Chloropicrin Movement and Fungitoxicity in a Decaying Southern Pine Laminated Timber

This paper reports on the use of chloropicrin to control decay in a southern pine laminated arch. A treatment plan was formulated to obtain information on 1) the effectiveness of a vapor wrap in containing fumigant vapors in the wood, 2) the effects of gluelines, finger-joints, and grain orientation on the diffusion of chloropicrin in the timber, and 3) how well decay fungi were eliminated from the wood. The results show that over a 13-month period, fungitoxic chloropicrin vapors diffused up to 2 m from the treatment sites near the center of the arch. The vapor wrap that enclosed a portion of the arch limited escape of chloropicrin from the wood and improved the effectiveness of treatment. Longitudinal diffusion along laminates was much greater than between laminates, indicating that transverse grain orientation and gluelines limit fumigant movement. Under the conditions of this experiment, we determined that decay could be controlled by applying 0.5 mL of chloropicrin per cm of crosssectional area at intervals of about 2 m along the timber. Spacing could be increased if a vapor barrier were used.

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