Potential of citronella oil as rodent repellent measured as aversion to food

Abstract

Repellents act by stimulating the primary or secondary defense mechanisms, causing the food to be rejected. Mature and healthy house rats, Rattus rattus, of both the sexes, were exposed to 5, 10, and 20% citronella oil applied as paint in laboratory pens in choice with no oil. Each concentration was applied through 3 different modes of application (daily, once and alternatively in a week). Repellent effect of oil was assessed by comparing food consumption from treated sides with those of untreated sides. The food consumption was recorded over a period of 4 days. In overall, food consumption was significantly (p≤ 0.05) lower from treatment side compared to the untreated side indicating significant repellent effect of the oil. Repellent effect of oil, however, did not differ significantly between the two sexes. Significant difference in average percent repellent effect between 5 and 10% concentrations was observed when oil was applied daily in both female and male rats with higher effect of treatment at 10%. The studies revealed higher potential of daily application of citronella oil as paint in repelling away rats of both sexes.

Full text

Applied Biological Research
16 (2): 191-198; (2014)
DOI: 10.5958/0974-4517.2014.00010.X
POTENTIAL OF CITRONELLA OIL AS RODENT REPELLENT
MEASURED AS AVERSION TO FOOD
Neena Singla* and Ramandeep Kaur
Department of Zoology, Punjab Agricultural University, Ludhiana 141004, Punjab (India)
*email: neenasingla1@gmail.com
(Received 9 June, 2014; accepted 6 September, 2014)
ABSTRACT
Repellents act by stimulating the primary or secondary defense
mechanisms, causing the food to be rejected. Mature and healthy house
rats, Rattus rattus, of both the sexes, were exposed to 5, 10, and 20%
citronella oil applied as paint in laboratory pens in choice with no oil.
Each concentration was applied through 3 different modes of application
(daily, once and alternatively in a week). Repellent effect of oil was
assessed by comparing food consumption from treated sides with those
of untreated sides. The food consumption was recorded over a period of
4 days. In overall, food consumption was significantly (p≤ 0.05) lower
from treatment side compared to the untreated side indicating significant
repellent effect of the oil. Repellent effect of oil, however, did not differ
significantly between the two sexes. Significant difference in average
percent repellent effect between 5 and 10% concentrations was observed
when oil was applied daily in both female and male rats with higher
effect of treatment at 10%. The studies revealed higher potential of daily
application of citronella oil as paint in repelling away rats of both sexes.
Key words: Citronella oil, food consumption, paint, Rattus rattus,
repellency
INTRODUCTION
Rodents belong to one of the most interesting groups of mammals. The damage and economic
losses caused by rodents in various field crops, horticulture and forestry, poultry farms, rural and
urban dwellings and storage facilities range from 2 to 15% in India (Parshad, 1999; Singla and
Babbar, 2010). Rodents also transmit a number of diseases to humans and animals (Singla et al.,
2008a,b, 2013a, 2014a,b). Several commonly used rodenticides and pesticides present a risk of
primary and secondary poisoning in non-target species. Thus, the development of a repellent capable
of mediating avoidance behaviour through volatile cues is desirable. Plants produce a wide range of
compounds that act as a defense against herbivory. The development and use of locally available
plant products with repellent activity is thus an alternative eco-friendly strategy for rodent control.
Renewed interest in plant-based repellents was generated after the US Environmental
Protection Agency added a rule to the Federal Insecticide, Fungicide, and Rodenticide Act (FIFRA)
in 1986 exempting compounds considered to be minimum risk pesticides (Barnard, 1999).
Substances that cause insects and other animals to move away from the source are called repellents.
All plants produce and store secondary metabolites which are unimportant for primary or energy
metabolism of a plant. Most secondary metabolites interfere with basic molecular targets of animals

Neena Singla and Ramandeep Kaur
192
or microbes and thus provide the plants adequate protection against a multitude of enemies.
Repellents are relatively inexpensive and a practical means of protection against a number of pests,
especially when other control measures are not feasible. Mills and Munich (1942) defined rat
repellents as the substances placed in runways of rats that prevent them from going where they
wish. These may include any object or device or a chemical substance which by touch, sound,
colour, taste or odour will ward off the animal or prevent an animal from feeding or gnawing.
Singla (2005) studied the effect of spiny twigs of Acacia in burrow desertion by rodents.
Botanicals have advantages over broad-spectrum conventional pesticides as they affect only
target pest and closely related organisms, are effective in very small amounts, decompose quickly,
and provide residue-free food and a safe environment to live. When incorporated into IPM
programmes, botanical pesticides greatly decrease the use of conventional pesticides or can be used
in rotation or in combination with other pesticides, potentially lessen the overall quantities applied
and possibly mitigate or delay the resistance development in pest populations (Khater, 2012).
Citronella oil is a volatile oil which is distilled using steam from the greenish blue, lemon-
scented leaves and stem of the plant Cymbopogon spp. and the main constituents are citronellal and
geraniol. Citronella oil is a colourless or light yellow liquid with a characteristic woody, grassy or
lemony odour. The essential oil from C. winterianus has repellent properties (Clay et al., 2005), but
relatively little work has been done on plant-derived repellents compared to other aspects of rodent
control. Singla et al. (2013b, 2014c) studied the potential of eucalyptus oil as repellent against R.
rattus. Singla and Parshad (2005) studied the potential of neem-based product as repellent against
R. rattus. No study has been made on evaluating the potential of citronella oil as repellent against
rodent pests. The present study was carried out to evaluate the potential of citronella oil as repellent
against R. rattus, a predominant rodent pest species.
MATERIALS AND METHODS
The present work was carried out in the Department of Zoology, Punjab Agricultural University
(PAU), Ludhiana (India) during the year 2012-13. Citronella oil was procured from the New Crops
Laboratory, Department of Agronomy, PAU, Ludhiana. The rats (R. rattus) of both sexes were
trapped with the help of multi-catch rat traps from poultry farms in and around the Ludhiana
(India). In laboratory, the rats were acclimatized individually in cages of 36×23×23 cm size for 15-20
days before the start of experiment. Food and water were provided ad libitum. Food consisted of a
mixture of mashed wheat, powdered sugar and groundnut oil (WSO) in 96:2:2 ratio. The metallic
trays were kept under each cage for the collection and disposal of urine and faeces. Animals were
used and maintained as per the guidelines of Institutional Animal Ethics Committee, Guru Angad
Dev Veterinary and Animal Sciences University, Ludhiana (India). After acclimatization, healthy
and mature rats of both sexes were weighed and selected for further studies.
A total of four laboratory pens, each of 252 × 100 × 72 cm size, were used for each
experiment. Each laboratory pen consisted of 3 chambers of equal size. One rat was released in
each chamber. Each chamber in a laboratory pen, on its opposite facing sides, was connected to 2
small nest boxes of 20 × 15 × 15 cm size each by means of holes of 6 cm diameter. Each rat had
free access to both the two nest boxes attached on opposite sides of a chamber. Three different
concentrations of citronella oil i.e., 5, 10 and 20% were tested. These concentrations were prepared
by dissolving citronella oil in isopropyl alcohol. Each concentration was tested on 12 rats (6 of each
sex). Treatment was given in the nest box of one side of a chamber of laboratory pen. Citronella oil
was applied as paint on all the inner sides of the nest box using cotton swab dipped in oil. Rats were
exposed to each concentration of oil through three different modes of application i.e., applied daily
(from monday to thursday), applied once a week (on monday only) and applied alternatively (on
monday, tuesday and thursday). Weighed quantity (20 g) of food i.e., WSO taken in a bowl was

Citronella oil as repellent against rats
193
placed in both the nest boxes of a chamber. Simultaneously 6 rats of either sex were exposed to the
vehicle isopropyl alcohol applied daily in choice with no vehicle. Repellent effect of vehicle was
determined based on consumption of food from treatment and untreated sides of a chamber for 4 days.
The repellent effect of oil was assessed on the basis of food consumption by rat from the food
bowls kept in 2 nest boxes of a chamber in a laboratory pen. Food consumption was recorded daily
after every 24 hr from both treated and untreated sides for 4 days in a week i.e. from tuesday to
friday to determine mean daily food consumption [g 100 g-1 body weight (bw)]. Based on mean
daily food consumption data, percent repellent effect was determined using the formula given
described by Singla et al. (2014c).
The values were determined as mean ± SD. The data on food consumption for 2 sexes, 3
concentrations of oil, 3 modes of applications, 4 days of application, and from treatment and
untreated sides was collected using factorial experiments in completely randomized design.
Analysis was done using general linear model (GLM) in SAS 9.3. All pair wise treatment
comparisons were made using Tukeys’ HSD test at 5% level of significance.
RESULTS AND DISCUSSION
In all, significantly (p<0.05) low consumption of food was noticed from treatment side as compared
to untreated side at all the 3 concentrations and modes of application (Tables 1-3) indicating repellent
effect produced by citronella oil when applied as paint. No significant difference in average percent
repellent effect of all the 3 concentrations of oil was observed between male and female rats at all
the 3 modes of application. The difference in mean daily food consumption by rats from untreated
side (8.62 ± 3.48 g 100 g-1 bw) of a chamber and side treated (7.20 ± 3.17g 100 g-1 bw) with
isopropyl alcohol provd non-significant indicating no repellent effect of the vehicle.
Table 1: Food consumption in response to application of 5% citronella oil as paint by Rattus rattus
Mode of
application
Days of
application
Mean daily food consumption (g 100 g
-
1
bw)
Female rats (n = 6)
(Body wt = 128.33 ± 8.97 g)
Male rats (n = 6)
(Body wt = 148.33 ± 12.13 g)
Treatment side
Untreated side
Treatment side
Untreated side
I
Day 1
14.78
±
2.75
a
16.34
±
4.77
a
8.01
±
4.08
a
12.04
±
2.06
b
Day 2
17.11
±
1.60
a
17.57
±
3.79
a
7.59
±
3.44
a
12.66
±
3.82
b
Day 3
13.68
±
4.05
a
15.89
±
4.46
a
8.70
±
4.08
a
13.66
±
5.41
a
Day 4
10.79
±
3.88
a
13.25
±
5.59
a
11.07
±
2.5
0
a
11.68
±
4.41
a
Average
14.09
±
2.27
A
15.74
±
1.55
A
8.84
±
1.34
A
12.51
±
0.75
B
II
Day 1
6.18
±
3.76
a
10.78
±
6.25
a
5.52
±
3.43
a
8.58
±
4.35
a
Day 2
7.09
±
2.86
a
10.22
±
5.87
a
8.25
±
4.15
a
5.18
±
1.03
a
Day 3
11.11
±
5.01
a
9.62
±
5.50
a
7.18
±
5.36
a
9.76
±
6.90
a
Day 4
8.08
±
3.52
a
5.70
±
7.31
a
6.55
±
1.89
a
4.81
±
3.77
a
Average
8.11
±
1.85
B
9.08
±
1.99
BC
6.87
±
0.99
A
7.08
±
2.13
A
III
Day 1
9.48
±
4.56
a
10.38
±
4.53
a
6.06
±
2.71
a
9.19
±
4.85
a
Day 2
6.89
±
5.72
a
8.96
±
1.77
a
3.37
±
2.21
a
5.77
±
1.12
a
Day 3
5.62
±
2.96
a
6.75
±
3.95
a
3.24
±
3.69
a
7.24
±
3.43
a
Day 4
5.64
±
5.04
a
12.38
±
4.3
b
5.28
±
5.18
a
11.85
±
3.67
b
Average
6.90
±
1.57
B
9
.61
±
2.05
C
4.48
±
1.21
B
8.51±2.27
A
Values are mean ± SD, I = daily, II = once a week, and III = alternatively.
The values with similar superscripts in a column for 4 days of application (a or b) and for average values (A,
B or C) at all the 3 modes of application indicate no significant difference. Values with different superscripts
in a row for each sex for 4 days of application (a-b) and for average values (A–C) at each mode of application
indicate significant difference at p ≤ 0.05.

Neena Singla and Ramandeep Kaur
194
The average mean daily food consumption by male rats was significantly low from treatment
side when 5% oil was applied daily and alternatively (Table 1). However when oil was applied once
a week the mean daily food consumption by male rats was not significantly lower from treatment
side indicating low repellent effect of oil in this mode of application. This may be due to the less
persistence of oil odour which was applied only on day 1 of week. In female rats, however, the
average mean daily food consumption was significantly lower from treatment side when citronella
oil was applied alternatively. No significant difference was seen in average food consumption
between treatment and untreated sides when oil was applied daily or once a week. When oil was
applied once a week, the food consumption significantly varied from treatment side on days 3 and 4
in female rats and on days 2 and 4 in male rats as compared to that observed on untreated side.
In male rats, average percent repellent effect with 5% citronella oil applied once a week was
significantly lower than that observed when the oil was applied alternatively and non-significantly
low when the oil was applied daily (Fig. 1). In female rats, no significant difference was found in
repellent effect among all the 3 modes of application. Apparently the repellent effect was non-
significantly high when oil was applied alternatively in both male (45.62%) and female (32.94%)
rats. At 5% concentration of citronella oil, no significant difference was found in repellent effect
between male and female rats on all the 4 days of application when the oil was applied once a week
and alternatively. However when the oil was applied daily, the repellent effect was significantly
high in male rats (41.2%) from that in female rats (10.29%) on day 2 of application (Table 4).
The average mean daily consumption of food by male rats was significantly (p ≤ 0.05) low
from treatment side when 10% oil was applied daily and alternatively (Table 2), however, when the
oil was applied once a week, the average mean daily food consumption by male rats was non-
significantly low from treatment side indicating low repellent effect of the oil at this mode of
application. At this mode of application, the food consumption was not significantly higher from
the treatment side on days 3 and 4. This may be due to the less persistence of the odour of the oil
which was applied only on day 1 of the week. In female rats, however, the average mean daily
Table 2: Food consumption in response to application of 10% citronella oil as paint by Rattus rattus
Mode of
application Days of
application
Mean daily food consumption (g
100
g
-
1
bw)
Female rats (n = 6)
(Body wt = 130.00 ± 5.77 g)
Male rats (n = 6)
(Body wt = 148.33 ± 10.67 g)
Treatment side
Untreated side
Treatment side
Untreated side
I
Day 1
5.75
±
2.30
a
10.19
±
3.78
b
3.15
±
2.09
a
7.51
±
3.70
b
Day 2
3.14
±
3.95
a
9
.77
±
3.69
b
3.92
±
2.75
a
8.48
±
3.10
b
Day 3
4.33
±
2.65
a
8.78
±
3.15
b
2.30
±
1.30
a
7.85
±
3.35
b
Day 4
2.05
±
1.85
a
12.44
±
1.85
b
4.45
±
2.90
a
7.24
±
2.68
b
Average
3.81
±
1.37
A
10.29
±
1.34
B
3.45
±
0.81
A
7.77
±
0.46
B
II
Day 1
5.34
±
6.94
a
14.55
±
4.31
b
4.57
±
1.38
a
6.80
±
2.01
b
Day 2
6.75
±
3.55
a
9.20
±
2.97
a
5.51
±
2.85
a
7.82
±
1.88
a
Day 3
7.19
±
2.66
a
6.75
±
2.21
a
5.68
±
1.85
a
4.88
±
0.89
a
Day 4
5.18
±
2.57
a
8.45
±
3.84
a
5.41
±
3.36
a
5.31
±
2.49
a
Average
6.11
±
0.
87
A
9.73
±
2.91
AB
5.29
±
0.42
A
6.20
±
1.17
AB
III
Day 1
6.31
±
2.99
a
10.92
±
2.79
b
4.00
±
2.88
a
10.70
±
2.36
b
Day 2
5.84
±
1.60
a
7.89
±
3.03
a
2.85
±
2.23
a
8.78
±
2.47
b
Day 3
6.84
±
4.23
a
6.71
±
2.71
a
3.87
±
1.39
a
7.46
±
3.78
a
Day 4
2.
97
±
2.64
a
6.35
±
2.92
b
5.86
±
3.19
a
6.20
±
3.44
a
Average
5.49
±
1.49
A
7.96
±
1.79
AB
4.14
±
1.08
A
8.28±1.66
B
Values are mean ± SD, I = daily, II = once a week, and III = alternatively. The values with similar
superscripts in a column for 4 days of application (a or b) and for average values (A, B, or C) at all the 3
modes of application indicate no significant difference. Values with different superscripts in a row for each
sex for 4 days of application (a-b) and for average values (A–C) at each mode of application indicate
significant difference at p ≤ 0.05.

Citronella oil as repellent against rats
195
Table 3: Food consumption in response to application of 20% citronella oil as paint by Rattus rattus
Mode of
application Days of
application
Mean daily food consumption (g
100
g
-
1
bw)
Fem
ale rats (n = 6)
(Body wt = 130.00 ± 5.77 g)
Male rats (n = 6)
(Body wt = 131.66 ± 13.43 g)
Treatment side
Untreated side
Treatment side
Untreated side
I
Day 1
5.15
±
3.16
a
10.05
±
2.61
b
3.35
±
2.01
a
7.95
±
2.59
b
Day 2
5.60
±
2.90
a
8.58
±
1.74
a
5.96
±
2.87
a
10.95
±
4.57
a
Day 3
12.63
±
2.56
a
15.09
±
1.87
a
10.96
±
1.09
a
12.21
±
1.54
a
Day 4
3.96
±
3.40
a
10.37
±
2.25
b
4.24
±
1.59
a
8.92
±
2.40
b
Average
6.83
±
3.39
A
11.02
±
2.44
A
6.12
±
2.94
A
10.00
±
1.66
A
II
Day 1
5.2
8
±
1.34
a
12.17
±
2.50
b
7.32
±
1.20
a
13.05
±
4.31
b
Day 2
8.16
±
4.91
a
7.41
±
3.44
a
6.71
±
3.42
a
11.87
±
3.14
b
Day 3
11.30
±
6.00
a
14.31
±
2.10
a
11.80
±
1.10
a
10.84
±
2.43
a
Day 4
5.30
±
3.81
a
11.15
±
5.95
a
8.43
±
3.59
a
7.23
±
2.89
a
Average
7.51
±
2.48
A
11.26
±
2.49
A
8.56
±
1.96
A
10.74
±
2.17
A
III
Day 1
5.94
±
2.97
a
8.30
±
3.86
a
4.00
±
1.26
a
7.73
±
3.26
b
Day 2
4.53
±
2.36
a
7.86
±
2.13
b
3.59
±
1.97
a
7.70
±
2.80
b
Day 3
9.79
±
3.86
a
10.46
±
3.70
a
7.74
±
2.80
a
5.69
±
2.86
a
Day 4
15.52
±
3.22
a
10.57
±
3.03
b
6.81
±
3.32
a
6.84
±
3.32
a
Average
8.94
±
4.25
A
9.29
±
1.22
A
5.53
±
1.77
AB
6.99
±
0.83
B
Values are mean ± SD, I = daily, II = once a week, and III = alternatively.
The values with similar superscripts in a column for four days of application (a or b) and for average
values (A, B, or C) at all the 3 modes of application indicate no significant difference. Values with
different superscripts in a row for each sex for 4 days of application (a-b) and for average values (A–C) at
each mode of application indicate significant difference at p ≤ 0.05.
consumption of food was significantly (p ≤ 0.05) low from treatment side when the citronella oil
was applied daily (Table 2). No significant difference was found in average food consumption
between treatment and untreated sides when the oil was applied once a week and alternatively.
When the oil was applied once a week, the food consumption was non-significantly different from
treatment side on day 3 in female rats and on days 3 and 4 in male rats as compared to that observed
on untreated side. Food consumption by female rats was also non-significantly high from treatment
side on day 3 when the oil was applied alternatively.
In male rats, the average repellent effect with 10% citronella oil applied once a week
(25.25%) was significantly low from that observed when the oil was applied daily (52.88%) or
alternatively (41.62%) [Fig. 1]. In female rats, when the oil was applied once a week, the average
repellent effect was significantly low (38.25%) from that observed when oil was applied daily
(61.4%). The same was non-significantly low from that observed when oil was applied alternatively
(40.77%). At 10% concentration of citronella oil, no significant difference was seen in repellent
effect between male and female rats on the all the 4 days of application when oil was applied once a
week. However, when the oil was applied daily, the repellent effect was significantly high in female
rats (82.41%) than those in male rats (47.99%) on day 4 of application (Table 4). When the oil was
applied once a week, the repellent effect was significantly high in female rats (68.41%) from that in
male rats (30.40%) on day 1 of application. The average mean daily consumption of food by male
and female rats was not significantly different from treatment side at all the three modes of
application of 20% citronella oil (Table 3). When the oil was applied once a week, the food
consumption was not significantly different from treatment side on days 3 and 4 in male rats and on
day 2 in female rats. When oil was applied alternatively, the food consumption was not
significantly different from treatment side on day 3 in male rats and significantly high on day 4 in
female rats. This may again be due to the decreased persistence of the odour of oil with time.
No significant difference was found in average percent repellent effect of 20% citronella oil
in male and female rats at all the three modes of application. Also no significant difference in average

Neena Singla and Ramandeep Kaur
196
Table 4: Percent repellent effect with citronella oil applied as paint using three different
concentrations against Rattus rattus
Mode
of
appli-
cation
Days
of
appli-
cation
Percent repellency
5% 10% 20%
Female rats
(n = 6) Male rats
(n = 6) Female rats
(n = 6) Male rats
(n = 6) Female rats
(n = 6) Male rats
(n = 6)
I
Day 1
15.70±19.22a
37.88±31.71ab
39.15±26.12a 46.04±36.34ab
50.73±21.35a 51.05±33.52a
Day 2
10.29±10.34a
41.20±28.93b
71.81±34.21a 58.02±27.87ab
21.17±36.60a 27.40±23.63a
Day 3
19.88±17.85a
42.16±32.20ab
52.24±19.51a 59.48±33.19ab
16.02±12.78a 11.02±7.52a
Day 4
23.59±23.14a
12.94±9.22ab
82.41±15.71a 47.99±35.39b
56.97±38.92a 52.24±15.10a
Mean
17.36±4.94A 33.54±12.00AB 61.40±16.79A 52.88±5.93A 36.22±17.85A 35.42±17.22A
II
Day 1
39.16±26.89a
40.19±35.85a
68.41±33.19a 30.40±22.51b
54.71±15.02a 36.57±21.03a
Day 2
32.11±32.86a
16.26±23.41a
29.69±27.60bc
31.63±33.77ab
19.15±29.71ab
15.03±17.67b
Day 3
23.77±27.90a
26.17±37.15a
11.39±16.34b 5.86±11.79ab
24.61±34.59ab
4.67±6.97b
Day 4
12.90±22.13a
5.23±7.41a 44.60±23.39ac
33.14±26.26ab
50.32±32.36a 15.33±15.52b
Mean
26.98±9.78A 21.96±12.86A
38.52±20.88B 25.25±11.24B
37.19±15.51A 17.90±11.60A
III
Day 1
17.41±27.93a
32.09±33.58a
43.74±17.46a 58.33±27.83ab
28.60±22.63ac
39.82±10.72a
Day 2
33.50±40.13a
44.61±32.15a
27.75±21.69a 61.75±34.63b
47.54±24.30c 53.37±18.44ac
Day 3
25.56±35.15a
57.84±41.46a
29.87±34.35a 25.81±31.81ab
22.42±29.95ab
5.60±8.56b
Day 4
55.31±33.53a
47.94±36.76a
61.75±23.11a 20.61±19.16b
1.77±2.54b 17.39±33.07ab
Mean
32.94±14.11AB
45.62±9.20B
40.77±13.57AB
41.62±18.54A
25.08±16.33A 29.04±18.66A
Values are mean ± SD, I = daily, II = once a week, and III = alternatively.
The values with similar superscripts in the column for 4 days (a or b) and for average values (A, B, or C) at
each mode of application indicate no significant difference in percent repellency.
Values with different superscripts in a row for 4 days (a-b) and for average values (A–C) at each mode of
application indicate significant difference in percent repellent effect between the 2 sexes at p ≤ 0.05.
-10
0
10
20
30
40
50
60
70
80
90
5% 10% 20% 5% 10% 20%
Female Male
Percent repellency
Daily
Once
Alternatively
A
A
A
B
A
AA
A
AB
AB
A
B
A
B
A
A
A
A
Fig. 1: Average percent repellent effect of citronella oil in Rattus rattus at three different
concentrations and three modes of application in both female and male rats.
repellent effect was found among all the 3 modes of application in both male and female rats (Table
4, Fig. 1). In female rats, repellent effect of 20% citronella oil when applied alternatively was
significantly high on day 2 (47.54%) compared to days 3 and 4. The same was, however,

Citronella oil as repellent against rats
197
significantly low on day 4 (1.77%) compared to days 1 to 3. In male rats, the percent repellency
was significantly high on day 1 (36.57%) from that observed on days 2 to 4 when the 20%
citronella oil was applied once a week. When the oil was applied alternatively, the percent repellent
effect in male rats was found to be significantly low on day 3 (5.60%) of application compared to
days 1 and 2 (Table 4).
Hile (2004) tested the repellent effects of six citronellyl compounds against European
Starlings. Citronella oil has been used for over fifty years both as an insect repellent and an animal
repellent (Koul et al., 2008). The oil of citronella provided 2h of complete repellency against
mosquitoes (Trongtokit et al., 2005; Koul et al., 2008). Insect repellent formu1ations consisting of
oil of citronella, spirits of camphor, oil of tar, oil of pennyroyal and castor oil have been shown to
provide long-lasting protection against insects (Dover, 1930; Skinner and Johnson, 1980). Not
much work has been carried out on potential of citronella oil as repellent against rodent pests.
Singla et al. (2013b; 2014c) have reported potential of daily application of 5 and 10% eucalyptus
oil in repelling away R. rattus of both sexes.
Conclusion: Percent repellent effect was more when the oil was applied daily and alternatively as
compared to when applied once a week indicating low persistence of the repellent effect due to
volatile nature of the oil. The present studies reveal higher potential of daily application of 10%
citronella oil as paint in repelling away R. rattus of both sexes.
Acknowledgments: The authors are thankful to Indian Council of Agricultural Research, New
Delhi, India, for providing financial assistance and Professor and Head of the Department of
Zoology, Punjab Agricultural University, Ludhiana, India, for the facilities provided.
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