Inhibitory effect of essential oils on decay fungi and mold growth on wood

Structural damage and potential health risks caused by wood decay and mold fungi in residential structures have been a major concern for homeowners, building contractors and insurance companies alike. The combined damage from decay fungi and mold claims exceeds several billion US dollars annually. Protection against decay and mold growth on wood is a critical economic concern for the building industry. An ideal compound for wood protection for interior applications must be nontoxic, hypoallergenic and able to provide long-term efficacy under high humidity. The objective of this study was to investigate the inhibitory effects of natural plant extracts, such as essential oils, on wood. Seven essential oils were evaluated for their ability to inhibit weight loss by brown-rot and white-rot fungi on southern pine in soil block tests. No weight loss occurred in specimens dip-treated with undiluted test oils. Essential oils were also evaluated for inhibition of mold growth in laboratory tests by two methods. Specimens dip-treated with thyme or geranium Egyptian oil inhibited growth of test mold fungi up to 22 weeks and specimens exposed to vapors of dill weed or rosemary oil also inhibited mold growth under laboratory conditions. We did not observe correlation between surface and vapor treatment for mold inhibition. These findings support the potential use of essential oils for natural wood protection against decay fungi or mold infestation for surface-treatment or fumigation of wood products.