Methods for the comparative analysis of organophosphate residues in four compartments of needles of Pinus ponderosa

The extent of interaction between vapor phase organophosphate pesticides and plant foliage is not known. Pesticide vapors may deposit onto foliage while bound to dust particles, sorb directly to the surface, sorb into the cuticle, or penetrate to the interior of the leaf. On the basis of these different modes of interaction, four compartments of leaves are identified as significant: water-dislodgable surface material; surfactant-soluble surface material; chloroform-soluble cuticular wax; and the remaining material after the removal of the first three compartments. Analytical methods have been developed for the comparative determination of organophosphate insecticides in these four compartments of Pinus ponderosa needles and of their oxons in the first three. Method recoveries and detection limits were determined with diazinon, methidathion, and chlorpyrifos and their respective oxons in extracts of untreated pines and were then field-tested with needles collected from ponderosa pines growing in the Arboretum of the University of California and from potted ponderosa pines placed in a peach orchard after application of a dormant spray containing diazinon.