Termite Resistance

Consumer Benefits of Naturally Termite and Decay Resistant Cypress

From Cypress NSW

NSW Cypress Industry Strategic Plan (NSW CISP) members, produce naturally termite and decay resistant Cypress products, which are independently certified and quality assured. Discerning and environmentally aware consumers in the domestic and international housing construction markets appreciate the benefits of using a chemical free, Class 1 timber from ecologically and sustainably managed native forests.

Natural Durability of White Cypress

Michael J Kennedy

Leader,

Forest Products Chemistry,

Queensland Forestry Research Institute

There is no doubt that the heartwood of the native Australian conifer, white cypress (Callitris glaucophylla Thompson et Johnson, syn. Callitris columellaris F Muell) is highly resistant to degradation by insects and wood decaying fungal organisms. The following are cited in support of this statement:

Recognition in Standards and other Authorities

White cypress is rated as Durability Class 1 (the highest level) in the Queensland Timber Utilisation and Marketing Act (1987). Timber of this class is suitable for use in the ground without requiring the additional preservative treatment to protect the heartwood. In Australian Standard AS 1604. 1-2000 Specification for preservative treatment Pt 1: Sawn and round timber, white cypress is rated as Class 2 (expected life in the ground of 15 years or more). Keating and Bolza, CSIRO (Characteristics, Properties and Uses of Timber, Volume 1, 1982) rate white cypress as Class 1, with a note that it is very resistant to termite and Anobium borers. Bootle (Wood in Australia, 1983) rates white cypress heartwood as durable, particularly resistant to termites. Smith et al (Building Timbers - Properties and recommendations for their use in Queensland, 1991) rate white cypress as Durability Class 1, and expect it to resist both decay and termite attack for at least 25 years and up to 50 years or more. They recommend it for use in ground contact and under other severe hazards, for weather-exposed framing and boards, cladding, fascias, barge boards, external decking, in addition to the usual range of weather-protected situations.

Examples of findings of scientific research

Rudman, P. (1963) The cause of natural durability in timber Pt Xlll: Factors influencing the decay resistance of cypress (Callitris columellaris F. Muell.) Holzforschung 17 (6) 183 - 188. Decay resistance of cypress heartwood was assessed by laboratory soil jar bioassays against four wood-rotting fungi. As has been observed with most durable timber species, wood within about 30mm of the pith of some trees was less durable than mature heartwood. Apart from this small proportion, cypress heartwood was decay resistant.

McEvoy, C. and GC Johnson (1989) A laboratory evaluation of the decay resistance of cypress pine, CSIRO Forestry & State Forest Products Divisional Report, 11pp. Cypress Heartwood was not caused by any of the four wood-rotting fungi to which it was exposed in a laboratory soil jar test. Western red cedar heartwood was resistant to three of these fungi, but decayed on the fourth. The authors conclude that cypress heartwood is very durable.

Rudman, P. and FJ Gay (1964) The causes of natural durability in timber Pt XIV: Intra-specific variations in termite resistance of cypress pine (Callitris columellaris F. Muell.) Holzforschung 18 (4) 114 - 116. Cypress heartwood from both slow-grown and fast-grown trees was consistently highly resistant to attack by the subterranean termite Coptotermes lacteus (Frogg). The results indicated that both toxicant and repellent compounds were present in the heartwood.

French, J.R.J., P.J. Robinson, Y. Yazaki and W.E. Hillis (1979) Bioassays of extracts from white cypress pine (Callitris columellaris F. Muell.) against subterranean termites Holzforschung 33 (5) 144 - 1148. Naturally-occurring compounds were solvent-extracted from cypress heartwood, impregnated into wood and filter papers, and exposed to termites in a laboratory test. The heartwood extractives were toxic to all three subterranean termite species tested -Coptotermes acinaciformis (Frogg.), Nasutitermes exitiosis (Hill) and Mastotermes darwiniensis (Frogg.).

Evans, P.D., J.W. Creffield, J.S.G. Conroy and S.C. Barry (1997) Natural durability and Physical properties of particleboard composed of white cypress pine and radiata pine Forests Products Journal 47 (6) 87 - 94. Resistance of particleboard to damage by termites and fungi during laboratory bioassays was increased by substitution of cypress heartwood for radiata pine. Particleboard made from cypress heartwood alone was as resistant to termites and fungi as insecticide or fungicide-treated radiata pine particleboard.