Insecticides resistance detection in field-collected populations of Pectinophora gossypiella (Saunders)

Abstract

In Egypt pink bollworm Pectinophora gossypiella (Lepidoptera: Gelechiidae) has recently developed resistance to various kinds of insecticide in the field. The resistance status of pink bollworm to several classes of insecticides currently used in cotton fields was evaluated in the Nile Delta (Kafr-Elsheikh and Menoufia) Egypt. Two field-collected P. gossypiella populations have developed resistance to several classes of insecticides. Toxicological bioassays were conducted in the laboratory, LC50's estimated by probit analysis and Resistance Ratio (RR) were calculated at the LC50 level. Of the seven insecticides tested four insecticides (chlorpyrifos, profenofos, thiodicarb and carbaryl) showed the Resistance Ratio (RR) values above 20 folds, against two field-collected populations whereas the other three insecticides (fenpropathrin, spinosad and abamectin) had RR values less than 10 folds. Also, the patterns of selection pressure by abamectin at the LC30 level to Kafr-Elsheikh (KFR)-and Menoufia (MNF)-field strains were determined by continuous insecticide application under laboratory conditions for eight successive generations. On the other hand, biochemical assays indicated that both KFR-and MNF-field strains expressed higher levels of Acetylcholinesterase (AChE) activity by 4.1 and 2.8-times, respectively, compared to that of susceptible strain. There were significant differences in esterase activities among the field-collected populations and susceptible strain. Analysis of protein patterns by (SDS-PAGE) showed some differences between resistant strains to abamectin, MNF-and KFR-field strains and the bands differed in intensity and molecular weights between all strains. These findings indicate that rapid biochemical assays coupled with biological assays are potential tools for estimating both the intensity of resistance in the field. © 2011 Academic Journals Inc.