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Recent advances in protection of unseasoned radiata pine wood in New Zealand
International Biodeterioration & Biodegradation 46 (2000) 83±88
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Recent advances in protection of unseasoned radiata pine wood in New Zealand R.N. Wakeling a,*, D.R. Eden a, B. Kreber a, C. Chittenden a, J.G. van der Waals a, B.E. Carpenter a, I. Dorset b, A. Price c a b
New Zealand Forest Research Institute Ltd., New Zealand Chemcolour Industries (NZ) Ltd., Auckland, New Zealand c Fletcher Challenge Forests Ltd., New Zealand Received 1 October 1999; accepted 15 June 2000
Abstract Radiata pine logs exported from New Zealand are susceptible to mould, sapstain and decay. Protection of logs from fungal degrade has not been achieved using conventional antisapstain treatments. A novel antisapstain treatment called Sentry1 meets the ecacy requirements of industry by overcoming some underlying diculties of treating logs by delivering a deep envelope of treated wood that remains intact for the duration of the protection period sought, and by arresting inevitable fungal infection that occurs during commercial log handling regimes. Sentry is a solubilised concentrate containing methylenebisthiocyanate (MBT) and 2-n-octyl-4-isothiazolin-3-one (OIA). Log mill trials compared the performance of Sentry with a commercial standard on logs of ages 1±14 days from felling. For log ages of 0, 2, 4, and 7 days, mean percentage sapstain for Sentry (equivalent to 0.5% w/v MBT plus 0.125% w/v OIA) was 0, 9, 21, and 32, respectively, compared to 3, 31, 54, and 54 for the commercial standard. The ability of Sentry to protect older logs is of considerable value to forestry operations because rapid extraction is often not feasible or increases costs. For block-stacked radiata pine boards stored for 12 weeks, Sentry, at the lowest concentration tested (equivalent to 0.125% MBT plus 0.025% OIA), gave equivalent protection to the highest concentrations of all the commercial standards. 7 2000 Published by Elsevier Science Ltd.
1. Introduction Plantation grown radiata pine typically contains a high percentage of sapwood, a rich food source to the plethora of mould, sapstain and decay fungi that ¯ourish in the New Zealand climate. Fungal attack of wood can only be prevented inde®nitely by drying lumber to a moisture content of 18% of its dry weight and maintaining moisture at that level (Eaton and Hale, 1993). Alternatively, logs can be placed under water sprinklers or in water (ponding) for temporary protection (Clifton, 1978), but this is not feasible during log transit. There are also concerns associated with the environmental impacts of run-o. When * Corresponding author.
ponding and drying are not feasible, an antisapstain treatment containing fungicides is applied to logs or lumber, usually by spray or dip application. Antisapstain treatments used in New Zealand have until recently given only 8±10 weeks of protection, and even this duration of protection is often achieved inconsistently resulting in large losses of commercial revenue (Price, 1997; Wakeling et al., 1997). There is also considerable unrealised revenue due to the loss of ongoing orders and from the eects of downgrading the image of the product that limits expansion within existing and new, high value export markets. Control of sapstain is more dicult for logs than sawn timber (Wakeling, 1997). The New Zealand Forest Research Institute is determined to solve this problem and has focused upon the following: . treatment of fungal pre-infection that is an inevita-
0964-8305/00/$ - see front matter 7 2000 Published by Elsevier Science Ltd. PII: S 0 9 6 4 - 8 3 0 5 ( 0 0 ) 0 0 0 7 2 - X
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R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
ble consequence of delays between tree felling and application of antisapstain treatment (Eden et al., 1997), using fungicide systems of an appropriate mobility in combination with durable fungicides that remain at the logs' surface; . eective treatment of an inherently uneven log surface that is prone to damage both before and after antisapstain treatment, using fungicide systems that provide a deep envelope of treated wood compared to the typically super®cial treatment provided by conventional treatments; . use of complementary combinations of fungicides that are eective against a broad spectrum of wood degrading fungi; and . design of stable micro-emulsions or surfactantassisted solutions of fungicides that overcome problems of spray blockage and/or solution concentration depletion, typical of less stable emulsions and suspensions. The use of diusible fungicides such as methylenebisthiocyanate (MBT) is not a new concept for antisapstain treatment of lumber (Williams et al., 1985; Williams and Eaton, 1987; Williams, 1990) or wood in-service where ¯uorides have been used (Richardson, 1978). The approach taken in this study was to develop a diusible or mobile treatment speci®cally for logs. Antisapstain log mill trials of Sentry1, an antisapstain treatment developed from this approach and now in commercial use in New Zealand, are reported in this paper. Results of block-stacked sawn timber trials of Sentry are also reported.
Sentry is a solubilised concentrate containing methylenebisthiocyanate (MBT) and 2-n-octyl-4-isothiazolin3-one (OIA) formulated to form a micro-emulsion upon dilution. A range of concentrations of Sentry were tested in log trials (Table 1) and sawn timber trials (Table 2). The performance of Sentry was compared with a commercial standard containing 3-iodo-2propynyl butyl carbamate (IPBC) plus didecyldimethyl ammonium chloride (DDAC) in Log Trial 1 and the sawn timber trial. In Log Trial 1 and all previous log trials this commercial standard consistently gave a level of performance below that required by industry, and it was therefore decided to discontinue its inclusion as a reference standard in preference to the inclusion of a wider concentration range of Sentry. Other commercial standards included in sawn timber trials are shown in Table 2. 2.3. Antisapstain treatment of logs Logs were either dip treated on the same day of tree felling or held for periods up to 14 days before treatment. Logs were totally immersed for 10 s in antisapstain solution. A minimum of eight replicate logs per treatment holding time were used.
Treated logs were stacked in the open at a central log processing facility for 16 weeks, before trucking to
2.1. Logs and sawn timber Pinus radiata D. Don pruned logs (25±30 years old), varying in length from 1.3 to 4.1 m and 35 to 45 cm diameter, were sourced from Kaingaroa forest in the central North Island of New Zealand, using a nonmechanised harvesting regime. Logs were debarked imTable 1 Antisapstain log treatments
1 1 2 2 2 2
2.2. Antisapstain treatment
2.4. Handling and storage of treated logs
2. Materials and methods
Trial
mediately prior to spray or dip application of the antisapstain treatment. However, large areas of bark are typically removed during forest extraction and haulage, providing sites for immediate fungal infection.
Treatment Type
Fungicides
Sentry Commercial standard Sentry Sentry Sentry Sentry
MBT/OIA IPBC/DDAC MBT/OIA MBT/OIA MBT/OIA MBT/OIA
Concentration (% w/v A.I.) 0.5/0.125 0.338/2.7 0.133/0.033 0.253/0.063 0.36/0.09 0.5/0.125
Table 2 Antisapstain sawn timber treatments Treatment Type
Fungicides
Sentry Sentry Sentry Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial
MBT/OIA MBT/OIA MBT/OIA Carbendazim/oxine copper Carbendazim/oxine copper Carbendazim/oxine copper IPBC/DDAC IPBC/DDAC IPBC/DDAC IPBC/DDAC MBT/chlorothalonil MBT/chlorothalonil MBT/chlorothalonil
standard standard standard standard standard standard standard standard standard standard
Concentration (% w/v A.I.) 0.125/0.025 0.25/0.05 0.5/0.1 0.038/0.038 0.075/0.075 0.15/0.15 0.075/0.06 0.15/1.2 0.3/2.2 0.6/4.8 0.15/0.15 0.3/0.3 0.6/0.6
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
the Fletcher Challenge Forests plywood plant at Mount Maunganui, for peeling (veneering) and assessment. 2.5. Assessment An estimate of percentage cover of sapstain was determined visually using the ®rst whole veneer-o of each log immediately after peeling. 2.6. Treatment of sawn timber Thirty Pinus radiata sapwood boards 40 100 1000 mm3), which had been sawn from logs 24±48 h previously, were individually given an agitated dip for 5 s in the antisapstain formulation. Following dipping, boards were block-stacked (6 tiers high and 5 boards wide) on a pair of 100 40 mm2 treated bearers placed on an asphalt-sealed surface. Treated packets were covered with plastic sheets for two days to prevent rain wetting and to allow chemical ®xation to occur before being exposed to the weather and natural fungal infection. The trial commenced in early summer (November 1997) and was completed by late summer (March 1998). 2.7. Assessment Percentage surface cover of fungal degrade was assessed at 5, 12, and 15 weeks after dipping using the following rating system: 0 1 2 3 4 5
No degrade Up to 5% surface coverage of fungal degrade 6±25% surface coverage of fungal degrade 26±50% surface coverage of fungal degrade 51±75% surface coverage of fungal degrade 76±100% surface coverage of fungal degrade
Tests of signi®cance of dierences between treatment formulations were performed for each assessment of each ®eld trial using the following procedure. The percentage cover rating of each board of all the treatments was ranked from best to worst. A conventional one-way analysis of variance (ANOVA) was then carried out on the ranks. As part of the ANOVA analysis a mean rank for the 25 boards in each treatment was obtained; where ANOVA indicated that signi®cant dierences existed, least signi®cant dierences (LSDs) were used to indicate which pairs of treatments differed signi®cantly at a 5% level of probability. Mean percent of surface coverage (%MSC) of fungal degrade was calculated for each treatment using a derived median percentage cover value for each rating. For example 15.5% is the median of the range 6±25% (rating of 2).
85
3. Results and discussion 3.1. Log trials Average percentage sapstain in untreated control logs after 16 weeks' storage was 65 and 42 for Trials 1 and 2, respectively, indicating a high sapstain hazard during the trial periods (Figs. 1 and 2). Sentry gave superior performance to the commercial standard for all log holding times tested. For example, for the 2-day holding time, the commercial standard had 31% sapstain compared to 9% for Sentry. On the basis that up to 10% sapstain is the maximum that is acceptable to industry, the commercial standard only gave adequate performance if the logs were treated on the same day as felling (Fig. 1). The maximum holding time for which Sentry gave adequate performance was 2 days in Trial 1 (concentration equivalent to 0.5% w/v MBT plus 0.125% w/v OIA) and 10 days in Trial 2 (concentration equivalent to 0.253% w/v MBT plus 0.063% w/v OIA). These dierences in maximum log holding time may have been due to the dierent degrees of hazard caused by dierent seasonal conditions that resulted from trials running at dierent times of the year, as indicated by the extent of sapstain in the controls. It may also have been related to dierent degrees of fungal pre-infection and dierent degrees of log surface damage and moisture content, factors that can aect antisapstain solution uptake (Wakeling et al., 1997). Log holding time had a profound eect on the performance of both the commercial standard and Sentry; however, the extent of sapstain for each holding time tested was consistently less for Sentry compared to the commercial standard. In Trial 1, at holding times 0, 2, 4, and 7 days, average sapstain cover for Sentry was 0, 9, 21, and 32% respectively, compared to 3, 31, 54, and 54% for the commercial standard. This eect of holding time on sapstain development in logs has been reported previously (Eden et al., 1997). The authors suggested that antisapstain treatment of older logs was less eective because they contained more pre-infection sapstain below the subsurface and could therefore not be eectively treated by conventional antisapstain formulations that remain largely on the logs' surface. Our working hypothesis purports that the mobile component of Sentry is able to arrest pre-infection, thereby giving more eective treatment of older logs. This is supported by the ®ndings of Eden et al. (1999). More work is required to accurately determine the relationship between log age, the degree of infection, and the eectiveness of Sentry. The mobility of MBT in wood has been reported previously (Williams et al., 1985; Williams and Eaton, 1987), although it is not clear what eect the nature of the formulation has on mobi-
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R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
Fig. 1. Average sapstain in 16-week-old logs (Trial 1).
lity. This is currently under investigation at the New Zealand Forest Research Institute. 3.2. Sawn timber trial Mean fungal degrade for the untreated control boards was 48 and 78% at 5 and 12 weeks respectively, indicating a high fungal degrade hazard level during the trial period (Fig. 3). Fungal degrade levels were low for all antisapstain treatments tested after 5 weeks of storage, with the majority of treatments having zero fungal degrade and the poorest treatment having 6% fungal degrade. After 12 weeks, the levels of fungal degrade had increased dramatically. Only timber treated with Sentry (0.5% w/v MBT + 0.1% w/v OIA) had zero degrade after 12 weeks Ð a level of protection signi®cantly better than all other treatments (Table 3). The lower concentrations of Sen-
try, equivalent to 0.25% MBT plus 0.05% OIA and 0.125% MBT plus 0.025% OIA, had 4.3 and 8.5% fungal degrade, respectively. At both these lower concentrations, protection given by Sentry was not signi®cantly dierent than that given by the highest concentration of the two best commercial standards, 0.6% MBT plus 0.6% CTLN and 0.6% IPBC plus 4.8% DDAC. After 15 weeks the highest concentration of Sentry gave signi®cantly better (5% level of probability) protection than all commercial standards at the highest concentrations tested. Furthermore, Sentry gave better protection at all concentrations tested than did all of the commercial standards except the highest concentration of MBT plus CTLN. The observation that 0.125% MBT plus 0.025% OIA gave equivalent protection to much higher concentrations of the fungicides contained in the commercial standard could be due in
Fig. 2. Average sapstain in 16-week-old logs (Trial 2).
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
87
Fig. 3. Fungal degrade on block-stacked radiata pine.
part to improved ecacy of the Sentry micro-emulsion system. The ability of MBT to penetrate boards is well known (Williams et al., 1985; Williams and Eaton, 1987; Williams, 1990), and this could result in a greater degree of protection of subsurface regions. A deeper envelope of treated wood could provide a more eective long-term barrier to fungal attack. It is possible that the wood surface harbors more aggressive fungicide depletion mechanisms than the subsurface regions where MBT migrates.
4. Conclusions Sentry gave consistently higher performance on logs than the commercial standard. The ability of Sentry to protect older logs is of considerable value within forestry operations where rapid extraction is often not feasible. High use rates of the commercial standards failed to give adequate protection to block stacked radiata pine in storage for 12 weeks. The high level of protection
Table 3 Relative eectiveness of formulations after 12 weeks of treatment Treatment (% w/v)
%MSCa
0 MBT(0.5) + OIA(0.1) IPBC(0.6) + DDAC(4.8) MBT(0.25) + OIA(0.05) MBT(0.6) + CTLN(0.6) MBT(0.125) + OIA(0.025) Carbc(0.15)Cu-8(0.15) IPBC(0.3) + DDAC(2.4) Carb(0.075)Cu-8(0.075) Carb(0.038)Cu-8(0.038) MBT(0.3) + CTLN(0.3) IPBC(0.15) + DDAC(1.2) MBT(0.15) + CTLN(0.15) IPBC(0.075) + DDAC(0.6) Control a
0.0 2.6 4.3 5.2 8.5 12.3 17.0 21.0 25.2 27.1 41.6 47.0 61.1 77.2
Signi®canceb
Number of boards in rating
30 17 8 3 8 4 2 4 1
1
2
10 17 21 14 10 7 5 1 4 2 2
3 5 6 4 12 16 16 11 15 6 6 7
3
4
5 a
4 4 3 8 12 7 10 9 2 3
2 1 2 2 8 7 8 7
2 3 6 13 20
Mean percent of surface coverage. Signi®cant dierences determined with Least Signi®cant Dierence (LSD) test at pR0:05:. c ``Carb'' = carbendazim.
b
b
c c c
d d
e e
f f f f
g g g
h h h
i i i
j j j
88
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
achieved by Sentry is in part attributed to the broad spectrum of fungicidal activity oered by MBT plus OIA and the micro-emulsion system used. The ability of the MBT to penetrate boards is believed to provide protection to subsurface regions.
References Clifton, B.C., 1978. Sprinkler storage of windblows proves eective and economic. World Wood (November): 26±27. Eaton, R.A., Hale, M.C.D., 1993. Wood: Decay, Pests and Protection. Chapman and Hall, London. Eden, D., Wakeling, R.N., Chittenden, C., Carpenter, B., van der Waals, J., 1997. Time limits for holding logs to achieve successful antisapstain treatment. In: Kreber, B. (Ed.), Proceedings of the Sapstain Symposium Ð Strategies for Improving Protection of Logs and Lumber, pp. 55±62 FRI Bulletin No. 204. Eden, D., Singh, T., Kreber, B., 1999. Eect of Mobile Fungicides on Fungal Pre-Infection in Radiata Pine. In: IRG WP 3019. International Research Group on Wood Preservation, Stockholm, Sweden. Price, D.A., 1997. Elimination of sapstain in radiata pine logs exported from New Zealand. In: Morrell, J.J., Dickinson, D.J. (Eds.), Proceedings of the Sapstain Symposium Ð Biology and
Prevention of Sapstain. Forest Products Society, Madison, WI, pp. 53±54. Richardson, B.A., 1978. Wood Preservation. The Construction Press, Lancaster, UK. Wakeling, R.N., 1997. Issues for successful protection of New Zealand radiata pine logs. In: Kreber, B. (Ed.), Proceedings of the Sapstain Symposium Ð Strategies for Improving Protection of Logs and Lumber, pp. 31±38 FRI Bulletin No. 204. Wakeling, R.N., Eden, D., Chittenden, C., Carpenter, B., Dorset, I., Wakemam, J., Kuluz, R., 1997. Water barriers for preventing sapstain in logs. In: Morrell, J.J., Dickinson, D.J. (Eds.), Proceedings of the Sapstain Symposium Ð Biology and Prevention of Sapstain. , Forest Products Society, Madison, WI, pp. 15±22. Williams, G.R., 1990. Observations on the Failure of Antisapstain Treated Timber under Non-Drying Conditions. In: IRG WP 1437. International Research Group on Wood Preservation, Stockholm, Sweden. Williams, G.R., Eaton, R.A., Lewis, D.A., 1985. Observations on the Penetration of Preservatives into Green Timber. In: IRG WP 3335. International Research Group on Wood Preservation, Stockholm, Sweden. Williams, G.R., Eaton, R.A., 1987. Studies on toxicity of biocides towards mould and sapstain fungi. In: Houghton, D.R., Smith, R.N., Eggins, H.O.W. (Eds.), Biodeterioration 7. Elsevier, Essex, UK, pp. 755±761.
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Recent advances in protection of unseasoned radiata pine wood in New Zealand R.N. Wakeling a,*, D.R. Eden a, B. Kreber a, C. Chittenden a, J.G. van der Waals a, B.E. Carpenter a, I. Dorset b, A. Price c a b
New Zealand Forest Research Institute Ltd., New Zealand Chemcolour Industries (NZ) Ltd., Auckland, New Zealand c Fletcher Challenge Forests Ltd., New Zealand Received 1 October 1999; accepted 15 June 2000
Abstract Radiata pine logs exported from New Zealand are susceptible to mould, sapstain and decay. Protection of logs from fungal degrade has not been achieved using conventional antisapstain treatments. A novel antisapstain treatment called Sentry1 meets the ecacy requirements of industry by overcoming some underlying diculties of treating logs by delivering a deep envelope of treated wood that remains intact for the duration of the protection period sought, and by arresting inevitable fungal infection that occurs during commercial log handling regimes. Sentry is a solubilised concentrate containing methylenebisthiocyanate (MBT) and 2-n-octyl-4-isothiazolin-3-one (OIA). Log mill trials compared the performance of Sentry with a commercial standard on logs of ages 1±14 days from felling. For log ages of 0, 2, 4, and 7 days, mean percentage sapstain for Sentry (equivalent to 0.5% w/v MBT plus 0.125% w/v OIA) was 0, 9, 21, and 32, respectively, compared to 3, 31, 54, and 54 for the commercial standard. The ability of Sentry to protect older logs is of considerable value to forestry operations because rapid extraction is often not feasible or increases costs. For block-stacked radiata pine boards stored for 12 weeks, Sentry, at the lowest concentration tested (equivalent to 0.125% MBT plus 0.025% OIA), gave equivalent protection to the highest concentrations of all the commercial standards. 7 2000 Published by Elsevier Science Ltd.
1. Introduction Plantation grown radiata pine typically contains a high percentage of sapwood, a rich food source to the plethora of mould, sapstain and decay fungi that ¯ourish in the New Zealand climate. Fungal attack of wood can only be prevented inde®nitely by drying lumber to a moisture content of 18% of its dry weight and maintaining moisture at that level (Eaton and Hale, 1993). Alternatively, logs can be placed under water sprinklers or in water (ponding) for temporary protection (Clifton, 1978), but this is not feasible during log transit. There are also concerns associated with the environmental impacts of run-o. When * Corresponding author.
ponding and drying are not feasible, an antisapstain treatment containing fungicides is applied to logs or lumber, usually by spray or dip application. Antisapstain treatments used in New Zealand have until recently given only 8±10 weeks of protection, and even this duration of protection is often achieved inconsistently resulting in large losses of commercial revenue (Price, 1997; Wakeling et al., 1997). There is also considerable unrealised revenue due to the loss of ongoing orders and from the eects of downgrading the image of the product that limits expansion within existing and new, high value export markets. Control of sapstain is more dicult for logs than sawn timber (Wakeling, 1997). The New Zealand Forest Research Institute is determined to solve this problem and has focused upon the following: . treatment of fungal pre-infection that is an inevita-
0964-8305/00/$ - see front matter 7 2000 Published by Elsevier Science Ltd. PII: S 0 9 6 4 - 8 3 0 5 ( 0 0 ) 0 0 0 7 2 - X
84
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
ble consequence of delays between tree felling and application of antisapstain treatment (Eden et al., 1997), using fungicide systems of an appropriate mobility in combination with durable fungicides that remain at the logs' surface; . eective treatment of an inherently uneven log surface that is prone to damage both before and after antisapstain treatment, using fungicide systems that provide a deep envelope of treated wood compared to the typically super®cial treatment provided by conventional treatments; . use of complementary combinations of fungicides that are eective against a broad spectrum of wood degrading fungi; and . design of stable micro-emulsions or surfactantassisted solutions of fungicides that overcome problems of spray blockage and/or solution concentration depletion, typical of less stable emulsions and suspensions. The use of diusible fungicides such as methylenebisthiocyanate (MBT) is not a new concept for antisapstain treatment of lumber (Williams et al., 1985; Williams and Eaton, 1987; Williams, 1990) or wood in-service where ¯uorides have been used (Richardson, 1978). The approach taken in this study was to develop a diusible or mobile treatment speci®cally for logs. Antisapstain log mill trials of Sentry1, an antisapstain treatment developed from this approach and now in commercial use in New Zealand, are reported in this paper. Results of block-stacked sawn timber trials of Sentry are also reported.
Sentry is a solubilised concentrate containing methylenebisthiocyanate (MBT) and 2-n-octyl-4-isothiazolin3-one (OIA) formulated to form a micro-emulsion upon dilution. A range of concentrations of Sentry were tested in log trials (Table 1) and sawn timber trials (Table 2). The performance of Sentry was compared with a commercial standard containing 3-iodo-2propynyl butyl carbamate (IPBC) plus didecyldimethyl ammonium chloride (DDAC) in Log Trial 1 and the sawn timber trial. In Log Trial 1 and all previous log trials this commercial standard consistently gave a level of performance below that required by industry, and it was therefore decided to discontinue its inclusion as a reference standard in preference to the inclusion of a wider concentration range of Sentry. Other commercial standards included in sawn timber trials are shown in Table 2. 2.3. Antisapstain treatment of logs Logs were either dip treated on the same day of tree felling or held for periods up to 14 days before treatment. Logs were totally immersed for 10 s in antisapstain solution. A minimum of eight replicate logs per treatment holding time were used.
Treated logs were stacked in the open at a central log processing facility for 16 weeks, before trucking to
2.1. Logs and sawn timber Pinus radiata D. Don pruned logs (25±30 years old), varying in length from 1.3 to 4.1 m and 35 to 45 cm diameter, were sourced from Kaingaroa forest in the central North Island of New Zealand, using a nonmechanised harvesting regime. Logs were debarked imTable 1 Antisapstain log treatments
1 1 2 2 2 2
2.2. Antisapstain treatment
2.4. Handling and storage of treated logs
2. Materials and methods
Trial
mediately prior to spray or dip application of the antisapstain treatment. However, large areas of bark are typically removed during forest extraction and haulage, providing sites for immediate fungal infection.
Treatment Type
Fungicides
Sentry Commercial standard Sentry Sentry Sentry Sentry
MBT/OIA IPBC/DDAC MBT/OIA MBT/OIA MBT/OIA MBT/OIA
Concentration (% w/v A.I.) 0.5/0.125 0.338/2.7 0.133/0.033 0.253/0.063 0.36/0.09 0.5/0.125
Table 2 Antisapstain sawn timber treatments Treatment Type
Fungicides
Sentry Sentry Sentry Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial Commercial
MBT/OIA MBT/OIA MBT/OIA Carbendazim/oxine copper Carbendazim/oxine copper Carbendazim/oxine copper IPBC/DDAC IPBC/DDAC IPBC/DDAC IPBC/DDAC MBT/chlorothalonil MBT/chlorothalonil MBT/chlorothalonil
standard standard standard standard standard standard standard standard standard standard
Concentration (% w/v A.I.) 0.125/0.025 0.25/0.05 0.5/0.1 0.038/0.038 0.075/0.075 0.15/0.15 0.075/0.06 0.15/1.2 0.3/2.2 0.6/4.8 0.15/0.15 0.3/0.3 0.6/0.6
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
the Fletcher Challenge Forests plywood plant at Mount Maunganui, for peeling (veneering) and assessment. 2.5. Assessment An estimate of percentage cover of sapstain was determined visually using the ®rst whole veneer-o of each log immediately after peeling. 2.6. Treatment of sawn timber Thirty Pinus radiata sapwood boards 40 100 1000 mm3), which had been sawn from logs 24±48 h previously, were individually given an agitated dip for 5 s in the antisapstain formulation. Following dipping, boards were block-stacked (6 tiers high and 5 boards wide) on a pair of 100 40 mm2 treated bearers placed on an asphalt-sealed surface. Treated packets were covered with plastic sheets for two days to prevent rain wetting and to allow chemical ®xation to occur before being exposed to the weather and natural fungal infection. The trial commenced in early summer (November 1997) and was completed by late summer (March 1998). 2.7. Assessment Percentage surface cover of fungal degrade was assessed at 5, 12, and 15 weeks after dipping using the following rating system: 0 1 2 3 4 5
No degrade Up to 5% surface coverage of fungal degrade 6±25% surface coverage of fungal degrade 26±50% surface coverage of fungal degrade 51±75% surface coverage of fungal degrade 76±100% surface coverage of fungal degrade
Tests of signi®cance of dierences between treatment formulations were performed for each assessment of each ®eld trial using the following procedure. The percentage cover rating of each board of all the treatments was ranked from best to worst. A conventional one-way analysis of variance (ANOVA) was then carried out on the ranks. As part of the ANOVA analysis a mean rank for the 25 boards in each treatment was obtained; where ANOVA indicated that signi®cant dierences existed, least signi®cant dierences (LSDs) were used to indicate which pairs of treatments differed signi®cantly at a 5% level of probability. Mean percent of surface coverage (%MSC) of fungal degrade was calculated for each treatment using a derived median percentage cover value for each rating. For example 15.5% is the median of the range 6±25% (rating of 2).
85
3. Results and discussion 3.1. Log trials Average percentage sapstain in untreated control logs after 16 weeks' storage was 65 and 42 for Trials 1 and 2, respectively, indicating a high sapstain hazard during the trial periods (Figs. 1 and 2). Sentry gave superior performance to the commercial standard for all log holding times tested. For example, for the 2-day holding time, the commercial standard had 31% sapstain compared to 9% for Sentry. On the basis that up to 10% sapstain is the maximum that is acceptable to industry, the commercial standard only gave adequate performance if the logs were treated on the same day as felling (Fig. 1). The maximum holding time for which Sentry gave adequate performance was 2 days in Trial 1 (concentration equivalent to 0.5% w/v MBT plus 0.125% w/v OIA) and 10 days in Trial 2 (concentration equivalent to 0.253% w/v MBT plus 0.063% w/v OIA). These dierences in maximum log holding time may have been due to the dierent degrees of hazard caused by dierent seasonal conditions that resulted from trials running at dierent times of the year, as indicated by the extent of sapstain in the controls. It may also have been related to dierent degrees of fungal pre-infection and dierent degrees of log surface damage and moisture content, factors that can aect antisapstain solution uptake (Wakeling et al., 1997). Log holding time had a profound eect on the performance of both the commercial standard and Sentry; however, the extent of sapstain for each holding time tested was consistently less for Sentry compared to the commercial standard. In Trial 1, at holding times 0, 2, 4, and 7 days, average sapstain cover for Sentry was 0, 9, 21, and 32% respectively, compared to 3, 31, 54, and 54% for the commercial standard. This eect of holding time on sapstain development in logs has been reported previously (Eden et al., 1997). The authors suggested that antisapstain treatment of older logs was less eective because they contained more pre-infection sapstain below the subsurface and could therefore not be eectively treated by conventional antisapstain formulations that remain largely on the logs' surface. Our working hypothesis purports that the mobile component of Sentry is able to arrest pre-infection, thereby giving more eective treatment of older logs. This is supported by the ®ndings of Eden et al. (1999). More work is required to accurately determine the relationship between log age, the degree of infection, and the eectiveness of Sentry. The mobility of MBT in wood has been reported previously (Williams et al., 1985; Williams and Eaton, 1987), although it is not clear what eect the nature of the formulation has on mobi-
86
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Fig. 1. Average sapstain in 16-week-old logs (Trial 1).
lity. This is currently under investigation at the New Zealand Forest Research Institute. 3.2. Sawn timber trial Mean fungal degrade for the untreated control boards was 48 and 78% at 5 and 12 weeks respectively, indicating a high fungal degrade hazard level during the trial period (Fig. 3). Fungal degrade levels were low for all antisapstain treatments tested after 5 weeks of storage, with the majority of treatments having zero fungal degrade and the poorest treatment having 6% fungal degrade. After 12 weeks, the levels of fungal degrade had increased dramatically. Only timber treated with Sentry (0.5% w/v MBT + 0.1% w/v OIA) had zero degrade after 12 weeks Ð a level of protection signi®cantly better than all other treatments (Table 3). The lower concentrations of Sen-
try, equivalent to 0.25% MBT plus 0.05% OIA and 0.125% MBT plus 0.025% OIA, had 4.3 and 8.5% fungal degrade, respectively. At both these lower concentrations, protection given by Sentry was not signi®cantly dierent than that given by the highest concentration of the two best commercial standards, 0.6% MBT plus 0.6% CTLN and 0.6% IPBC plus 4.8% DDAC. After 15 weeks the highest concentration of Sentry gave signi®cantly better (5% level of probability) protection than all commercial standards at the highest concentrations tested. Furthermore, Sentry gave better protection at all concentrations tested than did all of the commercial standards except the highest concentration of MBT plus CTLN. The observation that 0.125% MBT plus 0.025% OIA gave equivalent protection to much higher concentrations of the fungicides contained in the commercial standard could be due in
Fig. 2. Average sapstain in 16-week-old logs (Trial 2).
R.N. Wakeling et al. / International Biodeterioration & Biodegradation 46 (2000) 83±88
87
Fig. 3. Fungal degrade on block-stacked radiata pine.
part to improved ecacy of the Sentry micro-emulsion system. The ability of MBT to penetrate boards is well known (Williams et al., 1985; Williams and Eaton, 1987; Williams, 1990), and this could result in a greater degree of protection of subsurface regions. A deeper envelope of treated wood could provide a more eective long-term barrier to fungal attack. It is possible that the wood surface harbors more aggressive fungicide depletion mechanisms than the subsurface regions where MBT migrates.
4. Conclusions Sentry gave consistently higher performance on logs than the commercial standard. The ability of Sentry to protect older logs is of considerable value within forestry operations where rapid extraction is often not feasible. High use rates of the commercial standards failed to give adequate protection to block stacked radiata pine in storage for 12 weeks. The high level of protection
Table 3 Relative eectiveness of formulations after 12 weeks of treatment Treatment (% w/v)
%MSCa
0 MBT(0.5) + OIA(0.1) IPBC(0.6) + DDAC(4.8) MBT(0.25) + OIA(0.05) MBT(0.6) + CTLN(0.6) MBT(0.125) + OIA(0.025) Carbc(0.15)Cu-8(0.15) IPBC(0.3) + DDAC(2.4) Carb(0.075)Cu-8(0.075) Carb(0.038)Cu-8(0.038) MBT(0.3) + CTLN(0.3) IPBC(0.15) + DDAC(1.2) MBT(0.15) + CTLN(0.15) IPBC(0.075) + DDAC(0.6) Control a
0.0 2.6 4.3 5.2 8.5 12.3 17.0 21.0 25.2 27.1 41.6 47.0 61.1 77.2
Signi®canceb
Number of boards in rating
30 17 8 3 8 4 2 4 1
1
2
10 17 21 14 10 7 5 1 4 2 2
3 5 6 4 12 16 16 11 15 6 6 7
3
4
5 a
4 4 3 8 12 7 10 9 2 3
2 1 2 2 8 7 8 7
2 3 6 13 20
Mean percent of surface coverage. Signi®cant dierences determined with Least Signi®cant Dierence (LSD) test at pR0:05:. c ``Carb'' = carbendazim.
b
b
c c c
d d
e e
f f f f
g g g
h h h
i i i
j j j
88
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achieved by Sentry is in part attributed to the broad spectrum of fungicidal activity oered by MBT plus OIA and the micro-emulsion system used. The ability of the MBT to penetrate boards is believed to provide protection to subsurface regions.
References Clifton, B.C., 1978. Sprinkler storage of windblows proves eective and economic. World Wood (November): 26±27. Eaton, R.A., Hale, M.C.D., 1993. Wood: Decay, Pests and Protection. Chapman and Hall, London. Eden, D., Wakeling, R.N., Chittenden, C., Carpenter, B., van der Waals, J., 1997. Time limits for holding logs to achieve successful antisapstain treatment. In: Kreber, B. (Ed.), Proceedings of the Sapstain Symposium Ð Strategies for Improving Protection of Logs and Lumber, pp. 55±62 FRI Bulletin No. 204. Eden, D., Singh, T., Kreber, B., 1999. Eect of Mobile Fungicides on Fungal Pre-Infection in Radiata Pine. In: IRG WP 3019. International Research Group on Wood Preservation, Stockholm, Sweden. Price, D.A., 1997. Elimination of sapstain in radiata pine logs exported from New Zealand. In: Morrell, J.J., Dickinson, D.J. (Eds.), Proceedings of the Sapstain Symposium Ð Biology and
Prevention of Sapstain. Forest Products Society, Madison, WI, pp. 53±54. Richardson, B.A., 1978. Wood Preservation. The Construction Press, Lancaster, UK. Wakeling, R.N., 1997. Issues for successful protection of New Zealand radiata pine logs. In: Kreber, B. (Ed.), Proceedings of the Sapstain Symposium Ð Strategies for Improving Protection of Logs and Lumber, pp. 31±38 FRI Bulletin No. 204. Wakeling, R.N., Eden, D., Chittenden, C., Carpenter, B., Dorset, I., Wakemam, J., Kuluz, R., 1997. Water barriers for preventing sapstain in logs. In: Morrell, J.J., Dickinson, D.J. (Eds.), Proceedings of the Sapstain Symposium Ð Biology and Prevention of Sapstain. , Forest Products Society, Madison, WI, pp. 15±22. Williams, G.R., 1990. Observations on the Failure of Antisapstain Treated Timber under Non-Drying Conditions. In: IRG WP 1437. International Research Group on Wood Preservation, Stockholm, Sweden. Williams, G.R., Eaton, R.A., Lewis, D.A., 1985. Observations on the Penetration of Preservatives into Green Timber. In: IRG WP 3335. International Research Group on Wood Preservation, Stockholm, Sweden. Williams, G.R., Eaton, R.A., 1987. Studies on toxicity of biocides towards mould and sapstain fungi. In: Houghton, D.R., Smith, R.N., Eggins, H.O.W. (Eds.), Biodeterioration 7. Elsevier, Essex, UK, pp. 755±761.