Study On Resistance And Enzyme Activity Changes Of Tetranychus Urticae Koch To Abamectin

Tetranychus urticae Koch is a kind of globally prevalent injurious mite, whichhas seriously caused agricultural damages in many countries. Because the Abamectinhas high efficiency, low toxicity to humans, strong contact toxicities to pests, andcompatibility to environment, it is widely applied to pest management in orchards.However, frequent utilization of any novel pesticides might inevitably cause potentialinsecticidal resistance in pest populations. In order to delay the emergence ofinsecticidal resistance in T.urticae populations and prolong the working life ofAbamectin. this experiment researches the mechanisms of acaricidal resistance ofT.urticae, the cross-resistance, and Enzyme activity changes.The main results are asfollowing:1. The resistance selection of T.urticae Koch to abamectinThe T.urticae from Gansu Lanzhou National Forest Park Xinglong Mountainserves as sensitive strain (SS). By using indoor bioassay and biochemical analysismethods, the drug resistance and biochemical resistance mechanism of T.urticae toAbamectin are studied. The results indicate that the T.urticae Abamectin-Resistance24(Ab-R24), whose Resistance Index (RI) is321.5, is obtained after using abamectinto screen24generations.The T.urticae Koch’s cross-resistance to abermectin resistant strains (Ab-R24) istested by using15kinds of acaricides. The results show that T.urticae KochAbamectin-resistant populations have negative cross-resistance against Tebufenpyrad,Fenpyroximate, and stuck grams, whose resistance index (RI) values are0.89,0.9,and0.97, respectively. They have no cross-resistance against diafenthiuron,clofentezine, hexythiazox, chlorfenapyr, pyridaben, propargite, cypermethrin,deltamethrin, Spirodiclofen, and azocyclotin, whose resistance index (RI) values are1.08,1.09,1.1,1.12,1.2,1.6,2.4,2.9,3.3,3.4, and3.5, respectively. These data areless than5. They have cross-resistance against Avi pyridaben acaricide, whoseresistance index (RI) value is136.1. 2. The susceptible population of Tetranychus urticae Koch detoxifying enzyme ofabamectinThe analysis of detoxification enzyme activity of SS and Ab-R shows that theactivity of carboxylesterases (CarE), acetylcholin esterase (AchE), acid phosphatase(ACP), alkaline phosphatase (ALP), glutathione S-transferase (GSTs), and mixedfunction oxidase (MFO) in vivo of Ab-R24strain are separately1.43,1.18,1.56,1.48,1.55, and4.02times of the corresponding activity of SS. They reach the significancelevel (P<0.05). The analysis of SS and Ab-R detoxifying enzyme kinetic constantsshows that the km of AchE/GSTs and MFO in vivo of Ab-R24strain are separately1.14,2.31, and2.58times of the corresponding value of SS. Meanwhile, Vmax areseparately1.19,2.34, and1,76times of the corresponding value of SS. They alsoreach the significance level (P<0.05). In conclusion, the rise of Tetranychus urticae’sAbamectin resistance is closely related to the rapid rise of MFO`s activity. There is nodoubt that both AchE and GSTs participate in the formation of Abamectin resistance.3. the synergistic action of the synergists to the resistance populationUsing T.urticae Koch sensitive strain (SS) and the female mite of T.urticae Kochresistant strains Abamectin (Ab-R24) as test insects, the synergism of the mixture ofthe synergist (PBO, DEM, TPP, and chlorthalidone) and Abamectin (pharmaceuticalactive ingredients rate=3:1) is determined. The results show that PBO synergismAbamectin drug allergy efficiency ratio for the results of R/S is3.08, and theefficiency factor r0value is80.34. DEM, TPP, and chlorthalidone synergist forT.urticae Koch Sensitive populations efficiency ratio R/S values are2.02,1.69, and1.18, respectively, while the efficiency coefficient r0values are63.56,54.97, and31.17, respectively.