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Synergistic effect of boron on Streptomyces rimosus metabolites in preventing conidial germination of sapstain and mold fungi
1992 - IRG/WP 92-1565
We evaluated the synergistic effect of boron (4% BAE solution of Tim-Bor or 4% boric acid) on Streptomyces rimosus metabolites in preventing spore germination of sapstain and mold fungi using plate bioassay, Southern yellow pine and sweetgum block tests, and green pine log sections: sapstain -- Ceratocystis coerulescens, Ceratocystis minor, and Aureobasidum pullulans; mold fungi -- Aspergillus niger, Penicillium spp, and Trichoderma spp. Inhibition of spore germination in plate bioassay by metabolites with boron was more effective than without added boron. Treatment of wood samples with the mixture of boron and unconcentrated metabolites also resulted in the synergistic effect and completely inhibited spore germination of sapstain and mold fungi.
S C Croan, T L Highley

Response of the Formosan Subterranean Termite (Coptotermes formosanus) to Cellulose Insulation Treated with Boric Acid in Choice and No-Choice Tests.
2004 - IRG/WP 04-10532
The tunneling ability of the Formosan subterranean termite Coptotermes formosanus Shiraki through a cellulose insulation material containing11.1% boric acid was tested in choice and no-choice bioassays. We examined tunneling behavior and mortality of termites exposed to treated and untreated insulation material in miniature simulated wall voids. In a choice test termites tunneled through untreated insulation in all but one of the replicates used. Termites were unable to fully penetrate any of the replicates containing treated insulation and experienced a significantly higher mortality (78.4 ± 18.4%) than termites exposed to untreated insulation (11.6 ± 5.6%, F = 60.4, df = 1, P < 0.0001). In a no- choice test termites fully penetrated all replicates containing untreated insulation and experienced 37.1 ± 37.2% mortality. Termites exposed to treated insulation in this test experienced a significantly higher mortality of 100.0% (F = 14.3, df = 1, P < 0.005), and did not fully penetrate the treated insulation.
M E Mankowski, J K Grace

Boron treatments for the preservation of wood - A review of efficacy data for fungi and termites
1994 - IRG/WP 94-30037
Boron treatments have been used for many decades for protection of timber from biological attack and also as a fire retardant treatment. In recent years there has been an increased interest in boron treatments as an option for protection of structural timbers&apos; e.g. timber framing used in termite risk areas. This paper reviews efficacy data for both fungi and termites relevant to this end-use.
J A Drysdale

Preliminary results of investigations on screening test of chemical compounds suitable for the preservation of lignocellulosic materials against biodeterioration
1976 - IRG/WP 262
This paper investigates the possibilities of reducing the time needed for the determination of the effectiveness of chemical compounds from the point of view of their eventual application to lignocellulosic materials for preservation against decay and soft-rot.
K Lutomski, S S Neyman

The influence of boric acid on respiratory quotients and methane production of subterranean termites
1995 - IRG/WP 95-10136
The toxicity of boron compounds to subterranean termites (Reticulitermes lucifugus) was studied by analysing changes in the levels of oxygen uptake respiratory quotients and methane production. Termites were fed with filter paper treated at different levels of boric acid, the RQ was evaluated by constant volume manometry and the methane production by gas chromatography. Results are discussed in relation to termite gut symbiontes.
L Nunes, D J Dickinson

Comparative investigations on the influence of wood seasoning, wood properties and temperature on the toxic values of wood preservatives against Hylotrupes egg larvae
1970 - IRG/WP 28
Comparative tests carried out at three institutes indicated the influence of kiln temperature, position of wood specimens in the cross sectional area and test temperature on the toxic values determined in accordance with DIN 52165 with egg larvae of the house longhorn beetle (Hylotrupes bajulus L.). The preservatives applied were boric acid in distilled water and g-benzene-hexachloride dissolved in chloroform; the timber species used was pine sapwood, (Pinus sylvestris L.). The method of seasoning had no influence on the toxic values of boric acid. With the g-BHC, however, the toxic values gradually increased with rising kiln temperatures (20°C, 70°C, 105°C). With boric acid the position of the sapwood samples in the log had no influence on the toxic efficacy; with g-BHC the efficacy was slightly greater in the outer sapwood, compared with the inner sapwood. The test temperatures (20°C, 24°C, 28°C) yielded different toxicity results for boric acid. At 24°C and 28°C the threshold values were somewhat below those of 20°C; they agreed with the values obtained at 20°C after a longer test period. With g-BHC different temperatures did not affect the results. An explanation is suggested for the causes of the influence exerted by the kiln temperature and wood properties on the toxic values of g-BHC. There was good agreement between the toxic values obtained in the different institutes.
G Becker, T Hof, O Wälchli

Options for accelerated boron treatment: A practical review of alternatives
1985 - IRG/WP 3329
Boron wood preservatives are almost exclusively applied by momentary immersion and block diffusion storage. Alternative techniques are described which can be used to accelerate boron treatment. Diffusion coefficients have been derived to define the acceleration of diffusion with increasing temperature. Schedules are described for pressure impregnation of green timber, involving steam conditioning, evacuation and alternating pressure method treatment. Timber Preservation Authority penetration and retention requirements can be met in approximately 4-5 h. The optimum schedule, however, included a 12 hour holding period between steaming and preservative treatment. A method of applying boron preservatives as a vapour is described, Trimethyl borate vapour reacts with wood moisture to form boric acid. The kinetics of this reaction, however, are very fast. This limits treatment to timber dried to very low wood moisture contents.
P Vinden, T Fenton, K Nasheri

Movement of boron from fused boron rods implanted in Southern pine, Douglas fir, red oak, and white oak timbers
1995 - IRG/WP 95-30061
This paper reports the distribution of boron from fused boron rods installed into six-inch (15.2 cm) square timbers of Douglas-fir, Southern Pine, red oak and white oak exposed aboveground. The composition and size of rods was: sodium borate and sodium borate-copper oxide (8.5 x 100 mm²); sodium borate-copper, sodium borate and boric oxide-copper oxide (12 x 76 mm²). The boric acid equivalent was roughly monitored by the curcumin/salicylic acid color test and the presence of copper was detected by the chrome azurol-S reagent. One year after installation of rods, movement of boron was determined by application of curcumin dye to increment cores removed at various distances from the site of boron rod installation. A portion of a sodium borate treated Southern Pine timber was also analyzed by spraying curcumin dye on sawed longitudinal and transverse sections. At 2 years, one foot sections were removed from all timber species, sawed as above, and boron and copper detection reagent sprayed on the sawed surfaces. Movement of copper from rods in all timbers was virtually nil. Both transverse and longitudinal movement of boron from rods was greatest in Southern pine which also had the highest moisture content. Movement of boron was next best in red oak. There was little movement of boron away from the rods in white oak and Douglas-fir.
T L Highley, L Ferge

A new approach to the maintenance problems of wooden railway sleepers
1986 - IRG/WP 3392
The microenvironment of wooden railway sleepers is being investigated to assess their condition to determine the necessary treatment, repair and replacement criteria. The research work involves the development of an integrity tester to determine the condition of sleepers, a remedial treatment of sleepers by selective application of boric acid and a synthetic repair system.
W Beauford, P I Morris.

Diffusion treatment plants (Latin America - Africa)
1974 - IRG/WP 333
B N Prasad

In-situ pressure injection for preservation of rubber wood (Hevea brasiliensis Muel Arg.)
1992 - IRG/WP 92-3688
Rubber wood is widely used for the manufacture of furniture, doors for housing and packing cases. However in an untreated condition it is highley susceptible to sapstain and decay fungi and borers. Its utility gets considerably reduced if the wood is not treated well in time. Preservative treatment has to be given within the period of felling and transport to prevent not only loss of structural properties and wood material. Although Boucherie, hot-cold bath diffusion, pressure impregnation, vacuum-pressure impregnation processes for treating timbers have been successfully employed for protection, but the process in cumbersome and difficult to adopt at the site of extraction. Hence, it was found necessary to evolve a simple and convenient method to treat trees in-Situ. A simple pressure injection technique was adopted to treat the standing tree using an instrument designed at the Institute (IWST). This instrument is easy to operate and inexpensive. It was observed that the movement of preservatives was satisfactory and effective. Samples of wood taken from treated stem of such trees were subjected to attack by brown and white rot fungi in the laboratory. It was observed that wood samples treated with Borax, boric acid and Bavistin (1:1:0.2); Borax, boric acid and Sodium pentachlorophenoxide (1:1.5:1) and Bavistin and Ekalux (0.5:0.5) showed higher resistance to fungi and insect attack compared to boric acid and Borax (1:1) in both laboratory and field conditions. Treated wood also retained natural colour and was free from fungal and insect attack for over 24 months in storage. Studies in this method of treatment of plantations species are in progress.
H S Ananthapadmanabha, V R Sivaramakrishnan

Ground contact performance of wood treated by the MSU process
1990 - IRG/WP 3609
Environmental concerns have prompted a renewed interest in accelerated fixation schemes for CCA-treated wood. Results from stake tests of southern pine (Pinus sp.) treated using a conventional Bethell cycle are compared with matched stakes treated using the MSU Process. The effects of adding boric acid to the preservative formulation are also discussed. Differences among test plots are discussed.
H M Barnes, T L Amburgey, R W Landers

Vapour boron treatment of wood based panels: Mechanism for effect upon impact resistance
1994 - IRG/WP 94-40036
Samples of medium density fibreboard, chipboard and oriented strandboard (OSB) were treated to two retentions of boric acid by a vapour phase treatment. The results of a range of mechanical tests were reported by Hashim et al. (1992, 1993) in which a small reduction in impact resistance was observed. Several investigations were carried out to study how and where this loss in impact resistance occured. Possible mechanisms for the loss in impact resistance are discussed.
R Hashim, R J Murphy, D J Dickinson, J Dinwoodie

Sterilization of mango wood (Mangifera indica L.) without heat
1995 - IRG/WP 95-30065
Researches revealed that boric acid can play an important role for sterilizing wood instead of heating. Wet (green) mango boards (Mangifera indica L.) were pressure treated in treating cylinder at initial vacuum of 508 mm Hg for 15 minutes and impregnation pressure of 7 kg/cm² for 4 hours with 5% solution (w/v) of 1:1:1 commercial grade (95% pure) sodium dichromate, copper sulphate and boric acid. Penetratons of copper sulphate and boric acid were examined by using standard reagents. Copper sulphate penetrated superficially but boric acid penetrated completely through the boards. In most hazardous conditions during rainy season the treated boards were saved like heatsterilized boards from the attack of decay fungi and insects. Untreated boards (control) were found decayed and damaged within three months with the decrease of strength significantly. Where heatsterilization and kiln-drying are practically impossible during rainy season, wet timbers can be stored after impregnating those with at least 2% solution (w/v) of boric acid which diffuses through wet wood successfully and can protect wood from decay fungi, and wood destroying borers.
A K Lahiry

The reliability of colouring methods for the determination of biflourides and boron in spruce wood
1994 - IRG/WP 94-20036
From practical reasons, qualitative spraying methods are widely used for the detection of bifluorides and boron in wood. The main aim of this research was to detect whether the concentration of the active ingredient in the coloured area is equal or greater than the toxic value against basidiomycetes. Both colouring methods, Z-A reagent for fluorides and curcuma reagent for boric acid, are a reliable means for the determination of the toxic threshold value, (found in literature) against basidiomycetes in spruce wood. Quantitatively, for fluorides the Eriochromocyaninezirkoniumoxidchloride method (DIN 52161 part 4) and for boron the mannitol - azomethine method (Peylo, 1993; Merck, 1989) are easy to perform and accurate
R Grell, M G Sanders, W J Homan, H Militz

Leaching results of shower test on L-joints with boric acid, bifluoride and TBTO rods
1995 - IRG/WP 95-50051
As part of the EC-project "Improvement of a local preservation process for wood products with reduced environmental impact", TNO has performed a leaching test on L-joints treated with pills with boric acid (Defence corner), bifluorides (Woodpil 55) and TBTO (Woodcap). The L-joints were exposed in an adapted shower test during 10 days, using 70 liters of water per day. The experiment is designed to measure leaching under extreme service conditions. Spruce and pine, painted and unpainted L-joints were compared. In general leaching was the highest in spruce. The L-joints treated with boric acid pills showed the highest leaching, with very small differences between painted and unpainted L-joints. Leaching from fluoride and TBTO treated L-joints was even slightly higher than in painted L-joints. From these results it is suggested, that the active ingredients predominantly leach from the end grains in the open joint area of the timber. A higher water run off rate from longitudinal surfaces in painted L-joints could explain for the higher leaching rate in these samples
P Esser, M J Boonstra, W L D Suitela, A J Pendlebury

Bioefficacy of boric acid grafted onto wood
1999 - IRG/WP 99-30202
The use of borate treated wood in outdoor is limited because of the migration of borate. The objective of this study is to investigate the fixation of boric acid in wood using polyethylene glycol (PEG-400) to form polyester borate and isocyanato group as coupling agent. FT-IR was used to monitor the reaction between boric acid and PEG. Elemental analysis was conducted to evaluate the C, H, and N variation in weight before and after treatment. Very low to undetectable level of boron was leached from the grafted sample suggesting a good fixation of boron to the wood compounds through 4,4&apos;-Methylenediphenyl isocyanate (MDI) coupling agent. Laboratory soil block tests were conducted using white and brown rot fungi. At retention level of 0.79% BAE (Boric Acid Equivalent), an adequate protection against brown rot was obtained.
Weining Cui, D P Kamdem

Treatment of wood-based panel products with volatile borate
1990 - IRG/WP 3616
The paper presents recent developments in the use of volatile borate esters for the preservative treatment of wood based board materials. Several advances on previous reports are discussed. In laboratory studies, treatment times of approximately ten minutes at 20°C on boards at equilibrium moisture content provided full penetration and retentions of 1% wt/wt boric acid. Biological tests have been conducted on a wide variety of boards treated by the vapour boron method. In all cases a retention of 0.7% wt/wt boric acid gave complete protection from decay. These results are considered with regard to parallel studies on solid wood by colleagues at the Forest Research Institute, Rotorua. The advantages of vapour boron treatment for wood based board materials are discussed.
P Turner, R J Murphy, D J Dickinson

The efficacy of remedial treatments for controlling fungal decay in window millwork used in the United States
1987 - IRG/WP 3432
Conventional window millwork was subjected to basidiomycete decay by inoculation and sampled for active growth of the decay fungus before and eight months after remedial preservative treatment with fused disodium octaborate rods (IMPEL) at boric acid levels of 1.5 and 4.0 kg/m³ or liquid bifluoride injections (IMPROSOL) at 1 kg/m³. The elimination of decay fungus after remedial treatment was nearly 100% effective in all treated material regardless of remedial treatment used or chemical loadings. By contrast, isolation of decay fungi in the control samples increased overall from 27 to 69%. Color reagent dye tests for diffusion indicated excellent distribution of chemicals in wood material where moisture contents exceeded 25%.
M G Dietz, E L Schmidt

Laboratory evaluation of borate formulations as wood preservatves to control the subterranean termite coptotermes acinaciformis (isoptera: Rhinotermitidae) in Australia
2001 - IRG/WP 01-30266
The termiticidal efficacy of Borocol (sodium octaborate tetrahydrate), boric acid, bore-ester-7 and tri- methyl borate was evaluated in laboratory bioassays against Coptotermes acinaciformis (Froggatt). Seasoned sapwood blocks of Pinus radiata D. Don, and Eucalyptus regnans (F. Muell) were impregnated with the various borate compounds. There were marked differences in mass loss and mortality rate of the termite used in the bioassay units for different boron retentions. After 8 weeks the result suggested that, borate was toxic to termites in laboratory bioassay even at 0.20% m/m BAE and caused significant termite mortality. However, termites were not deterred from attacking the borate treated timber at higher retentions of > 2.0% m/m BAE. These laboratory results indicated that the minimum borate treatment required to protect timber against termites attack and damage was > 1.0% m/m BAE.
B M Ahmed, J R J French, P Vinden

A chemical and mycological evaluation of fused borate rods and a borate/glycol solution for remedial treatment of window joinery
1983 - IRG/WP 3225
The possibility of using fused borate rods (Impel Borpatron) and a borate/glycol solution (Boracol-40) for depot impregnation of window joinery has been examined in a co-operative project between The Swedish Forest Products Research Laboratory, The Swedish University of Agricultural Sciences and Prolignum AB. The fused Impel rod is a glassy rod composed of disodium octaborate which readily dissolves and is distributed as bore acid when introduced into moist timber. Boracol-40 is a liquid containing disodium octaborate dissolved in glycol which has an ability to disperse in timber with a moisture content below 25%. The study involved treatment of a large number of windows in service as well as chemical and biological laboratory tests on the distribution and protective effect of the preservatives. In the field study about 100 windows, selected at random in various buildings in the Stockholm and Gothenburg areas were treated in-situ.
M-L Edlund, B Henningsson, A Käärik, P-E Dickèr

Leaching characteristics, decay and termite resistance of treated wood with boron compounds, N'-N-(1,8-Naphthalyl) hydroxylamine (NHA-Na), and hydroxynaphthalimide (NHA-H)
2003 - IRG/WP 03-30307
Despite many advantages of boron wood preservatives, boron itself does not adequately protect wood in ground contact and exterior applications because its natural diffusibility and susceptibility to leaching. As a result of previous studies to limit or decrease boron leaching, several fixation systems have been developed. In this study, we evaluated the effects of N&apos;-N-(1, 8-Naphthalyl) hydroxylamine (NHA-Na) and hydroxynaphthalimide (NHA-H) on boron leaching and decay and termite resistance via boron precipitation in wood after NHA treatments at varying concentrations. Wood blocks were treated with disodium octaborate tetrahydrate (DOT), boric acid (BA) NHA-Na or NHA-H solutions. Preliminary results showed treatment of wood blocks with DOT, boric acid, and calcium borate and 1% or 0.1% NHA-Na solutions in sequential processes appears to somewhat reduce the susceptibility of boron to leaching. Blocks treated sequentially with boron compounds and then 1% NHA-Na solutions showed about 30% less boron leaching. In addition, the existence of boron and NHA in wood together showed a synergetic effect against wood degrading organisms and termites. We conclude that precipitation of NHA at higher concentrations decreases or limits boron leaching. On the other hand, the relationship between boron and NHA concentration in wood as regards precipitation possibilities appears to be predictive for reducing boron leachability.
S N Kartal, Y Imamura

Remedial treatments of glulam = diffusion of active ingredients through glue lines from solid wood diffusable preservatives
1996 - IRG/WP 96-30117
Diffusable preservatives are very suitable for use in remedial treatments of laminated beams in which too high moisture content involves the development of wood destroying fungi. The diffusion of active ingredients (boric acid, disodium octoborate, bifluoride) is well observed in solid wood but in a composite wood, the glue lines may appear not only as a barrier for the diffusion but also, may be mechanically affected by the diffused active ingredients. Shear tests were carried out on glulam specimens manufactured with different types of glues: resorcine (RF), ureaformaldehyde (UF), polyurethane (PUR) and polyvinylacetate (PVAc). Diffusion tests were also carried out in accelerated wetted glulam specimens with three diffusable solid preservatives differently exposed in the test samples. Results observed with boron compounds showed that their diffusion does not affect the mechanical resistance of the beams. In another hand, interesting results were obtained concerning the passage of boron and bifluoride through some types of glues. These results will contribute to the optimization of the remedial treatment of glulams.
D Dirol, S Mouras

The probable mechanism of action of boric acid and borates as wood preservatives
1990 - IRG/WP 1450
The tetrahydroxyborate ion [B(OH)4-] acts by complexation with poly-ols and probably attacks decay fungi through extracellular substrate sequestration; intracellular substrate sequestration; enzyme inhibition; and change in membrane function. Work was carried out to investigate this further and to try to explain certain phenomena observed in the area of boron preservation. The effect of Na borate in the presence of different concentrations or various carbohydrates upon the radial growth rate of certain fungi was investigated; along with parallel experiments on the activity of 6-phosphogluconate dehydrogenase as an example of a borate inhibited enzyme system. It was found that upon the addition of certain poly-ols, the inhibitory effect of borate on both fungal growth and enzyme activity could be reduced. These results have been used in the development of our understanding of the mechanism of action of borates as wood preservatives. The commonly held belief that certain mould species are resistant to borates may also need re-evaluation.
J D Lloyd, D J Dickinson, R J Murphy

Laboratory screening to determine the preventive effectiveness against blue stain fungi and moulds
1991 - IRG/WP 3677
This paper reports results of preservative treatment and leaching experiments, using borax, polybor and boracol 20, on small wood blocks of English oak and American pitch pine heartwood. Earlier experiments on the performance of various biocides as possible additives to bilgewater to prevent fungal decay of shipping timbers had suggested that some formulations of boron might be associated with physical changes to specific types of timber. Since samples of oak and pitch pine were to be supplied for remedial work on the historic ship RRS Discovery it became important to investigate more critically the effects of boron on such timbers. Variable factors investigated in this study included temperature, sample type, soaking time in preservative and time of leaching. Weight changes and dimensional changes were measured. Preliminary results indicate that there was little effect, at 10°C, on block weight or dimension. Some changes were found at 45°C indicating that the results obtained in earlier experiments may be unrepresentative of those which might be obtained when the biocide is used under service conditions.
M T De Troya, A M Navarrete

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