This standard outlines the laboratory procedure to establish the minimum toxic concentration of wood preservatives effective against borers, particularly powder post beetles like Lyctus brunneus and Minthia rugicollis. It involves treating wood samples with various preservative levels and monitoring beetle infestation under controlled environmental conditions. The guidelines serve manufacturers, researchers, and quality assurance personnel in evaluating preservative performance against beetle damage.
Overview
This standard outlines the laboratory procedure to establish the minimum toxic concentration of wood preservatives effective against borers, particularly powder post beetles like Lyctus brunneus and Minthia rugicollis. It involves treating wood samples with various preservative levels and monitoring beetle infestation under controlled environmental conditions. The guidelines serve manufacturers, researchers, and quality assurance personnel in evaluating preservative performance against beetle damage.
Audience
Contents
Structure
Defines laboratory techniques to identify threshold concentrations of wood preservatives for controlling powder post beetles, establishing minimal effective doses to inhibit infestation. Applies to various preservative-treated wood samples. Emphasizes rounding of results per IS 2:1960 and maintaining significant figures consistent with the standard's specifications. Procedure includes treating wood at multiple preservative levels, exposing to beetles, observing infestation, and determining effective concentration. Testing is supported by statistical analysis of infestation data.
Details rounding off of results as per IS 2:1960, with significant digits matching standard values. Describes conditioning treated wood samples at 25°C to 30°C and 70–75% relative humidity for two weeks to achieve approximately 15% moisture content, sealing end grains with paraffin to prevent preservative ingress through ends. Specifies sample quantities: ten treated per concentration, five solvent-treated, and five untreated controls, ensuring standardized preparation for reliable efficacy assessment.
Specimens conditioned in controlled environment (25–30°C, 70–75% RH) for two weeks to stabilize moisture near 15%. End grains sealed with paraffin or equivalent to block preservative penetration. Sample numbers per test include 10 preservative-treated specimens at each concentration, 5 solvent-treated, and 5 untreated controls. Rounding of test outcomes follows IS 2:1960 guidelines. The process ensures uniform moisture and consistent penetration conditions essential for comparative testing.
Samples conditioned under defined temperature and humidity, sealed at end grains, and grouped into treated, solvent-treated, and untreated control sets. Numbers per group specified. Emphasizes rounding of final data consistent with IS 2:1960. The test principle ensures uniform sample conditions to enable accurate determination of preservative toxicity thresholds.
Specifies conditioning parameters (25–30°C, 70–75% RH, two weeks) to attain ~15% moisture. End grain sealing prevents preservative migration through ends. Quantities per test are 10 treated per concentration, 5 solvent controls, and 5 untreated controls. Untreated controls also sealed similarly. Results rounded as per IS 2:1960 maintaining significant figures. Ensures standardized sample handling for consistent test results.
Preservative solutions prepared at a minimum of five concentrations around expected toxic limits, using geometric or arithmetic series as appropriate. Water-soluble preservatives use fresh aqueous solutions; insoluble types dissolved in volatile solvents like benzene to avoid toxic residues. Samples immersed for one minute starting from lowest concentration. Controls treated with solvent/emulsion without active preservative. Post-treatment involves shaking off excess, blotting, reweighing to calculate uptake, selecting specimens with uptake variation ≤15%, drying below 30°C until control weight stabilizes, conditioning for one month at room temperature. Ten treated, five solvent-treated, and five untreated specimens per concentration are used. Evaluation records exit holes and live larvae presence, defining toxic limits as intervals between highest infestation and complete control, expressed in kg/m³.
Adults of Lyctus brunneus and Minthia rugicollis, obtained from laboratory cultures initiated with naturally infested wood, are used. Cultures maintained on untreated feeder woods such as semul, mango, rubber, or tapioca chips with starch. Samples exposed individually in glass containers covered with cambric to four pairs of beetles. Testing conducted at 25–30°C and 70–75% relative humidity. Duration continues until all beetles die, typically 6–8 months. Samples examined for exit holes and larval presence to evaluate preservative effect.
Specimens are prepared from semul, rubber, or mango heartwood free from knots and defects. Dimensions are 100 mm length, 40 mm width, and 12.5 mm thickness, with grain orientation parallel to length and tangential face aligned to growth rings. Samples air-dried in ventilated rooms without kiln or heat. Starch content assessed visually per Annex A; samples with insufficient starch are rejected. Rounding of results follows IS 2:1960 standards.
Count and record treated and untreated samples exhibiting exit holes and treated samples lacking exit holes but containing live larvae. Threshold toxicity is the concentration range between the highest with beetle emergence or live larvae and the next higher concentration showing no emergence and complete larval death. Concentrations expressed in kg/m³ of wood. Reports include preservative concentration, diluent type, and time between impregnation and beetle exposure. Rounding of values adheres to IS 2:1960.
Specimens measuring 100 × 40 × 12.5 mm from semul, rubber, or mango heartwood are air-dried without heat treatment. Grain direction is longitudinal, with wide face tangential to growth rings. Visual starch test (e.g., iodine staining) performed to confirm adequate starch required for larval development. Samples failing this test are rejected before infestation experiments. Data recording and reporting follow guidelines in Clause 3.6.
The Timber and Timber Stores Sectional Committee (CED 9) oversees this standard, comprising members from government forestry departments, research institutes like Forest Research Institute and Institute of Wood Science & Technology, industry representatives from the plywood federation and bamboo society, as well as other organizations such as the Ministry of Defence and Rubber Board. The chairman is Shri Shyam Sunder, with Dr. R. V. Rao as convener of the subcommittee on timber terminology. Sample conditioning and testing protocols as per Clause 3.2.2 are integral to the standard.
Frequently Asked
The standard specifies using wood from semul, rubber, or mango species. Test specimens should be cut to dimensions of 100 mm in length, 40 mm in width, and 12.5 mm in thickness. The long axis must be aligned parallel to the grain, with the wide face oriented tangentially to the growth rings. Samples should be heartwood, free from knots or abnormalities. They must be air-dried in a ventilated environment without kiln heating and conditioned at 25–30°C with 70–75% relative humidity for two weeks to reach approximately 15% moisture content. Ends are sealed with paraffin wax or similar before preservative treatment. Per test, 10 samples are treated per preservative concentration, along with 5 solvent-treated and 5 untreated control samples.
Preservative solutions are prepared at a minimum of five concentration levels (weight/weight basis), centered around the expected toxic threshold. When the toxic limit is unknown, an initial geometric series of concentrations is used, followed by a finer arithmetic progression. Water-soluble preservatives are dissolved freshly in aqueous media, whereas insoluble types are dissolved in volatile solvents like benzene that leave no toxic residues. Wood blocks are immersed for one minute starting from the lowest concentration. Control samples receive solvent or emulsion treatments without active toxic agents. After dipping, excess liquid is removed by shaking and blotting, then samples are weighed to calculate preservative uptake. Specimens are dried below 30°C until weight stabilization and conditioned for one month before testing. Concentrations are expressed in kilograms per cubic meter of wood.
The test employs adults of two powder post beetle species: Lyctus brunneus and Minthia rugicollis. These insects are reared in laboratory cultures initiated using naturally infested wood sources. Untreated feeder materials such as semul, mango, rubber woods, or tapioca chips containing starch support the culture. Each wood sample is exposed individually to four pairs of adult beetles within glass containers covered by cambric. Environmental conditions are maintained at 25–30°C temperature and 70–75% relative humidity throughout the testing period, which lasts until all beetles perish.
To ascertain the preservative’s threshold toxicity, prepare at least five concentrations around the anticipated toxic level, starting with a geometric series if unknown. Wood blocks are immersed for one minute beginning with the lowest concentration. Solvent-only treated controls are included. After treatment, excess preservative is removed, and blocks are weighed to compute preservative uptake using the difference in weight multiplied by concentration. Samples with uptake variation within 15% are selected. They are dried below 30°C until weight stabilizes and conditioned for one month. After beetle exposure, data on emergence and larval survival are recorded. The threshold toxicity corresponds to the interval between the highest concentration where beetle emergence or live larvae are observed and the next higher concentration with no emergence and dead larvae. Concentrations are expressed in kg/m³ of wood.
The test environment requires strict control of temperature between 25°C and 30°C and relative humidity maintained at 70% to 75%. These conditions apply during the two-week conditioning period before treatment to stabilize moisture content near 15%, as well as throughout the beetle exposure phase until all insects die. Samples are stored individually in glass containers covered with cambric to prevent mite infestation. Maintaining these parameters ensures consistent beetle activity and reliable assessment of preservative efficacy.
Starch content is evaluated visually, typically using a staining method such as iodine application as described in Annex A. Samples sized 100 × 40 × 12.5 mm from semul, rubber, or mango heartwood are air-dried in a ventilated room without kiln or heat treatment before testing. Adequate starch is critical because it provides necessary nutrition for larvae of powder post beetles to develop. Without sufficient starch, larvae do not survive, invalidating infestation tests. Samples failing the starch content test are discarded to ensure only susceptible wood is used for preservative efficacy evaluation.
Validation involves including five untreated control samples and five solvent-only treated samples in each test batch alongside preservative-treated specimens. Test insects consist of lab-reared adults of Lyctus brunneus or Minthia rugicollis from naturally infested wood cultures. Testing is performed under controlled temperature (25–30°C) and humidity (70–75%). Observations record the number of samples exhibiting exit holes and treated samples with live larvae but no exit holes. The toxic threshold is defined by comparing infestation presence across treated and control samples, ensuring that results reflect preservative efficacy rather than environmental or procedural variability. Reporting includes preservative concentration, diluent type, and exposure interval.
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