|Abstract or Summary
- Over-the-counter (OTC) wood preservatives canprovide wood with both a moisture barrier and fungicidalprotection against biodeterioration
- Over-the-counter (OTC) wood preservatives canprovide wood with both a moisture barrier and fungicidalprotection against biodeterioration, yet there is littlecomparative data on the performance of thesepreservatives. In this study, the potential of variouslow-toxicity, OTC preservatives was evaluated on fivewestern wood species, western redcedar (Thuja plicata),western hemlock (Tsuga heterophylla), Douglas-fir(Pseudosuga menziesii),lodgepole pine (Pinus contorta),and coastal redwood (Sequoia sempervirens). The activeingredients tested were copper-8-quinolinolate, coppernaphthenate, zinc naphthenate, 3-Iodo 2-propynylbutlycarbamate(IPBC), Bis (tri-n-butyltin) oxide(TBTO), TBTOIPBC, TBTOchlorothalonil, and TBNtrichloromethylthio-phthalimide (Folpet). Small blocksand stakes of each species were dipped for 3 minutes inone of twelve OTC preservatives to simulate homeowner application. To examine the efficacy of thesepreservatives, treated blocks were subjected to amodified American Society of Testing and MaterialsStandards (ASTM) D2017-81 soil-block test to evaluateabove ground decay resistance as measured by wood weightloss following exposure to Postia placenta (Fr.) Cookeor Trametes versicolor (L:Fr.) Pilat, a brown and whiterot fungus, respectively. Test stakes were placed insoil-beds maintained in an environmentally controlledgreenhouse. The stakes were evaluated for the degreeof decay at 3 month intervals for the first year,followed by 18 and 24 month ratings. Preservativetreatments improved performance of most species exceptlodgepole pine; improvements were most noticeable insoil-bed trials with redwood and western redcedar. Theresults suggest that topical application of commerciallyavailable preservatives has merit for enhancing theperformance of naturally durable woods in soil contact,but their value for less durable woods is questionable.Wood used above-ground will benefit most from suchtopical treatments, however, for best performance ayearly reapplication might be necessary for the lessdurable wood species.