1
INVESTIGATORY PROJECT
THE EFFECTIVENESS OF LEMON GRASS (Cymbopogon citratus)
AS NATURAL INSECT REPELLENT
ABSTRACT
Insect repellents are important tools for prevention of insect-borne diseases as well as
painful or uncomfortable insect bites. And one of natural insect repellent is the lemon
grass (Cymbopogon citratus). Determining the effectiveness of lemon grass as insect
repellent is the main goal of the study. Specifically, it intends to apply the Steam
Distillation Technique in obtaining the natural elements and essential oil of lemon grass
such as citral and citronella. Using two candies as observation, one is with extract of
lemon grass and the other is without extract of lemon grass. In fourteen (14) minutes,
one candy that without lemon grass, approach by ants but the candy with lemon grass
is just ignored by ants. The study has found out that lemon grass is an effective and
alternative natural insect repellent. The result of the present study would provide
knowledge and information about lemon grass as insect repellent. Additionally, this
study will produce significant and relevant information for future studies regarding to
insect repellent.
I.
Background of the Study
Insect repellents are important public health tools for the prevention of vector-
borne infectious diseases (Goddard, 2002). Actions to reduce vector-borne diseases
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can result in major health gains and relieve an important constraint on development in
poor regions (Amerasinghe, 2006). And this insect repellents help to prevent and control
the outbreaks of insect-borne diseases such as malaria, lyme disease, dengue fever,
and bubonic plague (Wikipedia, 2011). Technically, an insect repellent is any chemical
or natural, that causes insects or other arthropods to make directed, oriented
movements away from the source of repellent. And lemon grass can use as natural
insect repellent (Helmenstine, 2011).
According to an article of new tech bio, lemon grass is a very popular and used
for medicinal, food and insect repellent products. The lemon grass oils are used in
cosmetics, soaps, perfumes, dyes and odorizes along with thousands of other products.
Lemon grass has thin stems, and the flowers are white, cream or green. It grows around
8 feet in height in some cases with the majority of species tapering off at 4 feet. Lemon
grass is mainly found in tropical Asia in countries such as India, Ceylon, Brazil,
Philippines, Malaysia, Myanmar, Guatemala, Madagascar, Mauritius, New Guinea and
countries in Africa and South America. In the Philippines, it has a local named known as
“tanglad”.
Many repellent products pertaining chemical compound like DEET (N,N-Diethylmeta-toluamide) used as active chemical ingredient in insect repellent, are now turn to
all natural ingredients as more and more negative data is released. Lemon grass is
extremely safe and is listed on the EPA’s GRAS list (generally regarded as safe).
People all over the world have come to rely on the potent insect repellent properties of
lemon grass and utilize it as a personal and area spray.
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II.
Problem of the Study
This study was conducted to answer the following problem:
Will extract of lemon grass is an effective way of natural insect
repellant?
III.
Hypothesis of the Study
If lemon grass will be extracted its natural components, and observe it by applying the
lemon grass over a subject that can easily approach by insects, then if it repel the insect
away, it is to be an effective natural insect repellent.
IV.
Objectives of the Study
A. General Objective:
The general objective of this study is to determine the effectiveness of lemon
grass as natural insect repellent.
B. Specific Objective:
1. To get the time (minutes) using stop watch to observe the time and duration of
the effectiveness lemon grass.
2. To observe the effectiveness of lemon grass using two candies, one candy is
treated with lemon grass and the other candy without lemon grass.
V.
Significance of the Study
The study will be conducted to determine the effectiveness of lemon grass as
natural insect repellent. Extraction of lemon grass is through Steam Distillation
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Technique. The children will benefit the most because knowledge of insect repellent
will enable them to prevent possible disease. Through this study, the knowledge of
parents regarding lemon grass as insect repellent would be increased and
prevention could be done to avoid more serious damage to their children’s health.
VI.
Scope and Limitation
The focus of this study is to determine the effectiveness of lemon grass as
insect repellent. Investigating the performance of these will be described by
observation of two candies. One candy will be treated with lemon grass and another
candy is without lemon grass. The study is performed during Christmas vacation.
The data used in the research is gathered through observation and Steam
Distillation Technique.
VII.
Design of the Study
A. Variable

Independent variables/manipulated variable
1. Ice
2. Water

Dependent variable/responding variable
1. 20 pieces of lemon grass leaves
B. Materials
1. Stainless pot with an integral strainer
2. Curve pot cover
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3. Stainless or steel glass receiving vessel
VIII.
Methodology
A. Collecting of Lemon Grass
About twenty (20) pieces of lemon grass leaves was collected near in the
house of the researcher in a vacant lot. Only green and fresh leaves were collected.
Additionally, this leaves is clean and dry to prevent the other organic substance to
be extract in extraction process. If the lemon grass is wet, let it be air dry first before
doing the extraction process.
Figure 1: Fresh and clean dry lemon grass
B. Procedure
The extraction process will be done through Steam Distillation Technique.
Due to lack of laboratory apparatus, the researcher intends to use an improvised
apparatus. It requires a stainless pot with an integral strainer, a curve pot cover, and
a stainless or steel glass receiving vessel. The Consumables are water, ice, and
lemon grass leaves to be extracted.
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Most essential oils available today are extracted using a steam distillation
process. It is believed by many to be the only way oils should be extracted. This
distillation process really is quite simple as long as this extraction process is closely
monitored, the steam will remain at a temperature that won’t damage the lemon
grass (essential of aromatherapy, 2011).
First, set the pot on the heat source and fill with purified water to level just
below the strainer bottom when it is in place. A strainer will be inserted and fill it with
lemon grass leaves. Clear the space in the center of the strainer to set the receiving
vessel. Position the pot cover on the top in vertically. Make sure that the drip tip is
centered over the receiving vessel. Fill the pot cover as much ice as it can hold. It is
not necessary to add water to the pot cover. Boil it up to 15-30 minutes. Get the
extract of lemon grass in the receiving vessel (Ragan, 2005).
Figure 2: The strainer filled with lemon grass leaves and a receiving vessel.
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(A)
(B)
Figure 3: An improvised set up of Steam Distillation Technique. (A) The researchers actual set up of
steam distillation, where extraction of lemon grass is on-going. (B) Labeled different parts of improvised
set up of steam distillation technique.
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Figure 4: The extracted product from lemon grass.
IX.
Observation
Using two candies as observation, one candy is treated with lemon grass and
the other candy is without lemon grass. Put it in the area were ants are present for
faster observation in both candies. Using stopwatch, get the time that ants will
approach to both candies and observe what candy ants will go to.
X.
Results and Discussion
A.
Observation
As the result, in the observation of two candies, one is with lemon grass
and the other is without lemon grass. After fourteen (14) minutes, the candy
without lemon grass are now approaching by the ants, but the candy with lemon
grass still no ants, because of the lemon grass that repel the ants away.
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(A)
(B)
Figure 5: Observation of two candies after 14 minutes. (A) The candy with lemon grass has no
ants at all. It is because the lemon grass repel the ants. (B) The candy without lemon grass. As
you can see, ants are now approaching to the candy.
B.
Discussion
Lemon grass oil is an essential oil used in deodorants, herbal teas, skin
care products, fragrances, insect repellents, and for aromatherapy (Dutta, 2007).
Lemon grass and closely related species belonging to the genus Cymbopogon
are popular used as insect repellents (Trongtokit, 2005) and various experimental
studies support its use as an insecticide of insect repellant (Girgenti, et al., 2002;
Heimerdinger, et al., 2006; Magesa, et al., 2006; Yaday, et al., 2006; Cloyd, et
al., 2009; Sakulku, et al., 2009). Lemon grass is an important essential oil
yielding plant. The plant yields lemon grass oil of commerce after steam
distillation of its leaves. And this oil used as insect repellent. One of the important
constituent of the oil is citral (3,7-dimethy-2,6-octadienal) (Ghosh, 2005). Citral is
therefore an aroma compound used in perfumery for its citrus effect. Citral is also
used as a flavor and for fortifying lemon oil. It also has strong antimicrobial
qualities (Onawunmi, 1989), and pheromonal effects in insects (Wikipedia, 2011).
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Citral has a toxic effect on the sensory nervous system in insect antennae
(Hapke, 2001) that affect the behavior and physiology of insects. That is why the
candy that has treated by lemon grass can repel the ants because of its citral
content that when the ants smell it using their antennae, it will have a
pheromonal effect to it. And another important constituent of lemon grass oil is
the citronella. Citronella oil is also renowned plant-based insect repellent, and
has been registered for this use in the United States since 1948 (U.S. EPA
Citronella Factsheet, 2007). The United States Environmental Protection Agency
considers oil of citronella as a biopesticide with a non-toxic mode of action (EPA
Citronella Registration Factsheet, 1997). And this biopesticide are naturally
occurring substance that control or directly kill or inactive the insects or pests
especially the mosquito (Wikipedia, 2011). With these two constituents of lemon
grass, it can repel the insects away and protect us from insect bites and vectorborne disease.
XI.
Conclusion
The hypothesis was right. Lemon grass can repel insect away and can be an
effective and alternative way of natural insect repellent.
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XII.
References
A. Journal
Amerasinghe, F. et al., (2002). Ecosystems and Vector-Borne Disease
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Dutta, B.K. (2007). Anticandidial Activity of Some Essential Oils of a Mega
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Heimerdinger, A. et al., (2006). Alcoholic Extract of Lemongrass
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http://chemistry.about.com/cs/howthingswork/a/aa050503a.htm
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http://www.essentials-of-aromatherapy.com/distillation_process.html
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