A novel wood preservative with vegetal extracts-cypermethrin mixture protects H2-weathered envelope-treated tropical hardwood kempas against Coptotermes termites
D Messaoudi, A H H Wong
In accordance with sustainability development initiatives by commercial wood protection to conceive of cost-effective, environmentally acceptable wood treatment solutions replacing traditional biocides, this paper reports an aboveground subterranean termite test of termite-susceptible heartwood blocks of the tropical (Malaysian) structural hardwood kempas (Koompassia malaccensis) envelope-treated (brush-on) with a novel wood preservative based on vegetal extracts-cypermethrin mixture (Biocide 1: 0.16% cypermethrin, 0.08% tebuconazole, 2% vegetal extracts). Commercial permethrin-based LOSP (Biocide 2: 0.2% permethrin, 1.8% tributyltin naphthenate, 0.1% dichlorofluanid) at 3 minute dip treatment served as the reference. Air dried treated kempas blocks were H2-weathered via a rigorous laboratory volatilization regime (representing long-term evaporative ageing of treated wood used aboveground indoors under prolonged H2-hazard class situation) and then exposed for 6 months aboveground inside a containerized termite test design (representing severe H2-hazard class situation with treated wood free from wetting, soil contact and weather) at a humid forest site targeting Coptotermes curvignathus subterranean termites. Results demonstrated irrefutably that untreated kempas heartwood was severely attacked by C. curvignathus (mean mass loss: 70.4% and 20,416 mg) with low mean visual termite rating (2.4). However, treated kempas was well protected at very low surface retention of Biocide 1 (mean negligible mass loss: 0.66% and 207 mg) and very low surface retention of reference Biocide 2 (mean negligible mass loss: 1.01% and 306 mg), with both treatments similarly yielding the highest mean visual termite rating for all replicate kempas specimens (rating 10). Performance of both biocides were similar but varied significantly (P<0.05) from the attacked untreated counterparts. Biocide 1 therefore has considerable anti-termite potential, and can substitute for traditional LOSP Biocide 2, to protect wood exposed to long-term H2-hazard class environment.