Metabolism of coumaphos in susceptible and resistant strains of Boophilus microplus (Acari: Ixodidae)

A study was made of the comparative fate of ( super(14)C)coumaphos in larvae and adults of coumaphos-resistant (R) and -susceptible (S) strains of Boophilus microplus (Canestrini) that originated in Mexico. There were no differences between R and S strains in rates of cuticular penetration or internal accumulation of radioactive material after topical treatments (0.05 mu g/tick) of unengorged adult females or after drench treatments (1 ppm) of larvae. Radioactive products of the metabolism of ( super(14)C)coumaphos in both larval and adult stages included the toxic oxygen analog (coroxon) and free and conjugated forms of chlorferon, the nontoxic substituted-coumarin ring moiety of the molecule. The rate of metabolic detoxification of absorbed coumaphos was more rapid in larvae than in adults of both strains.