Abstract
Toxicity of chlordimeform to eggs and adults of five kanzawa spider mite, Tetranychus kanzawai, was tested. In assays with 48- to 72-hr-old eggs, chlordime-form was effective on two organophosphate-susceptible strains as well as on organophosphate-resistant strains, but it showed less effect on dicofol-resistant and multiresistant strains. Relative susceptibility for 48hr after the treatment was 18.3 in dicofol-resistant and susceptible strains, and 27.8hr in multiresistant and dicofol-susceptible strains. In assays with adult mites, symptoms of poisoning were slow to appear; the value of LC50 for 48hr after the treatment was about 30 to 60 times lower than that for 24hr. Relative susceptibility after 48hr in organophosphate-resistant and susceptible strains was 1.03, but that in dicofol-resistant and susceptible strains was 2.38. These data, therfore, indicated a cross-resistance to chlordimeform with dicofol but not with organophosphates.
