Abstract
Susceptibility of Earias insulana and Pectinophora gossypiella collected from cotton fields to fenvalerate and fenpropathrin was studied by a simple dipping method. This method is suitable for monitoring susceptibility of lepidopteran pests to pyrethroids. In 1985, the LC50 of fenvalerate against the Multan colony of E. insulana was 1.5ppm and that against the Hyderabad colony was 1.8ppm. The LC50 value of fenpropathrin against this species was 0.46ppm. Against P. gossypiella, LC50 values of these two pyrethroids were almost equal: 10 to 13ppm respectively. The susceptibility of these species was monitored in Multan, Pakistan from 1985 to 1991. In 1990, fenvalerate was replaced by its active isomer, esfenvalerate. No difference in the susceptibility of each species to the pyrethroids was observed during this period.
