47
Les/Wood, Vol. 69, No. 1, June 2020
1		 INT R ODUC TION
1  UVOD
Inorganic as well as organic-based preservative 
formulations have long been used to protect wood 
against fungi, termites, and bacteria. The efficacy 
of copper compounds to control the growth of a 
wide range of microorganisms has been success-
UDK 630*845.3
Original scientific article / Izvirni znanstveni članek
Received / Prispelo: 29. 4. 2020
Accepted / Sprejeto: 25. 5. 2020
Vol. 69, No. 1, 47-56
DOI: https://doi.org/10.26614/les-wood.2020.v69n01a04
Abstract / Izvleček
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 Syd-
ney blue gum (Eucalyptus saligna) and Ayous (Triplochiton scleroxylon) against termites. Wood blocks were impreg-
nated 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/m
3
 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.
Keywords: Neem oil, copper, ethanolamine, wood, preservation, leaching, termite
Izvleček: Povpraševanje po za okolje varnih zaščitnih sredstvih za les narašča po vsem svetu. Ta študija je osredoto-
čena na oceno sposobnosti olja semen nima (Azadirachta indica) in baker-etanolaminskega pripravka za zaščito lesa 
evkalipta (Eucalyptus saligna) in sambe (Triplochiton scleroxylon) pred termiti. 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/m
3
. Vezavo zaščitnih sredstev v les smo določili z izpiranjem. Termiticidni 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, termiti
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	EV AL U A TION	OF	NEEM	(AZADIRACHTA INDICA) OIL AND
C OPPER-ETHANOLAMINE	IN	THE	PR O TE C TION	OF	W OOD	A GAINS T
A	SUB TERRANE AN	TERMITE	A T T A CK
OCENA	UČINK O VIT OS TI	NIMO VE GA	OL J A	(AZADIRACHTA INDICA)
TER	B AKER-ET ANOLAMINSKIH	PRIPRA VK O V	PRI	Z AŠČITI	LE S A	PRED
NAP ADOM	POD ZEMNE GA	TERMIT A
Tatiana Mbitnkeu Fetnga Tchebe
1
, Jean-Bosco Saha Tchinda
1
, Alexis Ngueteu Kamlo
2
,
Desiré Chimeni Yomeni
1
, Arnaud Maxime Cheumani Yona
1,3*
, Maurice Ndikontar Kor
1
fully exploited, and copper-based products formu-
lated with the addition of other metal compounds 
such as chromium to help in the fixation of copper 
in wood, and arsenate or boron to extend bioac-
tivity to copper-resistant agents of biodegradation 
(Freeman & Mcintyre, 2008; Hingston et al., 2001). 
Organic-based formulations 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 učinkovitosti nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zaščiti lesa pred napadom podzemnega termita
pentachlorophenol or naphtenates were once also 
widely used for preservation of wood. However, 
these products are now subjected to increasing re-
strictions or even banned in many countries around 
the world due to their potential health hazards 
and adverse environmental effects (the liberation 
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 alternatives with re-
duced environmental impact have been developed 
using nitrogen-based organic mediators such as 
azole or ethanolamine to facilitate the fixation 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 alternative products 
all over the world, natural organic products such as 
plant-extracts from wood or barks, vegetable oils, 
and essential oils have been investigated as alter-
native solutions (Adedeji et al., 2018, Dev & Nau-
tiyal, 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). Fatima and Morell (2015) 
studied the ability of various plant oils (Neem, Eu-
calyptus, jatropha and linseed oils) to inhibit damp 
wood termite (Zootermopsis angusticollis) growth, 
and concluded that most of these affect 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-
continent but is now widespread in Africa and Aus-
tralia, being classified as an invasive species in the 
latter. One special feature of this tree is that almost 
all its parts (leaves, fruits, seed, bark) exhibit bioac-
tivity against insects and fungi (Pankaj et al., 2011) 
and are used for medicinal applications (Subipri-
ya & Nagini, 2005). About 195 insect species have 
been found to show high sensitivity to Neem ex-
tracts, including insects that have become resistant 
to synthetic pesticides (Menn, 1990). Applications 
of Neem extracts for wood preservation are thus 
under investigation. For example, the bioactivity of 
extractives 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 formulations containing 
Azadirachtin extracted from Neem tree with a lignin 
or tannin compound added as a binding agent and 
usable as wood preservatives against termites.
This work reports the ability of Neem oil, 
copper-ethanolamine or a combination of both 
in the protection 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 distribution 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; Fatima & 
Morell, 2015; Himmi et al., 2013; Machado et al., 
2013; Sotannde et al., 2011; Syofuna et al., 2012) 
on the application of Neem oil as a wood preserv-
ative against termites were performed at lower re-
tention 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 
impregnation parameters were set to attain a high-
er oil retention rate.
2		 MA TERIA LS	AND	METH ODS
2		 MA TERIA LI	IN	MET OD E
2.1		 MA TERIAL S
2.1		 MA TERIAL I
Blue gum wood was collected from a local tim-
ber market in Bamenda in the North-West region 
of Cameroon while Ayous was obtained in a local 
timber market in Yaounde in the Central region. 
Sydney blue gum (Eucalyptus saligna) is an exotic 
wood species mainly cultivated 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 purification.

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.: Efficiency evaluation of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protection of wood against a subterranean termite attack
2.2		 W OOD	SP E CIMENS
2.2		 VZ OR CI	LE S A
Wood blocks with the dimensions of (6 x 2 x 2) 
cm
3
 were cut from each wood species and dried in 
the laboratory till 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 till constant mass was 
achieved. The moisture content was 11.9(±0.3)% 
and 11.1(±0.6)% for Sydney blue gum and Ayous, 
respectively.
2.3	IMPRE GNA TION	OF	W OOD	WITH
	 PRE SER V A TIVE	SOL UTIONS
2.3	IMPRE GNA CIJ A	LE S A	Z	RAZT OPINAMI
	 Z AŠČITNIH 	SREDS TEV
Homogeneous preservative solutions were 
prepared and used for impregnation of wood 
blocks under reduced pressure. Neem oil was di-
luted with acetone. The mass ratio of Neem oil 
(NO)/acetone of different solutions was 10:90 (NO 
10%), 30:70 (NO 30%), 50:50 (NO 50%) and 70:30 
(NO 70%). Copper-ethanolamine solution (Cu-EA) 
was prepared using distilled water as a solvent. The 
mass concentrations of copper and ethanolamine 
in the solution were 0.5% copper chloride and 1.4% 
ethanolamine. A combining treatment was carried 
out by impregnation of wood with Cu-EA, drying 
the wood for 24h, and finally a second impregna-
tion with NO 50%. Xylamon® (Syl), a commercial 
product still sold in Cameroon for wood protection, 
was used as a reference. Xylamon is a mixture of 
permethrin or cypermethrin, tebuconazole and 
benzalkonium chloride according to the former cer-
tification CTP-P+ 2002 of CTBA (today FCBA) (CTBA, 
2002). Impregnation process was carried out under 
reduced pressure in a 5 L round bottom flask. Care 
was taken to keep all wood blocks completely im-
mersed in the impregnation solution. Twelve wood 
blocks were used for each impregnation, and the 
impregnation was performed for 30 min using a tap 
water pressure reduction system. Afterwards, any 
excess solution on the surface of the impregnated 
wood samples was mopped up and the mass of the 
sample determined. The retention rate (%) was cal-
culated using Equation 1 (Sen et al., 2009):
(1)
Where (m
1
-m
o
) is the amount of impregnation 
solution retained by the wood in g, C the mass con-
centration of the solution in (%) and V the volume of 
wood block in cm
3
. m
1
 and m
0
 are the wood masses 
after and before impregnation, respectively.
The impregnated wood blocks were air dried 
in the laboratory till constant mass was obtained 
(after two weeks).
2.4	LABORA T OR Y	LE A CHING	EXPERIMENT S
2.4	LABORA T ORIJSKI	POSK USI	IZPIRANJ A
The impregnated wood blocks were divided 
into two groups: the first 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 modification. Wood blocks were in-
troduced in glass containers with 5 to 10 times 
their equivalent volume in distilled water. The 
glass containers were placed on a mixing mechan-
ical table (Edmund Bühler GmbH SM-30) and kept 
under agitation for four cycles of leaching (1h, 2h, 
4h and 8 h). The leaching water was changed after 
each time period. The leached wood blocks were 
air dried till constant mass was achieved (after two 
weeks) and then weighed. The percentage weight 
loss (PWLL) due to leaching was determined by 
Equation 2:
(2)
Where m
1
 and m
0
 are the formal masses of 
wood after and before impregnation respectively, 
and m
2
 the mass of wood after leaching.
2.5		 A C TIVITY	OF	TERMITE S	–	FIELD	TE S T S
2.5		 DEJ A VNOS T	TERMIT O V	–	TERENSKI	POSK US
Termites are highly destructive wood agents 
in many tropical regions, particularly in sub-Saha-
ran Africa. The efficiency of preservative products 
against a subterranean termite was assessed by 
a field 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 učinkovitosti nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zaščiti lesa pred napadom podzemnega termita
After the defined time, wood (or residual 
wood) was collected, cleaned and dried in an oven 
for 72h at 103 °C. Percentage weight losses (PWLT) 
due to termite attack were determined according 
to the equation 3.
(3)
m
0
 and m
3 
are the masses of the wood block 
before and after exposure to termites.
3		 RE SUL T S	AND	DISCUSS ION
3		 RE ZUL T A TI	IN	RAZPRA V A
3.1		 RETENTIO N	RA TE
3.1		 NA VZEM
The retention rates of the different solutions 
are presented in Figure 2. The retention rate gives 
the amount of active preservative substance in-
troduced in a wood block. As expected, Ayous 
showed a greater retention capacity than Syd-
ney blue gum. This difference in behaviour is at-
tributed to the difference in density, as the Syd-
ney blue gum and Ayous apparent densities were 
0.79(±0.06) g/cm
3
 and 0.36(±0.04) g/cm
3
, respec-
tively. Blue gum is thus less porous, and it is more 
difficult for the solution to ingress towards the 
depths of the wood. The results showed that rising 
concentration of Neem oil in the Neem oil-acetone 
mixtures significantly increased the retention rate 
even though the solutions were slightly more vis-
cous at higher Neem oil concentrations. Retention 
of Neem oil varied from 11.0 kg/m
3
 to up to 108.3 
kg/m
3
 under the conditions investigated, and 
these results are consistent with those in the liter-
ature (Can & Sivrikaya, 2016; Naveri et al., 2017). 
It is well recognized that retention depends on the 
concentration of active substances in the solution, 
as well as other parameters such as impregnation 
process and time. An increase in the concentration 
of preservative generally increases the retention 
(Naveri et al., 2017). Can and Sivrikaya (2016) re-
ported that, for impregnation of wood with tall-
oil in similar experimental conditions, the reten-
tion rate followed the same order. A combination 
of copper-ethanolamine and NO 50% showed a 
retention rate (67.0 kg/m
3
 for Sydney blue gum 
and 90.7% for Ayous) closer to that of the solu-
tion NO 50% (69.5 kg/m
3
 for Sydney blue gum and 
Figure 1. Wood blocks in a termitarium (Isoptera: Termitidae)
Slika 1. Leseni preskušanci v termitarju (Isoptera: Termitidae)
( )
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.: Efficiency evaluation of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protection of wood against a subterranean termite attack
88.3% for Ayous). For comparison, the retention 
rates for CCA preservative are around 4kg/m
3
 
for surface applications and around 40 kg/m
3
 for 
underground applications or those in salt water 
(American Wood-Preservers Association, 1997). 
For Alkaline-Copper-Quaternary (ACQ), retention 
is around 2.4 kg/m
3
 for above-ground treatments 
and 6.4 kg/m
3 
for underground wood (American 
Wood-Preservers Association, 2006). It can be 
noticed that the retention rates obtained in this 
study were significantly higher compared to the 
traditional preservative requirements for under-
ground applications of wood.
3.2		 LE A CHING
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-fixed preservatives, 
but also some extractives naturally present in wood. 
The extractive 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 extractive content 
Figure 2. Retention of preservatives 
in wood from the different impregna-
tion solutions. Abbreviations: NO X%: 
Neem Oil-Acetone with X% of Neem 
oil; Cu-EA: copper-ethanolamine for-
mulation, Cu-EA + NO: double treat-
ments with Cu-EA and NO 50%; Syl: 
pure Sylamon® formulation.
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 different preservative solu-
tions.
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 učinkovitosti nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zaščiti 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 penetration and amount of oil in the 
wood. Sydney blue gum, being denser, had less in-
depth impregnation and underwent more leaching. 
The higher oil content in Ayous could also confer to 
this wood a certain hydrophobicity limiting the in-
gress of leaching water. Wood impregnated with oil 
exhibited reduced water absorption, as reported 
in the literature (Can & Sivrikaya, 2016). The PWLL 
decreased for Ayous as retention increased. Cop-
per-ethanolamine was significantly leached from 
the woods. Thaler and Humar (2014) also reported 
a mass reduction 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		 EV AL U A TION	OF	TERMITE	A C TIVITY
3.5		 OCENA	AK TIVNOS TI	TERMIT O V
The percentage weight losses caused by ter-
mite activity (PWLT) after exposure of wood blocks 
to field 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) attack for Syd-
ney blue gum (Eucalyptus saligna) and 
Ayous (Triplochiton scleroxylon) im-
pregnated with different preservative 
solutions.
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) after 
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.: Efficiency evaluation of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protection of wood against a subterranean termite attack
Non-treated wood was completely consumed 
by termites, and thus the PWLTs were 100% for 
both wood species. Neem oil was globally less ef-
ficient in the preservation of wood against the in-
vestigated termites. For Sydney blue gum approxi-
mately 100% of wood was degraded at retentions 
lower than 69.5 kg/m
3
, but a significant reduction 
in PWLT was noticed at the retention of 96.6 kg/
m
3
. Ayous with a retention value of 108.3 kg/m
3
 
showed the most significant resistance to termites. 
Many research reports have been published on 
the efficiency of Neem oil for the preservation of 
wood with different experimental conditions and 
retention 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-
radation) (Ahmed et al., 2020; Fatima & Morell, 
2015; Himmi et al., 2013; Machado et al., 2013). 
Tests performed in field conditions (a graveyard) 
also revealed that wood treated with Neem oil 
was susceptible to termite attack, but the level 
of resistance was better than that seen with un-
treated wood (Adebawo et al., 2015; Sotannde et 
al., 2011). Given the higher retention rates tested 
compared to the values generally used with tra-
ditional commercial products for efficient preser-
vation, it can be concluded that Neem oil could 
not be applied alone for the protection of wood 
against termites.
At the concentration investigated, the treat-
ment of the wood blocks with copper-ethanola-
mine solution was not suitable. Copper is mostly 
a fungicide and has insufficient termiticide or in-
secticide activity. The addition of co-biocides (e.g. 
boron) to copper amine could improve the efficacy 
against termites, as reported by Kalawate (2013), 
who found no damage after 24 months and less 
than 5% average weight loss after 30 months for 
wood impregnated with copper-ethanolamine-bo-
ron formulations and exposed to a subterranean 
termite attack in a field test/graveyard test. Xy-
lamon showed significant activity with Ayous but 
much less with Sydney blue gum. Sydney blue gum 
was surprisingly (according to general perceptions) 
more sensitive to termites than Ayous. A combi-
nation of copper–ethanolamine and Neem oil was 
also tested in this study. The resistance of Sydney 
blue gum was significantly improved by the mixed 
preservatives. Further studies are under consider-
ation to understand the synergetic effects and ex-
plain the results.
The percentage weight losses due to termite 
infestation 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 effect 
of leaching with Ayous was mitigated, 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) after 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 učinkovitosti nimovega olja (Azadirachta indica) ter baker-etanolaminskih
pripravkov pri zaščiti lesa pred napadom podzemnega termita
nolamine followed by Neem oil showed the high-
est resistance to termites after leaching. Leaching 
generally removes part of active preservatives 
introduced in wood and increases wood biodeg-
radation. The significant difference between non-
leached and leached Sydney blue gum treated with 
the combined solutions suggested the loss of syn-
ergy between both preservatives.
4  CONCLUSIONS
4		 Z AKL JUČKI
Neem oil applied as a natural preservative 
showed a low efficiency in the protection of wood 
against termites in the field test. An increase in the 
retention increased the resistance to termite attack. 
Copper-ethanolamine used alone was also less suit-
able in the protection of wood at the experimental 
conditions investigated. A combination of Neem oil 
and copper-ethanolamine showed a promising im-
provement in the protection of wood. A reduction 
of the percentage weight loss due to termite activ-
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 attack after leaching. Fur-
ther research efforts are under consideration to un-
derstand the synergetic effects between these two 
products, increase the fixation of preservatives into 
wood and modulate their leaching.
5		 SU MMAR Y
5		 PO VZETEK
Anorganska in organska zaščitna sredstva so že 
dolgo v uporabi za zaščito lesa pred biološko razgra-
dnjo, ki jo povzročajo glive, termiti in drugi insekti 
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 alternative 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 možnosti 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 tisoč let, ker imajo izvlečki iz njenih lis-
tov, skorje in semen fungicidne, protibakterijske in 
insekticidne lastnosti in se uporabljajo za zdravila. 
Predhodne raziskave o uporabi nimovega olja za zaš-
čito lesa proti termitom so bile izvedene z manjšimi 
navzemi in so pokazale, da olje lahko povzroči smr-
Figure 7. Percentage weight losses 
due to termite activity (PWLT) for Syd-
ney blue gum (Eucalyptus saligna) and 
Ayous (Triplochiton scleroxylon) im-
pregnated with different preservative 
solutions and after leaching.
Slika 7. Izguba mase (%) zaradi ak-
tivnosti 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.: Efficiency evaluation of Neem (Azadirachta indica) oil and copper-ethanolamine
in the protection of wood against a subterranean termite attack
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 zaščiti lesa pred glivami in insekti v dru-
gih regijah. Pripravili smo vzorce lesa dimenzij (6 x 2 
x 2) cm
3
 iz jedrovine obeh lesnih vrst in jih posušili 
v laboratoriju do konstantne mase. Uporabili smo 
štiri 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 destili-
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/m
3
. Navzemi so bili v splošnem 
višji pri impregnaciji sambe, kar pripisujemo manjši 
gostoti 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/m
3
 in 93,5 % izgubo mase 
pri 96,5 kg/m
3
, medtem ko smo pri sambi zabeležili 
7,7 % in 3,5 % izgube mase pri navzemih 88,3 kg/
m
3
 in 108,3 kg/m
3
. Pri raziskanih koncentracijah 
obdelava obeh lesnih vrst z raztopino baker-etano-
lamina ni bila primerna. Rezultati kažejo, da upora-
bljenih zaščitnih sredstev samih ni mogoče upora-
biti za učinkovito zaščito lesa pred termiti. 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 
fiksacijo spojin v lesu, zmanjšali izpiranje in poveča-
li učinkovitost s kombiniranjem z različnimi drugimi 
anorganskimi sredstvi in pripravki naravnega izvora.
A CKNO WLEDGMENT
ZAHVALA
This work was supported by the University of 
Yaoundé 1 and the Ministry of Higher Education 
of Cameroon through the “Programme d’appui à 
la recherche”. The authors are also grateful to the 
Slovenian National Research Agency (ARRS) and 
University of Ljubljana for financial support of the 
project “Silwoodcoat”.
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