Response of Susceptible Strains of the Pacific Spider Mite and the Citrus Red Mite to O-Isopropyl O-(2,4,5-Trichlorophenyl) Phosphoramidate or Phosphoramidothioate

Abstract

A laboratory strain of the Pacific spider mite, Tetranychus pacificus McGregor, was relatively slow in developing resistance to O-isopropyl O- (2,4,5-trichlorophenyl) phosphoramidothioate or the phosphoramidate under selection pressure, as compared with the response of this strain to demeton and parathion. In large-scale field tests, however, the citrus red mite, Panonychus citri (McGregor), developed resistance to this phosphoramidothioate after 6 applications and to the phosphoramidate as a result of 3 treatments.

These and other studies mentioned suggest that laboratory selection pressure was of little value as a means of predicting that resistance may be slow in occurring. When, however, resistance develops rapidly under laboratory selection pressure it should be a good indication that resistance will develop rapidly in the field.