Laboratory Evaluation of Soft Rot Resistance of Non-Durable Lesser-Known Malaysian Hardwoods

Resistance of six non-durable lesser-known Malaysian hardwoods, Pulai (Alstonia spp.), Rubberwood (Hevea brasiliensis), Ludai (Sapium spp.), Jelutong (Dyera costulata), Gaham Badak (Blumeodendron tokbrai) and Kayu arang (Diospyros spp.) compared with temperate Scots pine sapwood (Pinus sylvestris), were evaluated using the unsterile soil burial (mixed with Chaetomium globosum) versus vermiculite-burial (of C. globosum only) laboratory techniques and decay rates expressed as either percent mass/mass or percent mass/volume basis. Scots pine was expectedly soft rot resistant but Pulai wood was almost immune to decay. Other wood species varied from being moderately to highly susceptible to soft rot decay. The vermiculite-burial technique favoured greater soft rot degradation activity than unsterile soil-burial. Results also suggest that soft rot decay rates of susceptible woods could also be accelerated with higher surface area/volume ratios of test blocks. The use of mass/volume basis indicated similar reduced degrees of soft rot resistance among most test wood species whereas apparent differences among woods were found using mass/mass comparisons probably due to variable basic densities among these timbers

Resistance of two commercial cement-bonded rubberwood particle composites to decay and termites

Two types of cement-bonded rubberwood (Hevea brasiliensis) particle composites (tradenames: CemboardTM” and PrimaflexTM in Malaysia), were evaluated for termite resistance (prevalent termite: Coptotermes curvignathus) in the field, and decay resistance (test white rot fungi: Schizophyllum commune and Pycnoporus sanguineus; test brown rot fungus: Gloeophyllum trabeum; test soft rot fungi: Phialophora fastigiata and compost-Chaetomium globosum mixed inocula) in the laboratory. Three termite- or decay- susceptible wood materials [rubberwood, kempas (Koompasia malaccensis) and radiata pine (Pinus radiata) pressed pulp] were also included for comparison. Both types of wood-cement composites were consistently shown to be immune to decay fungi and subterranean termites, recording also much lower final moisture contents of the composites compared with rubberwood, kempas and radiata pine pressed pulp. These wood-cement composites are therefore suitable for use in a severe decay and termite hazard

Performance of Two Imidacloprid-Treated Malaysian Hardwoods in an Accelerated Aboveground Termite Test

The performance of the chloronicotinyl insecticide imidacloprid as a wood protecting termiticide, under a simulated Malaysian biological hazard class H2 (exposure aboveground indoors against termites and wood borers), was evaluated by a novel termite field test protocol. Replicate end-grain sealed air dried test blocks (20 x 20 x 20 mm) of two Malaysian hardwoods, Kembang Semangkok (Scaphium spp.) and Rubberwood (Hevea brasiliensis) were vacuum-atmospheric pressure-impregnated in the laboratory in butanolic solution of imidacloprid to target retention of 0 (control), 1 and 3 g/m3. Halve the replicated blocks were then subjected to a prescribed water-leaching cycle, and conditioned blocks then installed in a novel aboveground H2 hazard class-type termite field test where Coptotermes curvignathus are prevalent. After 8 weeks exposure, untreated hardwoods were severely (termite ratings 1-2) or moderately attacked (ratings: 6.3-7.5), while, with the exception of occasional light grazing, none of the leached nor non-leached test blocks treated with imidacloprid to both target termiticide retention were regarded to be attacked (ratings: 9.8-10)

The High Decay Resistance in the Sapwood of the Naturally Durable Malaysian Hardwood Belian (Eusideroxylon zwageri)

It has long been assumed that the observed natural durability of the heartwood in certain timbers is perhaps associated with a relatively lower decay susceptibility also of the sapwood of these species. While the heartwood of Belian is reputedly highly decay resistant among the tropical hardwoods of Southeast Asia, laboratory decay tests reported in this paper have also confirmed the high decay resistance of the sapwood of this timber species. The sapwood of Belian is found to be resistant to decay by soft rot (Chaetomium globosum), white rot (Pycnoporus sanguineus & Coriolus versicolor) and brown rot (Poria sp. & Gloeophyllum trabeum) fungi after 12 weeks of decay testing, sustaining <2% mass loss, equivalent to that in its heartwood. The reference sapwood species Rubberwood (Hevea brasiliensis) and the heartwood of Kempas (Koompassia malaccensis) sustained significant mass losses from decay of up to 59% and 17%, respectively. Microscopic observations of Belian sapwood revealed extensive proliferation of extractives in the lumina of various cell types showing a pattern of extractive distribution similar extent to that in the heartwood tissues, although the extent of cell filling by extractives was not quite as high as for the heartwood. It is plausible that the inherent wood extractives deposited in the cells confer the same degree of anti-fungal properties to both the heartwood and sapwood of Belian

Comparative Laboratory Leaching Test Methods to Study Post-Treatment Storage Period Impacts on CCA Leachability and Fixation in Treated Kempas (Koompassia malaccensis) Heartwood

Three laboratory leaching test methods were compared to determine the effects of different post-treatment storage fixation periods on leachability/fixation of CCA components from treated kempas (Koompassia malaccensis) permeable heartwood. End-sealed test wood blocks of permeable were treated with CCA to target retention of 5.6 kg/m3, immediately stored to fix at ambient conditions for 0 and 48 hours, 1, 2 and 4 weeks, followed by a 2 weeks leaching test comparing 3 leaching tests: the methods of EN84 (consisting of initial vacuum impregnation of wood in water), EN84-1 (replacing initial vacuum impregnation with initial immersion of wood in water) and a new, and least severe, test EN84-2 (daily routine of soaking wood for 5 hours in water followed by drip drying for 19 hours). Leachates harvested from these leaching tests were analysed for cumulative leaching losses of copper (Cu), chromium (Cr) and arsenic (As) that occurred over the 2 weeks leaching period. Overall, leached CCA elements ranged from 0.48 – 4.02μg/ml Cu, 0.61 – 5.76 μg/ml Cr and 0.46 – 4.02 μg/ml As. There were significant variations in leaching losses (P<0.05) between unfixed and stored fixed blocks among the 3 laboratory leaching test methods. Significant variations of Cu, Cr and As levels existed between the least severe method and the other two methods that used prolonged immersion of wood in water. However, there were no significant differences in CCA leaching losses between EN84 method and the EN84-1 method, while the merits of the least severe leaching regime as indicators of realistic CCA leaching of “fixed” treated wood aboveground outdoors are discussed

Variation in infection rates of blue-stain, mould and white rot tropical fungi on mixed light Malaysian woods

The modified 3-week FRIM laboratory method for screening of anti-sapstain formulations against three representative tropical fungi causing blue-stain (Botryodiplodia theobromae), mould (Paecilomyces variotii) and white rot (Schizophyllum commune) infection of sapwood species was used to examine the relative resistance of the sapwood of eight mixed light Malaysian woods, Scots pine (Pinus sylvestris), medium density fibreboard produced from Rubberwood (Hevea brasiliensis) and the heartwood of Sentang (Azadirachta excelsa), to infection by these organisms. After 21 days it was found that Ramin (Gonystylus spp.), Rubberwood, Mersawa (Anisoptera sp.), Ludai (Sapium spp.), Yellow meranti (Shorea spp.), Scots pine and Jelutong (Dyera costulata) were highly susceptible to the pooled combinations of bluestain, mould or white rot infection often sustaining >50% overall mean fungal coverage or when at least one of the infection types has reached maximum mean coverage (75.5%) of the wood samples. However, the Rubberwood-based fibreboard, and particularly Sentang, and the softwood Agathis spp. from Kelantan (trade name: Damar minyak) and Sarawak (trade name: Bindang), were relatively moderately susceptible to infection, sustaining between 9 and 47% overall mean fungal coverage after 21 days, or even considerably less susceptible (5 – 20% overall coverage) after 14 days. There was absence of both blue-stain and white rot fungal growth on all samples dipped in a low (0.03%/0.03%) fungicide concentration of a MBT/TCMTB anti-sapstain formulation. Such laboratory test results could have significant implications to field or industrial sapstain control of sapwood timbers concerning the lag time between tree felling and anti-sapstain treatment and seasoning

Detection of Anti-Fungal Sapwood Extractives in Non-Durable Scots Pine (Pinus sylvestris), Rubberwood (Hevea brasiliensis) and Jelutong (Dyera costulata)

A general laboratory bioassay method of Woodward and Pearce (1985) was adopted to detect anti-fungal activity of sapwood or heartwood extractives of 5 Malaysian hardwoods [dark red meranti heartwood (Shorea spp.), red balau heartwood (Shorea spp.), kulim heartwood (Scorodocarpus borneensis), jelutong sapwood (Dyera costulata) and rubberwood sapwood (Hevea brasiliensis), including the temperate Pinus sylvestris (Scots pine sapwood). The heartwoods of these species and Scots pine sapwood are known to be highly resistant to decay by soft-rotting Ascomycetes and anamorphic fungi (about 1-7% wood mass loss), while the sapwoods of rubberwood and jelutong had much reduced soft rot resistance (respectively 35, 32% wood mass loss) but obviously prone to sapstain and mold attack, including that of Scots pine. Crude methanol extracts of woodmeal samples of each wood species were loaded on to thin-layer chromatography plates at between 0.003 and 0.1 g fresh mass equivalent of woodmeal per spot so as to optimize resolution of separated compounds, and developed with chloroform:methanol solvent (ratio 19:1). The dried plates were sprayed with fresh fungal spores of Cladosporium cucumerinum and incubated at >90% RH for 5 days in the dark. Presence of anti-fungal compounds was revealed by white regions along the solvent transect for each extract of each species where inhibited spore germination and mycelial growth of C. cucumerinum occurred. Comparisons of anti-fungal activity of extracts between species and between sapwood and heartwood were made. Results revealed that several zones of inhibitory activity, indicated by their Rf-values, were clearly visible on chromatographic separations of methanol extracts of these 5 wood species. The inhibitory zones for 2 heartwood extracts (except kulim) did not move from the origin which was also resistant to infection. However inhibition zones were also detected for the sapwoods of rubberwood, jelutong and Scots pine against C. cucumerinum despite the known sapstain and decay susceptibility of these wood substrates. The presence of hitherto unidentified anti-fungal compounds in the sapwoods of these species may elicit limited potency or narrow spectrum protection from fungal infection and onset of stain or decay

Laboratory Evaluation of the Formosan Subterranean Termite Resistance of Borate-treated Rubberwood Chipboard

Both no-choice and two-choice 4-week AWPA laboratory tests were performed to evaluate the resistance of borate-treated rubberwood (Hevea brasiliensis) chipboard prepared from a commercial mill run, against the Formosan subterranean termite Coptotermes formosanus. Boric acid (technical granular) was incorporated into the boards during manufacture to achieve loadings of 1.0% or 1.1% boric acid equivalents (BAE). In the no-choice test, both the untreated chipboard and solid rubberwood controls sustained heavy termite attack (respective mean visual ratings of 4.6 and 2.7 on a 10- point AWPA scale), while the two retentions of borate-treated chipboard showed only light grazing (mean rating 9.2). The two-choice test demonstrated a preference of termites for solid rubberwood (mean rating 2.4) instead of untreated chipboard (rating 8.4), and for untreated (mean rating 8.4 and 8.8) instead of borate-treated (mean ratings 9.8 & 9) chipboards. Complete termite mortality in the presence of borate-treated chipboard in both laboratory tests demonstrates the toxicity of borates to Formosan subterranean termites

KERUING and APITONG: A Timely Review of the Perfect ChoiceWood Species for Crossarms and Brace Arms, including Data on Copper Naphthenate Treatments

Apitong or the wood species more commonly known as Keruing is an important tropical hardwood known for its high strength to weight ratio and its reasonable durability and preservative treatability. This wood has been exported from managed permanent forest estates in Malaysia into the United States for over 4 decades for its widespread use in wooden utility industry brace arms and crossarms, yet currently it is not listed as an approved species by either ANSI or ASTM. Because it has not had any significant failures in its use patterns now for almost four decades, members of the AWPA Utility Users Task Group have asked for a comprehensive and Critical review of the species and its durability or treatability properties, since they have been using it and specifying it in their systems under product acception for years. This paper is meant to be a comprehensive review of both public domain data and privately sponsored studies to yield additional product information, for those using, specifying and treating this tropical, sustainable species from Malaysia