Article Type: Research Article Article Citation: Ettagbor Hans Enukwa, and Yilom Hyginus Ndang. (2020). EFFECTS
OF NEEM OIL ON THE PRESERVATION OF MILICIA EXCELSA: EVALUATION OF TERMITICIDAL
EFFECTIVENESS. International Journal of Research -GRANTHAALAYAH, 8(12), 315-322.
https://doi.org/10.29121/granthaalayah.v8.i12.2020.2873 Received Date: 14 November 2020
Accepted Date: 31 December 2020
Keywords: Deterioration Environmentally
Friendly Preservative Termites Weight Loss Wood usage has increased with time, thus, there is need to investigate how wood can be treated with human and environmentally friendly preservative which is effective in protecting wood from termites and other agents of wood deterioration, or improve the wood physical, chemical, mechanical and biological characteristics. The aim of this study was therefore to evaluate the effects of neem oil on Milicia excelsa wood preservation. Treated and untreated pieces of Milicia excelsa wood samples were used to carry out this experiment, a soil bed, and an internal wood exposure to termite’s test was carried out, and measurements taken using a digital weighing machine. The results obtained showed that, when Milicia excelsa is treated with neem oil, its Rate of Decay (ROD) reduces as compared to the untreated pieces. Also, neem oil treated wood when exposed to termite’s attack experiences a slower weight loss compared to untreated samples with significant weight loss. Neem oil is thus not only effective in preserving woods, but also non- toxic to human and the environment.
1. INTRODUCTIONThroughout
history, people have relied on wood for varied uses such as housing, furniture,
tools, transport, entertainment, learning, and multitude of other products.
Wood from time immemorial has been established as a construction material in
wood industries for variety of applications such as construction of buildings
such as stadia, ships, furniture items, bridges, boats, lorries, tractor wagons
and aircraft carrier. Wood is also used in the production of musical
instruments such as guitar, piano, violin, tambourines; in tool making such as hammer handles,
pick axes, pulp and paper for the production of exercise books, newspapers,
magazines; sports wares such as hockey sticks, tennis bats, tennis rackets and
cricket bails (Bamiro et al. 1986). The wide
range use of wood, technological advancement, wood deterioration, deforestation
and population increase in Cameroon have placed a remarkable rise in demand and
use of timber. The demand for timber is rising
in every part of the country without a balanced supply to meet this demand.
Gradually, durable wood is becoming scarce and expensive particularly in the
North West part of Cameroon and therefore there is need to find alternative
timber species to supplement the existing economic species commonly in use
which include some of the plants introduced during colonial period like
Eucalyptus, Callistemon viminalis, globulus and Syzygium staudtii;
agroforestry species like Calliandra callothyrsus, Leucaena
lleucocephala, and Casuarina equisefolia; the citrus
species such as Cupressus benthani and Pinus sylvestris; and the Podocarpus
species. Despite
its importance to the wood industries and the end users, there is however the
threat of wood degradation brought about by mechanical wear through abrasive
action, decomposition caused by physical agencts such
as prolonged heating or exposure to weather and chemical decomposition (Goodell
et al. 2003). Another common major cause of wood degradation is
bio-deterioration which is the action of foreign biological agents such as
fungi, insects, bacteria and marine borers. According to Wong and Cheok (2001),
wood degradation by termites is a chronic problem in many tropical and even
some temperate regions of the world, resulting in serious monetary, material
losses and an increasing demand for timber. Major
destructive agents to buildings constructed of sound materials and workmanship
are the termites (Wong and Cheok, 2001; Ezeji, 1984).
Termites mostly feed on dead plant material, mostly wood, leaf litter, soil, or
animal dung. According to Ezeji (1984), termites are
insects which live in communities and feed principally on wood substance called
cellulose. The cellulose is the structural framework of the primary cell wall
of wood which forms 45% to 50% of the wood substance. The major types of
termites that attack and feed on woods cellulose are identified as the
subterranean, damp wood and the dry wood termites (Ezeji,
1984; Jones et al. 2007). Termites
make narrow holes by eating out the timber and the galleries so made provide
accommodation for the various members of the colony. As the number of galleries
increases, they merge to form large cavities in the timber and the evidence of
their infestations can hardly be noticed until they eat up the wood leaving the
casing (Ezeji, 1984). Some evidences of wood
infestation by termites include weight loss, loss of form and shape, wood
easily breaks apart, development of shelter tubes, galleries or tunnels in an
irregular pattern, dull sound when tapped and structural weakness. In Cameroon,
the subterranean and dry-wood termites have been identified as major cause of
wood biodegradation (Femi-Ola & Aderibigbe, 2008;
Ezeji, 1984). Wood degradation by termites and other
insects over the years have been inhibited by using naturally resistant wood
species and the use of wood preservatives. Wood
preservative is any substance that is effective in preventing the development
and action of wood fungi, termites and pests of various kinds within a
considerable period of time. Bamiro al. (1986) and Kingsland (2011) enumerated the qualities of a
good wood preservative to be: poisonous to the destructive agents but harmless
to its operators, easy to handle and apply to wood, odourless, cheap and easily obtainable,
chemically stable for a long period, leach and evaporation proof. Wood preservatives are classified
into three general classes which are the Oil-type or Oil borne preservatives,
such as Creosote, Coal- Tar, Solignum and petroleum
solutions of pentachlorophenol; Water borne preservatives such as Chromated
Copper Arsenate, Ammoniacal Copper Zinc Arsenate and boron; and the
Organic-Solvent preservatives such as Chlorinated phenols and Sodium Pentachlorophenol.
These wood preservatives are applied on wood for either interior or exterior
wood constructions. The common methods of applying the wood preservatives are
brushing and spraying, dipping and soaking, hot and cold tank; and pressure
treatment. Preservatives
are applied based on how and where the products will be used, the expected
conditions of exposure to wood destroying agents in the ground, above the
ground and in marine environment. The length of time over which these chemicals
remain effective as stated by Ezeji (1984), depends
on a number of factors including the type of soil, exposure to weather and the
kind of termite involved. The
effectiveness of wood preservative against termites is established when the
preservative treated wood has high resistance to termite’s infestation in
situations close to the practical usage over a period without losing its
efficacy of protecting the wood (Edlund et al. 2006).
The question of effectiveness of the highly toxic chemical preservatives to
inhibit and destroy wood deteriorating agents and in particular termites is not
in doubt but the hazards associated with their use have led to their ban in the
United States of America and the 27 European Union countries (European Union
Commission, 2001; Dickey, 2003). The ban on the use of creosote, coal-tar, solignum, chromate copper arsenate, ammonical
copper arsenate, pentachlorophenol and several others due to the high level of
toxicity to the handlers of wood preservatives, residential and non-residential
users of treated wood and the environment, has opened up alternative
development of low and non-toxic wood preservatives in the EU countries and the
US. Some of these new wood preservatives such as alkaline copper quaternary,
concentrated borate, copper azole, biguanide, and polyenones are readily
available only mostly in the EU countries but very expensive and in most cases
unaffordable in non-EU countries (EU Commission, 2001). There is therefore need
for the developing countries like Cameroon to look for alternative wood pest
control preservatives that are low in toxic content or non-toxic to human
beings and the environment (Ohmura et al. 2000; Rodrigues et al. 2012; Syofuna et al. 2012). The possibility of getting an
effective, environmentally and human friendly wood preservative may be found in
organically based sources such as plants and tree extracts; a likely source
might be extracts from the neem tree. The neem
tree (Azadirachta Indica A. Juss),
is a tropical evergreen tree with wide adaptability and like the Mahogany tree,
it is known to be resistant to insect infestation (Giger 2001). Neem is one of
the most versatile, multifarious trees of tropics, with immense potentials, and
it possesses maximum useful non-wood products (leaves, bark, flowers, fruits,
seeds, gum, oil and neem cake) than any other tree species (Girish and Shankara (2008). These non-wood products are known to have
anti-allergenic, anti-dermatic, anti-feeding,
anti-fungal, anti-inflammatory, anti-pyorrhoeic,
anti-scabic, cardiac, diuretic, insecticidal,
larvicidal, nematicidal, spermicidal and other
biological importance, thus because of these enormous applications, neem has
become a green treasure tree in many countries (Giger, 2001; Girish & Shankara, 2008). Neem oil and extracts have been reported
to be active against termites, including Zootermopsis
nevadensis (Ohmura et
al. 2006), Reticulitermes speratus (Serit et al. 1992), Coptotermes
formosanus (Grace and Yates 1992, Doolittle et
al. 2007), and Incisitermes marginipennis
(Arcos-Roa et al. 2001). In Cameroon, neem tree is now
widely grown and thrives well in four of the 10 regions of the country. In the
North west region, there is high density of the trees especially in Boyo
division part of the region and the seeds are easy to collect from the ground
or could be harvested. Neem oil is extracted from the seeds of neem tree which
contain 45% of brown and bitter oil (Hayden, 1998; Giger, 2001). The wide
applications of neem extracts provided a window for its oil to be examined if
it can be used for wood preservation of predominant timbers in the Northwest
region of Cameroon, thus giving the basis for this study. This study is
therefore aimed at determining the efficacy of neem oil in its ability to
prevent Milicia excelsa
wood from termite destruction. 2.
MATERIALS AND METHODS
2.1. DESIGN OF STUDY
The research design employed in the study was
Research and Development (R & D), aimed at developing products and field
testing the products to confirm their efficacy before use (Gall et al. 2007).
Although costly and demanding, R&D activities provide valuable means of not
only developing new products but improving on existing ones for wider usage and
applications. The design was found appropriate
for the study since it focused on developing new products or finding
alternative applications for a product. Neem oil had been used for different
applications and the need to exploit its use for the treatment of Milicia excelsa
timber in the Northwest region is considered imperative. 2.2. STUDY AREA
This
study was conducted in Mezam division, North West
region of Cameroon, where Milicia excelsa wood is highly available
and frequently used for various wood constructions. This wood specie was found
susceptible to termites and other agents of wood degradation (Keay, 1989). It was noticed that in this area, there was
high prevalence of termite infestations which led to material loss, loss of
property, risk to human lives and the environment. 2.3. SAMPLE PREPARATION AND COLLECTION
Materials that were used for the collection
of the samples were: measuring rule/ tape, try-square, pencil, rip-saw,
cross-cut saw, sack, sensitive digital weighing scale, 25mm hand brush and open
oil can. The 3- meter measuring tape was used for measuring length of wood
samples cross-cut or ripped. The try-square was used to guide the measuring and
marking of the width and short length of wood samples that were cross-cut; the
same instrument was used in drawing perpendicular lines to the edge of wood
samples. The pencil was used to indicate marks for ripping and cross-cutting of
wood samples. The ripsaw was used to cut along the grain of planks following
the width line marks while the cross-cut saw was used to cut across the grain
of the planks. The jute sack was used to collect the cut wood samples from the
timber shade in the area of study and conveyed to the researcher’s workshop.
The weighing scale was used for pre-weighing and post-weighing the treatment
and control wood samples. The 25mm hand brush was used to clean the cut samples,
while the open Oil Can was used as the receiver of neem oil from the bottle
before dipping the wood samples. The sample collection and experiment were
carried out in two phases. Sixteen pieces each of Milicia excelsa measuring 30mm×50mm×150mm were
cut from defect free part of the timber obtained from timber market in the
study area. Eight pieces were randomly selected from the samples of defect free
wood samples cut from the timber and used as treatment and eight used as
control. This experiment was replicated. The selection of these timbers was based on the fact that Milicia excelsa woods are widely used for
various wood/building constructions in the Northwest region and are susceptible
to termite infestation. Processed neem oil was purchased from the local market
in the Northwest region for the treatment of the experimental samples. 2.4. EXPERIMENTAL DESIGN
The wood
sample pieces were prepared in accordance with the American Wood Preservers
Association (AWPA) E1-97[1999] and Nordic Wood Preservation Council (NWPC)
EN252 [2006] standards for the field trial tests. All the wood samples were
oven dried to ensure that the moisture content of each is not above 20%. The
reduction of the moisture content was to facilitate easier absorption and
penetration of the preservative in to the wood samples. All the samples were
randomly allotted letters, labeled with the first letter of the wood sample
type and either UT or T indicating untreated or treated sample; for example, AT
on wood sample meant Sample A Treated or BU meant Sample B
Untreated. The labeled wood samples were then randomly selected and grouped
into two, treatment and control (8 treated and 8 untreated). Each wood sample
in the two groups was then weighed for its pre-infestation weight using the
digital weighing scale and values of the pre-infestation weights recorded.
Eight pieces of wood of the defect free Milicia excelsa sample randomly selected were treated with neem
oil by immersing each test sample into the container filled with the oil. This
immersion was done twice for each sample within 24 hours to enable penetration
and drying of the treated pieces. All the treated samples were then air dried for 72 hours (3 days),
and weighed to ensure that the absorption of the oil treatment did not significantly affect the pre-test
weights of the samples. Two
termite infested locations both exterior and interior were chosen at the Royal
furniture Centre area at Mile 4 Nkwen Bamenda. This
location was chosen because of its high rate of termite infestation and for the
ease of close monitoring for the field test trial of both treated and untreated
wood samples. A termite mound for the exterior infested environment was
identified and dug to a depth of 15cm to ensure contact with termite activity
and protect wood samples from curious passersby while the roof trusses of a
motor garage infested with termites were used for the interior environment.
Eight wood samples comprising of the treated and untreated pieces were randomly
installed inside the termite mound and buried while another group of eight
treated and untreated wood samples were placed on the plates and beams of the
motor garage trusses according to AWPA E1-97 and NWPC EN 252 standards of field
testing of the effectiveness of wood preservatives. The placement of the
samples in both interior and exterior locations were mapped and recorded in
order to assist the researcher to recover the samples with their appropriate
labels. The wood samples both treated (experimental) and untreated (control)
were allowed for a period of nine weeks between March and May 2020 (a period
within which termite infestation is normal), before they were retrieved for
weighing and visual rating. 2.5. DATA COLLECTION
Data was
collected based on field experimental research principles through observation
(visual inspection), weighing of samples and recording of values.
Pre-infestation weights of wood samples were measured using a sensitive digital
weighing scale and the values recorded before exposure of samples to termite
infestations. Post-infestation weight of wood samples after nine weeks of
infestation were measured and values also recorded. Data on the extent of
infestation and deterioration of wood samples for the study were based on a 5-
point visual inspection rating adopted from the American Society for Testing
and Materials (ASTM), International D1758-06 (2010) standards of rating wood
for deterioration. The rating was done after the period of nine weeks of
exposure of treated and untreated wood samples to termites. Each of the pieces
of wood exposed to termite infestation was observed and rated based on the
5-point ASTM Durability Rating Scale (Table 1). Table 1: A 5-Point
ASTM Durability Rating Scale. Culled from the International Research Group
on Wood Protection (2010).
2.6. DATA ANALYSIS
Pre-infestation
weights of all wood samples were first recorded and then the post infestation
weight values after the period of experiment were also taken. Percentages and mean
weight losses were calculated from the pre-infestation weight and
post-infestation weight values to determine the effectiveness of neem oil in
preserving the wood samples from wood
weight losses as a result of termite infestations. Values from the visual
inspection ratings of the wood
samples were also noted to arrive at the mean values on the extent of deterioration and this data was
analyzed using the mean statistics. T-test analysis was used to compare between means of the untreated
and treated samples. 3.
RESULTS
AND DISCUSSIONS
3.1. ABSORPTION OF NEEM OIL BY IROKO SAMPLES
From the
total quantity of neem oil used for treatment of the experimental samples, it
was realized that a large quantity was not absorbed, while some amount of the
oil was absorbed (Table 2). Table 2: Absorption of neem oil by treated
iroko wood samples
The table
above indicates that when neem oil is effectively applied on iroko wood sample,
some of the liquid gets into the wood which is necessary to further enhance the
protection of the wood from agents of wood deterioration, especially termites.
This finding is in line with that of Olufemi et al. (2007) who reported an absorption
rate of over 9.42% neem oil by Khaya senegalensis when used for its
treatment against agents of wood deterioration. Considering that the iroko wood
samples used in this study were oven dried so as to reduce the amount of
moisture in them, and that neem oil was adequately applied to the samples,
these could have contributed to the significant absorption rate recorded. 3.2. INFLUENCE OF NEEM OIL ON PRESERVATION OF MILICIA EXCELSA
After the
nine weeks experimental period, the final weight of each treated and untreated
wood sample was recorded, and this revealed that weight loss for treated
samples was relatively lower compared to the untreated samples (Tables 3 &
4). Table 3: Weight loss
for termite infested Milicia excelsa untreated wood samples
Table 4: Weight loss for treated Milicia excelsa wood samples
Similar
findings were also reported by Olufemi et al. (2011) which indicated that when
wood is treated with neem oil, the rate at which its losses weight with time
when exposed to agents of wood deterioration especially termites is relatively
lower compared to untreated wood. 3.3. RATE OF TERMITE ATTACK ON TREATED AND
UNTREATED WOOD SAMPLES
Using the
5-Point ASTM Durability Rating Scale to verify the degree of termite attack on
the treated and untreated wood samples, it was realized that untreated wood
samples experienced significant destruction by termites compared to wood
samples treated with neem oil (Table 5 & 6). Table 5: Extent of termite attack on
untreated Milicia excelsa
wood samples
Table 6: Extent of timber attack on
treated Milicia excelsa
wood samples
The
reduction in the extent of termite attack on treated wood samples compared to
untreated samples suggest that, neem oil could be effective in limiting the
degree of wood destruction. Gilmara et al. (2013)
reported a lower rate of termite destruction on neem oil treated than untreated
wood samples. The use of neem oil on wood preservation is thus an effective
strategy, especially when well applied. To compliment this, well-seasoned neem
oil treated wood is highly recommended for use as it will be more resistant to
deterioration. Owing to the problems associated with wood biodeterioration,
especially in tropical countries, treatment techniques using preservatives are
imperative if wood is to be used in construction (Cavalcante, 1982). 4.
CONCLUSION
The nonapplication
of wood preservatives on wood makes it wide-open to termite infestation and
deterioration. This fact was established in the case of untreated Milicia excelsa wood
samples which suffered vast termite attacks as compared to the treated wood
samples which had significant levels of resistance to termite infestation. The
possibility of using neem oil as a preservative provides a window for its
adaptation as an alternative wood preservative that is safe for human handling
and to the environment. It can thus be inferred that neem oil has the potential
of being an effective wood preservative. It would be necessary to conduct
further experiments with a mixture of neem oil and other possible substances to
verify the behavior and effectiveness compared to using neem oil alone. SOURCES OF FUNDING
This
research received no specific grant from any funding agency in the public,
commercial, or not-for-profit sectors. CONFLICT OF INTEREST
The
author have declared that no competing interests exist. ACKNOWLEDGMENT
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