Analysis of permethrin (cis- and trans-isomers) and esfenvalerate on almond twigs and effects of residues on the predator mite Galendromus occidentalis (Acari : Phytoseiidae)

A gas chromatograph-electron capture detection method for-analysis of perme thrin (cis- and trans-isomers) and esfenvalerate on the surface of almond t wigs is described. Permethrin and esfenvalerate were extracted from the sub strate with a hexane sonication, Florisil solid phase extraction cleanup, a nd quantification try gas-liquid chromatography with electron capture detec tor with a megabore capillary column. The mean recoveries for all three ana lytes were 87% with a coefficient of variation <13% at fortification levels ranging From 50 to 1,000 nr for each analyte. The limit of detection was 1 4, 13, and 4 ng for cis-permethrin, trans-permethrin and esfenvalerate resp ectively for almond twigs. Field collected twig samples taken 7 mo after pe sticide application were found to contain measurable bark surface residues. Bioassays using those twigs indicated significant mortality to the benefic ial mite, Galendromus occidentalis Nesbitt.