Resistance Selection And Mechanisms In Tetranychus Cinnabarinus (Boisduval) To Cyflumetofen

The carmine spider mite, Tetranychus cinnabarinus (Boisduval)(Acarina: Tetranychidae), is one of the most important pest species responsible for significant yield losses. Due to the mites’short life cycle, a restricted area of activity with a short maturation period and a high reproductive rate and is frequently exposed to various pesticides, T. cinnabarinus have a high level of resistance compared with insects. Cyflumetofen is a novel acaricide which is highly active against phytophagous mites. It was first registered in Japan by the year of2007and quite safe to predatory phytoseiidae mites and other non-target organisms, while it was not used in China. The present study reports on selection of resistance and susceptible strains, assessment of the resistance risk, clarification of resistance mechanisms and so on, the main results are as follows:1. After several indoor selections for susceptible, the LC50of the cyflumetofen decreased from2.19mg/L to0.79mg/L. After28generations selection for indoor cyflumetofen resistant strain of T. cinnabarinus (CyR), the LC50increased from2.19mg/L to6.59mg/L, while after24generations selection for Beibei cyflumetofen resistant strain of T. cinnabarinus (BR), the LC50increased from2.27mg/L to6.77mg/L.2. The bioactivity of cyflumetofen to the different states of T. cinnabarinus was tested by the method of modified RCV. The result was that cyflumetofen showed the highest toxicity to larvas (LC50=0.046mg/L), and then were adults (LC50=0.79mg/L), but it had a lower efficiency to eggs (LC50=16.84mg/L). No cross-resistance was detected from AbR、FeR to cyflumetofen, while CyR had low cross-resistance with abamectin and fenpropathrin. Meanwhile, T. cinnabarinus showed different toxic symptom to cyflumetofen from to abamectin and fenpropathrin.3. Three synergists (PBO、DEM and DEF) had different degrees of inhibition to resistance strains, for CyR strain, the resistance ratio decreased from8.34to3.63,3.10,6.97respectively, and three mixed synergists decreased the resistance ratio to2.98; for BR strain, the resistance ratio decreased from8.57to3.70、3.45and7.02respectively, and three mixed synergists decreased the resistance ratio to3.30. Compared to the CS strain, detoxifying enzymes of CyR strain increased as follows:the specific activity of GSTs and MFO were increased2.61-,1.70-fold respectively, but specific activity of CarE changed little; detoxifying enzymes of BR strain increased as follows:the specific activity of GSTs and MFO were increased2.64-,1.74-fold respectively, while specific activity of CarE changed little too. Meanwhile, the study of esterase isozymes electrophoresis showed no difference between CyR strain、BR strain and CS strain.4. The results of realized heritability (h2) to two resistance strains was:CyR (0.055)、BR (0.074). The resistance risk of two resistance strains was assessed based on h2, to obtain10fold resistance ratio required45-20genetations for CyR strain and33-15genetations for BR strain under selective pressure of50%-90%mortality for each selective generation. The resistance monitoring of6field strains of T. cinnabarinus to cyflumetofen showed that the resistance ratio of cyflumetofen was1.56-2.11.