Abstract
Phenacoccus solenopsis Tinsley (Hemiptera: Pseudococcidae) is a pest with an economic impact on various crops and ornamental plants. Different classes of insecticides have been used for P. solenopsis control but rise in resistance is a major concern. Previously resistant selected field populations of P. solenopsis with chlorpyrifos (RR = 15,292-fold), acetamiprid (RR = 10,631-fold), emamectin benzoate (RR = 280-fold), and spinosad (RR = 15,233.84-fold) were used to study the biochemical mechanisms of insecticide resistance in the laboratory. Enzyme assays were performed using P. solenopsis adults in all these resistant populations to determine the activities of different detoxification enzymes associated to different resistance mechanisms to these chemicals. The results revealed that oxidases activity was increased significantly in all selected strains compared with the susceptible strain. The glutathione-S-transferase (GST) activity nevertheless showed a significant change. The esterases (EST) activity was significantly higher in all the selected strains except the emamectin benzoate selected strain compared to the susceptible strain. These results confirm the contribution of oxidases and esterases in detoxification of the tested insecticides in P. solenopsis. This information would help to formulate resistance management strategies for this pest.