P.D. Evans, S. Dimitriades, R.B. Cunningham, C.F. Donnelly
Medium Density Fibreboard Manufactured from Blends of White Cypress Pine and Non-Durable Wood Species Shows Increased Resistance to Attack by the Subterranean Termite C. lacteus
Summary
Medium density fibreboards consisting of blends of the naturally durable wood species white cypress
pine (Callitris glaucophylla) and non-durable wood species were manufactured in a commercial plant
and subjected to a bioassay using the subterranean termite species, Coptotermes lacteus. A board composed
of 30% cypress pine, 30% slash pine (Pinus elliottii) and 40% of the naturally durable hardwood
species spotted gum (Corymbia maculata) was also manufactured and bioassayed against C. lacteus. The
aims were to determine (i) whether boards containing cypress pine possessed increased resistance to termite
attack compared to a control manufactured entirely from non-durable wood species; (ii) the relationship
between the cypress pine content of boards and their resistance (if any) to termite attack; (iii)
whether the termite resistance of boards containing cypress pine could be further enhanced by the addition
of spotted gum fibre. There was an inverse relationship between the cypress pine content of MDF
specimens and mass losses of the specimens during the bioassay; the percentage mass losses of specimens
containing 11.4, 16.2 and 34.2% cypress pine being 20.3, 13.4 and 8.8%, respectively, compared
to 32.8% for the control, which consisted of non-durable slash pine (80%) and hoop pine (Araucaria
cunninghamii) (20%) fibre. There was strong evidence that the inverse relationship between the cypress
pine content of boards and mass losses during the bioassay was linear, although a statistically significant
quadratic (curvilinear) effect was also apparent. The addition of spotted gum fibre to boards did not
increase their resistance to termite attack. Cypress pine heartwood contains a variety of extractives that
are either toxic or repellent to termites, and the increased termite resistance of MDF containing cypress
pine compared to the control is probably due to the insecticidal effect of such chemicals on C. lacteus.
The incorporation of cypress pine fibre into MDF shows promise as an alternative to chemical biocides
for increasing the resistance of MDF to termites. However, the response of termites to heartwood extractives
varies between species, and therefore further experimentation is needed to test the resistance of
MDF containing cypress pine fibre to attack by greater range of wood destroying termites under test conditions
that more closely simulate field conditions.
Holzforschung, Walter de Gruyter
Print ISSN: 0018-3830
Volume: 54, 10/2000
Pages: 585 - 590
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