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Colonization of treated and untreated ponderosa pine exposed in Hilo, Hawaii
1995 - IRG/WP 95-20068
The rate of decay in above ground exposures is largely controlled by rainfall and temperature, factors which can be used to construct a climate index of decay hazard in above ground exposures. Developers of new biocide formulations have utilized this knowledge by establishing test sites in sub-tropical regions such as the Gulf Coast of the United States. More recently, field sites have been located in regions with even higher climate indices with more severe risks of decay. One such site is Hilo, Hawaii which receives nearly 4000 mm of rainfall per year and has near optimal temperatures for microbial growth. Previous field trials have shown that untreated control L-joints fail in as little as one year at such sites, but the organisms associated with these failures and their interactions in the deterioration process remain poorly understood. It has been suggested that results from such tests may be poor indicators of chemical performance under less severe exposures. To address this issue, the fungal flora colonizing wood was assessed in L-joints and deck boards exposed above ground in Hilo, Hawaii. The samples were either untreated or treated with 0.5% triazole 1, 0.5% tributyltinoxide, 0.5% 3-iodo-2-propynyl butylcarbamate, or 0.25% triazole 2 in mineral spirits or water. Selected samples were removed periodically and cultured for the presence of decay fungi. While basidiomycetes were not prevalent among the initial colonizers, they became increasingly abundant after 18 months of exposure. Among the fungi isolated were Trametes versicolor, Fomitopsis meliae, Schizophyllum commune, and Antrodia sinuosa. These fungi are also found under more temperate exposures suggesting that data from tropical sites represents a similar, albeit more accelerated, progression of decay organisms. Further studies on the decay capabilities of selected isolates are underway.
C M Freitag, J J Morrell, K J Archer
Microbial ecology of treated lap-joints exposed at Hilo, Hawaii for 12 months
1996 - IRG/WP 96-20089
Lap-joints made from Southern yellow pine treated with ACQ, DDAC or Propiconazole were exposed and sampled over 12 months. TnBTO treated Lap-joints were later exposed as a standard treatment. The moisture content of the joint area remained at 23% to 28%, but, away from the joint, varied between 20% to over 30%. Untreated samples had higher moisture contents and there was little difference between upper and lower members in all joints. Visual assessment, according to pr ENV 12037, indicated no failure but control samples were deteriorating internally, remote from the joint area. ACQ and Propiconazole treatments performed well, but, DDAC samples less so with regard to discoloration. Discoloration was less apparent in joint areas than on the external faces. Basidiomycetes had become more common at 12 months than previously, mainly on untreated samples. Mould and bacterial species were isolated less frequently on all samples after 12 months. Preservative tolerant organisms included Phialophora sp. (on ACQ), Aureobasidium pullulans (on TnBTO) and various bacteria on all treatments. Different microflora patterns could be clearly distinguished for each treatment.
S Molnar, D J Dickinson, R J Murphy
Microbial ecology of treated Lap-joints exposed at Hilo, Hawaii for 24 months
1997 - IRG/WP 97-20107
This paper is a continuation of previous work reported in IRG/WP 96-20089 by Molnar et al. (1996) in which Lap-joints, made from Southern yellow pine and treated with ACQ, DDAC or propiconazole were sampled over 12 months exposure at Hilo, Hawaii. 18 and 24 month samplings have since taken place and are reported here. TnBTO treated Lap-joints made of scots pine which were exposed later as a standard treatment (ENV 12037: 1996) have now been sampled up to 12 months. The observations and conclusions reached after the recent 18 and 24 month exposure period have, in the majority of cases, been consistent with those made from the earlier samplings. Visual assessments according to ENV 12037 indicated that only the untreated joints were starting to fail at 24 months. Visual assessment also indicated that ACQ treatments performed well but DDAC samples less so. It was observed from detailed sampling that the discoloration of a sample may give a misleading rating, many joints appearing poor but being internally sound. Differences in the pattern of colonisation of the Lap-joints after 24 months exposure were now more clearly associated with different treatments. Bacteria and moulds were common throughout the 24 months, although moulds were inhibited in TnBTO treated samples. Bacteria and yeasts were abundant in propiconazole and DDAC treated samples. Soft-rots were uncommon, with the exception of Phialophora sp. which occurred frequently with ACQ, and rarely in propiconazole treatments. Aureobasidium pullulans was a common stainer but was inhibited by propiconazole and ACQ treatments. A. pullulans was dominant on TnBTO treated Lap-joints. A limited number of Basidiomycetes were isolated, especially from the untreated samples, and these included Phellinus sp., Postia placenta and Gloeophyllum sp.
S Molnar, D J Dickinson, R J Murphy
Performance of dip and pressure treated wood in termite ground proximity exposures in Hilo, HI, and Colombia
2008 - IRG/WP 08-30491
A number of preservative systems were evaluated for their ability to control termite attack when applied as both dip and pressure treatments. With dip treatments, better performance was observed with southern pine than spruce-pine-fir using the same solution strength treatment, probably as a result of the about 50% greater uptake with southern pine and associated deeper preservative penetration. Boards that were cross-cut after treatment suffered much great attack, suggesting that the shell treatment does not provide any protection to post treatment cut ends. There were also indications that the type of cover used in the termite ground proximity test may greatly influence the activity of the termites in the arrays.
P Walcheski, A Zahora
Above ground testing at tropical test sites, what have we learned?
2011 - IRG/WP 11-20473
Three different above ground test methods have been utilized at a selection of five tropical and sub-tropical test sites with a variety of treated and untreated material. The results show that a multi-site approach to above ground field tests presents the opportunity for exposure to un-predicted biodeterioration hazards, which may be important for developmental products of poorly characterized fungicidal performance. The results also show that for tests exposed above ground on racks or fences, high climate index sites may benefit from canopy exposures of the samples rather than open field exposures. The Lap-joint test data from this study suggests that this method is a poor choice for providing rapid results even at test sites with high decay hazards
A Preston, A Zahora, Y Cabrera, L Jin, C Schauwecker, P Walcheski