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Potential toxicants for controlling soft rot in preservative treated hardwoods. Part 4: Evaluation of combined diffusion and toxicity
1979 - IRG/WP 2129
A large number of inorganic and organic preservatives were evaluated as potential soft rot control chemicals, by their degree of inhibition of fungal growth after allowing them to diffuse through a 6 mm thick wood slab. The tests were inoculated with wood powder from soft-rotted CCA treated poles. Pentachlorophenol was unable to diffuse quickly through the wood slab, although formulations with hexylene glycol showed some promise. Hydroxyisoxazole gave good results as did a number of other organic materials including "Busan 30", "Busan 52", "Permapruf T", sodium oxinate, sodium trichlorophenate, "Gloquat C", „Hyamine 1622", butyl icinol, and the commercial bandage materials "Osmoplast" and "Wolman pole bandage". Of the inorganic materials tested, good results were obtained with "Basilit BFB", with other Cu-F-B formulations including "Blue 7", and with fluoroborate and fluorosilicate preparations in general. Arsenates also showed some promise.
E W B Da Costa, O Collett

Efficacy of anhydrides as wood protection chemicals - II. Performance against soft rot fungi
1998 - IRG/WP 98-30174
Pine sapwood modified with various anhydrides and with butyl isocyanate was tested for its resistance to soft rot decay. Small stakes were exposed for 20 months in unsterile soil in a fungal cellar test. Wood modified with butyl isocyanate performed better than any of the anhydrides tested, with a threshold level of protection (less than 3% weight loss) at 12% weight percent gain (WPG). Stakes acetylated to 15% WPG did not give complete protection against soft rot. Stakes modified with alkenyl succinic anhydride showed increasing resistance to soft rot with WPG up to about 10% WPG, above which no further improvements were evident. Succinic anhydride and phthalic anhydride treated stakes showed little or no noticeable protection.
S C Forster, M D C Hale, G R Williams

The Role of Coformulants in Preventing Bacterial Biotransformation of IPBC
2002 - IRG/WP 02-10436
The inhibitory effects of disodium tetraborate decahydrate and benzalkonium chloride (BAC), two common coformulants of IPBC in antisapstain treatments, on an IPBC-transforming enterobacterial isolate ‘W1’ were determined by their effect on the specific growth rate constant in vitro. The IC50s of IPBC, BAC and borate were found to be 0.46, 0.026 and 5.7 mM respectively. The IC50 of the Arch antistain product AntibluTM Select was 0.024 mM, based on its BAC content. Although their IC50’s were significantly different, it was clear that the vast majority of the bacterial toxicity of the AntibluTM Select was due to its BAC content. The degradation of 0.4 mM IPBC by the bacterium W1, as measured by the accumulation of its degradation product, iodide, in liquid culture, was completely inhibited by BAC concentrations greater than 18 μM, and the toxicity of the spent culture medium to Aspergillus niger, as measured by an antibiotic assay disc assay, was not ameliorated above this concentration. Below 18 μM, the toxicity of the spent broth was significantly reduced, and the accumulation of iodide occurred rapidly. Demonstrating the toxicity of BAC to bacteria, and its consequent inhibition of IPBC degradation in vitro, are indicative of the importance of coformulation in controlling bacteria that might otherwise cause preservative loss, and of their significance in determining the ultimate environmental fate of cobiocides.
S R Cook, D J Dickinson

Low-toxicity DNBP wood preservatives
1987 - IRG/WP 3408
Low and very low toxicity single compound preservatives of both excellent insecticidal and fungicidal activity for interior, extrior and ground-contact applications are presented. These are ester derivatives of alkyl dinitrophenols, in particular of 2-sec-butyl-4,6-dinitrophenol (DNBP) and 2-sec-octyl-4,6-dinitrophenol. These esters, of much lower toxicity than DNBP impart to the treated timber comparable long term durability at much lower mammalian toxicity. These esters are shown in hydrolise to DNBP in the timber, explaining its long term durability.
A Pizzi, W E Conradie, A Jansen, R Vosloo

Water-borne DNBP wood preservatives - Preparation and performance
1987 - IRG/WP 3407
Three waterborne wide-spectrum ground-contact DNBP (2-sec-butyl-4,6-dinitrophenol) wood preservative formulations and their performance are presented. Two are double-treatment formulations in which insolubilization and precipitation of the preservative is attained by salt formation or by formation of a water insoluble Cu/NH3/DNBP complex of formula [DNBP]2 [Cu(NH3)2]2 the clarified structure of which is also presented. The third waterborne DNBP formulation is a single treatment water emulsion which has been produced for many years as an herbicide. It underwent ground-contact fungal and termite field tests for more than twenty years: these results are presented, evaluated and discussed.
W E Conradie, A Pizzi

Studies on the Toxicity of IPBC and Other Biocides to Bacteria
2004 - IRG/WP 04-10544
Twenty-six strains of bacteria were isolated from IPBC-, Bethoxazin- and creosote-enrichment. These were found to fall into six principal clades: enterics, pseudomonads, Stenotrophomonas, Actinomycetes, Alcaligenes and Bacillus. Of these, only the last group was largely incapable of the dehalogenation of IPBC. Six representative strains were chosen for further study, and the ability of these six bacteria to degrade IPBC was elucidated. The Bacillus and actinomycete were less capable of IPBC degradation than the four other clades. The IC50s of IPBC; its degradation product PBC; a representative biocide, Bethoxazin; a representative disinfectant, BAC; and a representative antibiotic, tetracycline, to the six bacteria were measured. No significant correlation between IPBC-resistance and coresistance to the other chemicals was found. A scheme for rational investigation of coformulants is presented. An effective coformulant targeted against those bacteria that would otherwise degrade a principal biocide should have acceptable bacteriocidal activity. However, it is also advantageous for bacterial resistance mechanisms against the coformulant and the principal biocide to be dissimilar, so to reduce the evolution of coresistance, and hence increase the sustainability of the biocidal product in the long term.
S R Cook, D J Dickinson

The Bacterial Biotransformation of IPBC
2002 - IRG/WP 02-10437
The bacterial biotransformation of the biocide IPBC, widely used as an antisapstain wood preservative, was investigated in bacteria isolated from failed wood, soil experiencing IPBC wash-off, and John Innes No. 2 compost. Nine strains of bacteria were isolated, belonging to the genera Alcaligenes, Enterobacter, Microbacterium and Pseudomonas. The sole organic degradation product in an enteric bacterium ‘W1’, isolated from failed wood, was PBC, which was produced at 1:1 stoichiometry. No further degradation products were isolated: PBC appeared to be the terminal product of transformation. Incubation of 0.8 mM IPBC in mineral medium with W1 for 90 hr caused the IPBC concentration to fall to undetectable levels, and the toxicity of spent broth was reduced to zero for four target fungi as measured by an antibiotic assay disc bioassay. Furthermore, the toxicity of PBC to the fungi as bioassayed, was c. 1/1000 that of IPBC. The widespread ability of common soil and wood bacteria to transform IPBC to less toxic products is an important contribution to an understanding the environmental fate of IPBC and its continued use under the auspices of the European Biocidal Products Directive (BPD).
S R Cook, J Sullivan, D J Dickinson

Performance of 3-iodo-2-propynyl butyl carbamate (IPBC) in L-joints under tropical conditions
2016 - IRG/WP 16-30688
The ability of 3-iodo-2-propynyl butyl carbamate (IPBC) to protect wood against fungal decay out of soil contact was evaluated using ponderosa pine L-joints at two exposure sites over a 12 year period. IPBC tended to provide better protection when formulated in an organic solvent and when applied using a double vacuum treatment. Performance also tended to be better when systems contained a water repellent. As expected, fungal damage occurred markedly more rapidly in the tropical site, but similar trends were beginning to be observed at the more temperate site.
J J Morrell