HPLC. The result showed that compared with that from SS strain, GABA content in AbR strain increased along with the growth of the age. In the period of the egg, the content in AbR strain of T. cinnabarinus was significantly lower than that in SS strain (0.56 fold, P< 0.05); No significant difference existed between two strains at the larval mite period. As fornymph and adult stages, the contents in AbR strain were significantly higher than those in SS strain (1.79 fold and 1.58 fold, respectively, P< 0.05).3. The measurement method for the activities of GAD and GABA-T has been successfully established. The result showed that the GAD activities between the SS and AbR strains expressed no significant difference forthe same stage. But the GAD activity in adult stage was about 10 times that in the immature stages. For GABA-T activity, the value of egg mitewas significantly lower in SS strain.No significant difference between two strains was recorded both for larval and nymph mite periods while the GABA-T activity of adult mites was significantly higher in SS than that in AbR strain.
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