October 2003

Texas Cooperative Extension, College Station, Texas

Wood Preservatives - What Are Some Of The Terms?

by Dr. Douglas F. Welsh, Extension Horticulturist,
Texas Cooperative Extension, College Station, Texas

Creosote.--For many years vegetable garden beds have sometimes been lined with railroad ties, soaked in black, oily creosote to impede destruction of wood by insects or microorganisms. The term 'creosote' covers a variety of products such as wood or coal tar creosote, and coal tar pitch. Perceived health risks led to limited availability, usually as railroad ties or treated telephone poles.

CCA-treated lumber.--Until now, the most commonly used wood preservation treatment, chromated copper arsenate conains arsenic for fungicidal and insecticidal qualities, copper for fungicide, and chromium to promote resistance to ultraviolet light. The lumber is usually tinged light green in color. CCA-treated lumber will only be available after December 31, 2003 for use in commercial, industrial or saltwater uses, not for decking or use as liners for garden beds.

ACZA.--Ammoniacal copper zinc arsenate is a CCA alternative with basically only marine applications.

ACQ.--Ammoniacal copper quat (a quaternary ammonium compound to give fungicidal treatment) has been an alternative to CCA materials.

CA.--Copper azole, a treatment containing an organic fungicide. The primary protecting substance in 'Wolmanized Natural Select' lumber.

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