Evaluation of the efficacy of selected thermal boron treatments in eliminating pests in freshly peeled Douglas-fir logs

The potential of thermal disodium octaborate tetrahydrate (DOT) treatments as a measure for eliminating insects, fungi, and nematodes from imported logs was examined. Douglas-fir logs (Pseudotsuga menziesii) were heated in DOT for up to 3 hours at 80?C while internal temperature was monitored. Boron levels were measured 1, 2, and 3 months after the DOT treatment. Although conditions near the surface of the logs approached those considered lethal for most organisms (71?C for 60 min.), temperatures in the pith were generally insufficient to eliminate established fungal infestations. Although boron levels near the surface were sufficient for fungal control, they declined rapidly below the surface; little residual boron was found in the wood at depths greater than 100 mm. Thus, thermal boron treatments may enhance protection of freshly sawn Douglas-fir logs, but should not be used as the sole means of pest control for this species.

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