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 tinder 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. INTRODUCTION Since the use of heavy metal-based wood preservatives such as chromated copper arsenate (CCA) was voluntarily withdrawn from housing markets in the U.S., research has been focused on developing new user friendly wood preservatives to protect wood against fungi, mold and insects (Kartal et aI.,2004b). Potential health risks caused by mold growth in houses and building structures are a major concern for homeowners, builders, contractors and insurance companies alike. Lawsuits claiming health problems caused by indoor mold exposure exceeded 2.8 billion dollars in 2002 (Hartwig and Wilkinson, 2003). Chemical fungicides that are commonly used to control the growth of mold and decay fungi on wood are not environmentally suitable for many indoor applications. Searching for natural alternatives that are user friendly and exhibit negligible toxicity to human are most desired. Natural plant extracts such as essential oils and their derivatives are well know for their antimicrobial properties that are utilized in pharmaceutical , healthcare, food, and packaging applications (Adam et al.,1998; Cowan..1999; Deferera et al.,2000: Hammer ci al.,1999 Hoffman et al..2004; Mau et al.,2001 Moretti et al..1998; Muanza et al. .1994,1995 MullerRiebau et al.,1995; Rakotonirainy and Lavedrine,2005;Scheffer and Duncan.1946; Sivropoulou et al.,1995,1997; Sridhar et al.,2003; Wang et al.,2005Yang and Clausen. 2007) The objective of this study was to investigate the antifungal effect of commercially available essential oils on wood against mold and wood decaying fungi by surface treatment and standard soil block test. The positive inhibitory effect of essential oils tested provides a promising wood protection alternative for construction and during storage.