.Insecticidal Neem and Lemon Grass - 1637921960000
.Insecticidal Neem and Lemon Grass - 1637921960000
.Insecticidal Neem and Lemon Grass - 1637921960000
1.0 INTRODUCTION
which mosquito is one of them. Mosquitoes are responsible for the transmission of
diseases such as malaria, Lymphatic filariasis, and dengue fever among others
(WHO, 2017) most especially in the tropical regions of the world. Out of these
sundaicus among others with Anopheles gambiae being the prominent one among
Plasmodium knowlesi are responsible for human malaria (Oddoux et al., 2011) but
P. falciparum and P. vivax are most notorious in terms of the number of cases they
are responsible for (WHO, 2018)They were an estimated 219 million cases of
malaria with 435,000 of them resulting in death in 2017 (WHO, 2018). In order to
stop or reduce the transmission of malaria parasites, there is need to control the
vector population. Several methods such as habitat modification (Jacups et al.,
2011), the use of synthetic chemical insecticides (WHO, 2018). and the use of
control the populations of mosquitoes (WHO, 2018). The major method that have
However, these chemical have been shown to have negative effect in the
to the chemicals, environmental pollution and toxicity to human and other non-
targeted organisms (Mahmood et al., 2015). Hence, there have been clamor by
vector species (Kwenti, 2017). This has led to the focus on developing
insecticides from botanical sources that are safe to use in the environment due
to the fact that they are easily degradable and less toxic to humans and non-
targeted organisms (Kwenti, 2017). Apart from the hazards caused by the use
of established pesticides and insecticides to man and livestock, they are also
very expensive to purchase; therefore, they are no more within the reach of
al., 2015).
Cymbopogon species is a tall, coarse grass with a strong lemon taste. Lemon grass
designates two different species; East Indian Cymbopogn flexuosus (DC.) and
and its leaves 1.9cm wide covered with a whitish bloom (Bashir et al., 2010).
Arabica, Azadirachta indica and Eleusive indica have been commonly used in the
past to control insects in many tropical counties (Bashir et al., 2010). The
essential oils obtained from the leaves and stems of this plant are used as remedy
for several health problems like fever, throat inflammations, ears or eyes a typical
example is the use of the leaves in the Eastern Nigeria to treat various heart
disorders (Laura Salvia et al., 2014). Research by (Moser and Joshi 2013),
indicated that globally the most important use of neem was as an insecticide.
Neem contains several aromatic compounds that can be used to repel insects from
biting humans and animals. Neem oil mixed with coconut oil gave up to 98.03%
conducted in Gujarat, India (Ojewumi and Owolabi 2012). Neem oil also
and Mansonia uniformis. Burning neem oil in a room is also said to repel
(Laura Salvia et al., 2014). Despite decades of malaria control efforts, malaria
continues to be a major worldwide public health issue with 3.3 billion persons at
risk in 106 countries and territories in the tropical and subtropical areas (Laura
Salvia et al., 2014). It is one of the significant reasons for maternal and childhood
morbidity and mortality, including low birth weight, stillbirths, and early infant
mosquitoes known globally, more than 50 species can transmit malaria from the
bite of the infected female Anopheles spp. (Moser and Joshi 2013). Presently,
measure other than vector control is available (Moser and Joshi 2013). Thus,
protection from mosquito bites is one of the best approaches to reduce the disease
incidence.
This situation calls for a re-evaluation of the strategies for effective and
are natural water bodies scattered around most urban areas that can support
mosquito breeding. This makes potential larval habitats numerous and larval
control seems a difficult. Therefore the data on these mosquito species would be
relevant in predicting their public health implications and planning strategies that
would help control diseases associated with these mosquito vectors in an endemic
environment.
1.3 Justification
Female Anopheles mosquitoes are the vectors of human malaria. The use of
pollution and insect. This suggests the need for the development of more potent
research will show the larvicidal activities of selected Nigerian plants species of
Neem and lemon grass leaf extracts against, Anopheles gambiae. Most plants
contain compounds that they use in preventing attack from phytophagous (plant
eating) insects. These chemicals fall into several categories, including repellents,
feeding deterrents, toxins, and growth regulators. Most can be grouped into five
ii. Terpenoids,
iii. Phenolics,
v. Growth regulators
phytophagous insects, many are also effective against mosquitoes and other biting
diagnostics, drug therapy, and vector control measures, the global burden of
high. It is hoped that these findings from this study will promote and improve
recognised in the 1960s and includes the most important vectors of malaria in sub-
falciparum (Yakob, 2021). It is one of the most efficient malaria vectors known.
Scientific classification
Kingdom: Animalia
Phylum: Arthropoda
Class: Insecta
Order: Diptera
Family: Culicidae
Subfamily: Anophelinae
Genus: Anopheles
falciparum malaria endemicity are common in Africa (Hay, 2017). In the Americas
and Asia, sub-tropical regions have predominantly P. vivax malaria, while the
tropical regions have a mix of P. falciparum and P. vivax malaria (Lorenz et al.,
2021). Plasmodium vivax malaria often has milder symptoms but it can stay
dormant for months or even years in patients, which makes it difficult to cure
people and identify carriers (Lorenz et al., 2021). Plasmodium malariae and P.
ovale malaria are less common. The recently described human malaria cases of P.
knowlesi are mostly limited to Malaysia, where they can be common (Mondal et
al., 2016).
vectors (most of these are indicated in Figure 2) (Hay, 2017). There are seven
Europe and the Middle East, there are six primary vectors species (Hay, 2017). In
the case of the Americas the nine dominant Anopheles species (or species
complexes) are An. albitarsis, An. marajoara plus the seven mentioned (Hay,
2017). In Pacific Asia, however, 26 Anopheles species (and species complexes) are
the primary vectors of human malaria which, apart from those mentioned include
An. aconitus, An. balabacensis, An. campestris, An. donaldi, An. koliensis, An.
lesteri, An. letifer, An. leucosphyrus, An. ludlowae, and An. nigerrimus (Hay,
2017).
Among the parasites of the genus Plasmodium four species have been
Plasmodium falciparum
Plasmodium vivax
Plasmodium ovale
Plasmodium malariae
Plasmodium knowlesi
Figure 2: Plasmodium falciparum
Scientific classification
Domain: Eukaryota
Phylum: Apicomplexa
Class: Aconoidasida
Order: Haemosporida
Family: Plasmodiidae
Genus: Plasmodium
hatching the larva passes through a pupal stage to develop into an adult (Figure 3).
The adult female mosquito deposits eggs on water at night (Lorens et al., 2021).
Ovipositing females show a preference for certain types of aquatic habitats which
depends on abiotic and biotic factors. Anopheles gambiae prefer small, sunlight
and transient, and often turbid habitats to lay their eggs (Service, 2012). Anopheles
stephensi and An. culicifacies prefer fresh water over sea water (Lorens et al.,
(Lorens et al., 2021). Anopheles gambiae lay more eggs in water with bacteria and
fewer eggs in water that contains conspecific larvae or contained predators, e.g.,
tadpoles and back swimmers (Kosova and Jonida, 2003). Eggs lie individually on
the water surface and are boat-shaped. Anopheline eggs cannot resist drought
(Peach and Gries, 2016). Anopheles gambiae eggs do not hatch after being exposed
Anopheles gambiae eggs can, therefore, survive and hatch on moist soil (Baylis,
2017). Anopheles larvae are legless. They breath air and feed on particulate matter
water surface and, therefore, spend more or less all of their time at the air-water
interface (Baylis, 2017). Anopheles stephensi larvae prefer shade and can be found
in man-made breeding sites in urban areas and rice fields, and polluted and saline
water habitats in rural areas (Hay, 2017). Anopheles gambiae sensu stricto and An.
Arabiensis.
pupa, and adult or imago. The first three stages—egg, larva, and pupa—are largely
aquatic. Each of the stages typically lasts 5 to 14 days, depending on the species
and the ambient temperature, but there are important exceptions (Kosova and
Jonida, 2003). Mosquitoes living in regions where some seasons are freezing or
waterless spend part of the year in diapause; they delay their development,
typically for months, and carry on with life only when there is enough water or
warmth for their needs. For instance, Wyeomyia larvae typically get frozen into
solid lumps of ice during winter and only complete their development in spring.
The eggs of some species of Aedes remain unharmed in diapause if they dry out,
and hatch later when they are covered by water. Eggs hatch to become larvae,
which grow until they are able to change into pupae. The adult mosquito emerges
from the mature pupa as it floats at the water surface. Bloodsucking mosquitoes,
depending on species, sex, and weather conditions, have potential adult lifespans
ranging from as short as a week to as long as several months. Some species can
2.4.1 Breeding
In most species, adult females lay their eggs in stagnant water: some lay near
the water's edge while others attach their eggs to aquatic plants. Each species
selects the situation of the water into which it lays its eggs and does so according
to its own ecological adaptations. Some breed in lakes, some in temporary puddles.
Some breed in marshes, some in salt-marshes. Among those that breed in salt water
(such as Opifex fuscus), some are equally at home in fresh and salt water up to
because certain ecological preferences keep mosquitoes away from most humans,
whereas other preferences bring them right into houses at night. Some species of
Some specialize in the liquid in pitchers of particular species of pitcher plants, their
larvae feeding on decaying insects that had drowned there or on the associated
bacteria; the genus Wyeomyia provides such examples — the harmless Wyeomyia
smithii breeds only in the pitchers of Sarracenia purpurea (Crans et al., 2013).
phytotelmata are dangerous disease vectors. In nature, they might occupy anything
from a hollow tree trunk to a cupped leaf. Such species typically take readily to
breeding in artificial water containers. Such casual puddles are important breeding
places for some of the most serious disease vectors, such as species of Aedes that
transmit dengue and yellow fever. Some with such breeding habits are
mosquitoes that breed and feed mainly in remote wetlands and salt marshes may
well remain uninfected, and if they do happen to become infected with a relevant
pathogen, might seldom encounter humans to infect, in turn (Crans et al., 2013).
Mosquito habits of oviposition, the ways in which they lay their eggs, vary
considerably between species, and the morphologies of the eggs vary accordingly.
The simplest procedure is that followed by many species of Anopheles; like many
other gracile species of aquatic insects, females just fly over the water, bobbing up
and down to the water surface and dropping eggs more or less singly. The bobbing
behavior occurs among some other aquatic insects as well, for example mayflies
and dragonflies; it is sometimes called "dapping" (Crans et al., 2013). The eggs of
Anopheles species are roughly cigar-shaped and have floats down their sides.
Females of many common species can lay 100–200 eggs during the course of the
adult phase of their life cycles. Even with high egg and intergenerational mortality,
over a period of several weeks, a single successful breeding pair can create a
relatives, the genus Coquillettidia, lay their eggs similarly, but not attached to
plants. Instead, the eggs form layers called "rafts" that float on the water. This is a
common mode of oviposition, and most species of Culex are known for the habit,
which also occurs in some other genera, such as Culiseta and Uranotaenia.
Anopheles eggs may on occasion cluster together on the water, too, but the clusters
do not generally look much like compactly glued rafts of eggs (Marten and Reid
2007).
In species that lay their eggs in rafts, rafts do not form adventitiously; the
female Culex settles carefully on still water with its hind legs crossed, and as it
lays the eggs one by one, it twitches to arrange them into a head-down array that
Aedes females generally drop their eggs singly, much as Anopheles do, but
not as a rule into water. Instead, they lay their eggs on damp mud or other surfaces
near the water's edge. Such an oviposition site commonly is the wall of a cavity
The eggs generally do not hatch until they are flooded, and they may have to
withstand considerable desiccation before that happens (Marten and Reid 2007).
They are not resistant to desiccation straight after oviposition, but must develop to
a suitable degree first. Once they have achieved that, however, they can enter
diapause for several months if they dry out (Marten and Reid 2007). Clutches of
eggs of the majority of mosquito species hatch as soon as possible, and all the eggs
in the clutch hatch at much the same time. In contrast, a batch of Aedes eggs in
diapause tends to hatch irregularly over an extended period of time. This makes it
much more difficult to control such species than those mosquitoes whose larvae
can be killed all together as they hatch. Some Anopheles species do also behave in
such a manner, though not to the same degree of sophistication (Huang et al.,
2006).
human body, in the form of sporozoites during a blood meal. Only a few
sporozoites (10-30) are injected at a time, and they migrate through the skin cells.
Some of the injected sporozoites reach the blood circulation and are rapidly
thousands of newly-formed merozoites in the liver cells, which are then released
into the bloodstream. The merozoites attach to and enter red blood cells and
replicate asexually within them. The red blood cells subsequently rupture and
release the merozoites, which attach to adjacent red blood cells and the asexual
replication cycle is initiated again (Sawada et al., 2017). The sexual stages, male
and female gametocytes, are also produced in the red blood cells. The male and
female gametocytes are taken up by a mosquito whilst feeding. Inside the mosquito
mid-gut, the gametocytes fuse to form a zygote that develops into a motile
ookinete. The ookinete enters the mid-gut epithelium and migrates to the outer
layer of the mid-gut, called the basal lamina. Here, the ookinete transforms into an
oocyst and after several mitotic divisions forms sporozoite buddings which contain
sporozoites. The sporozoites are released into the haemolymph and are transferred
to the salivary glands. These sporozoites are injected into the human skin by an
Anopheles female while blood feeding (Sawada et al., 2017). The development
malaria is limited to areas where the temperature is suitable for the Plasmodium
spp. to complete their development within the life span of the adult mosquito
38 days, which is longer than the adult mosquito life time. However, at 22 - 23 °C
between 0.5 and 2.5 indicates intermediate malaria transmission and <0.5 indicates
control as even a low density of Anopheles can maintain transmission (Peach and
Gries, 2016)). Vectorial capacity is the daily rate at which future inoculations
arise from a currently infective person. It directly depends on the man-biting rate,
(preference for animal blood meals)) and life expectancy of anophelines. Each
species has a different behaviour and, therefore, the vectorial capacity in a certain
area depends on the local Anopheles species. Anopheles gambiae s.s. and An.
funestus are highly anthropophilic and bite indoors. Anopheles arabiensis mostly
bites outdoors and is more opportunistic as it equally feeds on humans and animals
(Hay, 2017). Anopheles stephensi is mainly an urban mosquito but also found in
rural areas where, unlike in urban areas, it has a secondary role in malaria
transmission (Peach and Gries, 2016). One of the reasons for this secondary role is
that An. stephensi is zoophilic. In the urban areas An. stephensi feeds on humans
due to unavailability or low number of animal hosts and, therefore, plays a primary
(Peach and Gries, 2016). It is, therefore, important to understand the distinct
Presently, there are two strategies to control malaria, vector control and drug
prevention of malaria (Djouaka et al., 2011). Vector control aims to reduce vector-
human contact by targeting the larval or adult stage of Anopheles. The use of
larviciding is limited and considered suitable mostly for application in urban and
(President’s Malaria Initiative, 2011; WHO, 2010). Adult mosquito control is the
epidemiological models which predict that targeting adult female mosquitoes is the
most effective way of reducing malaria transmission (WHO, 2010). Adult control
involves indoor residual spraying (IRS), space spraying and insecticide treated bed
nets (ITNs) (Djouaka et al., 2011). The latter include long-lasting treated bed nets
(LLINs) and prevent mosquitoes from biting people. Only chemicals that are
2011). Indoor residual spraying targets female mosquitoes that enter the house and
rests, on the walls and iling, before and/or after a blood meal. The Global Malaria
Eradication Programme (1955 - 1969) was based on the use of IRS against the
Africa and Europe (WHO, 2006). The global eradication programme was halted in
1969 for technical and logistical reasons, leaving much of malaria in Africa
UNICEF and others. This initiative provided the foundation for the launch of the
Roll Back Malaria programme in 1998. With renewed vigour, malaria control was
malaria transmission; however, its effectiveness in areas with stable malaria is not
Insecticide-treated bed nets are more cost effective than IRS and have a high
insecticide-treated bed nets provide better protection than IRS (Oduola et al.,
2012). Nearly 254 million ITNs were distributed in Africa between 2008 and 2010
and a very high percentage (80%), of these available ITNs, is being used (WHO,
epidemics and is, therefore, used only in areas with unstable malaria transmission
the human body ((Oduola et al., 2012). Chloroquine is used for the treatment of P.
(WHO, 2010).
Vector Control
Malaria vector control aims to protect people against infective malaria mosquito
(Anopheles spp.) bites by reducing vector longevity, vector density and/or human-
disease. The two broadly used interventions for vector control are long lasting
insecticide treated bed nets (LLINs) and indoor residual spraying (IRS). Both
LLINs and IRS are directed against adult mosquitoes and involve the use of
(WHOPES) for IRS and among them only pyrethroids are recommended for use on
LLINs ((Oduola et al., 2012). WHO, 2010). These four chemical classes have only
compromises the vector control strategies currently being used in malaria- endemic
resistance mechanisms, the Anopheles spp. most resistant, the area over which
resistance has spread and why resistance emerged. Once all these data have been
Scaling up of IRS and LLINs (required for effective vectors control) puts a
In addition, even when both LLINs and IRS are effective they are limited in
targeting the resistant and/or outdoor. Anopheles population into malaria control
Larval control
Larval control targets the aquatic stages of Anopheles mosquitoes which results in
reduced adult emergence from breeding sites and, therefore, reduced numbers of
and is especially suitable for localities where breeding sites are few and/or fixed
and easy to identify, map and treat ((Oduola et al., 2012). Utzinger, 2001; WHO,
2010). Such areas include include highlands, desert-fringes, urban settings and
areas prone to epidemics. Larval control is also effective in rural areas when
carried out systematically (Oduola et al., 2012). Larval control can complement
resistant and/or exophagic Anopheles populations (Oduola et al., 2012). Over the
last decade the potential of larval control has been increasingly acknowledged on
larval control was carried out with petroleum oils, chemicals and/or environmental
development, petroleum products and chemicals are not suitable for larval control.
Many non-chemical tools for larval control are available but they have rarely been
Azad = Free,
dirakht = Tree,
(Oduola et al., 2012). and in Nigeria called dogoyaro or dogonyaro, (Barstow and
Deepu, 2018) is a tree in the mahogany family Meliaceae. It is one of two species
in the genus Azadirachta, and is native to the Indian subcontinent and most of the
Neem trees also grow on islands in southern Iran. Its fruits and seeds are the source
of neem oil. Neem is an attractive broad-leaved, evergreen tree which can grow up
to 30m tall and 2.5m in girth. Its trunk usually straight is 30-80 cm in diameter. Its
Figure 6: Neem
Scientific Classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Eudicots
Clade: Rosids
Order: Sapindales
Family: Meliaceae
Genus: Azadirachta
Species: A. indica
Description
Neem is a fast-growing tree that can reach a height of 15–20 metres (49–66 ft), and
rarely 35– 40 m (115–131 ft). It is deciduous, shedding many of its leaves during
the dry winter months. The branches are wide and spreading. The fairly dense
crown is roundish and may reach a diameter of 20–25 m (66–82 ft). The neem tree
et al., 2012). The opposite, pinnate leaves are 20–40 cm (8–16 in) long, with 20 to
30 medium to dark green leaflets about 3–8 cm (11⁄4–31⁄4 in) long. The terminal
panicles which are up to 25 cm (10 in) long. The inflorescences, which branch up
to the third degree, bear from 250 to 300 flowers. An individual flower is 5–6 mm
and male flowers exist on the same individual tree. The fruit is a smooth
(glabrous), olive-like drupe which varies in shape from elongate oval to nearly
fruit skin (exocarp) is thin and the bitter-sweet pulp (mesocarp) is yellowish-white
and very fibrous. The mesocarp is 3–5 mm (1⁄8–1⁄4 in) thick. The white, hard inner
shell (endocarp) of the fruit encloses one, rarely two, or three, elongated seeds
Products made from neem trees have been used in the traditional medicine
of India for centuries, (Oduola et al., 2012). but there is insufficient clinical
evidence to indicate any benefits of using neem for medicinal purposes. In adults,
no specific doses have been established, and short-term use of neem appears to be
safe, while long-term use may harm the kidneys or liver; in small children, neem
oil is toxic and can lead to death (YashRoy and Gupta 2000). Neem may also cause
properties and possibly as a good carbon dioxide sink. It is also used for
inhibitor. Animal feed: neem leaves can be occasionally used as forage for
twig.
Malabar grass, is a perennial grass native to India, Sri Lanka, Burma, and
Scientific classification
Kingdom: Plantae
Clade: Tracheophytes
Clade: Angiosperms
Clade: Monocots
Clade: Commelinids
Order: Poales
Family: Poaceae
Subfamily: Panicoideae
Genus: Cymbopogon
American and African continents. Australia and Europe are home to only a few
known by various other colloquial names throughout the world. The members of
the Cymbopogon genus produce volatile oils and thus are also known as aromatic
high citral content of its oil. The redolence of the oil enables its use in soaps,
as well as food industries. It is also the starting material for the manufacture of
Lemon grass contains several bioactive compounds that impart medicinal value to
countries.5 Apart from an overall description of lemon grass, this review article
also highlights its medicinal properties that make it a potent herb for
pharmacognostic applications.
feet in height and 4feet in width. It grows in clusters. It has long, slender, drooping
brightgreen leaves that measures from 1.3-2.5cm in width and 3feet in length.
Leaves are simple with entire margins. Flowers grow on spikes. It has a lengthy
Essential oils are extracted from flowers, herbs, trees and various other plant
associated with aldehydes, alcohols and ketones form the major chemical
component of such essential oils. AH (Zaibunnisa et al., 2013). Apart from being
grass contains 1-2% of essential oil on a dry weight basis.10 Lemon grass oil is
also known as citronella oil. Steam and hydro distillation are the conventional
(MAHD) not only reduces the extraction time but also retains the quality of oil.7
Essential oils are extracted from flowers, herbs, trees and various other plant
associated with aldehydes, alcohols and ketones form the major chemical
component of such essential oils (Adhikari et al., 2013). Apart from being used to
manufacture of perfumes, soaps, cosmetics and detergent, citronella oil also finds
dry weight basis (Desai and Parikh, 2015). Lemon grass oil is also known as
citronella oil. Steam and hydro distillation are the conventional methods of its
extraction. These procedures are however time consuming (Desai and Parikh,
reduces the extraction time but also retains the quality of oil.7 The benefits of
microwave radiation aided oil extraction technique over hydro distillation have
also been reported (Desai and Parikh, 2015). Pressurized liquid extraction using
nitrogen gas, is a novel technique and was found to yield better quality of oil in
extraction of citronella oil with CO2 under high pressure has also been investigated
produces. It has been used to treat fever, cough, elephantiasis flu, leprosy, malaria
and digestive problems among many other illnesses. The use of lemon grass in
Ayurveda is still relevant today due to its therapeutic value. Conventional medicine
has a lot of adverse effects. Therefore plant-based medicine has become a popular
alternative for synthetic medicine. Thus, this herbaceous plant may find many
grass in Indonesia) oil, to bring about a reduction in weight of rats fed with a high
in weight loss. The findings of this study were significant due to the fact that β-
citronellol caused a reduction in body mass without affecting the concentration and
activity of the liver enzymes (Garg et al., 2012). Weight loss is only one of the few
and periodontitis are oral health conditions caused due to dental plaque. Many
reports confirm that these dental caries are risk factors for ischemic stroke and
has been reported. Citronella grass may be used in formulating herbal drugs for
CHAPTER THREE
The study was carried out in the insectary laboratory, University of Abuja,
main campus along Nnamdi Azikiwe Airport Road, FCT, Abuja. The University of
Abuja is situated at lat 9° 32n and long 50°10e with a land mass of 11,824
hectares, Abuja has rich soil for cultivation and enjoys equable climate that is
neither too hot (35° c) none too cold (22°c) all year Round. The neem samples was
collected at Giri, Gwagwalada and the lemon grass was collected at Iddo,
water in an exposed bowl at Gausau, F.C.T. Abuja. The larvae were brought to the
Gwagwalada, Abuja. with enclosed mosquito net and then transferred into a beaker
with clear tap water covered with mosquito net for safety precautions in case of
fast emergence of the larvae into adult mosquito (Kamsuk et al., 2007).
leaves were washed separately with distilled water, shade dried, cut into small
pieces and grinded them then kept in insectary laboratory. The method of Olubiyi
et al., (2013) was employed and modified for preparation. 100 g of the
Cymbopogon flexuosus and Azadirachta indica powdered leaves were weighed and
dissolved in 1000 ml of the solvent and allowed to soak for 72 hours at room
temperature but stirred regularly at every 12 hours. The solvent was mixed with
distilled water. The resultant suspension was filtered into a 1000 ml beaker using
muslin cloth reinforced with Whatsman's No. 1 filter paper (Ohia et al., 2013).
Plate 1: A pictorial view of Neem tree Azadirachta indica
Plate 2: A pictorial view of Lemon grass Cymbopogon flexuosus
3.2 Anti-larval activity of Cymbopogon flexuosus and Azadirachta indica
extracts
mg/L, 80 mg/L, 120 mg/L and 160 mg/L with a set of control containing tap water.
All tested concentrations were replicated four times. The number of dead larvae
were counted and recorded accordingly after 24 hours of exposure. Dead larvae
were those unable of rising to the surface or without the characteristic diving
Data were subjected to analysis of variance and means were separated using
the new Duncan’s multiple range test. The log-Probit model analysis was carried
out on larvicidal bioassay results to assess the 50% lethal concentration (LC50)
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