Extracts obtained from a marine alga and white cypress pine (Callitris glaucophylla J. Thompson & L.J. Johnson) were examined for their ability to control marine borers. In a two week laboratory bioassay, filter papers were soaked in 0-8% extract concentrations, dried, and placed with Limnoria quadripunctata Holthuis in Petri dishes containing seawater. The 8% algal extract virtually prevented L. quadripunctata from boring holes through the paper. However, papers soaked in lower algal extract concentrations were attacked. Similar concentrations of C. glaucophylla extract failed to protect the filter papers from L. quadripunctata, despite some initial inhibition. Small blocks of Pinus radiata D. Don treated with the extracts and exposed in the sea were all destroyed within 13 months, except those blocks treated with the 8% algal extract which were just moderately attacked by Limnoria and Teredinids.

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