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Characterisation and evaluation of various chitosan oligomers, and decay resistance
2011 - IRG/WP 11-30562
Chitosan, a polymer of D-glucosamine, is known for its antimicrobial activity. However, the physicochemical properties of chitosan depend upon three principal factors, i.e. source of raw material, molecular weight and degree of deacetylation. Here, we report synthesis and characterization of chitosan oligomers prepared by deaminative depolymerization of chitosan (s) obtained from Sigma Aldrich and China (industrial grade). Subsequently their antifungal activies were evaluated using both agar nutrient medium and wood decay bioassays. The nutrient medium bioassay results showed that chitosan(s) and chitosan oligomers affected mycelial growth to different magnitudes. Nevertheless, two of the low-MW chitosan oligomers completely inhibited the growth of all the tested fungi as compared to high-MW chitosan oligomers. However, the work presented in this paper, depicts that antifungal activity increases by decreasing the degree of polymerization of chitosan oligomers, which is a contrary to the reported literature. The wood decay trial confirmed the antifungal activity of chitosan oligmers against basidiomycetes but highlighted the leachability of chitosan when exposed to water.
I Hussain, C Chittenden, T Singh
Current techniques for screening initial formulations against Basidiomycetes and soft rot
1978 - IRG/WP 2103
J D Thornton, H Greaves
Termiticidal chemicals derived from tropical tree resins
1991 - IRG/WP 1477
To test the hypothesis that defensive chemicals protect tropical primary forest trees against biological attack, a bioassay and fractionation program was conducted in Indonesia. Fresh dipterocarp resins were fed in no-choice tests to Neotermes dalbergiae termites on 4.5 cm filter papers, or tested for inhibition of fungal growth. Fractionation of biologically active resins via flash column chromatography, followed by subsequent bioassay and analytical chemical studies, revealed that several sesquiterpene compounds inhibited fungal growth and killed 50% of test termites in 3-7 days. Toxic fractions contained caryophyllene, caryophyllene oxide, alloaromadendrene, and other compounds. From the relatively non-toxic a-gurjunene, novel termiticidal compounds were synthesized, indicating the potential for manufacture of insecticides from natural products.
A Messer, K McCormick, D Richardson, Sunjaya, H Hagedorn, J Meinwald
A critical review of the AWPA standard method (M12-72) for laboratory evaluation to determine resistance to subterranean termites
1986 - IRG/WP 1298
The American Wood Preservers' Association standard (M12-72) for evaluation of candidate wood preservatives against subterranean termites is reviewed and suggestions for revision are made. The most serious flaws in the current test procedure involve a failure to recognize inter- and intraspecific variation and a lack of quantification of test results.
J P La Fage, M Jones
Baiting techniques for subterranean termite control
1983 - IRG/WP 1205
The use of artificial baits, with and without toxins, have proved effective in attracting large numbers of non-mound and mound building subterranean termites in both urban and rural areas. An outline is presented of a termite baiting program which emphasises concurrent laboratory and field investigations on termite ecology, behaviour and physiology
J R J French, J P Robinson
Screening potential termiticides: Some thoughts and suggestions on methodology
1988 - IRG/WP 1363
While laboratory bioassays on the efficacy of potential termiticides against subterranean termites continues both to dominate and influence research efforts, suggestions are presented for the need to develop laboratory bioassays that more closely simulate "natural conditions". Not only is this considered desirable, but it will offer more confidence in laboratory and field evaluations and their analyses.
J R J French
A case for adopting a standardised protocol of field and laboratory bioassays to evaluate a potential soil termiticide
2003 - IRG/WP 03-20275
The rationale for adopting a new approach to the field testing of potential soil termiticides is advocated on the grounds that current testing methods are limited to termite bioassays and do not address quantitatively the persistence and bioavailability of soil termiticides to foraging subterranean termites over time and in different soil types. Furthermore, the present testing regimes assume field situations of uniform high termite hazard across field sites. Our testing procedures require the random sampling of soil cores from test soil pads (500 x 500 mm) at several geographically different locations. The soil cores from treated and untreated soil pads are returned to the laboratory and the soil residues in half of the samples examined for each year of test by gas chromatography. The bioavailability of termiticide residues in the remaining soil samples are evaluated by termite bioassays using the field collected subterranean termite, Coptotermes acinaciformis (Froggatt). Both tunnelling distance and mortality are used as indicators of termiticide activity and availability. This paper compares the traditional soil test methods with our new approach, which addresses the problems of security with longevity of test, variability of termite hazard levels at different field sites, and a practical method for managing variables in assessing potential soil termiticides. Importantly, this technique prevents the direct destruction of natural populations of subterranean termites or the indirect contamination by contact from soil residues of termiticides applied in and around active termite colonies.
J R J French, B M Ahmed
Bioassays for rapid assessment of heavy metal toxicity in seawater
1998 - IRG/WP 98-50112
In evaluating the effect of CCA leachate on the establishment of fouling communities on wood exposed in the sea, three organisms were assessed as biological indicators of heavy metal toxicity. These were two macroalgae, Fucus serratus and Undaria pinnatifida. and the motile protist thraustochytrid, Schizochytrium aggregatum. The choice of these organisms for the tests carried out was based on the need for rapid methodology and relative simplicity in their isolation and cultivation. The two test algae were collected locally on the south coast of England, cleaned of surface contamination and prepared for release of their respective reproductive spore types. Toxic effects of a range of concentrations of CCA leachate were then measured in terms of spore/zygote germination using simple microscopic observations after 3-4 days incubation. The thraustochytrid was obtained from stock cultures held at the University of Portsmouth. The zoosporic stage in the life cycle of this organism was used to indicate the toxic effects of copper ions in seawater-based medium by measuring loss in motility over a 20 minute period. Data were collected using motion analysis equipment. Subsequent recovery of zoospores after 1 hour exposure to different copper levels was determined. Non-motile stages of the life cycle of thraustochytrid isolates were also used to determine copper toxicity. Tolerance of these organisms to heavy metals in CCA leachates will be discussed.
C J Brown, R L Fletcher, R A Eaton
Practicability of bioassays in the evaluation of environmental risks in wood protection
1996 - IRG/WP 96-50071
As an example for the proofing of the practicability of bioassays in the evaluation of environmental risks in wood protection the ecotoxicological behaviour of CCF-impregnated timber was examined. After vacuum pressure impregnation specimen from shaped pine poles were tested on ecotoxicological effects of leachable compounds using sensitive aquatic organisms like fish, Daphnia and algae as bioindicators. According to proper impregnation the influence of leachable compounds from treated timber was significantly lower when compared with the acute aquatic toxicity of the preservative and its ingredients. This indicates the existance of safety factors and allows a differentiated estimation of environmental risks for impregnated wood. A general proposal for an ecotoxicological screening procedure in wood protection is presented.
Determination of fixation properties by bioassays - A proposal for the assessment of safety indexes in wood protection
1990 - IRG/WP 3566
In the determination of environmental effects of chemicals tests with fishes, daphnia and algae have proved to be practicable. With respect to wood protection such bioassays are suitable to control effects of treated timber against aquatic organisms. By using the fish-acute-toxicity-test the development of a laboratory test method is described for the checking of the fixation rate of a copper-chromium wood preservative. By this the importance of the observation of a proper fixation period is demonstrated for the use of treated wood in water contact. Estimating ecotoxicological effects of leachable compounds using sensitive bioindicators allows a differentiated determination of environmental risks of impregnated timber. The comparison with the toxic effects of the compounds of a wood preservative are a first step in the assessment of safety indexes in wood protection.
Bioassays of extracts from scaly ash (Ganophyllum falcatum B1) against the subterranean termite Coptotermes acinaciformis (Froggatt)
1983 - IRG/WP 1206
Scaly ash, Ganophyllum falcatum B1. wood shavings were extracted by methanol, and fractionated with ethyl acetate, diethyl ether and water, and the anti-termitic properties of these materials bioassayed against the subterranean termite Coptotermes acinaciformis (Froggatt). Laboratory techniques were developed to overcome the problem of limited extractive materials. The results of the various bioassays indicated that the most toxic extractives were cold methanol extract water solubles, and cold methanol insolubles.
J R J French, J P Robinson, J W Creffield
Natural durability transfer from sawmill residues of white cypress (Callitris glaucophylla). - Part 2: Laboratory fungal bioassays
2000 - IRG/WP 00-20204
Extracts from sawmill residues of the naturally durable white cypress, Callitris glaucophylla were tested for fungicidal activity in a series of laboratory bioassays. The effects of different extraction solvents, techniques and sources of material on the biocidal efficacy of the resultant extracts were evaluated. Soil jar decay tests were used initially however, contractual time constraints necessitated the development of a more rapid screening technique. A modified sapwood agar media was developed and found to be suitable for testing the extracts. It could be applied to other non-diffusible wood preservatives. Ground white cypress sapwood was impregnated with a range of concentrations of various extracts and gamma irradiated. The treated sterilised sawdust was suspended in water agar. The media were inoculated with a white rot, Lopharia crassa, or a brown rot fungus Polyporus verecundus. Growth of the isolates was monitored for four weeks, enabling dose responses to be accurately determined. Methanol was determined to be the most effective extracting solvent, and toxic threshold values of the methanol extracts were estimated. Fractions of the total extract were also compared. Most fungicidal activity was found in the most abundant fraction, which contained significant proportions of terpenes and other non-polar, low boiling point compounds.
M A Powell, L M Stephens, L Francis, M J Kennedy
Further thoughts on standard principles of testing termiticides and/or wood preservatives
1992 - IRG/WP 92-1530
At the last annual meeting in Kyoto, Japan, there was a special session devoted to the standard principles of testing termiticides. There was definitely a perceived need by researchers and industry for some guidelines that spell out basic procedures required for any methodology in testing termiticidal formulations anywhere in the world. In the testing of new potential active ingredients, consideration for the field of application (or end-use) must be uppermost. However, in the testing of these potential termiticides, laboratory and field bioassays may also indicate their potential as wood preservatives. This paper describes the protocols carried out in our Division to evaluate the potential of both termiticides and/or wood preservatives. It is hoped that this will stimulate more discussion within the group and that we may be able to refine standard principles of testing that have merit when making global comparisons in the near future.
J R J French
Biocidal screening method of wood extractives by a direct use of cellulose TLC plate
2001 - IRG/WP 01-20226
Most of the methods to evaluate the biological durability of woods have focused on decay fungi and termite as deteriorating organisms and it is well known that one of the most important factors affecting the biological characteristics of wood is extractives. Bioassays for evaluating the biological activities of wood extractives have been mainly conducted with treated filter papers for termites or extractives- containing agar media for decay fungi. Using these methods, the separation of crude extracts and bioassays are very time consuming. Thin layer chromatography (TLC) is a useful method for separating the mixture of organic compounds. It is also applicable to the crude extracts of wood consisting of many compounds. In TLC, silicagel, cellulose and other materials are used as stationary phases and we speculated that it would be to sepatare the crude extract on cellulose TLC plate (Cell - TLC) and directly apply it to bioassays, since termites and decay fungi can use the cellulose layer in Cell - TLC as their carbon sources. In this paper we report the applicability of Cell - TLC for biocidal screening of wood extractives against termites and decay fungi.
R Yusiasih, T Yoshimura, T Umezawa, Y Imamura
Establishing standard principles for laboratory bioassays of termiticides with subterranean termites - progress, problems and prospects
1993 - IRG/WP 93-10013
Laboratory bioassays of termiticides, including wood preservatives, aim to give an indication of the likely concentrations effective in preventing damage to timber products and other materials in the field. In laboratory bioassays field conditions should be simulated as closely as possible. With a wide range of procedures in use around the world it may often be difficult to compare results between laboratories. Standardizing a number of principles could provide a solution to this problem. We discuss several topics of termite biology, pointing either to limitations in the extent to limitation in the extent to which standardization can be achieved or to the need for further collaborative research between laboratories: optimal physical environment for the test termites; variations in termite vigour and behaviour between colonies of a given species; origin of test termites, i.e. from feeding sites (traps) or the nest; group size; correlation between the size of test timber specimens and feeding activity of the termites; test duration. Satisfactory standardization of bioassays with subterranean termites, if it can be achieved, is a more complex and involved endeavour than implied from discussions at recent IRG meetings.
M Lenz, J W Creffield, Zhong Yun-hong, L R Miller
Laboratory bioassays with termites – The importance of termite biology
2005 - IRG/WP 05-10550
Subterranean termites are frequently used in bioassays to asses the effectiveness of insecticides or the resistance of materials. Termites which appear to be vigorous with high inherent levels of activity are often relied upon, yet at the end of the experiments survival may be very unsatisfactory, even in the favourable environment of controls. Consequently, results from such bioassays may be meaningless. Factors that can influence the vigorous performance such as: colony origin; quality of the termite supply; the physical environment; group composition and size; and the size of timber specimens, are discussed. The conclusion is that performance of a given termite source must be judged against standards and accepted levels of activity (i.e. for survival and wood consumption). Only if the experimental termites reach or exceed such minimum standards can a researcher be assured of the adequacy of the termite supply for the experiment in hand, and hence the reliability of the results of the assessment.
Intraspecific variability in feeding capacity of Coptotermes acinaciformis (Froggatt) (Isoptera: Rhinotermitidae)
1983 - IRG/WP 1175
This paper describes laboratory studies to evaluate the comparative feeding capacity within and between five mound colonies of Coptotermes acinaciformis (Froggatt). Matched specimens of mountain ash, pine and coachwood were exposed to five replicate 10 g groups of termites from each colony source. After an initial 8-week exposure period, all groups were assessed for vitality and continued feeding capacity on pine specimens for a further eight weeks. The investigation showed within-colony variations to be small, but wide variations between colonies were revealed.
C D Howick, J W Creffield
Screening of the efficacy of tall oils against wood decaying fungi
2004 - IRG/WP 04-30354
Tall oil is a by-product in pulping of resinous wood by the sulphate process. Tall oil contains a complex mixture of wood extractives. Some of these extractives act as natural protection against wood decaying fungi while other serve as nutrition for the fungi. This report describes a screening of the efficacy of four refined tall oils with different chemical composition on wood decaying fungi. Testing was performed as filter paper assay and mini-block assay. In the filter paper assay growth rates of the white rot fungus Coriolus versicolor and the brown rot fungus Poria placenta were inhibited by the tall oils. None of the oils caused total inhibition of the fungi but there was a clear pattern towards increased efficacy with increased portion of resin acids in the oils. Impregnated mini-blocks with approximately 200 kg/m3 retention of tall oil after leaching showed an evident effect against Coniophora puteana and Poria placenta compared to untreated control samples. However, using the criteria from EN 113 requiring less than 3% mass loss, tall oil failed. The results indicate that decay resistance of tall oil impregnated Scots pine sapwood to the retention level used in this study is comparable with the decay resistance of Scots pine heartwood. It was expected that the efficacy of the tall oils was related to chemical composition of the oils. This was confirmed for the filter paper assay where the efficacy increased with increasing amount of resin acids. However, this pattern was not found for the mini-block assay. The protective effect of the tall oils in wood seems therefore to be more related to their hydrophobic properties than to their fungicidal properties.
G Alfredsen, P O Flæte, A Temiz, M Eikenes, H Militz
Standard principles of testing termiticides: A discussion paper
1991 - IRG/WP 1502
Recent restrictions and banning of termiticides such as organochlorines in some countries has focussed attention on the need for new and novel compounds as termiticides. However, this poses problems for both wood preservative manufacturers and termitologists. Test procedures have to be devised to evaluate the new termiticides so that the tests are practical, encourage vigorous termite activity, and repeatable. Thus, irrespective of geographical location and particular species of subterranean termite considered most economicially important, test procedures need to be standardised in that they follow sound principles of testing, rather than slavishly adher to another countries standard test method. This would give industry and researchers a common base-line, and allow comparative evaluations and analyses. This paper is offered in order to stimulate discussion on this important topic.
J R J French
The loss of insecticidal action from synthetic pyrethroid-treated wood samples: The effect of high temperatures and relative humidities
1992 - IRG/WP 92-1569
This paper describes the results from bioassays using Hylotrupes bajulus, and chemical analyses, of pyrethroid-treated wood samples following storage for up to 3 years. A range of four storage environments was used consisting of combinations of two temperatures (20°C and 40°C) and two relative humidities (60% and 90%). It is concluded from the chemical analyses that, although losses at room temperature were small, at the higher temperature used in this study loss of insecticide was accelerated. Exposure of treated wood to high relative humidity did not appear to result in increased loss of insecticide. The bioassay results confirmed these conclusions. The significance of the bioassay results in relation to the long term efficay in service of preventive treatments is discussed and a logic proposed for deriving a service life on the basis of which an estimate of up to 58 years protection from current commercial formulations is derived.
R W Berry, S J Read
Comparison of various types of bait containers designed to aggregate large numbers of foraging subterranean termites from natural populations in below-ground mound colonies
1995 - IRG/WP 95-10116
At Walpeup in the semi-arid mallee country of north-west Victoria (350 km from Melbourne), there are several indigenous subterranean termite species, none of which build above-ground mound colonies but build their colonies below-ground and/or in trees. This paper describes a baiting experiment in which three types of bait containers were compared in their ability to aggregate large numbers of foraging subterranean termites of the Coptotermes species. These species were targeted as they are considered the most economically important termite "pests" of wood and wood products in Australia. The area was pre-baited with radiata pine timbers that were buried just below the surface of the soil and located around trees and vegetation that were infested with Coptotermes species. After foraging termites had located and attacked the pre-baits, the various types of bait containers were installed on top of the infested pre-bait material. Bait containers were removed after five weeks and each was replaced by fresh bait containers. This occurred three times. All bait containers were transported to our laboratory in Melbourne and the mass of aggregated termites in each container weighed and wood consumption estimated. Bait containers that were half buried in the ground and covered with large plastic sheets and soil proved the most "attractive" of the various containers used in this field experiment. Also, the wood consumption rates of the two Coptotermes species collected from the field were compared in laboratory bioassays.
J R J French, B M Ahmed
A case for ecosystem-level experimentation - A discussion paper
1986 - IRG/WP 1296
Although laboratory bioassays provide a first step in testing for potential termiticides and assist in formulating recommendations of these chemicals for regulatory agencies and users, they are not designed for predicting effects on natural populations (including humans) and on ecosystem-level features. To overcome this we need microcosm studies, carefully controlled experimental manipulations of whole ecosystems run in parallel with laboratory bioassays, the gathering of long term field data, and a sound theoretical basis for extrapolation.
J R J French
The density factor in termite bioassays
1985 - IRG/WP 1252
The initial and final floor surface and food block surface actually used by termites in a small container were converted to estimates of "Living Space" and "Feeding Space" densities for 1/32 to 1½ g groups of termites. The termites were provided with blocks of blotter paper as a food supply. Except where 1½ g groups exhausted the food, the survival of termites was uniformly high (averaging >96%). The growth, block weight loss, debris production and feeding rates declined progressively as densities increased; however, these rates stabilized where 1/2, 1 and 1½ g groups had equalized feeding densities. This stabilization demonstrated that feeding space density, but not living space density, affected the termite performance. The advantage and disadvantage of using a matrix in termite bioassays is discussed.
G R Esenther
Method to determine the depth of penetration of the biologically active components of wood preservatives
1978 - IRG/WP 2108
A time-saving method for determining the depth of penetration of the biologically active components of wood preservatives is described. The test specimens were obtained by cutting thin slices from the wood either parallel or perpendicular to the treated surface. The slices were then exposed to fungal attack. A good correlation was found between the test results obtained by the modified German Standard method (plane-off test), published by BECKER and STARFINGER (1971).
Efficacy of Avermectin B1 dust and bait formulations in new simulated and accelerated field tests
1985 - IRG/WP 1257
Avermectin B1 on a silica carrier dust was used in dust and bait formulations whose efficacy against Reticulitermes flavipes was assessed in new simulated and accelerated field tests. A 0.5 mg avermectin/mg dust and a bait with 50 ppm avermectin in paper pulp sandwiched between pieces of corrugated boxboard caused nearly complete mortality in bioassays and suppression of foraging in field tests. These results indicate that the formulations can be developed into control effective gallery injection and/or bait treatments.
G R Esenther