Placing logs in ponds or under water sprinklers to keep moisture levels high enough to prevent oxygen tensions rising above inhibitory levels, is a proven method of preventing sapstain. The objective of this experiment was to determine if water barriers significantly reduce the rate of sapstain penetration into logs by maintaining moisture contents, and consequently oxygen tensions, at inhibitory levels. Debarked radiata pine (Pinus radiata D. Don) log billets (20-25cm diameter x 1 metre long) were treated with several different formulations of water barrier, water barrier plus a commercial antisapstain formulation and the commercial formulation used alone. Log billets were subjected to two storage regimes: 25°C and 75%RH, and ambient temperature and humidity in a pole barn, for periods up to 16 weeks. Billets stored at 25°C were artificially inoculated with sapstain fungi. The extent of internal sapstain and external fungal degrade was assessed at 4, 8 and 16 weeks. The results showed that a water barrier applied as a layer approximately 0.5 -1 mm thick, to radiata pine stored under the conditions employed, gave significantly (5% level of probability) better protection from sapstain compared to the commercial antisapstain formulation. There was a strong positive correlation between the rate of moisture loss and the rate of sapstain development which suggested that moisture retention was the main mechanism of action of water barrier coatings. Whilst water barrier on it's own can give superior protection from sapstain compared to the commercial standard used, water barrier plus the commercial standard performed significantly (5% level of probability) better than water barrier alone.

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