Reduction of deer browsing of Douglas-fir (Pseudotsuga menziesii) seedlings by quadrivalent selenium

The feasibility of using selenite ion as a systemic deer repellent for the protection of Douglas-fir (Pseudotsuga menziesii) seedlings is evaluated. When applied to the soil, the selenite ion is absorbed by the seedling roots, transported to the foliage, and thereafter volatilized. Acute phytotoxicity is observed only when selenium foliar concentrations exceed 100 ppm, while animal repellency is demonstrated at concentrations as low as 1–2 ppm. The design of a slow release device, based on a sparingly soluble salt of selenious acid, is reported, and its evaluation in a series of field trials is described. Preliminary results indicate that statistically significant reduction of browse damage can be achieved.