Biodeteriorating Agents Associated with Three Tropical Timber Species M.M

Forest Ecology and Management 195 (2004) 311–323

Biodeteriorating agents associated with three tropical timber species M.M. Apetorgbor*, N.A. Darkwa, O. Frimpong, V.K. Agyeman Forestry Research Institute of Ghana, P.O. Box 63, UST, Kumasi, Ghana Received 13 November 2002; received in revised form 17 October 2003; accepted 20 February 2004

Abstract

Biodeteriorating agents are major problems of wood particularly in tropical Africa. Biodeterioration is widely observed in light coloured hardwood species especially Celtis mildbraedii, Ceiba pentandra and Pterygota macrocarpa. To determine biodeteriorating agents associated with these degradable woods, logs of C. mildbraedii, C. pentandra and P. macrocarpa were left for 6 weeks at the loading bay during the dry and wet seasons of the year 2001. The surfaces of logs were assessed for stain and mould after 7, 14, 28, and 42 days of storage. Pterygota macrocarpa harboured the highest fungal population count of 60:3 103 colony-forming units (CFU) with C. mildbraedii harbouring the least at 4:2 102 CFU after a week exposure in the dry season. Fusarium solani and Penicillium citrinum were the dominant surface moulds on log ends of wood samples, while Lasiodiplodia theobromae and Ceratocystis fagacearum were the dominant sapstain fungi. Pterygota macrocarpa and C. pentandra were more susceptible to woodborers than C. mildbraedii because of the lack of true heartwood and richer store of nutrients in its wood cells. # 2004 Elsevier B.V. All rights reserved.

Keywords: Biodeteriorating agents; Logs; Tropical timber; Sapstain; Ghana

1. Introduction conditions of optimum temperature and high humidity. In recent years, especially in the wet season timber The timber processing industries are beset with harvesting is being done all year round instead of the biodeteriorating agents, which cause serious eco- drier months only, to meet increasing local and inter- nomic losses of wood in Ghana. Reports (Ampong, national demand in tropical wood. The high incidence 1986) indicate that Ghana loses a considerable amount of biodeterioration is exacerbated due to the extraction of foreign exchange annually as a result of fungal procedures used by the timber contractors. For exam- staining of exported timber. It was estimated that about ple during extraction, the felled logs are extracted to a one-third of the timber produced is lost through bio- central location where they are left for periods of up to logical degradation (Liese, 1975). The biodeteriorat- 1 month due to impassable roads or breakdown of ing agents are aided by extremely favourable equipment and trucks. The logs become exposed to ad- verse climatic conditions and biological agents among which are fungi and insects. In these circumstances, * Corresponding author. Tel.: 233-51-60123/60373; þ the non-durable woods such as Obeche (Triplochiton fax: þ233-51-60121. E-mail addresses: [email protected], [email protected] scleroxylon) and Kyenkyen (Antiaris toxicaria) (M.M. Apetorgbor). deteriorate quickly (Momoh and Olujide, 1967).

Addo-Ashong (1967) observed that many Ghanaian (8 and 7 stems, respectively). However, the AAC for timber species especially the white woods are gener- C. mildbraedii was relatively high (140 stems) (FC, ally attacked by blue staining fungi soon after felling. 2002). Trees were felled in the rainy (June–July) and Lasiodiplodia theobromae was found to be the com- dry (February–March) felling seasons. For each of the monest sapstain fungus isolated from light coloured felling seasons, nine trees were felled and subse- tropical timber species in Ghana (Ofosu-Asiedu, 1973). quently cut into 1.2 m long logs. A total of 10 logs Previous studies (Addo-Ashong, 1967; Momoh and were obtained from each tree. Therefore a total of 90 Olujide, 1967; Ofosu-Asiedu, 1973) on deterioration logs per felling season were used for the trials. Thirty in tropical timber species in West Africa have focused logs per species were assessed for biodeterioration mainly on identiﬁcation of biodeteriorating agents, but effects. have not extensively studied variations in the suscept- All logs were kept inside the forest and observed by ibility of various timber species to biodeterioration visual inspection for staining and borer attack. The and effect of environmental factors on the develop- diameters of the logs were measured. The cross sec- ment of biodeterioration of felled hardwoods. This tional surface area was then demarcated into three study was therefore conducted to identify the relation- regions (outer layer, middle layer and inner layer). ships between climatic conditions, wood species and Insect borer holes were counted in each region and distribution of biodeteriorating agents on some wood samples of insects in them were collected and identi- species. Information from this study is aimed at ﬁed in the laboratory. Wood samples were also taken developing techniques to improve log preservation. from the periphery, middle and inner layer of the cross sectional surfaces of logs on the day of felling then at 1,2,4and6weeksforchemicalandpathologicalstudies. 2. Materials and methods Rainfall, temperature and humidity data for the observational period were obtained from the Meteor- 2.1. Site and species selection ological Survey Department in Kumasi.

Timber species were obtained from two adjoining 2.3. Pathological and entomological studies forest reserves; Nyamibe Bepo (68100N, 18220W) and Numia (68020N, 18240W) in the moist semi-deciduous The plate exposure method was used to estimate the forest zone of Ghana. The area is characterised by a level of air-borne spores at the sampling sites during mean annual rainfall of between 1200 and 1800 mm the rainy season. Five Petri dishes (9 cm diameter) and mean daily temperature of 27.4 8C(Hall and containing potato dextrose agar (PDA) were exposed Swaine, 1981). The moist semi-deciduous forest zone for 15 min on a 100 cm high laboratory stool placed in is the most important zone as far as timber production the open air at each site. The plates were then incu- is concerned. Three timber tree species of economic bated at 26 8C. Colonies, which appeared on the plates importance to the timber industry were selected; Esa after 5 days of incubation, were counted. After 7 days (Celtis mildbraedii Engl.), Onyina (Ceiba pentandra the colonies were isolated on Spezieller Na¨hrstofar- (Linn.) Gaertn.) and Kyere (Pterygota macrocarpa K. mer Agar (SNA) and 25% PDA and identified. Schum.). These timber tree species are very suscep- A batch of surface sterilised and non-sterilised sawn tible to biodeteriorating agents and are therefore wood samples (2 mm3) were plated on 25% PDA. relevant to the study. Another batch of sawn wood (10 g) was stirred in 100 ml of sterile distilled water and shaken vigorously 2.2. Wood sampling to obtain an evenly dispersed suspension of spores. One millilitre aliquot of the diluent (10À1 to 10À4) was Three trees of each of the three species were plated on 15 ml of cool (40 8C) molten PDA. Three randomly selected and felled per felling season. Three replicates were prepared for each sample. All plates trees per species were selected because the annual were incubated at 26 8C for 7 days. Fungal species that allowable cut (AAC) for the year 2001 in the two grew out were isolated, subcultured and identified reserves for C. pentandra and P. macrocarpa was low using identification manuals (Barnett and Hunter, M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 313

1972; Singh et al., 1991; Booth, 1971; Kinsey and generally described as any period where the rainfall Minter, 1997). The insects sampled were also identi- per month is less than 100 mm. Generally the drier fied using identification manual (Wagner et al., 1991). months had higher temperatures than thewetter months. Wood borer activity results were analysed to detect The fungal flora on the log ends of the three wood statistical differences between insect borer infesta- samples isolated through the dilution plate method is tions in the different timber species using analysis shown in Table 1a and b. Frequency count made on of variance based in SAS. freshly harvested wood samples was very low but increased as wood samples stayed longer on the forest 2.4. Chemical studies floor (Table 1a). The two seasons had different flora on the wood samples. In the rainy season (June–July), Representative samples of the three timber species between two to four fungal species were isolated from were ground separately in a Willey mill and screened. all fresh wood samples, while 6–10 were isolated in The fractions passing through 40-mesh screen the dry season (February–March). Even though the (0.40 mm diameter) but retained on 60-mesh screen number increased significantly with time on all wood (0.25 mm diameter) were air dried and moisture con- samples during both seasons, the flora count was lower tent determined. Two grams of moisture-free samples in the rainy season than the dry season. On the were analysed following the Technical Association of contrary, staining was more intense in the rainy season Pulp and Paper Industry (TAPPI, 1996) standard and than the dry season. This supports the findings of suggested procedures were: water solubility of wood; Holtman (Holtman, 1966) that the incidence of stain T1wd-75, 1% caustic soda solubility of wood; T4wd- varies with season and wood species. There were 75, alcohol:benzene solubility of wood; T6wd-73. differences in the way the wood species related with Three replicates were prepared for each experiment. count of micro-organisms. Pterygota macrocarpa harboured the highest population count with C. mildbraedii harbouring the least. Fusarium solani and P. 3. Results citrinum constituted the dominant surface mould species on log ends of wood samples felled in the 3.1. Environmental influence on biodeteriorating two seasons while L. theobromae, Cladosporium agents herbarum, Aspergillus niger and Ceratocystis fagacearum formed an intermediate group. The remaining The dry and wet sampling periods had contrasting fungi formed the third group of very low occurrence climatic condition (Figs. 1 and 2). Dry seasons are (Table 1a and b).

Fig. 1. Monthly ambient temperatures in the forest reserves during sampling period. 314 M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323

Fig. 2. Monthly rainfall and relative humidity at the forest reserves.

3.2. Fungi and insect borers on surfaces of logs the dominant flora in the air and F. solani, P. citreonigrum, L. theobromae and T. viride formed an inter- Fungal flora was observed on sterilised and non- mediate group. The rest formed the third group of sterilised wood samples when the dilution plating very low percentage occurrence (Table 5). Penicillium method was used (Table 4). F. solani and L. theobro- citrinum and F. solani comprised a major pro- mae occurred frequently on the surfaces of all three portion of aerial fungal flora hence their dominance wood species (Tables 2–4). Penicillium citrinum on surfaces of log ends throughout the sampling occurred on P. macrocarpa and C. pentandra in the period. two seasons, but occurred on C. mildbraedii during the dry season only. Similarly, Trichoderma viride 3.3. Biodeterioration of wood by stain fungi and occurred more on C. pentandra and C. mildbraedii insect borers than on P. macrocarpa (Tables 3 and 4). Ceratocystis fagacearum, F. pallidoroseum and A. niger constituted Visual observation showed that staining in P. an intermediate group, while A. flavus, C. herbarum, macrocarpa was uniform and covered the entire end Curvularia lunata, F. oxysporum, F. sacchari, Cun- surface of the log, while on C. mildbraedii and C. ninghamella sp., and F. decemcellulare occurred only pentandra there was a slight distinction between sap- sporadically and constituted the third group of low wood and heartwood, with staining more intense at the occurrence (Tables 2–4). Schizophyllum commune was periphery (Plate 1). Sections of stained wood samples present on the surfaces of C. mildbraedii samples in of P. macrocarpa were observed during the sampling the rainy season 6 weeks after felling, but was not period (Plate 2). Microscopic examination of the observed in the dry season. stained sections revealed the mycelium of a stain Survey of aerial environment for fungal flora at the fungus in the vessels, ray parenchyma and axial sampling sites did reflect the same quantitative and parenchyma cells of the sapwood. Staining covered qualitative pattern of microflora as observed on the exposed log ends to a depth of 1.0–2.0 and 0.3–1.8 cm wood samples with the exception of C. herbarum, F. on C. mildbraedii and C. pentandra, respectively, in pallidoroseum and P. citreonigrum (Table 5). C. her- the rainy season while in P. macrocarpa it was to a barum, F. pallidoroseum and P. citrinum constituted depth of 1.0–4.0 cm. Table 1 Mycoflora on wood samples felled in moist semi-deciduous forest during the dry season (a) (February–March) rainy season (b) (June–July)

Fungal species Frequency (%) count of micro-organism on wood samples

0 week (101 CFU) 1 week (102 CFU) 2 weeks (103 CFU) 4 weeks (103 CFU) 6 weeks (104 CFU)

Kyere Esa Ceiba Kyere Esa Ceiba Kyere Esa Ceiba Kyere Esa Ceiba Kyere Esa Ceiba ..Aeogo ta./Frs clg n aaeet15(04 311 (2004) 195 Management and Ecology Forest / al. et Apetorgbor M.M. (a) Dry season (February–March) Aspergillus flavus 0.0 13.5 0.4 0.9 0.7 2.5 0.0 24.4 0.4 0.4 31.3 11.4 0.0 7.8 0.9 A. niger 0.0 0.0 0.0 6.9 0.0 0.0 9.4 0.0 0.8 2.8 0.3 0.0 0.0 13.0 0.0 Ceratocystis fagacearum 0.4 0.0 7.6 3.0 2.2 2.5 15.9 22.1 2.7 0.0 0.0 1.8 0.7 0.0 0.0 Chaetomium globosum 0.0 35.1 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 0.0 0.0 Cladosporium herbarum 4.4 13.5 13.6 2.9 3.2 0.0 4.7 0.7 0.0 1.7 0.0 0.0 1.0 6.5 2.3 Fusarium pallidoroseum 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 6.0 F. solani 8.5 13.5 2.6 10.4 0.5 0.9 11.5 0.9 67.1 60.3 20.9 62.7 31.9 25.2 41.4 L. theobromae 0.0 0.0 1.8 2.9 0.0 0.0 0.0 0.0 1.7 4.2 0.0 4.9 0.0 0.0 12.0 Neurospora crassa 1.6 0.0 0.4 4.9 13.2 1.6 4.4 0.0 0.0 1.4 0.0 0.4 0.0 0.9 0.6 Nigrospora sp. 0.4 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Penicillium citreonigrum 24.8 0.0 28.4 1.9 0.0 3.1 20.8 55.7 6.7 1.9 0.9 0.0 0.0 5.2 14.9 P. citrinum 50.4 8.1 41.6 61.0 64.7 86.8 30.4 65.1 18.9 27.4 37.2 18.4 49.3 54.3 10.9 Trichoderma viride 0.0 0.0 2.8 0.0 0.0 0.0 1.8 0.7 0.0 0.4 0.8 0.9 4.4 0.0 0.0 Mean no. of colonies per plate 49.5 3.7 45.7 60.3 40.2 31.8 130.0 74.5 119.7 125.8 62.3 55.5 29.8 23.0 35.0

(b) Rainy season (June–July) Aspergillus niger 0.0 0.0 38.5 1.2 4.2 1.4 0.4 0.0 0.0 0.0 1.7 2.7 0.0 0.0 0.0 Ceratocystis fagacearum 0.0 0.0 0.0 54.0 70.0 61.2 3.2 39.4 47.0 0.9 1.7 3.5 0.0 0.0 0.0 Chaetomium globosum 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.7 0.0 0.0 2.5 1.9 0.0 0.0 0.0 Cladosporium herbarum 0.0 0.0 0.0 0.0 0.0 0.0 2.6 0.3 0.0 0.0 11.8 1.2 16.8 0.0 3.3 F. pallidoroseum 0.0 0.0 0.0 0.0 0.0 0.0 10.8 4.7 22.4 0.0 1.7 3.1 0.0 0.0 6.0 F. solani 19.3 30.0 15.4 32.7 15.5 30.9 46.7 47.9 28.6 26.2 46.2 64.0 30.2 44.2 40.4 –

L. theobromae 0.0 0.0 0.0 3.1 0.0 6.6 16.2 0.0 0.3 62.1 14.3 11.6 28.7 0.0 32.7 323 Penicillium citreonigrum 0.0 0.0 0.0 5.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Rhizopus nigricans 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 1.0 Schizophyllum commune 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 7.6 0.0 Trichoderma viride 0.0 0.0 0.0 2.8 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 Mean no. of colonies per plate 8.3 2.0 1.3 108 40.7 57.2 49.3 72.8 181.8 34.3 11.9 25.8 45.3 39.4 52.0 315 316 M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323

Table 2 Fungal species present on wood samples felled in moist semi-deciduous forest

Fungal species Frequency of occurrence of fungal species on P. macrocarpa

Dry season (February–March) Rainy season (June–July)

0 week 1 week 2 weeks 4 weeks 6 weeks 0 week 1 week 2 weeks 4 weeks 6 weeks

Aspergillus flavus þÀÀÀÀÀÀÀÀÀ A. niger Àþ þþþÀÀÀÀ Ceratocystis fagacearum þþþþþÀþÀþÀ Chaetomium globosum þÀÀÀþÀÀÀÀþ Cladosporium herbarum þþÀÀþÀÀÀÀÀ F. pallidoroseum þÀÀÀþÀþþÀÀ F. solani þþþþþÀþþþþ L. theobromae þþþþþÀþþþþ Neurospora crassa ÀþþþþÀÀÀÀÀ Penicillium citreonigrum þþþÀÀþÀþÀÀ P. citrinum þþþþþþÀþþþ Rhizopus nigricans þþÀÀÀÀÀþÀÀ Trichoderma viride þÀÀþþÀÀÀÀþ

Woodborer activity in logs increased with time in P ¼ 0:005; F ¼ 7:502, d:f: ¼ 18, P ¼ 0:004) in rela- the field (Tables 6 and 7). On P. macrocarpa there is a tion to insect infestation. In the rainy season, C. significant difference at 5% level (F ¼ 4:918, pentandra recorded the highest woodborer infestation d:f: ¼ 17, P ¼ 0:47) in insect infestation between followed by P. macrocarpa. Celtis mildbraedii had the the dry and wet season. In the dry season, P. macro- least infestation. The outer layer, the sapwood, had carpa was the most susceptible wood to borer more insect holes than the heartwood. Nine different insects followed by C. pentandra and C. mildbraedii species of woodborers from three different families of in decreasing order (Table 6). There were significant the order Coleoptera were collected from C. pentan- differences among the three wood species in dra (Table 7). Woodborers from the family Bostrichi- both seasons at 5% level (F ¼ 7:192, d:f: ¼ 18, dae were recorded only on C. pentandra during the

Table 3 Fungal species present on wood samples (Ceiba pentandra) felled in moist semi-deciduous forest

Fungal species Frequency of occurrence of fungal species on Ceiba pentandra

Dry season (February–March) Rainy season (June–July)

0 week 1 week 2 weeks 4 weeks 6 weeks 0 week 1 week 2 weeks 4 weeks 6 weeks

Aspergillus flavus þÀÀÀÀÀÀÀÀþ A. niger ÀÀÀþþþþþþÀ Ceratocystis fagacearum þþþÀÀÀþþþÀ Chaetomium globosum ÀÀÀÀþÀÀÀÀÀ Cladosporium herbarum þÀþþÀÀÀþÀÀ F. pallidoroseum þþþÀþÀÀþÀÀ F. solani þþþþþþþþþþ L. theobromae þþþþþþþþþ Neurospora crassa þþþþþÀþÀÀÀ Penicillium citreonigrum ÀÀÀÀÀÀþÀÀÀ P. citrinum þþþþþþþþÀþ Rhizopus nigricans þþÀÀÀÀÀÀþÀ Trichoderma viride Àþþþþþþþþþ M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 317

Table 4 Fungal species present on wood samples (Celtis mildbraedii) felled in moist semi-deciduous forest

Fungal species Frequency of occurrence of fungal species on Celtis mildbraedii

Dry season (February–March) Rainy season (June–July)

0 week 1 week 2 weeks 4 weeks 6 weeks 0 week 1 week 2 weeks 4 weeks 6 weeks

Aspergillus flavus ÀþþþÀÀÀÀÀÀ A. niger ÀÀþþþþþþþÀ Ceratocystis fagacearum Àþþþþ þþþÀ Chaetomium globosum þÀþÀÀÀÀÀÀÀ Cladosporium herbarum þÀþÀþÀÀÀÀÀ F. decemcellulare ÀÀÀÀÀÀÀþÀÀ F. pallidoroseum þÀÀþþ þÀþ F. solani þÀþþþþþþþþ L. theobromae þÀÀþþþþþþþ Nuerospora crassa þþþþþÀÀþÀÀ Penicillium citreonigrum ÀÀþÀÀÀÀþÀÀ P. citrinum þþþþþþÀÀÀÀ Rhizopus nigricans ÀþþþþÀÀÀþÀ Trichoderma viride þÀþþþþþþþþ rainy season. The borers were found to use the splits in than those extracted in the dry season (Table 8). the bark as breeding grounds. Pterygota macrocarpa showed the highest percentage increase with respect to alcohol:benzene extraction. 3.4. Chemical changes in biodeteriorating wood Here the percentage increase in the rainy season was almost double that in the dry season (281.0 versus There was a general increase in all the soluble 142.9). The other signiﬁcant percentage increase was extracts analysed for the three wood species. The the hot water extract of C. pentandra, which was much amounts extracted in the wet season were all higher higher than in the other two species. In the dry season,

Table 5 Mycoﬂora in aerial environment of moist semi-deciduous forest

Fungal species Relative density (%) in aerial environment

Dry season (February–March) Rainy season (June–July)

0 week 1 week 2 weeks 4 weeks 6 weeks 0 week 1 week 2 weeks 4 weeks 6 weeks

Aspergillus flavus 1.6 0.0 0.7 2.0 0.4 0.8 0.0 0.0 0.0 0.0 A. niger 0.0 0.0 0.0 0.0 0.0 4.6 6.4 0.0 4.2 0.0 Ceratocystis fagacearum 0.0 0.0 0.0 0.0 0.0 0.8 9.2 11.6 0.0 0.0 Cladosporium herbarum 20.3 6.7 2.7 49.2 29.3 16.3 14.9 16.8 15.3 6.5 Curvularia lunata 2.5 0.1 1.0 1.5 0.0 0.0 0.0 2.8 0.0 9.7 F. pallidoroseum 0.8 0.8 0.2 3.9 2.3 5.0 17.4 10.4 27.4 3.2 F. solani 4.8 1.1 1.5 0.0 5.1 25.6 16.5 26.8 16.3 50.0 L. theobromae 2.7 0.0 0.0 6.3 5.3 20.9 8.6 10.0 19.5 8.1 Neurospora crassa 0.0 0.1 0.0 0.9 0.4 0.0 0.3 0.0 0.0 0.0 Penicillium citreonigrum 24.3 11.1 1.2 4.3 1.6 0.8 3.9 5.6 0.0 1.6 P. citrinum 36.8 78.5 54.5 21.6 53.8 6.2 12.2 12.4 7.4 9.7 Rhizopus nigricans 0.3 1.1 1.1 2.3 0.1 0.0 0.0 0.0 0.0 1.6 Trichoderma viride 0.8 0.0 1.8 1.5 0.9 0.8 9.2 3.2 4.2 0.0 Mean no. of colonies per plate 112.5 210.5 245.5 88 213 25.8 65.4 50.0 38.0 12.4 318 M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323

4. Discussion

Sapstain fungi and insect borers are among the biological agents responsible for wood deterioration in freshly felled logs and sawn timber. Spores of the fungi responsible for stain such as L. theobromae, C. fagacearum and P. citrinum are extremely prevalent on exposed wood surfaces during the felling seasons. L. theobromae and F. solani are the most abundant and common fungi isolated from all wood samples imme- diately after felling. L. theobromae is a dominant sapstain fungus known to cause bluish black stain on surfaces as well as the inside wood of many tropical hardwoods (Florence et al., 1998; Masuka and Kar- iwo, 1992; Fougerousse, 1985; Ofosu-Asiedu, 1973; CABI, 1976). Findlay and Pettifor (1939) isolated L. theobromae as the staining fungus of T. scleroxylon sapwood while Savory (1958) identified the same species as the only staining fungus in Gossypiosper- mus praecos. Momoh (1966) also isolated the same fungus as the organism causing blue stain in the sapwood of A. toxicaria. Ceratocystis species cause reddish purple stain on alder (Morrel, 1987) and Hevea brasiliensis (Florence et al., 1998), which reduces lumber wood value. In Nigeria, fungal stains caused by Ceratocystis species were thought to reduce yield of C. pentandra, Terminalia superba and T. scleroxylon while Ceratocystis species and L. theobromae have been mentioned as responsible for mod- erate losses in Podocarpus and Pinus timber species (Gibson, 1964). Examination of the aerial environment to identify the sources of fungal inoculum showed that most of the moulds, which were isolated from log surfaces, were also members of the aerial mycoflora. F. solani Plate 1. Stain intensities in wood logs: (A) Pterygota macrocarpa; (B) Ceiba pentandra; (C) Celtis mildbraedii at a loading bay in and P. citrinum were extremely prevalent while L. Boin Forest Reserve. theobromae and C. fagacearum did not occur frequently in the air at the logging sites. In the forest, C. pentandra recorded a percentage increase of 112.2, the infection of logs by L. theobromae is caused by air- followed by C. mildbraedii and P. macrocarpa with borne spores, which are associated with cocoa planta- 63.2 and 53.0, respectively. Celtis mildbraedii and P. tions that are found throughout the natural forest macrocarpa had the lowest extract with respect to 1% territory and which are preferred host of L. theobro- NaOH extractive in both dry and rainy seasons mae, so that the risk of log infection is high and (Table 8). Celtis mildbraedii has the highest specific permanent. gravity among the three species (Addae-Mensah et al., The total count of aerial mycoflora was influenced 1989; Okoh, 1977). The texture of C. pentandra is by seasons. The relative density of fungi in the aerial more porous and much lighter in weight than that of environment was higher in the dry season than in the the other two tree species. rainy season. However, staining was more intense in M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 319

Plate 2. Micrographs showing sections of Pterygota macrocarpa with fungal hyphae in: (A) freshly; (B) 1 week; (C) 2 weeks; (D) 4 weeks felled wood logs. the rainy season than in the dry season in all wood season. In Nigeria infection of felled logs of A. species studied. A major factor controlling the atmo- toxicaria by L. theobromae was usually more severe spheric spore concentration is rainfall. Rain reduces during the rainy season than the dry season (Oloﬁn- the number of spores available for aerial dispersal by boba and Lawton, 1968). The rate of penetration of washing the spores out of the air (Apetorgbor, 1994). stain is faster in the rainy season than in the dry season On the other hand, a pertinent role of rainfall might be (Momoh, 1966). the raising of atmospheric humidity (Fig. 2) and The moisture content of the sapwood in a living tree subsequent encouragement of spore germination and is usually high, therefore staining fungi are unable to hyphal growth on log surfaces. Even though more develop until some drying occurs (Da Costa, 1954). colonies of fungal species were obtained from the Even though there is no staining in freshly felled wood surfaces of wood samples in the dry season than in the with initial moisture content ranging from 56.4 to rainy season, the higher humidity of the rainy season 150.9%, infection had taken place (Table 4). Sapstain supported more ﬂora development. Micro-organisms and mould fungi develop rapidly under favourable therefore utilised more of the wood substrate to pene- wood moisture content of around 65% and tempera- trate, establish and colonise the tissues in the rainy tures 20–30 8C(Holtman, 1966). When moisture 320 M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323

Table 6 Insect holes recorded on logs during two felling seasons

Felling period Species Log diameter Number of insect holes/m2 at different regions on wood samples (m) 2 weeks 4 weeks 6 weeks

123123123

Dry season Ceiba pentandra 1.51 8 4 1 12 6 2 15 10 6 Celtis mildbraedii 0.77 9 0 0 13 7 2 19 9 2 Pterygota macrocarpa 0.69 50 35 11 69 43 16 74 45 27 Rainy season Ceiba pentandra 1.47 20 9 3 27 19 8 35 25 10 Celtis mildbraedii 0.81 10 2 0 16 10 8 16 8 8 Pterygota macrocarpa 0.60 35 0 0 56 14 7 71 21 11

1, 2 and 3 refer to sapwood, intermediate wood, and heart wood, respectively. content of the wood reduced to less than about 20%, slight distinction between sapwood and heartwood, further growth of fungi in felled logs is prevented. stained more at the periphery than the heartwood. The Therefore, on freshly felled tropical timber logs, sapwood does not contain extractives such as tannins infection by fungi takes place as soon as the wood and other phenolic substances known to be toxic to becomes exposed and this occurs more rapidly than fungi, borers and termites and is therefore perishable insect infestation (Fougerousse, 1985). As far as fun- (Bakshi et al., 1967; Findlay, 1985). Savory (1953) gal spores of the atmosphere are concerned, any reported that in T. scleroxylon the sapwood is readily exposed material capable of forming a food base discoloured by staining fungi since it contains con- becomes a microhabitat. The composition of fungal siderable amount of sugars and starches on which the species, which depends on the quality and quantity of fungi thrive. The rapidity with which L. theobromae a particular substratum, is determined by the available invades felled logs of Antiaris toxicaria could be nutrient and to some extent by the influencing envir- attributed in part to the presence of the large sapwood onmental conditions. (Olofinboba and Lawton, 1968). It was difficult to Stain fungi and insects do not usually affect the visualise the onset of the staining on C. mildbraedii heartwood and there are wide variations in the sus- and C. pentandra. Besides, removal of the bark ceptibility of sapwood among different timber species. increased staining of C. pentandra and P. macrocarpa. Celtis mildbraedii and C. pentandra, which have Keirle (1978) and Masuka and Kariwo (1992)

Table 7 Woodborers identiﬁed on the three timber species

Insects Presence of insect species on wood samples of

Family Name Ceiba pentandra Celtis mildbraedii Pterygota macrocarpa

Bostrychidae Apate monachus (Schauf) þÀÀ Pityophthorus busseae (Sch) þÀÀ Cytogenius cribripennis (Sch) þÀÀ Platipodidae Doliopygus unispinosus (Schauf) þþþ B. chapuisi (Duv) þþþ Xyleborus confuses (Eichh) þþþ Xyleborus eichhoffi (Schr) þþþ Strombophorus ericius (Schauf) þþþ Hypothenemus camerunus (Egg) þþþ Scolytidae Xyleborus africanus (Egg) þÀÀ M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 321

Table 8 Chemical analyses of the three timber species

Time (weeks) Alcohol:benzene (%) Hot water (%) 1% NaOH (%)

Dry Rainy Dry Rainy Dry Rainy

Celtis mildbraedii 0 3.2 3.3 5.7 5.4 12.1 11.9 1 4.0 4.9 7.1 7.6 12.4 13.6 2 4.5 5.6 7.9 8.4 13.8 14.3 4 4.6 5.7 8.6 9.6 14.2 14.8 6 4.7 6.1 9.3 10.8 14.3 15.1 % increasea 48.9 84.8 63.2 100 18.2 26.9 Pterygota macrocarpa 0 2.1 2.1 6.8 6.3 15.9 15.3 1 3.8 4.2 7.9 7.1 20.1 21.5 2 4.3 6.7 8.6 8.3 21.5 22.6 4 5.7 7.7 9.7 9.6 23.1 23.7 6 5.8 8.0 10.4 10.4 23.7 24.2 % increasea 142.9 281.0 53.0 65.1 49.1 58.2 Ceiba pentandra 0 4.7 4.9 7.4 7.3 16.2 16.4 1 5.4 6.0 8.2 13.2 21.5 22.0 2 6.0 6.1 12.1 13.4 23.7 23.7 4 6.5 6.3 15.6 16.5 24.9 24.8 6 6.5 7.9 15.7 16.8 27.3 28.1 % increasea 38.3 61.2 112.2 130.1 68.5 71.3

a % increase ¼ final À initial=initial 100. observed that degradation of pine logs was usually rials in wood (Teyegaga and Ofosu-Asiedu, 1973). more severe in debarked logs in all seasons. This is an The sapstain fungi are known to excrete extracellular indication that the bark is an effective barrier against enzymes capable of breaking down these carbohy- fungi in some wood species. Similarly the high sus- drates into products that can be directly metabolised ceptibility of C. pentandra in the rainy season and P. by the fungi to provide nutrients for growth and macrocarpa in the dry season to woodborers is a result development (Abraham et al., 1998). The dense mass of lack of true heartwood as found in T. scleroxylon of produced mycelium store some of these compo- (Cobbinah, 1991). The sapwood contains a consider- nents in their tissues which might have led to the able amount of sugars and starches on which the increase in soluble products during the hot water and insects live (Findlay, 1985). The borers were found 1% NaOH extraction. to use the splits in the bark as breeding grounds, which The wood samples of P. macrocarpa showed the corroborates with the findings that the main groups of highest percentage increase in alcohol:benzene extrac- timber borers recorded in Ghana from the families tives. Tabiri (1980) working on C. pentandra reported Scolytidae, Platypolydidae and Bostrichidae have that with the action of these sapstain fungi there was a their activities largely confined to the sapwood (Cob- loss in weight, which was reflected in the loss of binah, 1991). soluble compounds from the wood. The stain fungi There has been an increase in all the soluble extracts do not significantly degrade the actual components of analysed for the three wood species and this seems to the wood cell walls such as cellulose, hemicellulose be at variance with documented literature. Hot water and lignin (Fougerousse, 1985). When the sapstain soluble extract increased with time in these wood fungus L. theobromae attacks, there is an increase in species. Sapstain fungi feed on the sap material, which the colouration of the wood surface as a result of the contains sugars, and starches, which are soluble mate- mycelium rapidly becoming light blue thus giving to 322 M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 the infected wood a bluish black colour. These dark, References melanin-based pigments (Zinc and Fengel, 1990) might have led to the increase in alcohol:benzene Abraham, L., Hoffman, B., Gao, Y., Breuil, C., 1998. Action of extract that has been observed. Fougerousse (1985) Ophiostoma piceae proteinase and lipase on wood nutrients. observed that the richer the store of reserve nutrients in Can. J. Microbiol. 44 (7), 698–701. Addae-Mensah, J., Ayarkwa, J., Mohammed, A.I., Azerengo, E., the wood cells, the denser the mass of produced 1989. Users Guide of Some Ghanaian Secondary and Primary mycelium, and the darker the blue stain. The increase Timber Species Based on Strength and Related Properties. in alcohol:benzene extractives for P. macrocarpa Forest Products Research Institute Information Bulletin No. 9. might therefore be due to the intense staining observed Information and Publications Section, FORIG, Kumasi, Ghana. in the wood by the stain fungi. Addo-Ashong, F.W., 1967. Blue-stain and its control. FPRI Newslett. 2, 11–13; Ampong, F.K., 1986. Proceedings of the National Housing Seminar on the Wood Preservation Industry in Ghana: The Past, 5. Conclusion Present and the Future, UST, Kumasi, Ghana, March 17– 22. Moulds such as F. solani and P. citrinum cover the Apetorgbor, M.M., 1994. Studies on okra (A. esculentus), onion (A. cepa var. cepa), pepper (C. annuum) and tomato (L. esculentus) log surfaces of the three timber species while L. plants and their stored products. Ph.D. Thesis. University of theobromae and C. fagacearum form the dominant Ghana, Legon, Accra, Ghana. sapstain fungi. Staining was uniform, intensive and Bakshi, B.K., Puri, Y.N., Singh, S., 1967. Natural decay resistance covered the entire surface of P. macrocarpa logs. C. of India Timbers. I. Introduction and method. II. Decay pentandra recorded the highest wood borer infestation resistance of Sal and Teak. India Forester 93 (5), 305–328. Barnett, H.L., Hunter, B.B., 1972. Illustrated Genera of Imperfect in the rainy season while in the dry season P. macro- Fungi, 3rd ed. Burgess Publishing Company, Minneapolis, carpa was the most susceptible. Bark damage should Minnesota, 241 pp. be minimised during handling of C. mildbraedii and P. Booth, C., 1971. The Genus Fusarium. Commonwealth Mycolo- macrocarpa logs to avoid profuse staining of log ends. gical Institute, Kew, Surrey, UK, pp. 32–35. A short-term preservation measure such as prophy- CABI, 1976. CMI Descriptions of Pathogenic Fungi and Bacteria. Botryodiplodia theobromae. No. 519. lactic treatment should be done to keep these organ- Cobbinah, J.R., 1991. Insects associated with the major export isms at bay before logs are transported to the log deck. timber species of Ghana. In: Presented at the 10th World Besides, in forests where these three timber species Forestry Congress, 16–27 September, Paris, France. exist, felling operations at the peak of the wet season Da Costa, E.W.B., 1954. Control of Blue Stain. D.F.P. Newsletters should be confined to C. mildbraedii and C. pentandra 258 and 259. Forestry Commission, 2001/2002. Affum-Baffoe, K. (Ed.), Multi- while felling of P. macrocarpa should be done only in resource Inventory Results for the High Forest Zone of Ghana. the dry season. Resource Management Centre, FSD, Ghana, Unpublished, 185 pp. Findlay, W.P.K. (Ed.), 1985. Agents of Destruction. Preservation Acknowledgements of Timber in the Tropics. Martinus Nijhoff/Dr. W.Junk Publishers. Findlay, W.P.K., Pettifor, C.B., 1939. Effect of Blue-stain on the strength of Obeche (Triplochiton scleroxylon). Emp. For. 18, This work was supported by the International Tro- 259–267. pical Timber Organization (ITTO) and the Govern- Florence, E.J.M., Sharma, J.K., Gnanaharan, R., 1998. Sapstain ment of Ghana (GOG) under the Project No. ITTO PD fungi associated with softwood species in Kerala, India. In: 4/98 Silviculture and Economics of improved Natural Paper prepared for the 29th Annual Meeting of IRG, Forest Management. The support of AG Timbers in Maastricht, Netherlands. International Research Group on Wood Preservation. Document No. IRG/WP/98-10260. allowing the use of their concession areas for the field Fougerousse, M., 1985. Protection of logs and sawn timber. In: studies is also acknowledged. The authors would also Findlay, W.P.K. (Ed.), Preservation of Timber in the Tropics. like to express their sincere appreciation to Mrs. Diana Martinus Nijhoff/Dr. W. Junk Publishers, Dordrecht. Fiati of the Forestry Services Division and Dr. J.R. Gibson, S., 1964. The impact of disease on forest production in Cobbinah (Director of Forestry Research Institute of Africa. FAO Report. Hall, J.B., Swaine, M.D., 1981. Destruction and ecology of Ghana) for their field and technical assistance, respec- vascular plants in a tropical rain forest. Forest Vegetation in tively. Ghana. Dr. W. Junk Publishers, The Hague, Boston. M.M. Apetorgbor et al. / Forest Ecology and Management 195 (2004) 311–323 323

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