| Thrips hawaiiensis (Morgan) is one of the most common flower-inhabiting pests of banana crops. Currently, managing damage of T. hawaiiensis mainly relies on chemical control. In order to more scientific and suitable controlling such pest by insecticides, and to confirm the field resistance level and mechanism of insecticides resistance on T. hawaiiensis, investigation of effect of three bioassay methods on insecticide toxicity and toxicities of twelve insecticides to against larvae and adult of T. hawaiiensis, insecticide resistance mornitoring of regional T. hawaiiensis field populations, preliminary conduction of biochemical mechanism of resistance to major insecticides on T. hawaiiensis were measured on the basis of establishment of superior rearing method for expanding laboratory population in present paper. The results were as follows:1. Establishment of rearing method of T. hawaiiensis in laboratory.The shortest developmental period, the highest survival rate, longevity, fecundity, and the fastest speed of population growth were observed on the food of banana flower plus honey solution plus tea pollen. Life table parameters showed that R0=104.3853, Rm=0.1845, λ=4.2026, T=25.1977d, t=3.7576d when T. hawaiiensis were reared on above food. Thus, banana flower plus honey solution plus tea pollen being the optimal food can be used for rearing T. hawaiiensis to expand laboratory population.2. Effect of three bioassay methods on insecticide toxicityThe results revealed that centrifuge tube residual bioassay, leaf-dip and leaf-tube residual bioassay could establish toxicity equation. The toxicity order of five insecticides by using above three bioassay methods were almost consistent, showing emamectin-benzoate> chlorpyrifos>imidacloprid>betacy-permethrin> buprofezin. Owing to stronger controllability, better repeatability of centrifuge tube residual bioassay, this method was selected for following bioassay. 3. Toxicities of twelve insecticides to against larvae and adult of T. hawaiiensisThe results showed that the toxicity of emamectin-benzoate>chlorpyrifos>abamectin>acetamiprid>betacy-permethrin>imidacloprid>thiamethoxam>clothianidn> monosultap>cyhalothrin>buprofezin>pymetrozine was displayed by using centrifuge tube residual bioassay, when above insecticides were used to against the2-instar larvae of T. hawaiiensis. Toxicity order was mostly consistent with adult, moreover larvae thrips were more sensitive than adult.4. Resistance level of regional T. hawaiiensis field populations to insecticidesAnnual changes on resistance level of T. hawaiiensis collected from Danzhou (DZ), Lingao (LG), Chengmai (CM) and Haikou (HK) to imidacloprid, betacy permethrin, emamectin benzoate, chlorpyrifos, abamectin and acetamiprid were conducted by centrifuge tube residual bioassay in the year of2012and2013. In general, field populations of T. hawaiiensis maintained in susceptivity or declined susceptivity to the tested insecticides. For imidacloprid, T. hawaiiensis collected from DZ, LG, CM and HK pergormed higher resistance than other insecticides, the resistance ratios showed that5.08,14.28,10.87,3.16-fold. For emamectin benzoate, above field T. hawaiiensis acted lower resistance level, for1.68,2.19,2.81,2.03-fold compared to susceptive strain. T. hawaiiensis from LG displayed comparative higher resistance to imidacloprid, betacy permethrin, chlorpyrifos, abamectin and acetamiprid than other regional T. hawaiiensis, the resistance ratios were14.28,5.21,9.26,6.64and9.56-fold for above insecticides, respectively. However, this was small in HK, resistance ratios were3.16,2.20,3.83,2.45and4.58-fold for above insecticides. These results provided fundamental datas on insecticide resistance mornitoring and management for T. hawaiiensis.5. Comparasion of detoxification enzymes activity from T. hawaiiensis populationsActivity of MFO, CarE, GST were increased in T. hawaiiensis collected from LG and HK from the year of2012to2013. Above activities of detoxification enzymes in LG which displayed comparative higher resistance were also significantly higher than susceptive strain and HK (field population of minimum resistance). Those results demonstrated that insecticide resistance of T. hawaiiensis was associated with enhancement of MFO>CarE and GST, furthermore changes on resistance level of field population were much related to detoxification enzymes. 6. Synergism of enzyme inhibitor to major insecticidesThe results showed that DEM, PBO and DEF performed significant synergism to imidacloprid, indicating resistance of T. hawaiiensis to imidacloprid involves in GST, MFO and non-specific esterase. TPP and DEM showed significant synergism to betacy permethrin, this meant resistance of T. hawaiiensis to betacy permethrin was related to CarE and GST. PBO, TPP had excellent synergism to emamectin benzoate, it indicates that resistance of T. hawaiiensis to emamectin benzoate is associated with MFO and CarE. For chlorpyrifos, PBO、DEF performed significant synergism, it demonstrated that enhancement of MFO and non-specific esterase played an important role inresistance of T.hawaiiensis to such insecticide. Only PBO displayed significant synergism to abamectin, suggesting MFO acted vital role in resistance to this insecticide. Resistance of T.hawaiiensis to acetamiprid was most likely relevant to enhancement of CarE, because TPP displayed significant synergism to acetamiprid in this study. |
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