IRG Documents Database and Compendium


Search and Download IRG Documents:



Between and , sort by


Displaying your search results

Your search resulted in 2 documents.


Comparative studies on penetration and retention of CCA (C) and creosote in wood from APHID-killed and sound Kenyan-grown Mexican cypress (Cupressus lusitanica)
2006 - IRG/WP 06-40352
Properties of wood from Kenyan-grown Mexican cypress (Cupressus lusitanica), attacked and killed by the cypress aphid (Cinara cupressi), in terms of density and treatability, were investigated in comparison to the properties of wood from sound trees. Density in small wood samples from aphid-killed trees was found lower than density in samples from sound trees, and reduced with tree age in samples from both. However, differences were slight, being 3.8%, 2.5% and 2.3% lower than density in samples of sound trees aged 10, 12 and 14 years respectively. Conversely, penetration and retention of both CCA and creosote were higher in samples from aphid-killed trees of the 3 age classes. Along the grain penetration of CCA was higher by 3.6%, 4.5% and 6.2%, and across the grain penetration higher by 3.8%, 7.0% and 11.3% in samples from aphid-killed trees of the 3 age classes respectively, compared to penetration achieved in samples from sound trees. Higher penetration of creosote in samples from aphid-killed trees was in the order 3.9%, 5.8%, 7.1% along the grain, and 3.7%, 6.2%, 11.9% across the grain. Along the grain retention of CCA in samples from aphid-killed trees was higher by 1.2%, 1.5%, 2.0%, and across the grain higher by 5.1%, 6.3% and 7.4% for the 3 age classes. Similarly, retention of creosote in samples from aphid-killed trees of the 3 age classes was higher by 3.2%, 4.5%, 5.6% along the grain, and 2.6%, 3.2%, 4.6% across the grain. Differences in density and treatability could not be properly explained, but was assumed associated with extensive sap depletion by aphids, interference with tree growth and normal wood formation, hence lowering of wood cell wall materials and increased cellular spaces within the wood cell wall structure of wood from aphid-killed trees. However, the results revealed that differences between wood from aphid-killed and sound C. lusitanica were minimal, and did not warrant wood from aphid-killed trees being branded as of lower quality, and restricted end uses.
R Venkatasamy, F M Opar


Comparing microbial colonisation and Decay Rates of Wood from Sound and Aphid-Killed Kenyan-Grown Mexican Cypress (Cupressus lusitanica)
2006 - IRG/WP 06-10599
Samples of wood from 10, 15, and 30-year old trees attacked and killed by the cypress aphid (Cinara cupressi) and sound Kenyan-grown Cupressus lusitanica trees were investigated for variations in moisture content, density and susceptibility to microbial decay. MC varied with tree age, a normal trend, and between samples from aphid-killed and sound trees. In samples from 10, 15 and 20-year old sound trees, MC was higher by 11.1%, 8.6% and 7.8% respectively, than in samples from aphid-killed trees. Similarly density varied with age, to be expected, and between samples from aphid-killed and sound trees, being 3.5%, 2.6% and 2.1% higher in samples from sound trees of the 3 age classes. Exposure to riverwater and soil revealed a pattern of microbial colonisation and degradation normal for each environment. In riverwater, samples were mainly colonised by bacteria, actinomycetes, stain fungi, and softrot fungi, bacteria and softrot fungi being the main wood degraders, but their action on samples were slow and generally moderate in severity of attack. Exposure to soil followed a similar pattern of colonisation, the principal wood decaying organisms being bacteria and softrot fungi, and to a lesser extent brown and white rot fungi. Samples from both aphid-killed and sound trees were colonised and decayed in a similar fashion, but microbial decay in the soil environment was more pronounced than in riverwater. The soil block test recorded low weight losses after 2 weeks exposure, rising to between 29% and 36% after 12 weeks, with no significant differences between weight losses in samples from aphid-killed and sound trees, or tree age. The results of the study revealed that there are no significant differences between microbial decay susceptibility of wood from aphid-killed and sound trees, and that slight differences in MC and density did not influence decay rate. Consequently, wood from aphid-killed cypress trees should not be considered as of inferior quality, in terms of decay susceptibility, by wood processors and consumers.
R Venkatasamy