Termite resistance of beech wood treated with zinc oxide and zinc borate nanocompounds*

The field of wood protection is currently changing due to the restrictions imposed by the Biocidal Products Regulation. The need for development of new wood protection technologies is therefore growing. In this work, the resistance of European beech (Fagus sylvatica L.) wood impregnated with nano-dispersions of zinc oxide (nano-ZnO) and zinc borate (nano-ZnB) against the termite Reticulitermes grassei Clement was investigated. Three different concentrations (0.5%, 1%, 2%) of the nanocompounds were tested. The effects of water leaching were also investigated. A severe effect in terms of termite workers mortality was induced by both dispersions, even at the lowest concentration. In terms of termite feeding, nano-ZnO dispersions appeared to be more efficient than nano-ZnB as they induced significant improvement at concentrations as low as 0.5%. Nano-ZnB was applied at 1% or higher concentrations in order to impart similar changes. Nano-ZnB dispersions were efficient in terms of termite resistance for a concentration at least 1%. Further increasing concentration to 2% resulted in a respective increase of wood efficacy against termites. For both tested nanocompounds, water leaching did not result in any significant increase of termite feeding.     

Behavioral responses of the arboreal termite Nasutitermes corniger (Isoptera: Termitidae) to wood extracts

The termite Nasutitermes corniger is attracted to weathered wood, but it is not known whether this attraction is of chemical or physical nature. This work examines whether wood extracts can change the attraction of N. corniger to a food substrate. In a first experiment, filter paper impregnated with a eucalyptus extract, Eucalyptus grandis, and another one with a solvent were placed in the foraging arena of N. corniger nests under laboratory conditions. The extracts used were from weathered or unweathered wood. During the second experiment, two tests were performed using eucalyptus wood. First, a piece of unweathered wood was impregnated with an extract of weathered wood (treatment) or solvent (control). In the second test, a piece of weathered wood was impregnated with an extract of unweathered wood (treatment) and another one with solvent (control). At the end of the tests, the number of termite recruitment on each substrate was quantified. Filter paper recruited more termites when treated with unweathered wood extracts or with extracts of weathered wood than when impregnated with the solvent. Unweathered wood treated with extracts of weathered wood recruited more termites than the control. However, weathered wood impregnated with extracts of unweathered wood recruited similar numbers of termites as the same wood impregnated with the solvent. It was verified that chemicals from weathered or unweathered wood increased the foraging activity of N. corniger in neutral substrates, but only chemicals from weathered wood altered the attraction of N. corniger to eucalyptus wood.     

Enhancement of the biological resistance of wood by phenylboronic acid treatment

Phenylboronic acid (PBA) was tested in terms of boron leachability from treated wood. In addition, the fungal and termiticidal efficacy of PBA-impregnated sugi (Cryptomeria japonica D. Don) wood was tested against the decay fungi Coriolus versicolor (L. ex Fr.) Quel. and Tyromyces palustris (Berk. et Curt) Murr., representing white-rot and brown-rot fungi, respectively, and the Formosan subterranean termite Coptotermes formosanus Shiraki. Ion chromatography analysis of hot water extracts of treated wood before and after leaching indicated that PBA is considerably resistant to water leaching, and saturation of the treatment solution increased the fixation ratio of boron in wood, whereas boric acid could not remain in wood impregnated even with the saturated solution. Decay test results revealed the excellent bioactive performance of PBA. Wood treated with 0.34% PBA solution was found resistant to both decay fungi, even after running-water leaching for 10 days and treatment with 1.00% PBA completely inactivated the Formosan subterranean termite for the leached specimens. Weight gain levels were 0.18% w/w (0.46kg/m³) and 0.99% w/w (2.49kg/m³) for these concentration levels, respectively, after being leached by running water. Contrary to the general belief that boron is a slow-acting toxicant against termites and unable to prevent mass loss of treated wood, PBA acted rapidly, and the mass loss caused by termites was low.This study was presented in part at the 47th annual meeting of the Japan Wood Research Society, Kochi, April, 1997     

Laboratory evaluation of the termiticidal efficacy of copper HDO

A laboratory no-choice termite bioassay was conducted to evaluate the ability of copper HDO (CX-A or copper xyligen) to protect radiata pine (Pinus radiata D. Don) wood samples from attack by two subterranean termite species, Reticulitermes speratus and Coptotermes formosanus. A series of sapwood samples were pressure treated with either 0.25%, 0.50%, 0.75%, or 1.00% copper HDO solution. Samples treated with equivalent concentrations of a benchmark preservative, CCA-C, were used as treated controls. All samples (including controls) were subjected to an artificial weathering schedule before the bioassay. The samples were exposed to 30-day R. speratus tests and 3-week C. formosanus tests. Copper HDO was shown to deter termites from significant feeding on the treated wood. At a retention of 5.8 kg/m3 (treated with 0.75% solution) or higher, the mass loss from termite feeding did not exceed 3% for both the 30-day R. speratus tests and the 3-week C. formosanus tests. At each of the retentions tested, copper HDO performed comparably with equivalent retentions of CCA-C; however, field data are needed to validate these laboratory results. The preliminary findings are that copper HDO pressure treatment has potential as a viable method of protecting wood from attack by both termite species tested.     

Changes of decay and termite durabilities of Japanese larch (Larix leptolepis) wood due to high-temperature kiln drying processes

We investigated the effects of high-temperature drying schedules (120°–130°C) on decay and termite feeding of Japanese larch timbers. Thermogravimetric analysis was conducted to investigate changes of the wood components. Decay and termite feeding tests showed that specimens dried under high-temperature schedules were susceptible against a decaying fungus Fomitopsis palustris and attacks from termites Coptotermes formosanus and Reticulitermes speratus. These drying schedules changed chemical components, which were suggested by the thermal analytical result compared to the control sample. The results of this study indicated that the acceleration of termite feeding takes place even under temperatures that are comparatively lower than that used in our previous research in which 170°C steaming treatment was applied to Japanese larch wood. Decay durability against a brown rot fungus also decreased, possibly from production of low molecular weight fragments when hemicellulose decreased during the high-temperature drying processes.     

Cytochemical localization of cellulases in decayed and nondecayed wood

Summary Enzyme assay showed that the commercial cellulase from Trichoderma reesei degraded several polysaccharide substrates; highest activity was on xylan. Transmission electron micrographs showed that the T. reesei cellulase degraded nondecayed wood extensively; the attack always progressed from the point of contact into the cell wall. Cytochemically prepared wood that had been decayed by Poria placenta showed uniform distribution of electron-dense particles throughout the walls; the same results were observed with added T. reesei cellulase. In wood decayed by Ganoderma applanatum without or with added T. reesei cellulase, the progress of degradation was similar to that in nondecayed wood. Negatively stained T. reesei cellulase had 3–7 nm diameter for the smallest particles; the smallest diamaters of electron-dense particles in wood ranged from 3–7 nm. This suggests that the electron-dense particles probably are cellulase molecules.     

Studies on the control of subterranean termites by inorganic pesticides

Studies on the wood preserving techniques against subterranean termites have been undertaken with a view to promote the use of inorganic indigenous pesticides in our country. The thin films of gelatine solution (glue of animal hides) containing 10% calcium carbonate or 5% copper sulphate as well as sodium silicate solution containing 12% calcium carbonate +10% zinc oxide coated separately on wooden stakes prevented termite attack in soil up to 2, 4 and 5 years, respectively. Whereas control wooden stakes were found to be severely damaged by termites within 6 months. Stakes coated with Solignum^®-white used as standard wood preservative for comparison remained free from termite infestation for a period of 5 years.     

Termite resistance and wood-penetrability of chemically modified tannin and tannin-copper complexes as wood preservatives

We examined the ability of chemically modified tannin and tannin-copper complexes to penetrate wood and the ability of the treated wood to resist termites. Only the tannin-treated wood retained the agents after treatment. Wood with untreated mimosa tannin (MT) retained the least amount, followed by wood with resorcinolated tannin (RMT) and that with catecholated tannin (CMT). When RMT or CMT was mixed with ammonia-copper, the wood retained twice as much of these solutions as the MT -ammonia-copper solution. The degree of retention of RMT-NH₃-Cu and CMT-NH₃-Cu ranged from 268 to 326kg/m³. The solutions penetrated 2–13 mm from the tangential sections of the logs. We also measured the termite resistance conferred by these solutions. Most of the tannin-NH₃-Cu solutions showed contact lethality for termites in the contact toxicity test. However, the termites were fed cellulose treated with those solutions and most survived the oral toxicity test (14 days). Moreover, these solutions reduced the amount of damage to the wood by termites. However, the mortality rate of the termites during the eating-damage test (>21 days) did not reach 100% for any of the solutions except for RMT. As a result of the field stake test with the same log's used for the penetrability test, the mass loss of wood treated with RMT or CMT alone or with RMT + NH₃ + CuCl₂, was about one-third to one-half that of the controls. Because these solutions have good wood penetrability and good termite resistance, they have potential use as low-toxicity wood preservatives.     

Assemblages and species diversity of wood destroying termites in different land use systems in Western Ghat, India

Spatial distribution, abundance and assemblage of termites depend mainly on the local conditions and habitats in which they thrive. Striking differences are observed in the species richness, number of clades and functional diversity of termite assemblage between different habitats. This study aim was to examine effect of human interference in the diversity of wood destroying termite in forest areas as well as managed and unmanaged plantations in South India. Termites attacking trees and wooden logs were collected from forest areas, managed plantations and unmanaged plantations. The termites collected were identified and compared for species abundance, richness and species diversity. Results show that the species composition and species diversity of the wood destroying termites vary according to the conditions. The species diversity measures revealed that there is a significance variation among the forest fauna and plantations. The forest areas have the highest species composition compared to plantations. Species richness is high forest areas. Even though the abundance of termites are more in unmanaged plantations, there is no significant difference related to species diversity among the managed and unmanaged plantations.     

Termite resistance of DMDHEU-treated wood

Four field trials were conducted with wood modified with dimethyloldihydroxy-ethyleneurea (DMDHEU) in contact with subterranean termites. Trials 1 to 3 were conducted with Coptotermes acinaciformis (Froggatt); 1 and 2 in south-east Queensland, and 3 in northern Queensland, Australia. Trial 4 was conducted in northern Queensland with Mastotermes darwiniensis (Froggatt). Four timber species (Scots pine, beech, Slash pine and Spotted gum) and two levels (1.3 M and 2.3 M) of DMDHEU were used. The tests were validated. DMDHEU successfully prevented damage by C. acinaciformis in south-east Queensland, but not in northern Queensland. It also did not protect the wood against M. darwiniensis. Except for beech in trial 4, DMDHEU led to reduced mass losses caused by termite attack compared to the unmodified feeder stakes. Slash pine (in trials 1 and 3) and Spotted gum (in trial 1) presented low mass losses. Modification of Scots pine was more effective against termite damage than the modification of beech.     

Variation in the natural termite resistance of teak (Tectona grandis Linn. fil.) wood as a function of tree age

? Tree age is one of the most important factors to affect the natural durability of wood.

? The purpose of this study was to determine the natural termite resistance of heartwood and sapwood of teak (Tectona grandis Linn. fil.) for trees aged 8, 30 and 51 years. Reticulitermes speratus Kolbe was employed as a test termite using a no-choice feeding method.

? The heartwood and sapwood of all of the trees tested exhibited antitermitic activity. Based on the mean mass loss due to termite activity, the sapwood and heartwood regions of 8-year-old trees are the most susceptible to termites while the heartwood regions of the 30-year-old trees showed termite resistance similar to the termite resistance of 51-year-old trees.

? The mass loss is moderately correlated with n-hexane extractive content, total extractive content, brightness and redness of the wood.

     

Evaluation of the concentrations of hydrogen and methane emitted by termite using a semiconductor gas sensor

A gas detection apparatus equipped with a semiconductor gas sensor was employed for qualitative and quantitative measurement of hydrogen and methane emitted by termites. A gas sample of 2.5 ml was injected into the semiconductor gas sensor through the gas detection apparatus, and the maximum voltage of the sensor was converted into gas concentration. The gas samples were collected from three distinct experiments: (1) five combinations of workers and soldiers of Coptotermes formosanus with and without a wood specimen; (2) C. formosanus under six temperature conditions; and (3) four different termite species, C. formosanus, Reticulitermes speratus, Incisitermes minor, and Zootermopsis nevadensis. The hydrogen and methane concentrations increased with an increase in the number of termites. Concentrations were higher in samples with a wood specimen than without it. Both hydrogen and methane concentrations were the highest for the samples at 35 °C and were lowest at 15 and 5 °C. The concentrations were very low at 45 °C because all the termites had died in a few hours. The concentrations of hydrogen and methane were highest for Z. nevadensis, the dampwood termite, among the four species, and no methane was detected for I. minor, the drywood termite, at 28 °C and 75 % RH.     

铲头堆砂白蚁原始繁殖蚁形成的周期

铲头堆砂白蚁Cryptotermes declivis Tsai et Chen是破坏木材及木制品的重要干木白蚁,其有翅成虫通过分飞配对后建立新群体,是其重要繁殖扩散途径。本文对铲头堆砂白蚁原始繁殖蚁形成周期进行了研究。以似桂木Paratocarpus sp.、团花Anthocephalus chinensis(Lam.) Rich. et Walp.和球花豆Parkia sp.作为该种白蚁食料,研究其原始繁殖蚁配对后从新建群体的形成到产生下一代的原始繁殖蚁,完成1个世代生活周期。结果表明,铲头堆砂白蚁在室温下,新建群体的形成、发展、发育至下一代原始繁殖蚁形成的周期约5 a,不同寄主材料对铲头堆砂白蚁生活周期没有显著性影响,但与群体数量多少显著相关。本研究首次明确了铲头堆砂白蚁群体发育成熟的周期,对该害虫的检疫与防控研究具有重要参考价值。     

Überleben und Entwicklung der Trockenholz-Termite Cryptotermes brevis (Walker) in Berlin

Survival and development of the dry-wood termite Cryptotermes brevis (Walker) in Berlin The infestation of museum material and furniture in a private home in Berlin by the dry-wood termiteC. brevis is described. In spite of unfavourable climatic conditions the termites could - in the first case - survive and develop for more than 5 years. Other termite introductions, ecology and economic importance of dry-wood termites are mentioned.     

Biological activity of soils under rubber trees (Hevea brasiliensis) affected by trunk phloem necrosis

Trunk phloem necrosis (TPN) is currently one of the most economically important diseases of the rubber tree (Hevea brasiliensis). Investigations of the aetiology of the disorder have failed to identify any biotic causal agents but a multidisciplinary study has recently suggested that the disease may be caused by a combination of exogenous and endogenous stresses. These stresses can affect plant physiology and may also have an impact on soil biology and soil biochemistry. In this study, macrofauna diversity and soil enzyme activities were compared for the soils under trees affected by TPN and under healthy trees. Principal component analysis revealed associations between TPN and macrofauna diversity and soil enzyme activities. Groups of ants and termites were associated with the soil under healthy and trees affected by TPN respectively. Polysaccharidase (cellulase, xylanase and, particularly, amylase) activities were lower in the soil under trees affected by TPN whereas N‐acetylglucosaminidase activity was higher. These findings suggested that termite density and N‐acetylglucosaminidase activity are useful indicators of TPN, while lower values of polysaccharidases activities are the consequence of this disease. The impact of TPN on soil ecosystem was discussed.     

Electron-dense particles in wood decayed by Ganoderma applanatum

Summary Hemlock sawdust samples degraded by Ganoderma applanatum showed no electron-dense particles either in hyphae or in wood cell walls after aldehyde/OsO₄ fixation. After KMnO₄ fixation at early stage of attack, particles were in hyphae, hyphal sheath and wood cell walls. In samples prepared by a cytochemical technique which localizes cellulase activity at the ultrastructural level, particles were in hyphae, hyphal sheath and wood cell walls. The smallest diameter range of the particles lay between 3 and 7 nm which corresponds to the size of cellulases. Larger diameter particles were peresent which are probably aggregates of the smaller units. We believe that particles present in hyphal cytoplasm and hyphal sheath are cellulolytic enzymes. Whether particles present in attacked wood cell walls are enzymes or degradation products cannot be determined by this study. Nevertheles, the particles reveal the decay pattern in wood by the white-rot fungus G. applanatum.     

Assessment of technologies and dogs for detecting insect pests in timber and forest products

Abstract

Lack of accurate tools for detecting insect infestation in timber remains a big challenge for pest management authorities. Seven non-destructive insect detection technologies were used to assess their effectiveness in detecting insect borers and termites in timber samples. These technologies were: Termatrac®; Tramex Moisture tester; Acoustic Emission Device (AED-200L®); X-ray, thermal imaging camera; a termite detector dog; and trained quarantine inspectors using standard visual inspection (VI). The timber samples of Acacia parramattensis and Acacia decurrens used for the trial were naturally infested timber branches; timber blocks inoculated with lyctine beetles; timber blocks naturally infested with termites; and un-infested controls. All timber samples used were destructively sampled at the end of the trial to confirm the presence or absence of insects. The detector dog was 100% effective in detecting natural infested termite colonies but was totally ineffective in detecting termites on artificially inoculated timber blocks. The moisture metre and the thermal image camera were 100% effective in detecting large termite colonies but ineffective in detecting other insects in dry timber samples. The effectiveness of other methods of detecting insects or termites varied considerably. The AED was 79% effective, Termatrac 70%, X-ray 40% and VI 35%. Implications of these findings for quarantine and inspection purposes are discussed.     

Effect of an oil heat treatment on the teachability and biological resistance of boric acid impregnated wood

Vegetable oils provide boron retention of about 30% of initial amount depending on oil drying properties. Linseed oil is the most efficient, followed by soybean oil and rapeseed oil. Durability of C. japonica and F. crenata wood specimens has been enhanced by application of linseed oil alone but not enough to reduce termite’s attack of Coptotermes formosanus. Treating wood with a 1.0% w/w boric acid solution prior to oil treatment protects C. japonica from termite and fungi degradations. Efficiency against termites is mainly due to boron retention by oil but hydrophobic oil also forms a barrier decreasing fungi penetration. Boron efficacy threshold around 0.7 kg/m³BAE, lower than classical boron treatments thresholds indicates that oil water-repellence reinforces boron biostatic effect.     

Protection of wood particle board against termites

Summary Particle boards are of increasing economic importance. Without special treatment they are destroyed by termites. Deterioration of unprotected material as well as possibilities and present knowledge of preservation against termite attack are briefly described. Recent laboratory experiments with particle board treated to make it resistant to humidity and basidiomycete fungi showed that only one organic preservative out of four protected the boards also against termite attack; one of two water-soluble preservatives gave promising results. Heterotermes indicola (Wasmann) from India proved to be more aggressive and resistant to the preservatives than Coptotermes amanii (Sjöstedt) from Kenya and Nasutitermes nigriceps (Haldemann) from Guatemala. Kalotermes flavicollis (Fabr.) from Italy was also very tolerant to the fungicidal preservatives. Further development of treatments of particle board against termites is required.Part of this paper was prepared for the World Consultation on the Use of Wood in Housing, Vancouver, B. C., Canada, July 5–16, 1971.     

Evaluation of the temperature and relative humidity preferences of the western dry-wood termite <Emphasis Type="Italic">Incisitermes minor</Emphasis> (Hagen) using acoustic emission (AE) monitoring

Twenty-four different combinations of six temperatures (15°, 20°, 25°, 30°, 35°, and 40°C) and four relative humidity (RH) (60%, 70%, 80%, and 90%) conditions were used for pseudergates of the western dry-wood termite Incisitermes minor (Hagen). The feeding activities of the termites were monitored by the detection of generated acoustic emission (AE) events from feeder wood blocks in a test chamber. Temperature and RH showed independent and interactive significant effects on the feeding activity of I. minor. The optimal temperature and RH conditions for the feeding activities were 35°C and 70%, respectively, and the optimal combinations were 35°C-70% and 35°C-80% with an exceptionally higher feeding activity at the combination condition of 30°C-70%.