Clofentezine toxicity and fate in the bulb mite Rhizoglyphus echinopus (Acari: Acaridae)

Clofentezine was toxic to bulb mite, Rhizoglyphus echinopus (Fumouze and Robin), eggs and larvae; however, it was not toxic to adults alone or in the presence of piperonyl butoxide. When adults were exposed to radioactive clofentezine, the acaricide was absorbed, metabolized and excreted. After 48 h exposure, 49.8% of the recovered radiocarbon was parent compound with 37.1, 9.1 and 3.6% detected in the container rinse, mite rinse and internal fraction, respectively. Homogenates of adults extensively metabolized clofentezine. The most active fraction was the 12 000 g supernatant plus glutathione followed in decreasing order by the supernatant, supernatant plus NADPH and the whole homogenate, each of which metabolized at least 16% of the acaricide. In the presence of piperonyl butoxide, in vitro metabolism of clofentezine by each of these active fractions was increased approximately 10%. Although it is possible that rapid metabolism could have contributed to the lack of toxicity of clofentezine to bulb mite adults, it is more likely that another major mechanism was involved. Perhaps adult bulb mites lack the sensitive target found in immature mites.