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Microbial tolerance and biodetoxification of organic and organometallic biocides
1990 - IRG/WP 1464
Ten organic and organometallic biocides were assessed for toxicity towards a range of wood decay and spoilage fungi. Minimum inhibitory concentrations indicated selective toxicity of biocides towards particular fungal types. Certain species of fungi demonstrated tolerance to a range of biocides. Further tests using the biocides in soil and wood enrichment cultures resulted in isolation of highly tolerant bacterial populations. Subsequent tests using these isolates and pure fungal cultures have demonstrated detoxification of a number of the biocides tested. The implications of these observations are discussed in relation to the use of biodegradable organic biocides as wood preservatives.
P A Briscoe, G R Williams, D G Anderson, G M Gadd

Testing of alkylammonium compounds
1981 - IRG/WP 2152
Following laboratory soil block tests which showed that Bardac 20 possessed a fungicidal threshold similar to that of chromated copper arsenate, treated ponderosa pine sapwood stakes were installed in a field test site near Vancouver, Canada. Two years after installation all the stakes show signs of fungal degradation. Seven stakes have been removed from the test due to total loss of strength after only two years, and many others are near failure due to extensive decay. It may be concluded from this study, that under the conditions of the test, Bardac 20 has failed to prevent wood-destroying fungi from decaying the stakes. Further investigation of treated "check" stakes and failed field tested stakes has revealed an uneven distribution of the chemical in some stakes treated to low retentions.
J N R Ruddick

Calculation of preformance index of Bardac 20 (an alkylammonium compound) evaluated in a field stake test
1982 - IRG/WP 3206
Bardac 20 treated stakes have been in test for three years at the Westham Island test site near Vancouver, B.C. The Performance Index for the preservative was calculated and found to be 0.009 which infers that, at the standard retention, Bardac 20 added 0.9 y to the life of the stake. It may be concluded that when tested using a standard field stake test using ponderosa pine (Pinus ponderosa Laws) sapwood at a standard retention of 6.35 kg/m³ Bardac 20 did not fulfil the expectations indicated from the laboratory screening test conducted earlier. Studies are in progress to determine the cause of this discrepancy in performance with a view to improving this class of compound as a wood preservative for use in ground contact situations.
J N R Ruddick

Field testing of alkylammonium wood preservatives
1983 - IRG/WP 3248
The field test performance of five alkylammonium wood preservatives is described. The relative effectiveness of three unmodified formulations was determined by calculation of a Performance Index. Of the three, didecyldimethylammonium chloride was found to be superior to octyldecyldimethylammonium chloride, and both were more effective than alkyltrimethylammonium chloride. However, none were considered to have potential for use as wood preservatives. The addition of cupric chloride to octyldecyldimethylammonium chloride did not improve its effectiveness. Initial results for alkyldimethylbenzylammonium chloride modified by the addition of tributyltin chloride indicated that the preservative performance may be significantly improved.
J N R Ruddick

Marine trial progress report
1980 - IRG/WP 453
In May 1977 and May 1978, tests of new chemical formulations for the protection of timber in the sea were installed in Mt. Maunganui Harbour. Investigation into new preservatives for such usage was urgently required since it had been found that there was progressive leaching of copper from copper-chrome-arsenate treated marine piles which could lead to a reduction in their service life. Hochmann (2) showed that few compounds exhibit the same toxicity to both Limnora and Teredo species. In the past it has been found that organotin compounds are among the more toxic chemicals to marine organisms. Representative chemicals of this type were therefore included in this test together with CCA retentions of 24 and 48 kg/m³ as standards from which performance of new formulations can be judged. Alternative inorganic formulations (acid copper chromate, copper silicate and ammoniacal copper arsenate) have also been included in this test. Since alkyl ammonium compounds (AAC) have been shown to exhibit some toxicity to marine borers, one of these compounds was included in the initial tests. To supplement the single formulation used in this series, copper salt-modified and alternate formulations of AACs were introduced for testing in May 1978. The treated stakes are being examined for resistance to both biological attack and leaching. In this report however, performance of the different treatments is rated by visual assessment and X-ray photographs of biological attack taken at sixmonthly intervals; chemical analyses to determine leaching rates have yet to be undertaken.
A F Preston, C M Chittenden

A field evaluation of modified and unmodified alkylammonium compounds
1987 - IRG/WP 3436
Laboratory soil block studies of alkylammonium compounds (AAC's) at Forintek and other research establishments have shown that they can prevent decay by standard wood-destroying fungi. Their performance in field tests, however, has been disappointing. Following investigation of possible causes for this poor field performance, stakes treated with modified AAC's were installed at Westham Island. All three formulated AAC's have shown greatly improved performance over the unmodified material. The inclusion of ammoniacal copper oxide with Barquat MB 80 (an alkyldimethylammonium chloride) is providing excellent performance after four years with log scores of 100 at retentions of 7 kg/m³ (total preservative). Stakes treated with the same AAC modified with tributyltin chloride to a retention of 1.2 kg/m³ (total preservative) had a log score of 87 after five years.
J N R Ruddick