The preservative-treated shell around Douglas-fir piling is an excellent barrier to attack by marine borers; however, damage to this shell can permit marine borer attack. The feasibility of using fumigants to enhance piling performance was examined by exposing fumigant-treated Douglas-fir sections in marine waters off Newport, OR, or Port Hueneme, CA. The piling were inspected annually and increment cores were removed for chemical assays. Fumigant treatment protected the exposed, untreated wood at the end of the pile for the first year, but marine borer activity generally increased after an additional year of exposure. The fumigants appeared to be most effective against shipworm attack. Chemical levels were generally lowest near the attacked region. Fumigant treatment does not appear to be a long-term solution for preventing marine borer attack of untreated wood exposed during construction or usage; however, the treatment does provide short-term protection and may have some use in ports where a regular maintenance program would insure that damage to treated wood was repaired within one year.

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