Toxic action of phosphine on the adults of the copra mite Tyrophagus putrescentiae [Astigmata : Acaridae]

The inhibitory effects of phosphine gas on cytochrome C oxidase and catalas e, both in vivo and in vitro, and gas uptake by adults of Tyrophagus putres centiae were determined. The activities of both enzymes were reduced by the gas. Relative inhibition rates of the enzymes were : in vivo catalase > in vitro catalase, in vivo cytochrome C oxidase < in vitro cytochrome C oxida se, and the inhibition effects of in vitro enzymes were proportional to the exposure period of phosphine applied to the cytosolic extracts. Although t he uptake of phosphine by adults increased with an increase of phosphine co ncentration and exposure period, the rate of uptake was relatively slower t han at low concentration and short exposure period. The absorption mechanis m of phosphine between insects and mites appears to be different.