Abstract
Populations of T. kanzawai were selected and reversely selected with ESP [0, 0-Dimethyl S-(1-methyl-2-ethylsulfinyl) ethyl phosphorothiolate] at LC50 level for 20 generations. ESP-selected strain became cross-resistant to organophosphates but not to carbamates. The use of organophosphorus carboxylesters such as malathion and Papthion with carbamates or synthetic synergists showed synergism on ESP-selected and ESP-reversely-selected strains. Mixtures of malathion or Papthion with acaricidal carbamates, such as PHC or MIPC, showed a remarkably synergistic action. On the contrary, mixtures with no acaricidal carbamates, such as BPMC or MPMC, showed little synergistic action. Combinations of organophosphate and carbamate showed the highest degree of synergism when they were mixed at the same dosages. K-1, one of the saligenin cyclic phosphorus esters, showed remarkably high synergism with malathion. This suggests a difference between mite and insect in substrate affinity. However, K-1 showed little synergism with Papthion. This suggests that K-1 may be a selective carboxylesterase inhibitor in T. kanzawai.
