Chlorpyrifos, O,O-diethyl O-(3,5,6-trichloro-2-pyridyl) phosphorothioate, is a broad-spectrum insecticide used worldwide for the control of many insect pests. As a wood preservative, chlorpyrifos is registered with the United States Environmental Protection Agency for protection of seasoned and green lumber and logs from attack by wood destroying insects such as termites, carpenter ants, ambrosia beetles, powderpost beetles, old house borers, and other wood boring beetles. Chlorpyrifos can be applied by either spraying, brushing, dipping, or pressure treatment using oil or water based solutions at concentrations up to 1.0%. In the United States, chlorpyrifos is currently used with IPCB for pressure treatment of wood products in Hawaii and as an insecticidal additive to IPCB and TCMTB for anti-sapstain and millwork treatments. In this paper, several research trials on the evaluation of chlorpyrifos as a wood treatment termiticide is reviewed. In the review laboratory tests, a treatment threshold was not reached for chlorpyrifos even when it was applied at 0.1%. Long-term ground contact field test with stakes that had been treated with cominations of chlorpyrifos plus a variety of fungicides support an anti-termitic threshold of 0.019 pounds per cubic foot. Based on the results of these studies, chlorpyrifos shows considerable promise as a component of wood treatment systems.

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