J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 26
Assessing the Effect of Timing and Felling Techniques on the Susceptibility of Acacia seyal (Del) to Wood Borers. Mohamed T. A. Eltayb¹ and Talaat D. Abdel Magid*² ¹ Forest National Corporation Sinnar State E-mail: emohamedtom@yahoo.com ² University of Bahri, College of Natural Resources and Environmental Studies, E-mail: talaat1957@yahoo.com (Received: October 15,2012, Accepted: November 6, 2012)
Abstract— The objective of the study was to determine whether the A.seyal variety seyal (A.seyal) is able to produce healthy wood (rebellious to A.seyal borer), suitable to be used in building poles, firewood and charcoal when applying particular type of felling process, in particular period. The study confirmed the possibility, of producing endurable amount of A.seyal wood, not infested by A.seyal borer, when felled during April and June using charcoal felling process, and October and January when girdling process was used. The study also revealed that, the moisture content in A.seyal wood has noticeable effect; on the revival of the insect activity i.e. A.seyal borer was active only when the moisture content was in the range of 27-30% in the wood which seldom occurred in autumn due to rainfall frequency. Index Terms— Acacia seyal, Felling process, Endurable A.seyal wood, Revival of the insect activity, A.seyal borer
I. INTRODUCTION
A
cacia seyal predominantly a tree of the cracking clay soil found in large almost pure stands or mixed with A. senegal and Balanites aegyptiaca under rainfalls of 250 to 1000 mm. under low rainfalls on water- receiving sites and depressions. Confined in the Flood Region to low elevation intermittently flooded by rain. It is also found in depressions on sandy soils derived from Nubian Sandstone under rainfalls of 200 mm or above. It occurs in northern Sudan fringing the flood plains of rivers and in basins at the upper edge of Acacia nilotica forests. It tolerates high pH and salinity [1]. Acacia seyal is considered as tree number one in Sudan, as reported by [2] that has potential never been fully explored, but they are promising. The global demand for A.seyal gum is to be noted. The species is an important multipurpose tree for the rural population. In Sudan, the tree varieties occur naturally in the low rainfall savannah zone and extend from Gadarif, Blue Nile and White Nile to the clay plains around Nuba Mountains and the Darfur Region. In the savannah
* corresponding author
region of Sudan Acacia seyal has been subjected to large scale deforestation from mechanized farming, over grazing, fires and other human factors [3; 4]. It produces a gum arabic known as “talha”, which is of inferior quality to that produced by A. senegal making about 10% of Sudan’s gum arabic exports. The gum is produced from cracks or wounds caused by drought, fire, insects or wounds. Pods and bark contain about 20% tannin and smoke from the wood is a good insect repellent. Women use the aromatic smoke to tan and perfume their skin. The tree does not respond to tapping, and the gum is collected from natural exudation. There are numerous medicinal uses, mainly bark, and leaves [1 and 5]. A.seyal poles were widely used for telegraph poles during the war II era. The Forest and Plant Protection Authorities resorted to submerging poles in the river instantaneously after felling to leach as much carbohydrates as possible. The limited research and studies which were subsequently investigated the varies ways of seasoning, for protecting A.seyal wood against damage by A.seyal borer. [6, 7]. The susceptibility of A.seyal wood insect borer required more considerable efforts [2]. A.seyal borer (Sinoxylon senegalense ) infects A.seyal wood immediately after felling , turning it into powder in short time in such a manner that render it useless, even for firewood or charcoal, let alone to building poles. The borer also infested sap wood of most wood species and bamboo. The most destructive agents to forests and their products are insects, particularly of the orders Coleoptera, Isoptera and Thoptera which affect growth of trees, quality and quantity of wood products [2]. Over 40 species of insects are reported associated with A. seyal. These include 10 species of bruchid beetles which may damage high proportion of stored seeds. The relationship between the wood moisture content and the insect attack was investigated by [8] who stated that, there are two types of pests, one lives only in green timber, but other do not appear until the wood is at least seasoned to 30% moisture content. In case of the first type of insect who live in green timber its activity feeble as the wood dries out. Wood seasoned below 30% moisture content is less susceptible to insect attack.
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 27 A.seyal wood has a wide range of uses in Sudan, particularly in rural areas, where villagers or peasantry people use A.seyal wood for hut construction, charcoal, firewood. Branches and pods are used as fodder for their animals. Insect causes a large damage to A.seyal wood which may cause complete destruction to tree plantation by chewing and chambering inside the main stems and branches. Then trees enormously completely damaged and fall down. FNC loss plenty of its revenues due to this damage caused by the borer against A.seyal wood. As peasantries are perturbing of this insect, they have used several types of treatments to protect A.seyal wood against insect. In Gedarif, Blue Nile and Sennar States, the villagers when cut A.seyal trees, emerged the wood immediately after cut into river or lagoon for six weeks, before used for hut. Sometimes set fire, on dry grass covered it immediately, after cutting and before using it. Charcoal and firewood producers in Gedarif State, said that when you need to avoid the attack of borer insect to A.seyal wood, you have to cut it avoid moony days i.e. not under the moon light. Other people reputed that, the best period of felling A.seyal trees is during the rainy season (July and August) when the wood left to direct rainfall, until the end of rainy season (end of October), by the end of rainy season the wood collected and the bark should be removed, this process will give a healthy wood, suitable for fire wood, building, and charcoal. Some people cut trees; split the wood dry them under direct sunlight, this type of wood use as bundles for firewood. Art of killing trees by girdling the stems as a process was stated by [9 and 4]. They reported that the reduction of moisture content in girdling occurs slowly and the death of trees may take place during a period of a year. Stem girdling usually result in killing the roots of tree, but the degree of killing depends on root´s nutrient storage and the degree of exhausting it. So girdling should be done when the tree in feeble condition and the death of upper part should be done gradually [10, 11] stated that insects attack the wood but durability may be improved by water storage. This study is aimed to determine, the best period and type of harvesting A.seyal trees, to produce healthy wood, suitable for fire wood, building poles and other uses.
II. MATERIALS AND METHODS Location of study area The study was located in Rawashda forest, Gedarif state eastern Sudan. It lies between latitude 12º 45´ and 14º 15´ N, longitude 34º to 37º E and altitude 600 m above sea level. Two experiments were used; field and laboratory experiments. Field experiment One Feddan (60×70m) (Feddan = .024ha) was selected in Rawashda forest, well stocked by A.seyal trees plate (1). The area was fenced, using metallic posts and barbed wire. The site was divided, into nine plots of the same dimension (20× 23.3) m. The trees in each plot were sorted and classified according to their bark color. All trees were numbered, measured for their diameters at breast height (DBH) using caliper.
Plate (1): View shows the selected site of experiment. The mean diameters at breast heights were calculated for each
plot. Two types of felling were used for harvesting A.seyal trees, charcoal felling (CF) in which the tree was completely felled, left only 30 cm stump above ground level. The other treatment of killing tree was girdling (G) where the tree’s bark was removed completely, encircling the stem at a point 30 cm above ground level , and left it stand, to be killed gradually like dieback disease. The first felling of both treatments (CF and G) were applied in two plots, selected randomly in April, plot A1CF and A2G, where ten trees in each plot were treated. The second treatment was done in June plot B 1 and B2 and the treatments (B1 C F and B2 G) were used for ten trees in each plot. The first treatment (April period) was called summer treatment and here the trees had already shed their leaves. The second treatment (June period) was called autumn treatment, in which the trees returned their leaves back. The third treatment was done in October, two plots (C1F and C2 G) were treated, during that time the trees were starting dropping their leaves. The last treatment (January) was done in plots (D1F and D2G) where trees were shed their leaves, and called it winter treatment. Two plots were used for each period of felling, and ten trees were treated for each type of felling. One plot was used as standard plot, Figure 1.Temperature and rain fall were recorded during the period of the experiment. The damage occurred, by insect borer in A.seyal wood, in each plot was observed and recorded. D2
B1
A2
C1
Standard
C2
A1
D1
B2
Figure (1): Design of experiment Laboratory experiment
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 28 Ten pieces, of the same length, of A.seyal wood were cut, from green healthy trees, five pieces, from white bark tree (B) and the other five from red bark tree (A) on October, Plate (2) in Rawashda Forest.
Plate (2): Specimens for experiment. The weight of each specimen was determined every day, with well observations, to A.seyal borer attack to them. The weights and observations were recorded, until we reached constant weight, of each piece of specimen. Data were analyzed to determine, the optimum or ideal moisture content, for insect borer to attack A.seyal wood. The same treatments were used, for other specimens, in the period of June, during the rainy season and data were recorded and analyzed.
The result showed that the girdling process, gave reversal results, with that of charcoal felling process where April and July treatment, produced badly A.seyal wood, with high damaged by borer insect 100% loss. While October and January produced 100% healthy wood, suitable for all type of uses. The result showed that, the death of tree in girdling process, required about one year and the girdling trees during October and January period were receiving the supply of water and food material from the root, while the leaves exhausted the storage material in the trunk and branches, reduced the carbohydrates in the wood [9] beside that the death of trees were occurred in the rainy season, that help on washing more of carbohydrates and increase the moisture content above the ideal moisture content of the insect to attack the wood. This result in line with [9 and 4] who stated that the death of tree in girdling, may take place during a period of a year, and the reduction in moisture content secured by girdling occurs slowly while the leaves exhaust some of the water and the food substances present in the trunk causing gradually death to the tree. The result also in agreement with that reported by [10] on girdling process. From this result we found that the best period of felling by charcoal process was June (during rainy season) to produce healthy A.seyal wood (98%). This was in agreement, with the thoughts of charcoal and fire wood producers that said, cutting of A.seyal tree, during the rainy season, is possible for producing healthy wood, protected against A.seyal borer. Because the trees were cut, after they had exhausted some quantity of storage carbohydrates, for building their leaves. Besides that, the frequency of direct
III. RESULTS AND DISCUSSION Field study The result of this study revealed that, the relation between the period of felling and type of treatment, for producing healthy A.seyal wood was reversal i.e. when specific type of felling produced healthy wood, in specific period of treatment, the other type of felling, produced badly wood in the same period of felling (Table 1). The girdling felling process in the period of April and July. Figure. 2 produced A.seyal wood infected with various rates by A.seyal borer. While charcoal felling in the same period Figure 3 produced healthy wood suitable for fire wood, charcoal and building poles (plate 3, 4 & 5). January and October girdling felling period, produced healthy wood suitable for building poles, fire wood (plate 6) Figure 2.
rainfall on the wood help on washing away some part of carbohydrate, and increasing or rising up moisture content of wood above the optimum point of the borer insect (plate 7 and 8). Plate (3): Charcoal felling process (April period) produced Healthy wood (fire wood) and forks.
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 29 Table (1) Effect of period, and felling techniques on quality of A.seyal wood Period of felling
Tree diameter class cm
No. of treated trees red white
Ave. temp.(â—ŚC)
Wood %age attack (loss) red white
April
A1CF A 2G B 1Cf B 2G C 1CF C 2G D 1CF D 2G
5 5 5 5 5 5 5 5
35
0.00 100.0 0.02 100.0 20.00 0.00 48.00 0.00
July October January
8-23 6.6-12.3 9-14 7.2-16.7 9.1-14 7-16.5 5.6-17.8 6.6-15
5 5 5 5 5 5 5 5
34 36.3 36
0.10 100.0 0.02 100.0 20.00 0.00 50.00 0.00
Figure 2: Effect of period and type of felling (GF) of Acacia seyal tree in production of healthy A.seyal wood.
Plate (4): Charcoal felling process (April period) produced healthy wood
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 30
Figure 3: Effect of period and type of felling (CF) of Acacia seyal tree in production of healthy A.seyal wood.
Plate (5): Charcoal felling process, (July period) produced healthy wood.
Plate (6): Girdling process, (October period) produced healthy wood.
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 31
Plate (7): Larvae of A.seyal borer (Sinoxylon seneglense), the active impaired stage of A.seyal wood.
Plate (8): The borer insect, penetrated inside the wood, laid its eggs, hatched and damaged the A. seyal sapwood, converted it into powder. Laboratory study The result in this study showed that the insect of A.seyal borer Sinoxylon senegelense had attacked A.seyal wood only, when the moisture content of the wood had been in the range of 2730%. This is the ideal point of moisture content, for insect to corrode the wood and laid their eggs inside. The larvae live inside the wood and damaged it (plates: 7and 8) .The result revealed that, moisture content has a marked effect, on the revival of the insect activity, to damage A.seyal wood. (Figure 4, 5, 6 and 7) from these figures, it was clearly observed, the attack of insect was happened, when the specimen moisture content in the range of fiber saturated point (27 -30%) particularly in October felling specimen, without any
difference between red and white tree bark. While July felling, the attack was completely slight, in view of the fact that the optimum point of moisture content was fluctuated, difficult to be attained because of the rainfall. (Figure 8 and 9).This result is in agreement with [8], who stated that wood that seasoned below 30% moisture content (fiber saturation point), is less susceptible to insect attack and also supported by [12, 1, 11]. This result is also supported and consolidate the peasantry presumption and traditional type of treatments, that used by local people, to preserve A.seyal wood against insect, like emerging wood in water, or set fire on it immediately after
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 32 felling, in addition to that, report of [2] on reserved process, of A.seyal poles against borer by The Forests and Plant
Protection Authorities during war II was laid in the same trend of the result of this study.
Figure 4: Effect of A.seyal wood’s moisture content (on October felling) on revival of A.seyal borer attack.
Figure 5: Effect of A.seyal wood’s moisture content (on October felling) on revival of A.seyal borer attack.
Figure 6: Effect of A.seyal wood’s moisture content (on October felling) on revival of A.seyal borer attack.
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 33
Figure 7 : effect of A.seyal wood’s moisture content (on October felling) on revival of A.seyal borer attack.
Figure 8: Effect of A.seyal wood’s moisture content (on July felling) on revival of A.seyal borer attack.
Figure 9: Effect of A.seyal wood’s moisture content (on June felling) on revival of A.seyal borer attack.
J OURNAL OF FOREST PRODUCTS & INDUSTRIES, 2012, 1(2), 26-34 34
IV. CONCLUSIONS The abundance of the tree means that it is one of the most important sources of fuel wood in the Sudan. The charcoal is of good quality. Branches are used to make thorny fences and for forage. Pods and bark contain tannin and smoke from the wood is a good insect repellent. Women use the aromatic smoke to tan and perfume their skin. The result of this study indicated that Acacia seyal variety seyal is a reasonable species as indigenous tree in the Sudan that can be managed, to produce protected A.seyal wood against A.seyal borer (Sinoxylon senegalense ), suitable for fire wood and building poles. However, April and July should be a reasonable period for felling, using charcoal felling process, to produce healthy wood, further more girdling of trees should be applied during October and January periods to attain healthy wood. According to the result of this study the favorable period and suitable technique of felling Acacia seyal trees to produce healthy wood well preserve against a devastated insect (Sinoxylon senegalense) is April and July for charcoal felling techniques and January October for girdling felling. These periods and felling techniques showed significant measures to be used to manage Acacia seyal stands.
(4) Wickens, G.E; Seif Eldin, A.G; and Nahal, I. (1995). Role of Acacia species in the rural economy of dry Africa and the Near East. FAO Conservation Guide 27. Rome. (5) Vogt, K, (1996). Common Trees and Shrubs of Dryland Sudan. SOS Sahel International (UK), London. (6) Peak,F.G.G. (1952). ABruchid seed borer inAfrica.Memoirs of Research Division No.29.Agricultural publications Committee, Ministry of Agriculture Khartoum, Sudan. (7) Bushara,M.G. unpublished (1979) . Some Aspects of the biology of Acacia wood. Borer Sinoxylon senegalense karsh.Bostrychidae.Coleoptera.M.Sc. Thesis Zoology Department, Faculty of Science, University of Khartoum. (8) Koch,P.(1985).Utilization of Hardwood Growing on Southern Pin Site.Vol.1.Raw material.U.S. Department of Agriculture, Forest Service. (9) McMillin.J.M.and.Wengert´s E.M (1975). Dry eastern hard-wood lumber.
REFERENCES (1) Badi, K.H and Abdel Magid, T.D. (2011). Manual of silviculture for selected tree species in Sudan. Part 1. Indigenous species (2) Abdel Nour, H.O. (2008). Integrated Pest Management in Sudan’s Forests A strategy to protect what is left of Sudan’s Forest. (3) Mustafa, A F.(1997). Regeneration of Acacia seyal forests on the dry land of the Sudan clay plain. Tropical Forestry Report No. 15. PhD Thesis. Department of Forest Ecology. Helsinki University Printing House.
(10) Babikir.A.E (2003). Vision for Eradication of mesquite tree. Agricultural Research Corporation (ARC), Study paper 1-10. (11) Maydell.H-J, (1990).Trees and Shrubs of the Sahel, the characteristic and uses,139. (12) Jackson, J. K. (1962). Manual of Silviculture. Unpublished Manuscript. Forests Department, Ministry of Agriculture and Forests, Khartoum.