بررسي حساسيت دو جمعيت شپشك آرد آلود مركباتPlanococcus citri (Risso) (Hom.: Pseudococcidae) به پرمترين

An Investigation on Susceptibility to Permethrin in Two Populations of Planococcus citri (Risso) (Hem.: Pseudococcidae)

Planococcus citri (Risso) is an important pest of crop and of ornamental plants worldwide. The high reproductive potential of P. citri and its fairly short life cycle along with the frequent application of insecticides (required to maintain P. citri populations below economic thresholds), enhances resistance development and results in control failures. In this research, susceptibility to Permethrin in two populations of P. citri were studied. Insecticide bioassays were carried out on 2nd instar nymphs using dipping method and formulated insecticide. The results indicated LC50s of Permethrin on Rasht and Tehran populations as 363.4 and 1102.3 ppm, respectively. There was a significant difference observed between LC50 of Rasht and Tehran populations (P<0.05), with Tehran population being 2.89 times more tolerant to Permethrin than the Rasht population. An assessment of esterase activity indicated on optimal pH of 8. Esterase activity in the case of Tehran population was 1.33 fold Rasht population. The crude extracts of P. citri populations were analyzed through native PAGE. Following esterase activity (staining using a-NA and [3-NA substrates), a single band of esterase was detected for either one of the strains and with similar electrophoretic migration. There was not any difference observed between Rasht and Tehran populations as regarded gluthathion-S-transferase activity