Phytophthora ramorum is a relatively newly described pathogen present in the forests of Northern California and southwest Oregon in the United States. This organism has an extremely wide host range, including a number of commercial important conifers, among them Douglas-fir (Pseudotsuga menziesii). The continuing expansion of the range of P. ramorum will result in an increasing quarantine area with the need for methods to mitigate the risk of spread on logs moving from this area. One mitigation approach would be a dip-diffusion treatment using boron in combination with other fungicides. Boron inhibited growth of P. ramorum in petri dish tests at concentrations of 0.5 to 5 % and concentrations above 1.5% were lethal. Further tests are underway to determine the ability of boron to diffuse through bark and into the xylem of Douglas-fir logs.

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