Efficiency evaluation of Neem (Azadirachta indica) oil and copper-ethanolamine in the protection of wood against a subterranean termite attack

Abstract

The demand for environmentally safe preservatives for wood is increasing all around the world. This study is focused on the evaluation of the ability of Neem (Azadirachta indica) seed oil and copper-ethanolamine to protect Sydney blue gum (Eucalyptus saligna) and Ayous (Triplochiton scleroxylon) against termites. Wood blocks were impregnated with solutions of Neem oil in acetone and/or an aqueous solution of copper-ethanolamine. Impregnated woods with a retention rate of up to 108.3 kg/m3 were obtained. A leaching experiment was used to determine the fixation of preservatives in wood. The termicidial effect of the preservatives was studied through exposure in a termitarium. Neem oil was less efficient for Sydney blue gum but showed significant protection for Ayous at a higher retention rate. At the concentration investigated, the treatment of both wood species with copper-ethanolamine solution was not suitable. However, a combination of copper-ethanolamine and Neem oil showed an improvement in the protection of Sydney blue gum wood. Nevertheless, the impregnated woods still suffered an increased termite attack after leaching.

Full text

47
Les/Wood, Vol. 69, No. 1, June 2020
1 INTRODUCTION
1 UVOD
Inorganic as well as organic-based preservave
formulaons have long been used to protect wood
against fungi, termites, and bacteria. The ecacy
of copper compounds to control the growth of a
wide range of microorganisms has been success-
UDK 630*845.3
Original scienc arcle / Izvirni znanstveni članek Received / Prispelo: 29. 4. 2020
Accepted / Sprejeto: 25. 5. 2020
Vol. 69, No. 1, 47-56
DOI: hps://doi.org/10.26614/les-wood.2020.v69n01a04
Abstract / Izvleček
Abstract: The demand for environmentally safe preservaves for wood is increasing all around the world. This study is
focused on the evaluaon of the ability of Neem (Azadirachta indica) seed oil and copper-ethanolamine to protect Syd-
ney blue gum (Eucalyptus saligna) and Ayous (Triplochiton scleroxylon) against termites. Wood blocks were impreg-
nated with soluons of Neem oil in acetone and/or an aqueous soluon of copper-ethanolamine. Impregnated woods
with a retenon rate of up to 108.3 kg/m3 were obtained. A leaching experiment was used to determine the xaon
of preservaves in wood. The termicidial eect of the preservaves was studied through exposure in a termitarium.
Neem oil was less ecient for Sydney blue gum but showed signicant protecon for Ayous at a higher retenon rate.
At the concentraon invesgated, the treatment of both wood species with copper-ethanolamine soluon was not
suitable. However, a combinaon of copper-ethanolamine and Neem oil showed an improvement in the protecon of
Sydney blue gum wood. Nevertheless, the impregnated woods sll suered an increased termite aack aer leaching.
Keywords: Neem oil, copper, ethanolamine, wood, preservaon, leaching, termite
Izvleček: Povpraševanje po za okolje varnih zaščitnih sredstvih za les narašča po vsem svetu. Ta študija je osredoto-
čena na oceno sposobnos olja semen nima (Azadirachta indica) in baker-etanolaminskega pripravka za zaščito lesa
evkalipta (Eucalyptus saligna) in sambe (Triplochiton scleroxylon) pred termi. Lesene preizkušance smo impregnirali
z raztopinami nimovega olja v acetonu in / ali baker-etanolaminski vodni raztopini. Količina navzema v impregnira-
nem lesu je znašala 108,3 kg/m3. Vezavo zaščitnih sredstev v les smo določili z izpiranjem. Termicidni učinek zaščitnih
sredstev je bil raziskan z izpostavitvijo v termitariju. Nimovo olje je bilo manj učinkovito za zaščito lesa Evkaliptus
saligna, pomembno zaščitno učinkovitost pa je pokazalo za les Triplochiton scleroxylon pri višjem navzemu. Pri upora-
bljeni koncentraciji baker etanolaminskega pripravka za zaščito obeh preučevanih lesnih vrst ni bila zadostna. Vendar
je kombinacija baker-etanolaminskega pripravka in nimovega olja pokazala pomembno izboljšanje zaščite lesa evka-
lipta. Kljub temu je bil impregnirani les po izpiranju zopet bolj dovzeten za napad termitov.
Ključne besede: nimovo olje, baker, etanolamin, les, zaščita, izpiranje, termi
1 Macromolecular Research Team, Faculty of Science, University of Yaoundé 1, P.O. 812, Yaoundé, Cameroon
2 Department of Chemistry, École Normale Supérieure, University of Yaoundé 1, P.O. Box 47 Yaoundé, Cameroon
3 Department of Wood Science and Technology, Biotechnical Faculty, University of Ljubljana, Jamnikarjeva 101, SI-1000 Ljubljana, Slovenia.
* e-mail: acheumani@gmail.com
EFFICIENCYEVALUATIONOFNEEM(AZADIRACHTA INDICA) OIL AND
COPPER-ETHANOLAMINEINTHEPROTECTIONOFWOODAGAINST
ASUBTERRANEANTERMITEATTACK
OCENAUČINKOVITOSTINIMOVEGAOLJA(AZADIRACHTA INDICA)
TERBAKER-ETANOLAMINSKIHPRIPRAVKOVPRIZAŠČITILESAPRED
NAPADOMPODZEMNEGATERMITA
Taana Mbitnkeu Fetnga Tchebe1, Jean-Bosco Saha Tchinda1, Alexis Ngueteu Kamlo2,
Desiré Chimeni Yomeni1, Arnaud Maxime Cheumani Yona1,3*, Maurice Ndikontar Kor1
fully exploited, and copper-based products formu-
lated with the addion of other metal compounds
such as chromium to help in the xaon of copper
in wood, and arsenate or boron to extend bioac-
vity to copper-resistant agents of biodegradaon
(Freeman & Mcintyre, 2008; Hingston et al., 2001).
Organic-based formulaons containing creosote,

48 Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Ocena učinkovitos nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zašči lesa pred napadom podzemnega termita
pentachlorophenol or naphtenates were once also
widely used for preservaon of wood. However,
these products are now subjected to increasing re-
stricons or even banned in many countries around
the world due to their potenal health hazards
and adverse environmental eects (the liberaon
of toxic carcinogen metals such as chromium and
arsenate, emissions of organic non-biodegrada-
ble pollutant as creosote) (Hingston et al., 2001;
McMahon & Chen, 2001; Tobia et al., 1994). To
address these issues, copper alternaves with re-
duced environmental impact have been developed
using nitrogen-based organic mediators such as
azole or ethanolamine to facilitate the xaon of
copper in wood and thus prevent leaching (Free-
man & Mcintyre, 2008; Humar et al., 2006; Thaler
et al., 2013; Zhang & Kamdem, 2000). Owing to the
increasing demand for more and more environ-
mentally friendly, sustainable alternave products
all over the world, natural organic products such as
plant-extracts from wood or barks, vegetable oils,
and essenal oils have been invesgated as alter-
nave soluons (Adedeji et al., 2018, Dev & Nau-
yal, 2004; Gilmara et al., 2013; González et al.,
2015; Hyvönen et al., 2005; Muktarul et al., 2009,
Saheb & Mouhouche, 2016; Singh & Singh, 2012;
Syofuna et al., 2012). Fama and Morell (2015)
studied the ability of various plant oils (Neem, Eu-
calyptus, jatropha and linseed oils) to inhibit damp
wood termite (Zootermopsis anguscollis) growth,
and concluded that most of these aect protozoa
in the hindgut of termite workers and that protozoa
loss was closely followed by termite mortality.
Neem (Azadirachta indica) is a tree species of
the Meliaceae family growing in the tropical and
semi-tropical regions of the world (Girish et al.,
2008). This species originated from the Indian sub-
connent but is now widespread in Africa and Aus-
tralia, being classied as an invasive species in the
laer. One special feature of this tree is that almost
all its parts (leaves, fruits, seed, bark) exhibit bioac-
vity against insects and fungi (Pankaj et al., 2011)
and are used for medicinal applicaons (Subipri-
ya & Nagini, 2005). About 195 insect species have
been found to show high sensivity to Neem ex-
tracts, including insects that have become resistant
to synthec pescides (Menn, 1990). Applicaons
of Neem extracts for wood preservaon are thus
under invesgaon. For example, the bioacvity of
extracves from Neem leaves was tested against
wood destroying fungi and termites by Dhyani et
al. (2004), Machado et al. (2013) and Venmalar
and Nagaveni (2005). Moreover, Subbaraman and
Brucker (2001) examined formulaons containing
Azadirachn extracted from Neem tree with a lignin
or tannin compound added as a binding agent and
usable as wood preservaves against termites.
This work reports the ability of Neem oil,
copper-ethanolamine or a combinaon of both
in the protecon of wood against termites. For
this purpose, two wood species from Cameroon
were tested: Sydney blue gum (Eucalyptus salig-
na) and Ayous (Triplochiton scleroxylon). Sydney
blue gum was the main targeted wood because of
its use for electricity poles for the distribuon of
power in Cameroon and neighbouring countries.
Untreated wooden poles are rapidly eaten by ter-
mites, leading to a short service life (5-10 years).
Previous research (Adebawo et al., 2015; Fama &
Morell, 2015; Himmi et al., 2013; Machado et al.,
2013; Sotannde et al., 2011; Syofuna et al., 2012)
on the applicaon of Neem oil as a wood preserv-
ave against termites were performed at lower re-
tenon rates and showed the ability of the oil to
cause the mortality of termites, although with an
undesirable weight loss of wood. In this work, the
impregnaon parameters were set to aain a high-
er oil retenon rate.
2 MATERIALSANDMETHODS
2 MATERIALIINMETODE
2.1MATERIALS
2.1MATERIALI
Blue gum wood was collected from a local m-
ber market in Bamenda in the North-West region
of Cameroon while Ayous was obtained in a local
mber market in Yaounde in the Central region.
Sydney blue gum (Eucalyptus saligna) is an exoc
wood species mainly culvated in the high moun-
tains of West and North-West Cameroon, while
Ayous (Triplochiton scleroxylon) comes from the
natural forests located in the Center, South and
East regions. Heartwood was used for both species.
Neem oil was extracted from Neem seeds by a cold
mechanical process. The copper chloride, ethanol-
amine and acetone were reagent grade and used
without further puricaon.

49
Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Eciency evaluaon of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protecon of wood against a subterranean termite aack
2.2WOODSPECIMENS
2.2VZORCILESA
Wood blocks with the dimensions of (6 x 2 x 2)
cm3 were cut from each wood species and dried in
the laboratory ll constant mass was obtained (af-
ter about one month). The moisture content of the
wood was determined by drying some dedicated
samples in an oven at 103 °C ll constant mass was
achieved. The moisture content was 11.9(±0.3)%
and 11.1(±0.6)% for Sydney blue gum and Ayous,
respecvely.
2.3IMPREGNATIONOFWOODWITH
 PRESERVATIVESOLUTIONS
2.3IMPREGNACIJALESAZRAZTOPINAMI
 ZAŠČITNIHSREDSTEV
Homogeneous preservave soluons were
prepared and used for impregnaon of wood
blocks under reduced pressure. Neem oil was di-
luted with acetone. The mass rao of Neem oil
(NO)/acetone of dierent soluons was 10:90 (NO
10%), 30:70 (NO 30%), 50:50 (NO 50%) and 70:30
(NO 70%). Copper-ethanolamine soluon (Cu-EA)
was prepared using dislled water as a solvent. The
mass concentraons of copper and ethanolamine
in the soluon were 0.5% copper chloride and 1.4%
ethanolamine. A combining treatment was carried
out by impregnaon of wood with Cu-EA, drying
the wood for 24h, and nally a second impregna-
on with NO 50%. Xylamon® (Syl), a commercial
product sll sold in Cameroon for wood protecon,
was used as a reference. Xylamon is a mixture of
permethrin or cypermethrin, tebuconazole and
benzalkonium chloride according to the former cer-
caon CTP-P+ 2002 of CTBA (today FCBA) (CTBA,
2002). Impregnaon process was carried out under
reduced pressure in a 5 L round boom ask. Care
was taken to keep all wood blocks completely im-
mersed in the impregnaon soluon. Twelve wood
blocks were used for each impregnaon, and the
impregnaon was performed for 30 min using a tap
water pressure reducon system. Aerwards, any
excess soluon on the surface of the impregnated
wood samples was mopped up and the mass of the
sample determined. The retenon rate (%) was cal-
culated using Equaon 1 (Sen et al., 2009):
(1)
Where (m1-mo) is the amount of impregnaon
soluon retained by the wood in g, C the mass con-
centraon of the soluon in (%) and V the volume of
wood block in cm3. m1 and m0 are the wood masses
aer and before impregnaon, respecvely.
The impregnated wood blocks were air dried
in the laboratory ll constant mass was obtained
(aer two weeks).
2.4LABORATORYLEACHINGEXPERIMENTS
2.4LABORATORIJSKIPOSKUSIIZPIRANJA
The impregnated wood blocks were divided
into two groups: the rst consisted of six blocks
that were used for the leaching experiment,
while the second six blocks were kept as the non-
leached samples. The leaching experiment was
performed according to the standard NF X41-565
with a slight modicaon. Wood blocks were in-
troduced in glass containers with 5 to 10 mes
their equivalent volume in dislled water. The
glass containers were placed on a mixing mechan-
ical table (Edmund Bühler GmbH SM-30) and kept
under agitaon for four cycles of leaching (1h, 2h,
4h and 8 h). The leaching water was changed aer
each me period. The leached wood blocks were
air dried ll constant mass was achieved (aer two
weeks) and then weighed. The percentage weight
loss (PWLL) due to leaching was determined by
Equaon 2:
(2)
Where m1 and m0 are the formal masses of
wood aer and before impregnaon respecvely,
and m2 the mass of wood aer leaching.
2.5ACTIVITYOFTERMITES–FIELDTESTS
2.5DEJAVNOSTTERMITOV–TERENSKIPOSKUS
Termites are highly destrucve wood agents
in many tropical regions, parcularly in sub-Saha-
ran Africa. The eciency of preservave products
against a subterranean termite was assessed by
a eld test. Non-impregnated, impregnated and
leached wood samples were placed in a termitarum
located on the university campus. Wood samples
were covered with a black polyethylene sheet to be
in the dark. The test was performed for 16 weeks
(see Figure 1).
( ) ( )
10 3
C
R % 10 ( / )
V
mm x kg m
−×
=
12
10
100
mm
PWLL x
mm
−
=−

50 Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Ocena učinkovitos nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zašči lesa pred napadom podzemnega termita
Aer the dened me, wood (or residual
wood) was collected, cleaned and dried in an oven
for 72h at 103 °C. Percentage weight losses (PWLT)
due to termite aack were determined according
to the equaon 3.
(3)
m0 and m3 are the masses of the wood block
before and aer exposure to termites.
3 RESULTSANDDISCUSSION
3 REZULTATIINRAZPRAVA
3.1RETENTIONRATE
3.1NAVZEM
The retenon rates of the dierent soluons
are presented in Figure 2. The retenon rate gives
the amount of acve preservave substance in-
troduced in a wood block. As expected, Ayous
showed a greater retenon capacity than Syd-
ney blue gum. This dierence in behaviour is at-
tributed to the dierence in density, as the Syd-
ney blue gum and Ayous apparent densies were
0.79(±0.06) g/cm3 and 0.36(±0.04) g/cm3, respec-
vely. Blue gum is thus less porous, and it is more
dicult for the soluon to ingress towards the
depths of the wood. The results showed that rising
concentraon of Neem oil in the Neem oil-acetone
mixtures signicantly increased the retenon rate
even though the soluons were slightly more vis-
cous at higher Neem oil concentraons. Retenon
of Neem oil varied from 11.0 kg/m3 to up to 108.3
kg/m3 under the condions invesgated, and
these results are consistent with those in the liter-
ature (Can & Sivrikaya, 2016; Naveri et al., 2017).
It is well recognized that retenon depends on the
concentraon of acve substances in the soluon,
as well as other parameters such as impregnaon
process and me. An increase in the concentraon
of preservave generally increases the retenon
(Naveri et al., 2017). Can and Sivrikaya (2016) re-
ported that, for impregnaon of wood with tall-
oil in similar experimental condions, the reten-
on rate followed the same order. A combinaon
of copper-ethanolamine and NO 50% showed a
retenon rate (67.0 kg/m3 for Sydney blue gum
and 90.7% for Ayous) closer to that of the solu-
on NO 50% (69.5 kg/m3 for Sydney blue gum and
Figure 1. Wood blocks in a termitarium (Isoptera: Termidae)
Slika 1. Leseni preskušanci v termitarju (Isoptera: Termidae)
( )
03
0
mm
PWLT % x100
m
−
=

51
Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Eciency evaluaon of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protecon of wood against a subterranean termite aack
88.3% for Ayous). For comparison, the retenon
rates for CCA preservave are around 4kg/m3
for surface applicaons and around 40 kg/m3 for
underground applicaons or those in salt water
(American Wood-Preservers Associaon, 1997).
For Alkaline-Copper-Quaternary (ACQ), retenon
is around 2.4 kg/m3 for above-ground treatments
and 6.4 kg/m3 for underground wood (American
Wood-Preservers Associaon, 2006). It can be
noced that the retenon rates obtained in this
study were signicantly higher compared to the
tradional preservave requirements for under-
ground applicaons of wood.
3.2LEACHING
3.2IZPIRANJE
The percentage weight losses caused by leach-
ing (PWLL) of wood impregnated with Neem oil or
copper-ethanolamine are shown in Figure 3.
Leaching can extract non-xed preservaves,
but also some extracves naturally present in wood.
The extracve contents (ethanol-toluene and hot
water) obtained from those wood species were
3.4% for Ayous (non-published research work) and
5.0% for Sydney blue gum (Chokouadeu Youmssi
et al., 2017). The PWLL obtained for almost all the
treatments was higher than the extracve content
Figure 2. Retenon of preservaves
in wood from the dierent impregna-
on soluons. Abbreviaons: NO X%:
Neem Oil-Acetone with X% of Neem
oil; Cu-EA: copper-ethanolamine for-
mulaon, Cu-EA + NO: double treat-
ments with Cu-EA and NO 50%; Syl:
pure Sylamon® formulaon.
Slika 2. Navzem zaščitnih sredstev v
lesu evkalipta in sambe iz različnih im-
pregnacijskih raztopin. Okrajšave: NO
X %: Mešanica nimovega olja in aceto-
na z X % nimovega olja; Cu-EA: formu-
lacija bakra in etanolamnina, Cu-EA +
NO: dvojna obdelava s Cu-EA in NO 50
%; Syl: čista formulacija Sylamon®.
Figure 3. Leaching of wood impreg-
nated with dierent preservave solu-
ons.
Slika 3. Izpiranje iz lesa, impregnirane-
ga z različnimi raztopinami zaščitnih
sredstev.

52 Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Ocena učinkovitos nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zašči lesa pred napadom podzemnega termita
of the woods and showed that Neem oil as well
as copper-ethanolamine were both leached. The
PWLLs were generally lower with Ayous than with
Sydney blue gum. This result can be explained by
the depth of penetraon and amount of oil in the
wood. Sydney blue gum, being denser, had less in-
depth impregnaon and underwent more leaching.
The higher oil content in Ayous could also confer to
this wood a certain hydrophobicity liming the in-
gress of leaching water. Wood impregnated with oil
exhibited reduced water absorpon, as reported
in the literature (Can & Sivrikaya, 2016). The PWLL
decreased for Ayous as retenon increased. Cop-
per-ethanolamine was signicantly leached from
the woods. Thaler and Humar (2014) also reported
a mass reducon of the copper content of around
3-5% for wood impregnated with copper-ethanol-
amine, based on laboratory leaching tests. Sylam-
on® was the most leached product for both wood
species.
3.5EVALUATIONOFTERMITEACTIVITY
3.5OCENAAKTIVNOSTITERMITOV
The percentage weight losses caused by ter-
mite acvity (PWLT) aer exposure of wood blocks
to eld termites are shown in Figure 4.
Some degraded wood blocks at the experi-
mental site are shown in Figures 5 and 6.
Figure 4. Percentage weight losses
due to termite (PWLT) aack for Syd-
ney blue gum (Eucalyptus saligna) and
Ayous (Triplochiton scleroxylon) im-
pregnated with dierent preservave
soluons.
Slika 4. Izguba mase (%) zaradi na-
pada termitov (PWLT) lesa vrst evka-
lipta (Eucalyptus saligna) in sambe
(Triplochiton scleroxylon), impregnira-
nega z različnimi raztopinami zaščitnih
sredstev.
Figure 5. Ayous (Triplochiton scleroxylon) wood impregnated with NO 10% (a) and NO 30% (b) aer
16 weeks in a termitarum.
Slika 5. Les sambe (Triplochiton scleroxylon), impregniran z NO 10 % (a) in NO 30 % (b), po 16 tednih
v termitarju.
(a) (b)

53
Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Eciency evaluaon of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protecon of wood against a subterranean termite aack
Non-treated wood was completely consumed
by termites, and thus the PWLTs were 100% for
both wood species. Neem oil was globally less ef-
cient in the preservaon of wood against the in-
vesgated termites. For Sydney blue gum approxi-
mately 100% of wood was degraded at retenons
lower than 69.5 kg/m3, but a signicant reducon
in PWLT was noced at the retenon of 96.6 kg/
m3. Ayous with a retenon value of 108.3 kg/m3
showed the most signicant resistance to termites.
Many research reports have been published on
the eciency of Neem oil for the preservaon of
wood with dierent experimental condions and
retenon rates. It is shown that Neem oil and oth-
er vegetable oils (linseed oil, jatropha) are toxic to
termites and can cause 100% death in laboratory
tests, but with a certain loss of wood weight (deg-
radaon) (Ahmed et al., 2020; Fama & Morell,
2015; Himmi et al., 2013; Machado et al., 2013).
Tests performed in eld condions (a graveyard)
also revealed that wood treated with Neem oil
was suscepble to termite aack, but the level
of resistance was beer than that seen with un-
treated wood (Adebawo et al., 2015; Sotannde et
al., 2011). Given the higher retenon rates tested
compared to the values generally used with tra-
dional commercial products for ecient preser-
vaon, it can be concluded that Neem oil could
not be applied alone for the protecon of wood
against termites.
At the concentraon invesgated, the treat-
ment of the wood blocks with copper-ethanola-
mine soluon was not suitable. Copper is mostly
a fungicide and has insucient termicide or in-
seccide acvity. The addion of co-biocides (e.g.
boron) to copper amine could improve the ecacy
against termites, as reported by Kalawate (2013),
who found no damage aer 24 months and less
than 5% average weight loss aer 30 months for
wood impregnated with copper-ethanolamine-bo-
ron formulaons and exposed to a subterranean
termite aack in a eld test/graveyard test. Xy-
lamon showed signicant acvity with Ayous but
much less with Sydney blue gum. Sydney blue gum
was surprisingly (according to general percepons)
more sensive to termites than Ayous. A combi-
naon of copper–ethanolamine and Neem oil was
also tested in this study. The resistance of Sydney
blue gum was signicantly improved by the mixed
preservaves. Further studies are under consider-
aon to understand the synergec eects and ex-
plain the results.
The percentage weight losses due to termite
infestaon of leached impregnated woods are pre-
sented in Figure 7. The samples of leached Syd-
ney blue gum for all the treatments were almost
completely decomposed by termites. The eect
of leaching with Ayous was migated, probably
because of the lower leaching rate in some sam-
ples. Ayous blocks impregnated with copper-etha-
Figure 6. Sydney blue gum (Eucalyptus saligna) wood impregnated with Cu-EA and NO 50% (a) and NO 10%
(b) aer 16 weeks in a termitarum.
Slika 6. Les evkalipta (Eucalyptus saligna), impregniran s Cu-EA in NO 50 % (a) in NO 10 % (b), po 16 tednih
v termitarju.
(a) (b)

54 Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Ocena učinkovitos nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zašči lesa pred napadom podzemnega termita
nolamine followed by Neem oil showed the high-
est resistance to termites aer leaching. Leaching
generally removes part of acve preservaves
introduced in wood and increases wood biodeg-
radaon. The signicant dierence between non-
leached and leached Sydney blue gum treated with
the combined soluons suggested the loss of syn-
ergy between both preservaves.
4 CONCLUSIONS
4 ZAKLJUČKI
Neem oil applied as a natural preservave
showed a low eciency in the protecon of wood
against termites in the eld test. An increase in the
retenon increased the resistance to termite aack.
Copper-ethanolamine used alone was also less suit-
able in the protecon of wood at the experimental
condions invesgated. A combinaon of Neem oil
and copper-ethanolamine showed a promising im-
provement in the protecon of wood. A reducon
of the percentage weight loss due to termite acv-
ity from 100% (Sydney blue gum impregnated with
copper-ethanolamine or with Neem oil) to 7.4%
(Sydney blue gum impregnated with combined cop-
per-ethanolamine and with Neem oil) was observed.
Nevertheless, the impregnated wood samples were
more exposed to termite aack aer leaching. Fur-
ther research eorts are under consideraon to un-
derstand the synergec eects between these two
products, increase the xaon of preservaves into
wood and modulate their leaching.
5 SUMMARY
5 POVZETEK
Anorganska in organska zaščitna sredstva so že
dolgo v uporabi za zaščito lesa pred biološko razgra-
dnjo, ki jo povzročajo glive, termi in drugi insek
ter morski lesni škodljivci. Tradicionalna zaščitna
sredstva na osnovi spojin bakra, ki vsebujejo strupe-
ne spojine kroma in arzena ali organski sredstvi kre-
ozot in pentaklorofenol (PCP), so podvržena vse ve-
čjim omejitvam in so v mnogih državah po svetu celo
prepovedana. V iskanju okolju prijaznejših izdelkov
kot zanimive alternave preučujejo baker-aminske
pripravke in različne naravne organske proizvode,
kot so na primer rastlinski izvlečki iz lesa ali skorje
dreves in grmov, rastlinska olja in eterična olja. Ta
študija je osredotočena na oceno možnos upora-
be olja nima (Azadirachta indica) in baker-etanola-
minskega sredstva za zaščito lesa evkalipta (Eucalyp-
tus saligna) in sambe (Triplochiton scleroxylon) pred
napadom zemeljskega termita. Omenjeni evkalipt je
pomembna lesna vrsta, ki se uporablja za električ-
ne drogove v Kamerunu in sosednjih državah. Nim
(Azadirachta indica) je drevesna vrsta družine Meli-
aceae - melijevke, ki raste v tropskih in subtropskih
območjih. Vrsta izvira z indijske podceline, danes pa
je razširjena v Afriki in Avstraliji. Ta vrsta je znana
že vsaj dva soč let, ker imajo izvlečki iz njenih lis-
tov, skorje in semen fungicidne, probakterijske in
insekcidne lastnos in se uporabljajo za zdravila.
Predhodne raziskave o uporabi nimovega olja za zaš-
čito lesa pro termitom so bile izvedene z manjšimi
navzemi in so pokazale, da olje lahko povzroči smr-
Figure 7. Percentage weight losses
due to termite acvity (PWLT) for Syd-
ney blue gum (Eucalyptus saligna) and
Ayous (Triplochiton scleroxylon) im-
pregnated with dierent preservave
soluons and aer leaching.
Slika 7. Izguba mase (%) zaradi ak-
vnos termitov (PWLT) pri lesu vrst
evkalipta (Eucalyptus saligna) in sam-
be (Triplochiyton scleroxylon), im-
pregniranega z različnimi raztopinami
zaščitnih sredstev in po izpiranju.

55
Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Eciency evaluaon of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protecon of wood against a subterranean termite aack
tnost termitov ob sicer neželeni izgubi mase lesa. V
tej študiji smo prilagodili parametre impregnacije,
da bi dosegli višje navzeme olja. Preučen je bil tudi
baker-etanolaminski pripravek, ki se je izkazal kot
učinkovit pri zašči lesa pred glivami in insek v dru-
gih regijah. Pripravili smo vzorce lesa dimenzij (6 x 2
x 2) cm3 iz jedrovine obeh lesnih vrst in jih posušili
v laboratoriju do konstantne mase. Uporabili smo
šri načine impregnacije in za vsakega uporabili po
dvanajst vzorcev. V ta namen smo pripravili nimovo
olje, razredčeno z acetonom pri masnih razmerjih
nimovo olje / aceton: 10:90, 30:70, 50:50 in 70:30.
Baker-etanolaminski pripravek smo pripravili z me-
šanjem bakrovega klorida in etanolamina v desli-
rani vodi, tako da smo dosegli koncentracijo bakra in
etanolamina 0,5 % oziroma 1,4 %. Za referenco je bil
uporabljen xylamon, komercialno zaščitno sredstvo.
Impregnirane vzorce lesa (šest vzorcev na poizkus)
smo izpirali po standardu NF X41-565, ki smo ga
nekoliko prilagodili. Lesni vzorci so bili šestnajst te-
dnov izpostavljeni termitom v poljskem termitarju
(Isoptera: Termiditae). Z nimovim oljem smo dosegli
navzem do 108,3 kg/m3. Navzemi so bili v splošnem
višji pri impregnaciji sambe, kar pripisujemo manjši
gosto lesa (ki je skoraj za polovico nižja od gostote
lesa proučenega evkalipta). Nimovo olje je bilo manj
učinkovito za zaščito lesa evkalipta, a je pokazalo
pomembno zaščito lesa sambe pri višjem navzemu.
Za evkalipt smo izmerili skoraj 100-odstotno izgubo
mase pri navzemu 69,4 kg/m3 in 93,5 % izgubo mase
pri 96,5 kg/m3, medtem ko smo pri sambi zabeležili
7,7 % in 3,5 % izgube mase pri navzemih 88,3 kg/
m3 in 108,3 kg/m3. Pri raziskanih koncentracijah
obdelava obeh lesnih vrst z raztopino baker-etano-
lamina ni bila primerna. Rezulta kažejo, da upora-
bljenih zaščitnih sredstev samih ni mogoče upora-
bi za učinkovito zaščito lesa pred termi. Vendar
je kombinacija baker-etanolamina in nimovega olja
pomembno izboljšala zaščito lesa evkalipta. V tem
primeru so bili vzorci lesa impregnirani z baker-eta-
nolaminsko raztopino, 24 ur sušeni na zraku in po-
novno impregnirani z nimovim oljem in acetonom v
razmerju 50:50. Kljub temu so bili impregnirani vzor-
ci po izpiranju izpostavljeni povečanim napadom
termita. Predvidene so nadaljnje študije, da bi bolje
spoznali sinergijo obeh zaščitnih sredstev, izboljšali
ksacijo spojin v lesu, zmanjšali izpiranje in poveča-
li učinkovitost s kombiniranjem z različnimi drugimi
anorganskimi sredstvi in pripravki naravnega izvora.
ACKNOWLEDGMENT
ZAHVALA
This work was supported by the University of
Yaoundé 1 and the Ministry of Higher Educaon
of Cameroon through the “Programme d’appui à
la recherche”. The authors are also grateful to the
Slovenian Naonal Research Agency (ARRS) and
University of Ljubljana for nancial support of the
project “Silwoodcoat”.
REFERENCES
VIRI
Ahmed, S., Fama, R., & Hassan, B. (2020). Evaluaon of dierent
plant derived oils as wood preservaves against subterranean
termite odontotermes obesus. Maderas, Ciencia y tecnología,
22(1): 109-120.
Adebawo, F. G., Ajala, O. O., Olatunji, O. A., & Adekanbi, T. J. (2015).
Potenals of Azadirachta indica seed oil as bio-preservave
against termite aack on wood. Pelagia Research Library, Asian
Journal of Plant Science and Research 5(12):1-5.
Adedeji, G. A., Ogunsanwo, O. Y., Eguakun, F. S., & Eluoye, T. O.
(2018). Chemical composion and termicidal acvity of kha-
ya ivorensis stem bark extracts on wood. Maderas, Ciencia y
tecnología 20(3): 315-324.
American Wood-Preservers Associaon (AWPA), Book of Standards,
Woodstock, MD 2006, P 1-4.
American Wood-Preservers Associaon (AWPA), Standard method
for laboratory evaluaon to determine resistance to subterra-
nean termites, 1997, P 15-17.
Can, A., & Sivrikaya, H. (2016). Dimensional stabilizaon of wood
treated with tall oil dissolved in dierent solvents. Maderas,
Ciencia y tecnología 18(2): 317 – 324.
Chokouadeu Youmssi, D. V., Modtegue Bampel, Y. D., Njankouo, J. M.,
Saha Tchinda, J.-B., Ndikontar Kor, M. (2017). Chemical compo-
sion of some plantaon wood species (Eucalyptus saligna, Cu-
pressus lusitanica and Eucalyptus paniculata) and assessment
of compability with plaster. J Indian Acad Wood Sci 14(2):146–
153. DOI: hps://doi.org/10.1007/s13196-017-0200-3
Dev, I., Nauyal, S. N. (2004). An eco-friendly wood preservave for-
mulaon (CRCNSL). Journal of Timber Development Associa-
on of India, 50 (1-2): 19–25.
Dhyani, S., Tripathi, S., & Indra, D. (2004). Preliminary screening of
Neem (Azadirachta indica) leaf extracves against Poria mon-
colada wood destroying fungus. Journal of Indian Academy of
Wood Science, 1-2, 2004, P 103–112.
Fama, R., & Morell, J. J. (2015). Ability of plant-oil to inhibit damp-
wood termites (Zootermopis auguscollis) acvity. Maderas,
Scienca y technologia, 17(3):685-690.
Freeman, M. N., & Mcintyre, C. R. (2008). A comprehensive review of
copper-based preservaves with a focus on new micronized or
dispersed copper systems. Forest Products Journal, 58(11):6-27.

56 Les/Wood, Vol. 69, No. 1, June 2020
Mbitnkeu Fetnga Tchebe, T., Saha Tchinda, J.-B., Ngueteu Kamlo, A., Chimeni Yomeni, D., Cheumani Yona,
A. M., & Ndikontar Kor, M.: Ocena učinkovitos nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zašči lesa pred napadom podzemnega termita
Gilmara, O. M., Cookson, J. L., Christoforo, L. A., Polito, L., Wagner,
L. P., Silva, R. M., Carlito, C. J., & Lahr, R. A. F (2013). Wood
Preservaon Based on Neem Oil: Evaluaon of Fungicidal
and Termicidal Eecveness. Forest Products Journal, 63(5-
6):202-206.
Girish, K., & Shankara, B. S. (2008). Neem-A green Treasure. Electron-
ic Journal of Biology, 4: 97-102.
González, L. F. R., Rosales, C. M., Rocha, G. E. N., Gallegos, I. A. J.,
Moreno, J. R. M., & Karchesy, J. J. (2015). Wood Preservaon
using the Natural Products. Madera y Bosques, 21:63-76.
Himmi, S. K., Tarmadi, D., Ismaya, M., & Yusuf, S. (2013). Bioecacy
performance of Neem –based formulaon on wood protecon
and soil barrier against subterranean termite, Coptotermes ge-
stroi mwasmann (Isoptera: Rhinotermidae). Procedia envi-
ronmental Sciences 17:135-141.
Hingston, J. A., Collins, C. D., Murphy, R. J., & Lester, J. N. (2001).
Leaching of chromated copper arsenate wood preservaves: a
review. Environmental Polluon, 111: P 53-66.
Humar, M., Pohleven, F., & Žlindra, D. (2006). Inuence of water
properes on leaching of copper-based preservaves from
treated wood. Wood Research 51(3): 69-76.
Hyvönen, A., Piltonen, P., & Niinimäki, (2005). Biodegradable sub-
stances in wood protecon, in: d.o.P.a.E. Engineering (Ed.),
University of Oulu.
Kalawate, A. (2013). Evaluaon of Copper Ethanolamine Boron
Based Wood Preservave to Control Wood Destroying Insects.
Molecular Entomology, 4 (2): 6-12.
Machado, G. de O., Cookson, L., Christoforo, A. L., Polito, W. L., Roge-
rio da Silva, M., Calil, C., & Lahr, F. A. R. (2013). Wood Preser-
vaon based on Neem Oil: Evaluaon of fungicidal and termi-
cidal eecveness. Forest Products Journal 6385(6): 202-206.
McMahon, T. F., & Chen, J. (2001). Hazard Idencaon and Toxi-
cology Endpoint Selecon for Inorganic Arsenic and Inorganic
Chromium. FIFRA Scienc Advisory Panel Background Docu-
ment.
Menn, J. J. (1990). USDA interest in Neem research in: Locke, J. C.,
Lawson, R. H. (Eds), Proceedings of a workshop on Neem’s
potenal in pest management program, USDA-ARS, Besville,
MD, PP 1-3, ARS-86.
Muktarul, I., Iekhar, S., Ilias, M. N. G., & Obaidullah, H. (2009). Pro-
tecve anfungal eect of Neem (Azadirachta indica) extracts
on mango (Mangifera indica) and rain tree (Albizia saman)
wood. Internaonal Biodeterioraon & Biodegradaon 63:
241-243.
Naveri, R. H, Tarmian, A., Abdulkhani, A., & Ebrahimi. G. (2017). De-
cay resistance of wood impregnated with monoethanolamine
and sodium bisulte pulping black liquors. Maderas. Ciencia y
tecnología 19(4): 507 - 516, 2017.
NF X41-565 (1998) «Produits de préservaon des bois - Entraîne-
ment par l’eau de composants acfs des produits de préserva-
on à parr des bois traités»
Pankaj, S., Lokeshwar, T., Mukesh, B., & Vishnu, B. (2011). Review on
Neem (Azadirachta indica): thousand problems one soluon.
Internaonal research journal of pharmacy 2: 97-102.
Saheb, D., & Mouhouche, F. (2016). Chemical composion and com-
parave study of inseccidal acvity by contact and vapour of
four essenal oils against Sitophilus oryzae (L.) (Coleoptera:
Curculiopidae). Advances in Environnement Biology, 10: 60-69.
Sen, S., Tascioglu, C., & Tırak, K. (2017). Fixaon, leachability, and de-
cay resistance of wood treated with some commercial extracts
and wood preservave salts. Internaonal Biodeterioraon &
Biodegradaon, 63: 135–141.
Singh, T., & Singh, A. P. (2012). A review on natural products as wood
protectant. Wood Science and Technology (2012) 46:851–870.
Sotannde, O. A., Yager, G. O., Zira, B. D., & Usman, A. (2011). Ter-
micidal Eect of Neem Extracts on the Wood of Khaya sen-
egalensis. Research Journal of Forestry, 5: 128-138.
Subapriya, R., & Nagini, S. (2005). Medicinal properes of Neem
leaves: A review, Current Medicinal Chemistry-An-Cancer
Agents, 5:149-156.
Subbaraman, R. B., & Brucker, B. (2001). Method for using Neem ex-
tracts and derivaves for protecng wood and other cellulosic
composites. United States Patent 6294571.
Syofuna, A., Banana, A. Y., & Nakabonge, G. (2012). Efciency of nat-
ural wood extracves as wood preservaves against termite
aack. Maderas Ciencia y Tecnologia 14(2):155–163.
Thaler, N., Lesar, B., & Humar, M. (2013) performance of copper-eth-
anolamine impregnated scots pine wood during exposure to
terrestrial microorganisms. BioResources 8(3): 3299-3308.
Thaler, N., & Humar, M. (2014). Copper Leaching from Copper-etha-
nolamine treated Wood: Comparison of Field Test Studies and
Laboratory Standard Procedures. BioResources 9(2), 3038-
3051.
Tobia, R. J., Camacho, J. A. M., Augusn, P., & Frederick, R. M. (1994).
Washing studies for PCP and creosote-contaminated soil. Jour-
nal of hazardous materials, 38 (1) : 145-161.
Venmalar, D., &. Nagaveni, H. C. (2005). Evaluaon of copperised ca-
shew nut shell liquid and Neem oil as wood preservaves. IRG/
WP/ 05-30368. The Internaonal Research Group on Wood
Protecon, Stockholm.
Zhang, J., & Kamdem, D. P. (2000). FTIR characterizaon of cop-
per-ethanolamine wood interacon for wood preservaon,
Holzforschung 54 (2000): 119-122.