Glue and Preservative Effects on the Properties and Durability of Engineered Bamboo Boards

Philippine Journal of Science 147 (4): 601-616, December 2018 ISSN 0031 - 7683 Date Received: 21 Mar 2018

Marina A. Alipon*, Carlos M. Garcia, and Elvina O. Bondad

Forest Products Research and Development Institute (FPRDI), Department of Science and Technology (DOST), College, Laguna 4031 Philippines

The effect of glue and preservative treatments on the physico-mechanical properties and durability against bamboo-destroying insects, respectively, of engineered bamboo boards from kauayan-tinik (Bambusa blumeana J.A. & J.H. Schultes) and giant bamboo [Dendrocalamus asper (Schultes f.) Backer ex Heyne] were evaluated. Costs of glues to bind the bamboo slats and chemical treatments were computed. Six glue types were used: polyvinyl acetate (PVAc) for interior and exterior use (Glue 1); PVAc for interior use (Glue 2); urea formaldehyde (UF, Glue 3); Glue 3 + 5% isocyanate (Glue 4); Glue 3 + 1.5% isocyanate (Glue 5); and phenol formaldehyde (PF) (Glue 6). The chemical used included: permethrin (T1); fenvalerate (T2); deltamethrin (T3); propiconazole (T4); deltamethrin + propiconazole (T5); and disodium octaborate tetrahydrate. (DOT, T6) Standard procedures were applied in evaluating the physical (relative density and moisture content) and mechanical (modulus of rupture, modulus of elasticity in static bending, hardness, and shear) properties of the bamboo boards. Engineered bamboo samples glued with PF and UF did not pass the US Formaldehyde Emission Limits (FEL) for composite wood products. However, both passed the FEL for composite wood products in Japan, although UF fell in the average limit category. Overall, the combination of PVAc + deltamethrin is highly recommended for high-end products such as housing components (floor tiles, balusters, windows, and doors). The UF + deltamethrin combination was also cost-effective. However, the strength properties of UF – particularly shear which measures the bonding strength of glue – was significantly lower than samples glued with PVAc.

Key words: durability, engineered bamboo, glue, physical and mechanical properties, preservatives

INTRODUCTION second-growth forest. On the other hand, bamboo is among those exempted in the moratorium. It showed In recent years, the importance of bamboo as a renewable promising potential as alternative materials to timber. natural resource has received international recognition due to worldwide concern about the destruction of tropical Similarly, bamboo's characteristics such as its fast growth, rainforests, the increasing demand for forest products, and short harvesting or rotation cycle, and regeneration make the need for the sustainable supply of forest resources. it an ideal material to replace wood (Refidah 2010). Forestry statistics showed that Philippine forest covers Researches on the structure – as well as the physical, was reduced from 17,025,111 ha in 1976 to 6,839,832 mechanical, chemical, and technological properties of ha. Consequently, EO No. 3 dated 2011 imposes a bamboo – have resulted in the development of numerous moratorium on the harvesting of timber in natural and bamboo-based products (Espiloy & Espiloy 1999), including engineered ones (Anwar & Zaidon 2004). *Corresponding author: [email protected]

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Engineered bamboo (or “E-bamboo”) refers to bamboo every 3 m starting from the bottom, subsequently cross- materials that are processed into slats, slivers, scraps, cut to 1.0 m long using a circular saw cutting tool, and and spokes that are treated, pressed, and laminated to arranged parallel to kiln length in the FPRDI furnace form bamboo planks. The planks are then converted into lumber dryer until 8–10% MC was attained. The culms furniture, floor and wall panels, and other products (EO were stripped into 30 mm slats producing 5–10 strips using 879 2010). Fungicides and or insecticides are applied twin rip saw blade machine. External budging of the nodes before and or after processing the products to prolong was manually removed using a bolo. The outer and inner their service life (Garcia et al. 1998). skin of the strips was removed using the thickness planer machine, obtaining uniform rectangular cross sections Bamboo is susceptible to fungal (brown rot, white rot, with plane surfaces. Each strip was properly marked for soft rot) and insect (beetles, termites) attack; it needs matching of samples, applied with preservative treatment, preservative treatment to make it durable. Chowdhury assembled, and and glued into a three-layer board using a (1992) reported that while chemically treated bamboo spreader at 100–140 g/m2 to form bamboo boards ≈ 200 culms cost about 25% more than untreated, its durability mm (w) x 15 mm (t) x 1000 (l) mm using a composing increases to almost 5–6 times. jigs with several screws to clamp the strips together and Glue and chemical treatments are necessary in producing pressed overnight at room condition (≈25–28°C, 12 hrs, E-bamboo. Glue must provide proper penetration and 8 kg/m2) using the FPRDI hydraulic presser. After the interface bond between the fibers and laminae (Boasiako glue has set, the product was removed from the press and & Appiah 2012). On the other hand, the effectiveness samples for various property tests were taken. of chemical treatments to increase the service life of bamboo products has been established. Although non- Preparation of Samples for Properties Testing chemical method like soaking in water greatly improved Static Bending. The method of preparing and testing the the resistance of bamboo to bio-deteriorating agents, the specimens followed the procedures specified in ASTM chemical applications are generally the most effective D1037. The specimen measuring 50 mm x 400 mm x method (Reyes 1993, Garcia et al. 1997). Several studies actual depth was loaded at the center of the span through on plywood and veneers using different glues with and a load bearing block 76 mm wide and 22.5 mm radius without preservative treatments reported to have either of curvature at a uniform rate motion of the movable similar or different results (Shukla 1991, Dimri & Kumar crosshead of the testing machine of 5 mm/min. The load 1998) and for bamboo laminates as well (Boasiako & deflection curves to maximum load were taken. Static Appiah 2012, Hanim et al. 2013). Interactions between bending properties such modulus of rupture (MOR), stress glue and preservatives should be considered to ensure the at proportional limit (SPL), and modulus of elasticity quality of E-bamboo; hence, this study. (MOE) were computed based on standard formula. The specific objectives of the study were as follows: 1) Hardness Test. The method of preparing and testing the determine the physical (moisture content and relative specimens followed the procedures specified in ASTM density) and mechanical properties (hardness, static D1037. The dimension of specimens (50 mm x 150 mm) bending, shear), delamination, and formaldehyde was tested using a modified ball with 11.28 mm diameter. emission of bamboo boards; 2) test the efficacy of The load was applied continuously throughout the test at chemical treatments on bamboo boards; 3) compute the a uniform rate motion of the movable crosshead of the cost of producing glued and treated E-bamboo boards; testing machine of 6 mm/min. Two penetrations of a least and 4) recommend the best cost effective adhesive and 25 mm from the edges were made. The penetration of the preservative treatment combination bamboo boards. ball to one half its diameters is the measure of hardness. Shear Test. Method of preparing the specimens followed the procedure described in ASTM D1037. The shear- MATERIALS AND METHODS parallel-to plane was made on 50 mm x 63 mm samples, notched to have the plane of the shear parallel to the Twenty-five (25) poles each of 3 to 4 year-old kauayan- surface of the samples and failure midway between the tinik (Bambusa blumeana Schultes) and giant bamboo two surfaces. The test followed the procedure described in [Dendrocalamus asper (Schultes f.) Backer ex Heyne] Section 90–94 of ASTM D143. A shear testing tool with were collected from Magdalena, Laguna, Philippines. 3 mm offset between the inner edge of the supporting surface and the plane was used. The specimen was placed Preparation of Bamboo Boards in the shear tool and the crossbar adjusted so that the edges The procedure for preparing the strips began as the outer of the specimen are vertical, and the end rests evenly on skin of bamboo culms was scraped. Each culm was cut the support over the contact area. The load was applied

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continuously throughout the test at a uniform rate of Plus isocyanate (1.5 grams) motion of movable crosshead of the testing machine of Glue 6 Phenol formaldehyde (PF) 0.60 mm/min. The maximum load and type of failures are recorded. The ratio of maximum load to the area is Glues 1, 2, and 6 were applied as commercially prepared. the shear strength, a measure of how the glue binds the Glue 1 is a wood working adhesive (D3) with 50% lamina together. minimum solid content, excellent moisture, and water- resistant bonding, while Glues 2 and 3 have low water Moisture Content (MC). The procedure described in resistance and recommended for interior products. For ASTM D143–52 was followed. Test was done on 25 mm Glue 4, a 5% (5 g) isocyanate was mixed with Glue 3 x 25 mm specimens surfaced on all sides and shaved components, while Glue 5 was similar to Glue 4 except smoothly at the ends. The initial weight of the specimens that the isocynate mixed with Glue 3 was 1.5% (1.5 g). was taken afterwards placed in an oven set at 103+2°C until constant weight was attained. The MC of the The sample boards’ strength properties data were specimens was computed using the formula: subjected to Analysis of Variance (ANOVA), while the difference between means was analyzed using Duncan initial – weight oven-dry Multiple Range Tests (DMRT). MC (%) = x 100 (1) oven-dry weight The costs of glues to bind 200 mm x 1000 mm three-ply bamboo boards were computed. Relative Density. The procedure for described in ASTM D143–52 with slight modifications on size of samples was followed. Test was done on 10 mm x 10 mm Preparation of Samples for Durability Tests specimens. The volume was measured using the mercury Bamboo slats from giant bamboo and kauayan-tinik displacement method. The specimens were placed in an measuring ≈ 8 mm x 25 mm x 1000 mm were prepared oven set at 103+2°C until constant weight was attained. and conditioned at 12% MC. Bamboo slats were grouped into their respective treatment prior to 5 min dipping in The relative density of the specimens was computed using the following chemical solutions: permethrin (ready to the formula: use, RTU); fenvalerate (1 L:100 L water); deltamethrin Relative Density = oven-dry weight/volume (2) (1 L:100 L water); propiconazole (1 L:50 L water); deltamethrin + propiconazole (1 L:100 L water + 1 L:50 where: volume = weight of displaced liquid/density of L water); and disodium-octaborate tetrahydrate (DOT) mercury (13.6 g) (125 g/L water). The ratio of chemical solutions refers to chemicals and water mixture. For instance, 1 L:50 L water Delamination Test. The method of preparing and testing means that for 1 L of chemical, 50 L of water was added of specimens followed the procedures specified in PNS: to form a mixture of chemical preservative solutions for 2000. All specimens for delamination tests were soaked treatment of specimens. An untreated group from each in water for 6 h and dried in the oven set at 40°C for 24 h. bamboo species was provided for comparison. Treated The various glues were formulated using the following and untreated slats were air-dried prior to production of components: E-bamboo board using the six glue types. Laminated bamboo boards measuring ≈ 15 mm x 300 mm Components Parts by weight x 300 mm were prepared from treated slats. The cut edges Glue 3 Urea formaldehyde (UF) 200 of the samples were re-treated with chemical solution and Catalyst R46 - 350 10 air-dried for 10 d prior to exposure to test insects. Industrial wheat flour 40 Water 50 Efficacy of Preservative Treatment to Wood- Glue 4 UF 200 destroying Insects Catalyst R46 - 350 10 The efficacy of preservatives in protecting bamboo boards Industrial wheat flour 40 was evaluated using three insects: Los Baños termites Water 50 (Microcerotermes losbañosensis Oshima), drywood Plus isocyanate (5 grams) termites (Cryptotermes dudleyi Light), and powder-post Glue 5 UF 200 beetles (Dinoderus minutus F.). These were considered as economically important post-harvest pests of bamboo Catalyst R46–350 10 (Garcia & Morell 2009, Giron & Garcia 2005) and Industrial wheat flour 40 wooden components of house and buildings (Garcia & Water 50 Giron 2004).

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Subterranean Termites, M. losbañosensis The efficacy of treatment against beetle attack was rated A termite nest containing active populations of M. as follows: losbañosensis was collected from the field. It was implanted into the soil contained in half-sawn plastic No. of beetle holes Classification drum termite chamber. Termite population was established 0 or no hole except Effective for boring attempts before introducing the bamboo board samples. 1–5 beetle holes Moderately effective Forty-five (45) samples were prepared for each bamboo 6–10 beetle holes Slightly effective species. Samples were exposed to termites above ground holes Not effective for 4 mo. Each treatment was replicated three times and untreated boards were used as control. ≥ Formaldehyde Test Test boards were inspected every month for termite tunnel Samples were tested according to PNS ISO 12460– invasion and the degree of termite damage was determined 4:2009. Ten (10) pieces were used per trial. PF bonded on the fourth month. Damage was based on the volume of bamboo boards measured 50 mm x 150 mm x 16 mm, board lost at the end of the exposure period. while the UF-bonded measured 53 mm x 154 mm x 11 The efficacy of treatment was rated using the following mm. arbitrary rating: Absorbance of background formaldehyde solution was 0.

% of Termite Damage Efficacy of Treatment Statistical Analysis 0 Highly effective, no evidence of termite Results of various tests were subjected to analysis of attack variance (ANOVA) using completely randomized design 1–25 Moderately effective, from initial nibbling (CRD). The Duncan Multiple Range Test (DMRT) was to almost ¼ board sample is lost used to determine the differences between and/ or among 26–50.1 Slightly effective, more than ¼ to ½ of is significant variables. lost 51–100 Not effective, severely destroyed by termites RESULTS AND DISCUSSION Dry Wood Termites Forty-five (45) board samples for each bamboo species Properties Performance were prepared. Treated and untreated boards (15 mm x 20 mm x 60 mm) were individually kept in a 90 mm petri dish Mechanical Properties that served as the termite chamber. One hundred (100) Table 1 shows the ANOVA for mechanical including workers plus two soldiers were introduced per chamber. physical properties of bamboo boards, while Table 2 Each treatment was replicated three times. Untreated presents the DMRT between and among sources of boards were provided for comparison. Board samples were variations. exposed to drywood termites for 12 mo. New batches of Modulus of Rupture (MOR) and Modulus of Elasticity termites were introduced after 6 mo. (MOE) in Static Bending (SB). The MOR in SB measures Termite damage in individual boards was recorded every the magnitude of load required to cause failure in the after 3 mo. The efficacy of treatment was rated following materials and determine their fitness for use as rafters, the rating used for subterranean termites. stringers, girders, floor joists, and scaffold platforms. On the other hand, MOE in SB measures the material’s ability to retain its original shape when load is applied. Powder-post Beetles, D. minutus It is a very important indicator of the materials’ relative Eighty (80) boards (15 mm x 20 mm x 60 mm) for each suitability for various end-uses. bamboo species were prepared. The specimens in each set-up were kept in covered plastic trays at ordinary room The effects of glue (G), treatments (T), species (S) x G, temperature. Each treatment was replicated five times. An and G x T and S x G x T on MOR and MOE were highly untreated board was provided for comparison. significant at α=0.01, while the effect of S and S x T was not. The results indicate that the MOR and MOE were All boards were monitored and the number of beetle holes affected by glue type, preservative treatment type, as well was counted every 3 mo. New batches of infested bamboo as the interactions of glue (G) to treatment (T), species slats with powder-post beetles were introduced after 6 mo. to glue (S x G), glue to treatment (G x T), and species to glue to treatment (S x G x T). Generally, Glue 1 (PVAc)

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Table 1. Analysis of variance (ANOVA) for E-bamboo properties. Source of Df MOR MOE Hardness Shear Relative Density Moisture Content Variation MS F-Value MS F-Value MS F-Value MS F-Value MS F-Value MS F-Value Species (S) 1 313.6 2.47ns 1.78 2.58ns 0.29 1.56ns 0.70 2.91ns 0.013 3.57ns 0.68 1.58ns Glue (G) 5 2657.1 20.9** 24.1 35.1** 0.22 44.4** 7.81 32.3** 0.013 3.62** 12.7 29.3** S X G 5 699.2 5.51** 3.90 5.67** 0.72 3.90** 3.09 12.8** 0.002 0.64ns 1.19 2.76* Treatment (T) 6 1005.2 7.92** 9.31 13.5** 2.75 14.8** 4.45 18.4** 0.010 2.73* 1.37 3.17** S x T 6 210.9 1.66ns 3.95 5.74** 1.33 7.16** 0.90 3.74** 0.009 2.45* 0.45 1.04ns G x T 30 336.1 2.65** 6.57 9.56** 0.84 4.55** 1.21 5.01** 0.007 2.06** 0.93 2.14** S x G x T 30 265.0 2.09** 1.81 2.63** 0.44 2.38** 0.70 2.89** 0.004 1.08ns 0.47 1.08ns Error 168 127.0 0.69 0.18 0.24 0.004 0.43 R2 (%) 67 80 78 78 47 63 CV (%) 13.4 7.11 8.46 9.98 9.52 6.02 *significant at 95% probability level **highly significant at 99% probability level nsnot significant

Table 2. Duncan Multiple Range Test (DMRT) for physical and mechanical properties of E-bamboo. Species MOR MOE Hardness Shear RD MC (MPa) (GPa) (kN) (MPa) (%) Kauayan-tinik 92.1a 11.7a 5.12a 4.98a 0.640a 10.97a Giant Bamboo 89.9a 11.6a 5.06a 4.87a 0.625a 10.87a Glue Glue 1 97.8a 12.6a 5.93a 5.68a 0.652a 10.56d Glue 2 93.4c 11.6d 5.15b 5.15b 0.615c 10.57d Glue 3 80.7d 10.9e 4.64d 4.70d 0.608c 10.59d Glue 4 97.7a 12.3b 4.94c 4.69d 0.647a 11.07b Glue 5 81.2d 10.7f 4.97c 4.48e 0.642a 11.97a Glue 6 95.2b 11.8c 4.91c 4.86c 0.629b 10.76c Treatment (T) Permethrin (T1 ) 91.7b 12.0b 5.34b 4.95b 0.639b 10.85c Fenvalerate (T2) 85.0c 11.3d 4.96c 4.96b 0.605d 11.07b Deltamethrin (T3) 82.8d 11.3d 5.37ab 5.41a 0.640b 10.85c Propiconazole (T4) 95.7a 11.3d 5.42a 5.35a 0.655a 10.69d Delta + Propi (T5) 96.2a 12.6a 4.91cd 4.67c 0.642b 10.90c DOT (T6) 94.8a 11.7c 4.87d 4.64c 0.620c 11.28a Untreated (Control, T7) 90.9b 11.1d 4.76e 4.51d 0.626c 10.80c Note: Means with the same letter are not statistically different

had significantly highest MOR and MOE than the other bending strength PRF. glue types. For preservative treatments, deltamethrin (T3) and propiconazole (T4) had highest MOR while Hardness. Hardness is a measure of the material’s T4 with highest MOE. The MOR and MOE of bamboo resistance to indentation, wear, or scratch. It is a good boards did not vary between kauayan-tinik and giant indicator of the desirability of a species for use as floors, bamboo (S) regardless of the treatments. Sinha (2016) paving blocks, bearings, rollers, and similar other uses. reported that glue laminated bamboo beams fabricated The effects of all sources of variations were highly using two different glues, [isocyanate resin (ISO) and significant except between species. phenol-resorcinol formaldehyde (PRF)] both showed high stiffness (MOE), with comparable values and less Hardness increased with treatment application of variability compared to structural wood species while permethrin, fenvalerate, deltamethrin, propiconazole, bamboo glulam (BGL) with ISO performed better in deltamethrin + propiconazole, and DOT – as shown by

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the control’s (no treatment) statistically lowest values properties in the present study were higher than the (4.76 kN) than those of treated samples (4.87–5.42 kN). previous report. It has been established that RD is directly The results conformed to the previous findings by Alipon correlated to strength properties, the higher the RD the et al. (2011). Jin (2016) reported that the physical and higher the strength properties (FPRDI 2000). mechanical properties of panels bonded with phenol Moisture Content (MC). MC refers to the amount of formaldehyde and chemical preservatives were not also water contained in a material. The effect of glues (G) affected. The properties of all treated panels exceeded and preservative treatments (T) and its interactions the requirements specified for standard category panels. (G x T) was significant. The MC of Glues 1, 2, and 3 (Boasiako & Appiah 2012) mentioned that such effects did not differ significantly and exhibited significantly were due to the interactions of bonding sites of the bamboo lower values than the other glue types. In all cases, the elements to the glue and preservatives differences of MC among glues ranged 0.1–1.41% and Shear Strength. Shear strength is the ability of the 0.21–0.59% among preservative treatments. While the material to resist forces that tend to cause one part to MC was controlled to get ≈ 12% MC, the difference in slide to an adjacent part. Similarly, the shear strength of actual MC values at test is beyond control due to the E-bamboo products is a measure of how the glue binds applied glues and preservatives, which may have behave the lamina together. differently in the process of conditioning and maintaining the 12% MC. Regardless of species, all sources of variation significantly affected shear strength. Shear strength significantly Dried specimens were conditioned in a constant climate increased with treatment application. conditions (28°CDBT and 23°C WBT, 65% RH) after gluing and preservative treatments. It is expected that all Lin (1983) reported that dry shear along the glue line specimens will be at 12% MC. The lower MC may be 2 should exceed 1.4–2.0 MPa (14.27–20.39 kg/cm ) for attributed to the differences in glues and preservatives as flooring used under light and medium traffic conditions, their reacted to drying under controlled conditions. respectively. Accordingly, Alipon et al. (2011) mentioned that there is no standard or state regulation yet locally Overall, specimens bonded with PVAc (Glue 1) exhibited with properties requirements for physical and mechanical better mechanical properties than other glue types properties of bamboo as flooring materials. The properties regardless of the preservative treatments. of bamboo floor board are usually compared with wood Regardless of glue, propiconazole (T4), deltamethrin + species traditionally used for floorings. propiconazole (T5), and DOT (T6) gave the highest MOR; Studies on plywood and veneers glued using different T5 and T1 (permethrin) the highest MOE; although in adhesives with and without preservative treatments had hardness and shear, deltamethrin (T3 ) and T4 obtained either similar or different results (Shukla 1991, Dimri & the highest. Kumar 1998). Regardless of the species, locally available plywood conforms to both PNS and ISO Standards for Delamination Test exterior I plywood as long as the adhesive used was phenol The standards states that “specimen fails when any formaldehyde (Jimenez et al. 2015). single delamination along the glue line is greater than 51 mm in continuous length and over 3.6 mm depth at any B. Physical Properties point.” All specimens showed no opening along the glue Relative Density (RD). RD was significantly affected lines, indicating that all glue types bonded well with the by G, T, S x T, and G x T but not by S, S x G, and S x bamboo slats G x T. The insignificant variations on the mechanical properties between species could be due to insignificant Formaldehyde Emission Test differences in RD of the species. In most cases, PVAc Average formaldehyde concentration was 0.194 ppm for (Glue 1) specimens with the highest RD had also PF and 2.751 ppm for UF (Table 3). E-bamboo glued highest strength properties (MOR, MOE, hardness, and with either phenol formaldehyde (PF, Glue 6) and urea shear. For preservative treatments, deltamethrin (T3) formaldehyde (UF, Glue 3) did not pass the formaldehyde with highest RD had also highest strength properties emission limits (FEL) for composite wood products in except in MOE. USA (0.05–0.13 ppm). However, PF passed the FEL for In the previous study by Alipon et al. (2005), the RD of composite wood products in Japan (≤0.3 ppm in plywood, kauayan-tinik (0.582–0.650) and giant bamboo (0.538– ≤0.5 ppm in particleboard, and ≤ 1.5 in fiberboard), while 0.636) was lower than in the present study (0.60–0.670) UF fell under the average limits for all composite boards and (0.620–0.646), respectively. Consequently, strength (ASTM E–1333) (JIS 2003). In the Philippines, the limits

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boards became attached to the concrete foundation due Table 3. Formaldehyde emission test values for E-bamboo. to the construction of the termite tunnels. Average Formaldehyde Formaldehyde Sample Replicate concentration Based on the results, complete protection of bamboo concentration (ppm) boards was observed in samples treated with permethrin (ppm) (T1), fenvalerate (T2), deltamethrin (T3), and combined phenol 1 0.186 deltamethrin + propiconazole (T5) regardless of glue type. formaldehyde 2 0.199 0.194 (PF) Likewise, DOT (T6) treatment with Glues 2, 5, and 6 was E-bamboo 3 0.199 effective prevention against termite attack. urea 1 2.817 The earthen tunnels noted had no active termite population formaldehyde 2 2.678 2.751 due to the effect of treatment. Thus, the invasion of the (UF) E-bamboo 3 2.758 samples did not necessarily mean that the board was already damaged. Some of the boards had only initial nibblings on the surface. The attack stopped because they provided for formaldehyde emissions in plywood are were not acceptable to the termites as host. adopted from the Japan Agricultural Standard (JAS) for DOT was moderately effective against termites when plywood. applied to giant bamboo boards using Glues 1, 3, and 4 – with 3.3–13.3% termite damage. Durability On the other hand, the untreated samples except those Efficacy of Treatment Against Wood-destroying Insects with Glues 4 and 6 were all invaded by the subterranean termites as early as 1 mo of exposure. Boards were Subterranean Termites, M. losbañosensis invaded by M. losbañosensis after 2 mo. Based on glue Giant Bamboo Boards. The degree of invasion on types used, the resistance to subterranean termites varied engineered giant bamboo boards by M. losbañosensis at 3 mo and 4 mo. varied among treatments, glue types, and period of exposure (Table 4). The boards treated with permethrin The untreated giant bamboo boards with Glues 2 to 5 were (T1) using Glues 3 and 6 – and fenvalerate (T2) with moderately resistant to subterranean termites with 30.0– Glues 4 or 6 – were also not invaded by M. losbañosensis 43.3% damage. In contrast, the untreated specimens with Glues 1 and 6 had greater termite damage of 56.7–73.3%, For deltamethrin (T3), only giant bamboo boards respectively, and classified as slightly resistant. treated with Glues 1, 4, and 6 and boards treated with propiconazole (T4) and DOT (T6) with Glues 4 and 6 Based on the results, the combined effect of toxic had no termite mud trails during the same period. The chemicals and the inherent resistant property of giant combined deltamethrin and propiconazole (T5) applied bamboo enhanced the protection of bamboo boards against on boards with Glues 1 to 4 were likewise not invaded. the attack of subterranean termites. The untreated boards The rest were immediately inhabited by subterranean were resistant to beetle attack after 4 mo of exposure to termites by 33.3–100%. subterranean termites. The earthen tunnels of M. losbañosensis invaded other boards as shown by the added mud trails constructed on Kauayan-tinik Boards the surface in 2 mo. Boards treated with deltamethrin (T3) Except for DOT (T6) with Glues 1 to 3, all chemical with Glue 1 and 4 and deltamethrin + propiconazole (T5) treatment regardless of glue type prevented termite with Glues 1 to 3 were free from termite invasion. invasion of engineered kauayan-tinik boards after 1 mo exposure (Table 4). However, regardless of glue, boards After 3–4 mo, the only boards not invaded were those treated with deltamethrin (T3) and combined deltamethrin treated with combined deltamethrin + propiconazole + propiconazole (T5) laminated with Glues 1 to 3 (T5) with Glues 1 to 3 and deltamethrin (T3) with Glue remained uninvaded for 2–4 mo. Termite invasion did 1. The rest of the boards were invaded from 33.3% to not spread to the other samples, suggesting that the other 100% in 2–4 mo. treatments prevented further foraging of M. losbañosensis. The termite tunnels started on the wall of the concrete Permethrin (T1), deltamethrin (T3), and combined block and extended towards the top where the bamboo deltamethrin + propiconazole (T5) regardless of glue type boards were installed. Termite invasion began at the were highly effective in preventing subterranean termites bottom and extended towards the sides, entered between from damaging the boards. All kauayan-tinik boards had slat layers, cut-ends, or on the board’s surface. Invaded 0% damage, except for some nibbling. On the other hand,

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Table 4. Invasion and degree of damage on giant bamboo and kauayan-tinik board by M. losbañosensis after 4 mo exposure. Giant Bamboo Kauayan-tinik % of Boards Invaded/Mo % of Boards Termite Treatment Glue Termite Invaded/Mo Damage Damage Type 1 2 3 4 1 2 3 4

permethrin (T1) 1 33.3 33.3 66.7 100 0 HE 0 100 100 100 0 HE permethrin (T1) 2 33.3 66.7 66.7 66.7 0 HE 0 100 100 100 0 HE permethrin (T1) 3 0 66.7 100 100 0 HE 0 100 100 100 0 HE permethrin (T1) 4 100 100 100 100 0 HE 0 100 100 100 0 HE permethrin (T1) 5 100 100 100 100 0 HE 0 100 100 100 0 HE permethrin (T1) 6 0 100 100 100 0 HE 0 100 100 100 0 HE

fenvalerate (T2) 1 33.3 100 100 100 0 HE 0 100 100 100 3.3 ME fenvalerate (T2) 2 66.7 100 100 100 0 HE 0 100 100 100 0 HE fenvalerate (T2) 3 66.7 66.7 100 100 0 HE 0 100 100 100 0 HE fenvalerate (T2) 4 0 100 100 100 0 HE 0 100 100 100 6.7 ME fenvalerate (T2) 5 66.7 100 100 100 0 HE 0 100 100 100 0 HE fenvalerate (T2) 6 0 100 100 100 0 HE 0 100 100 100 0 HE

deltamethrin (T3) 1 0 0 0 0 0 HE 0 0 0 0 0 HE deltamethrin (T3) 2 33.3 33.3 33.3 33.3 0 HE 0 0 0 0 0 HE deltamethrin (T3) 3 33.3 33.3 33.3 33.3 0 HE 0 0 0 0 0 HE deltamethrin (T3) 4 0 0 0 0 0 HE 0 100 100 100 0 HE deltamethrin (T3) 5 33.3 33.3 33.3 33.3 0 HE 0 100 100 100 0 HE deltamethrin (T3) 6 0 0 0 0 0 HE 0 100 100 100 0 HE

propiconazole (T4) 1 66.7. 100 100 100 26.7 SE 0 100 100 100 13.3 ME propiconazole (T4) 2 66.7 100 100 100 60 NE 0 100 100 100 0 HE propiconazole (T4) 3 33.3 100 100 100 20 ME 0 100 100 100 0 HE propiconazole (T4) 4 0 100 100 100 28.3 SE 0 100 100 100 20 ME propiconazole (T4) 5 66.7 100 100 100 66.7 NE 0 100 100 100 0 HE propiconazole (T4) 6 0 100 100 100 20.0 ME 0 100 100 100 0 HE deltamethrin 1 0 0 0 0 0 HE 0 0 0 0 0 HE +propiconazole (T5) deltamethrin 2 0 0 0 0 0 HE 0 0 0 0 0 HE +propiconazole (T5) deltamethrin 3 0 0 0 0 0 HE 0 0 0 0 0 HE +propiconazole(T5) deltamethrin 4 0 100 100 100 0 HE 0 100 100 100 0 HE +propiconazole (T5) deltamethrin 5 33.3 100 100 100 0 HE 0 100 100 100 0 HE +propiconazole(T5) deltamethrin 6 33.3 100 100 100 0 HE 0 100 100 100 0 HE +propiconazole (T5)

DOT (T6) 1 100 100 100 100 6.7 ME 100 100 100 100 1.7 ME DOT (T6) 2 66.7 66.7 66.7 66.7 13.3 ME 66.7 66.7 66.7 66.7 3.3 ME DOT (T6) 3 100 100 100 100 0 HE 100 100 100 100 1.7 ME

Table 4 continues next page. . . .

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DOT (T6) 4 0 100 100 100 3.3 ME 0 100 100 100 3.3 ME DOT (T6) 5 33.3 100 100 100 0 HE 0 100 100 100 0 HE DOT (T6) 6 0 100 100 100 0 HE 0 100 100 100 0 HE

Control (T7) 1 100 100 100 100 56.7 SR 100 100 100 100 20.0 R Control (T7) 2 100 100 100 100 33.3 MR 100 100 100 100 26.7 MR Control (T7) 3 100 100 100 100 30.0 MR 100 100 100 100 20.0 R Control (T7) 4 0 100 100 100 43.3 MR 0 100 100 100 20.0 R Control (T7) 5 33.3 100 100 100 36.7 MR 0 100 100 100 23.3 R Control (T7) 6 0 100 100 100 73.3 SR 0 100 100 100 26.7 MR

the efficacy of fenvalerate (T2), propiconazole (T4), and Drywood Termites, C. dudleyi DOT (T6) varied. Fenvalerate (T2) and propiconazole Giant Bamboo. Except for propiconazole (T4), all (T4) samples with Glues 2, 3, 5, and 6 prevented termite the chemicals [permethrin (T1), fenvalerate (T2), attack while fenvalerate (T2) and propiconazole (T4) with deltamethrin (T3), deltamethrin + propiconazole (T5) and Glues 1 and 4 were moderately effective with 3.3–20% DOT (T6)] regardless of glue type were highly effective termite damage. Likewise, the DOT (T6) applied in boards in protecting giant bamboo boards against the attack of with Glue 5 and 6 provided complete protection. DOT drywood termites (C. dudleyi) for 12 mo (Table 5). The treated samples with Glues 1–4 were moderately damaged. residual film of the chemicals applied on the board’s They sustained 1.7% to 3.3% termite damage after 4 mo. surface killed termite populations introduced at the onset of the test. Likewise, the new batches of re-introduced The resistance of the kauayan-tinik boards to M. C. dudleyi after 6 mo were inhibited by the treatment losbañosensis might have been influenced by the types regardless of chemical and glue type. of glue applied in lamination. Untreated sample boards laminated with Glues 1 and 3–5 were resistant with 20% The treated boards only showed nibbling on the surface termite damage while untreated boards laminated with as a sign of attempted termite attack. Propiconazole (T4) Glues 2 and 6 were moderately resistant with 26.7% is an anti-fungi chemical that served as a complimentary damage. treatment for comparison with deltamethrin +

Table 5. Percent termite damage on giant bamboo and kauayan tinik boards by drywood termite C. dudleyi after 12 mo of exposure. Giant Bamboo Kauayan-tinik %Termite Damage Efficacy of %Termite Damage (Month) Efficacy of Treatment (Month) Treatment Glue Type Treatment 1 2 3 4 1 2 3 4 permethrin (T1) 1 0 0 0 0 HE 0 0 0 0 HE permethrin (T1) 2 0 0 0 0 HE 0 0 0 0 HE permethrin (T1) 3 0 0 0 0 HE 0 0 0 0 HE permethrin (T1) 4 0 0 0 0 HE 0 0 0 0 HE permethrin (T1) 5 0 0 0 0 HE 0 0 0 0 HE permethrin (T1) 6 0 0 0 0 HE 0 0 0 0 HE

fenvalerate (T2) 1 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 2 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 3 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 4 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 5 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 6 0 0 0 0 HE 0 0 0 0 HE

Table 5 continues next page. . . .

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propiconazole (T4) 1 1.7 3.3 5.0 6.7 ME 0 0 1.7 3.3 HE propiconazole (T4) 2 3.3 5.0 6.7 8.3 ME 0 0 0 5.0 HE propiconazole (T4) 3 3.3 5.0 6.7 10. ME 1.7 3.3 3.3 5.0 HE propiconazole (T4) 4 3.3 5.0 6.7 8.3 ME 1.7 1.7 1.7 5.0 HE propiconazole (T4) 5 3.3 6.7 6.7 8.3 ME 0 0 0 5.0 HE propiconazole (T4) 6 5.0 5.0 8.3 10. ME 1.7 1.7 3.3 5.0 HE

deltamethrin + 1 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5) deltamethrin + 2 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5) deltamethrin + 3 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5) deltamethrin + 4 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5) deltamethrin + 5 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5) deltamethrin + 6 0 0 0 0 HE 0 0 0 0 HE propiconazole (T5)

DOT (T6) 1 0 0 0 0 HE 0 0 0 0 HE DOT (T6) 2 0 0 0 0 HE 0 0 0 0 HE DOT (T6) 3 0 0 0 0 HE 0 0 0 0 HE DOT (T6) 4 0 0 0 0 HE 0 0 0 0 HE DOT (T6) 5 0 0 0 0 HE 0 0 0 0 HE DOT (T6) 6 0 0 0 0 HE 0 0 0 0 HE

Control (T7) 1 3.3 5.0 5.0 8.3 R 1.7 3.3 5.0 8.3 R Control (T7) 2 1.7 6.7 6.7 15.0 R 1.7 1.7 6.7 10.0 R Control (T7) 3 1.7 1.7 6.7 15.0 R 3.3 5.0 6.7 10.0 R Control (T7) 4 0 3.3 8.3 16.7 R 0 0 5.0 6.7 R Control (T7) 5 5.0 6.7 10.0 15.0 R 1.7 1.7 5.0 10.0 R Control (T7) 6 5.0 8.3 10.0 20.0 R 1.7 3.3 3.3 11.7 R

propiconazole (T5). A 5–10% increase in termite damage of untreated boards was observed on the ninth month. During the 12th month, In untreated giant bamboo boards, initial damage except the damage in untreated samples remained slight at in boards with Glue 4 was observed on the surface after 8–20%. Pellet like materials were observed in the termite 3 mo. Termite damage ranged 1.7–5.0%. Active drywood chamber. termites were observed on the surface while few drywood termites bored between the layers. However, all untreated The slight degree of damage meant that the untreated samples were invaded after 6 mo with 1.7%–8.3% boards were resistant to the attack of C. dudleyi. The slight damage. degree of damage caused by C. dudleyi to untreated giant bamboo boards might be attributed to inherent resistance

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property of giant bamboo. Drywood termites were still The chemical treatment killed powder-post beetles in the active at the end of the test and further destruction on the chamber containing treated boards. All the insecticides boards is expected if no chemical will be applied. [permethrin (T1), fenvalerate (T2), deltamethrin (T3), deltamethrin + propiconazole (T5), and DOT (T6)] were Kauayan-tinik Boards. Except propiconazole (T4), highly effective in providing complete protection against percent damage on engineered kauayan-tinik boards the attack of D. minutus. On the other hand, propiconazole by drywood termites after 12 mo provided complete (T4) treated board sustained from 6.7 to 10 beetle holes protection against C. dudleyi throughout the exposure after 12 mo – suggesting that the chemical should be period. All the samples were still sound with 0% termite combined with deltamethrin (T3) to obtain complete damage from the 3rd until the 12th month (Table 5). protection for the boards. The population introduced into the set-up and the one The number of beetle holes in untreated giant bamboo introduced after six months had 100% mortality regardless of varied with glue type. The boards with Glues 1, 2, and 6 chemicals applied. Only termite nibbling and initial damage were free from beetle attack, but the ones with Glues 3–5 were noted in treated boards regardless of glue type. Nibbling had 0.6 to 2.6 beetle holes after 3–6 mo of test. However, on the treated surface is a taste test activity for termite to see all untreated giant bamboo boards regardless of glue had whether or not the host is acceptable as food source. beetle attack after 9 mo. Chemical treatment resulted in the failure of termites to The number of beetle holes ranged from 0.4 to 4.6. continue feeding on the boards. In propiconazole (T4) The powder-post beetles were still active and powdery treated giant bamboo, the degree of damage ranged from materials were noted on the beetle chambers. The number 3.3% to 5.0% in 12 mo. Based on the results, permethrin of holes remarkably increased on the 12th month and (T1), deltamethrin (T3), deltamethrin + propiconazole ranged from 0.4 to 5.4. Untreated samples with Glues (T5), and DOT (T6) were highly effective in protecting 1–5 were resistant to beetle attack with 2.6–5.4 beetle the samples against C. dudleyi. holes, while those with Glue 6 were highly resistant with Only untreated kauayan-tinik boards with propiconazole an initial beetle hole of 0.4 on the 12th month. (T4) had no termite damage after 3–6 mo. The rest showed Kauayan-tinik Boards. All of the chemicals used initial termite attack of 1.7–5% within the period. On prevented the attack of D. minutus after 3–6 mo. All the ninth month, drywood termites invaded all untreated boards remained sound or only had initial attack. No active boards regardless of glue with 3.3–5% damage. feeding was observed within the period. The efficacy of The degree of termite damage slightly progressed after 12 the residual films of various chemicals remained effective mo (6–11.7%). Based on the degree of damage, engineered for 9 mo (Table 6). kauayan-tinik was resistant to the attack of C. dudleyi. After 12 mo, only samples with permethrin (T1), However, the initial damage and continued minimal fenvalerate (T2), deltamethrin (T3), and deltamethrin + feeding activity by the drywood termites on untreated propiconazole (T5) remained protected in beetle attack. boards warrant treatment application. Likewise, those with propiconazole (T4) with Glue 3 Giron and Garcia (2005) reported that bamboo is showed only initial damage. susceptible to termite attack. Subekti et al. (2015) In contrast, DOT (T6) and Glue 3 were moderately explained that there are differences on the % mass loss effective (1 beetle hole) while the rest of the glues were of bamboo but none of the five (5) bamboo species used highly effective (0.2–0.8 hole). in their study can withstand termite attack. In untreated kauayan-tinik boards, the degree of beetle attack The differences in the degree of damage among bamboo varied with glue type. The samples laminated with Glues species were due to the variation in chemical composition 1, 2, 5, and 6 had 0–0.8 beetle hole compared with 1–7.2 between bamboo species (Dhawan & Mishra 2007). beetle hole in boards with Glues 2, 3, and 4 after 3–6 mo. After 9 mo, only untreated boards with Glue 6 had initial Powder-post Beetles, D. minutus beetle attack (0.2) and the boards laminated with the rest of Giant Bamboo Boards. All treated giant bamboo boards the glues had slight to moderate number of holes (1.4–4.8). regardless of type of chemical and glue were completely The number of holes slightly increased in 12 mo. free from the attack of powder-post beetles (D. minutus) in 3–12 mo. The boards were still sound or only had The untreated boards with Glues 1–4 and 6 sustained nibbling (Table 6). 1.4–1.6 beetle holes and classified as resistant to powder- post beetles. Those with Glue 5 were slightly resistant with beetle holes of 11.2.

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Table 6. Number of holes on giant bamboo and kauayan-tinik boards caused by powder-post beetles D. minutus after 12 mo of exposure. Giant Bamboo Kauayan-tinik Number of Beetle Holes Number of Beetle Holes Efficacy of Efficacy of Treatment (Month) (Month) Treatment Glue Type Treatment 1 2 3 4 1 2 3 4 permethrin (T1) 1 0 0 0 0.2 HE 0 0 0 0 HE permethrin (T1) 2 0 0 0.2 0.2 HE 0 0 0 0 HE permethrin (T1) 3 0 0 0.2 0.2 HE 0 0 0 0 HE permethrin (T1) 4 0 0 0 0.2 HE 0 0 0 0 HE permethrin (T1) 5 0 0 0.2 0.2 HE 0 0 0 0 HE permethrin (T1) 6 0 0.2 0.2 0.2 HE 0 0 0 0 HE

fenvalerate (T2) 1 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 2 0.2 0.4 0.6 0.6 HE 0 0 0 0 HE fenvalerate (T2) 3 0 0 0 0.2 HE 0 0 0 0 HE fenvalerate (T2) 4 0 0 0 0 HE 0 0 0 0 HE fenvalerate (T2) 5 0.2 0.4 0.6 0.6 HE 0 0 0 0.2 HE fenvalerate (T2) 6 0 0 0 0.2 HE 0 0 0 0 HE

deltamethrin (T3) 1 0 0 0 0 HE 0 0 0 0 HE deltamethrin (T3) 2 0 0 0 0 HE 0 0 0 0 HE deltamehtrin (T3) 3 0 0 0 0 HE 0 0 0 0 HE deltamethrin (T3) 4 0 0 0 0 HE 0 0 0 0 HE deltamethrin (T3) 5 0 0 0 0 HE 0 0 0 0 HE deltamethrin (T3) 6 0 0 0 0 HE 0 0 0 0 HE propiconazole (T4) 1 0 0.2 1.2 2.0 ME 0 0.2 0.4 1.2 ME propiconazole (T4) 2 0 0.2 1.8 2.8 ME 0 0.4 0.6 1.0 ME propiconazole (T4) 3 0 0 0 0 HE 0.2 0.4 0.4 0.8 HE propiconazole (T4) 4 0 0.2 2.2 2.8 ME 0.2 0.2 0.4 1.8 ME propiconazole (T4) 5 0 0.2 3.0 4.6 ME 0.2 0.2 0.4 1.6 ME propiconazole (T4) 6 0 0 0 0 HE 0.4 0.4 0.4 1.0 HE

DOT (T6) 1 0 0.6 0.8 0.8 HE 0.2 0.2 0.4 0.8 HE DOT (T6) 2 0 0.4 1.2 1.2 ME 0 0 0.4 0.6 HE DOT (T6) 3 0 0 0 0.6 HE 0 0.2 0.4 1.0 ME

Table 6 continues next page. . . .

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DOT (T6) 4 0 0 0 0.8 HE 0 0 0 0.2 HE DOT (T6) 5 0 0 0 1.0 ME 0 0 0 0.2 HE DOT (T6) 6 0 0 0.2 0.2 HE 0 0 0 0.2 HE

Control (T7) 1 0 0 2.2 2.6 R 0 0.2 1.4 1.4 R Control (T7) 2 0 0 2.0 3.4 R 1.0 1.6 1.8 1.8 R Control (T7) 3 2.6 2.6 4.6 5.4 R 1.0 3.6 4.2 4.8 R Control (T7) 4 1.0 1.2 2.0 3.2 R 6.8 7.2 8.6 11.2 SR Control (T7) 5 0.6 0.6 1.0 1.4 R 0.8 0.8 1.4 3.8 R Control (T7) 6 0 0 0.4 0.4 HR 0 0.2 0.2 1.6 R

The powder-post beetle (Dinoderus minutus F.) is a major bamboo slats absorbed 7.79 ml of deltamethrin (T3), post-harvest pest of bamboo and the attack resulted in 8.27 ml of deltamethrin + propiconazole (T5), and 4.85 severe damage or complete destruction of raw materials ml of permethrin (T1). Less chemicals were absorbed and finished products (Garcia 2005). Split bamboo is by kauayan-tinik slats: 6.25 ml of deltamethrin (T3), more susceptible to powder-post beetle attack than the 7.02 ml of deltamethrin + propiconazole (T5), and 4.74 round culms (Sulthoni 1983); thus, chemical treatment ml of permethrin (T1). The variation in the volume of is necessary to extend the service of bamboo (Casin & preservatives absorbed might be due to the species’ Mosteiro 1970, Liese 1980, Sulthoni 1987). Results of differences in the size of metaxylem vessel, which affect the study showed that deltamethrin provided complete penetrability of chemical solution. Liese (1998) reported protection of B. vulgaris against the attack of D. minutus that smaller vessel size restricts liquid flow compared to (Garcia 2005). bigger vessel. No data are available on the vessel diameter of giant bamboo, but it is presumably larger than the 165 µm vessel diameter of kauayan-tinik (Espiloy 1987). Cost of Glue and Preventive Treatment The cost of Glue 1, 2, and 3 to bind 200 mm x 1000 mm The cost of labor at US$0.008 (Php 0.40 per board) was three-ply E-bamboo boards were US$0.00048, US$0.50, constant regardless of chemical used. The cost of treatment and 0.312 (Php 75.00, Php 25.00, and Php 15.60), per bamboo slat of giant bamboo and kauayan-tinik using respectively. Only the three types of glue were used deltamethrin (T3) alone was US$0.0012 and US$0.011 since they were the most affordable and have properties (Php 0.59 and Php 0.55), respectively. The application of acceptable for construction. deltamethrin + propiconazole (T5) was more expensive at US$0.0176 and US$0.0192 (Php 0.88 and Php 0.96) per Only deltamethrin (T3), deltamethrin + propiconazole slat. Permethrin (T1), a ready-to-use preservative, was the (T5), and permethrin (T1) were considered in computing most expensive at US$0.0364–0.0372 (Php 1.82–1.86) for treatment cost since these provided complete per slat. protection to the boards regardless of type of bamboo, glue, and insect types. Eight (8) treated bamboo slats were required to produce bamboo boards measuring of 25 mm x 300 mm x 300 The estimated costs, including labor of treatment mm. Treatment cost of boards are US$0.088–0.094 (Php application of bamboo slats and bamboo boards by dipping 4.40–4.72) per board for deltamethrin (T3); US$0.1408– method, are presented in Table 7. Bamboo slats measured 0.1536 (Php 7.04–7.68 per board) for deltamethrin + 8 mm x 25 mm and 1000 mm. The chemicals costs were propiconazole (T5); and US$0.2912–0.298 (Php 14.56– US$0.00048 (Php 0.024) per ml for deltamethrin (T3) 14.88) per board for permethrin (T1). alone, US$0.0014 (Php 0.068) per ml for deltamethrin + propiconazole (T5), and US$0.006 (Php 0.30) per ml for The least expensive treatment was using deltamethrin permethrin (T1). (T3) (US$0.088–0.0944 or Php 4.40–4.72 per board) and recommended for bamboo slats with moisture Fifty (50) bamboo slats per batch can be treated and piled content below 20%. Permethrin (T1) was more expensive in 30 min, which can produce about 800 treated boards in (US$0.2912–0.2976 or Php 14.56–14.88 per board) one day. At the rate of US$6.4 (Php 320.00) per day, the because it is a ready-to-use preservative. Deltamethrin cost of labor was US$0.008 (Php 0.40) per bamboo slat. + propiconazole (T5) possessed a dual action, highly The volume of preservative absorbed by bamboo slats effective in controlling both wood insect pests and fungi, varied with the type of chemical and bamboo. Giant with mixture cost of US$0.1408–0.1536 (Php 7.04–7.68).

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Table 7. Treatment cost for bamboo slats and boards by dipping method. Variables Qty/Dimensions/Cost

1 Dimension of slat 8 mm x 25 mm x 1000 mm

2 Quantity of slats per batch of soaking 52 pcs 3 Quantity of slats to make 25 mm x 300 mm x 300 mm boards 8 pcs Cost of chemical per liter (li of chemical: li of water) deltamethrin (1:100) US$48 4 deltamethrin (1:00) + propiconazole (1:50) US$48 + US$88 permethrin (Ready to Use) US$6.0 Cost of chemical solution per ml deltamethrin US$0.00480 5 deltamethrin + propiconazole US$0.0014 permethrin US$0.006 6 Time of applying treatment, draining and piling of treated slats (50 pcs) 30 min 7 Cost of labor per 800 slats @ US$6.4 per day US$0.008/slat 8 Volume of chemicals absorbed and cost of chemical solution Cost of Chemical & Labor (US$)

Vol. of chemical Cost of Total cost of treatment absorbed chemical per Labor (US$) Treatment US$16per per slat ml Chemical Boards (ml) (US$) slats 25 mm x solution slats US$6.4 /day 300 mm x 300 mm a. Giant Bamboo deltamethrin 7.79 0.0048 0.19 0.40 0.0118 0.0944 deltam + propiconazole 8.27 0.0014 0.56 0.40 0.0192 0.1536 permethrin 4.85 0.006 1.46 0.40 0.0372 0.2976 b. Kauayan-tinik deltamethrin 6.25 0.0048 0.15 0.40 0.011 0.088 deltam + propiconazoe 7.02 0.0014 0.48 0.40 0.0176 0.1408 permethrin 4.73 0.006 1.42 0.40 0.0364 0.2912

CONCLUSION AND paneling, table tops, cabinets, drawers, etc. On the other RECOMMENDATIONS hand, Glue 1 is recommended for moderately high to medium strength construction such as door, windows, Generally, the properties of PVAc (Glue I) was significantly balusters, etc. higher than Glue 2 to 6. Between species, kauayan-tinik exhibited higher strength properties than giant bamboo, Deltamethrin + propiconazole (T5) have a dual action, although not statistically significant in some properties. highly effective in controlling both wood-destroying insects and fungi. While these preservatives are already Urea formaldehyde (Glue 3) is preferred over Glues 1 commercially available, it is highly recommended and 2 in terms of cost, but its strength properties were that finishing technologies to prevent the emission of lower than the other two adhesives. Moreover, one chemicals be used and to continuously seek to develop major drawback in using Glue 3 is its high formaldehyde indigenous non-toxic preservatives. emission. Overall, E-bamboo boards glued with PVAc (Glue 1) and Since all samples passed delamination tests regardless of treated with deltamethrin + propiconazole (T5) is highly adhesive, Glues 2 and 3 may be used to produce bamboo recommended for high end-products such as in-housing boards for interior construction purposes requiring components (floor tiles, balusters, window, and doors). medium to moderately low strength such as furniture,

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