Occurrence of etoxazole resistance individuals of the two-spotted spider mite, Tetranychus urticae Koch from a limited region.

The development of resistance to a new acaricide, etoxazole, was found in p opulations of the two-spotted spider mite, Tetranychus urticae, collected f rom apple orchards in Soma-Mura village, Aomori Prefecture. Laboratory test s showed that a few mite populations of the 30 populations collected from a n approximately 7x5 km area were insensitive to the acaricide, even though they have never been exposed to this acaricide. We selected a resistant and a susceptible strain from an insensitive population through selection and reciprocal selection by etoxazole. The resistance ratio calculated from the LC(50)s of the resistant and susceptible strain was more than 20,000. Cros sing tests between the two strains indicated that the resistance to etoxazo le was under control of a completely recessive single gene.