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Chris Peterson and Joel Coats from the Department of Entomology at Iowa State University, USA, review the history of insect repellents from the 1920s down to recent work on plant-derived repellents.
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154 Pesticide Outlook – August 2001 DOI: 10.1039/b106296b
This journal is © The Royal Society of Chemistry 2001
Insect repellents are an alternative to the use of insecticides.
They may be applied to the skin to protect an individual
from the bites of mosquitoes, mites, ticks and lice or, less
commonly, may be used to exclude insects from an area,
such as in packaging to prevent infestation of stored
products. In our opinion, these latter uses are under-
exploited at the current time. With increasing problems of
insecticide resistance and increasing public concerns
regarding pesticide safety, new, safer active ingredients are
becoming necessary to replace existing compounds on the
market. Furthermore, the use of repellents in an integrated
pest management program has been ignored to a large
extent. This article comprises a review of insect repellents,
followed by some new research conducted in our laboratory
on plant-derived insect repellents. Much of the current work
is condensed from Peterson (2001).
History of insect repellents
The use of insect repellent compounds dates back to
antiquity, when various plant oils, smokes, tars, etc. were
used to displace or kill insects. Before the Second World
War, there were only four principal repellents: oil of
citronella, sometimes used as a hair dressing for head lice,
dimethyl phthalate, discovered in 1929, Indalone
, which
was patented in 1937 and Rutgers 612, which became
available in 1939. At the outbreak of World War II, the
latter three components were combined into a formulation
for use by the military known as 6-2-2; six parts dimethyl
phthalate, two parts Indalone and two parts Rutgers 612.
Other military repellent formulae for use on clothing were
developed during the war, but they all failed to provide
desired protection of military personnel deployed around
the world. As a result, by 1956 the United States
government had screened over 20,000 potential mosquito
repellent compounds. In 1953, the insect repellent properties
of N,N-diethyl-m-toluamide (DEET, Figure 1) were
discovered and the first DEET product was introduced in
1956. DEET is still the most widely used mosquito repellent.
It has generally been regarded as safe, but toxic effects have
been recorded, including encephalopathy in children,
urticaria syndrome, anaphylaxis, hypotension and decreased
heart rate.
Several other compounds have been evaluated for
repellent activity, but none have had the commercial success
of DEET. For example, N,N-diethylphenyl acetamide
(DEPA) is licensed for use as a cockroach repellent in India
(Prakash et al., 1990) and Colgate-Palmolive has released in
Europe a cockroach repellent floor cleaner, Ajax Expel
, the
active ingredient of which is N-methyl neodecanamide. This
product has been shown to cause cockroaches to leave their
harborages and cockroaches are less likely to re-infest
previously occupied areas after treatment with the cleaner
(Brenner et al., 1998). Bayer AG plans to market a mosquito
repellent with the name BayRepel
, the active ingredient of
which is 1-piperidinecarboxylic acid, 2-(2-hydroxyethyl)-1-
methylpropylester (KBR 3023) (Yap et al., 2000). Active
ingredients for some insect repellents are shown in Figure 1.
Insect repellents of natural origin
Natural ingredients are included in some formulations of
insect repellents. Of 65 formulations of non-US-produced
insect repellents, 33 contained DEET and the remainder
contained natural oils (Schreck and Leonhardt, 1991). Of
901 substances (872 synthetics and 29 botanical oils) tested
Chris Peterson and Joel Coats from the Department of Entomology at Iowa State University, USA, review the
history of insect repellents from the 1920s down to recent work on plant-derived repellents
This is journal paper J-19451 of the Iowa Agriculture and Home
Economics Experimental Station, Iowa State University, Ames, Iowa
50011, USA.
Figure 1. Structures of several insect repellents.
for repellency to four species of domiciliary cockroaches by
the US Department of Agriculture (USDA) between 1953
and 1974, 127 repelled 94% or more of the German
cockroaches, 61 repelled 100% and 13 repelled 100% of all
four species tested. None of those 13 was a botanical
extract, but many were analogs of natural products. 1,4-
Naphthoquinone has many substituted forms that occur in
nature (such as vitamin K). Klun et al. (2000) found that
Anopheles mosquitoes were differentially repelled by
isomers of some piperidines.
In the United States, citronella is a popular botanical
ingredient in insect repellent formulations. Candles and
incense containing oil of citronella are sold as insect
repellents. The insecticidal properties of this oil were
discovered in 1901, and it was used for a time as a hair
dressing for the control of fleas and lice. Few studies have
been undertaken to evaluate the efficacy of such products.
Despite popular conception, Lindsay et al. (1996) reported
that citronella candles or incense were ineffective for
reducing the biting pressure of mosquitoes. It was found
that burning an unscented candle had the same effects on
reducing the biting rate of mosquitoes in the field as a
citronella candle.
Three commercial products were recently evaluated for
repellency in a laboratory olfactometer against Aedes
aegypti. Buzz Away
(containing citronella, cedarwood,
eucalyptus and lemongrass oils), Green Ban
citronella, cajuput, lavender, safrole-free sassafras,
peppermint and bergaptene-free bergamot oils) and Skin-So-
Soft (containing various “oils and stearates”) failed to cause
any repellency in the olfactometer, though DEET formula-
tions were effective (Chou et al., 1997).
Neem oil, from Azadirachta indica, when formulated as
2% in coconut oil, provided complete protection (i.e. no
confirmed bites) for 12 hours from Anopheles mosquitoes
(Sharma et al., 1993). A neem extract proprietary product,
AG1000, has been shown to be repellent to the biting midge
Culicoides imicola, which can spread cattle diseases
(Braverman et al., 1999).
Quwenling, a popular Eucalyptus-based repellent
product, contains a mixture of p-menthane-3,8-diol (PMD),
isopulegone and citronellol. Quwenling has largely replaced
dimethyl phthalate as the insect repellent of choice in China
(Trigg, 1996). Eucalyptus oil itself, the principal ingredient
of which is PMD, provided protection comparable to DEET
in repelling Anopheles mosquitoes in field studies (Trigg,
1996). Although repellent to Culicoides impunctatus,
Eucalyptus oil was attractive to C. imicola (Braverman et
al., 1999).
A common practice is to place red cedar blocks or sachets
in closets to repel clothing moths. This is probably why
many hope chests are made of red cedar for protection of
heirloom clothing. Milled red cedar flake boards were found
to be repellent to the German cockroach, but not to
American or brown-banded cockroaches (Appel and Mack,
Insect repellent mode of action
In many cases, it has been found that behavior that can be
labelled as repellency may be the result of any number of
physiological or biochemical events. Mosquito repellency
caused by DEET is thought to be due to the blocking of
lactic acid receptors, abolishing upwind flight, resulting in
the insect “losing” the host (Davis and Sokolove, 1976).
Oleic and linoleic acids have been indicated in death
recognition and death aversion (repellency) in cockroaches,
and the term “necromone” has been proposed to describe a
compound responsible for this type of behavior (Rollo et al.,
Lactic acid is present in warm-blooded animal body odor
and sweat, and is attractive to female mosquitoes. In
behavioral studies lactic acid is essential to attraction of
Aedes aegypti, but lactic acid by itself is only mildly
attractive, indicating synergism with other unidentified
human odor components (Geier et al., 1996). Further
evidence for the role of lactic acid in host seeking comes
from studies examining mosquito physiology following a
blood meal. Host-seeking behavior in Aedes aegypti stops
after taking a blood meal. It has been found that following a
blood meal, the sensitivity of lactic acid sensitive neurons
drops, and this drop is co-incident with the cessation of
host-seeking behavior. Lactic acid sensitivity returns to
normal after oviposition (Davis, 1984). This serves to
support the hypothesis that host seeking behavior may be
modified by affecting the lactic acid receptor mechanisms of
a mosquito.
It is unclear if repellents work by common mechanisms in
different arthropods, and conflicting evidence exists in the
literature. On the one hand, DEET is effective against many
other Diptera of medical importance, as well as
hematophagous Hemiptera, Siphonaptera, Hymenoptera,
Acarina and Gnathobdellidae (an annelid family), suggesting
that DEET operates on a fundamental physiological basis
common to members of the arthropod-annelid evolutionary
line (Rutledge et al., 1978, and references therein). Ticks
detect repellents on the tarsi of the first pair of legs (Haller’s
organ) and insects detect the same substances on the
antennae. These structures are thought to be serially
homologous between the two classes. Furthermore, the
differences in sensitivity to repellents between different
classes, orders and families are differences of degree only; no
fundamental differences in the type of response are observed
(Rutledge et al., 1997). On the other hand, virtually no
sequence homology was found between genes coding for the
olfactory receptors of Drosophila and Caenorhabiditis
elegans (Vosshall et al., 1999). Furthermore, there is not yet
any comparison of olfactory gene sequence among the
various arthropods, and there is no record of the response of
C. elegans to DEET or other arthropod repellents.
Different insects differ in their sensitivity to insect
repellents. Differences are loosely related to the taxonomic
distance between the groups compared. Among mosquitoes,
observed ED
values for DEET differed by as much as 1.75
times between different strains of Aedes aegypti, as much as
3.45 times among species of the same genus (observed in
Anopheles) and as much as 7 times between different
genera. The most sensitive species of Culex, Cx. pipiens, is
6.9 times more sensitive than the most tolerant species of
Anopheles, An. albimanus; An. quadrimaculatus, however,
Pesticide Outlook – August 2001 155
is not significantly more tolerant than Cx. tarsalis.
Differences in sensitivity were stable over several
generations, indicating a genetic, heritable basis of tolerance
(Rutledge et al., 1978). DEET tolerance was found to be
incompletely dominant (Rutledge et al., 1994).
Structure-activity relationships of repellents are unclear,
and little definitive work has been done. Visual examination
of Figure 1 shows that when an insect repellent incorporates
a ring structure, there is often a carbonyl group immediately
removed from the ring. Davis (1985) mentions other sources
that report that an oxygen functional group is necessary for
activity. In one study, patterns of sensitivity were similar
among some chemicals of unrelated structure, but some
differences existed between the sensitivity to compounds of
similar structure. Observed non-correlation of structure
with activity suggests that repellent tolerances may be non-
adaptive; i.e. evolved by random drift of selectively neutral
mutations (Rutledge et al., 1997). Although effective topical
mosquito repellents fall in a range of molecular weights of
150–250 (Taylor et al., 1996), vapor pressure is the only
parameter significantly related to mosquito repellent activity
(Davis, 1985). Partition coefficient, molecular weight,
infrared absorption, viscosity, surface tension, molecular
polarizability, and Hammett substituent constants have all
failed to be correlated to repellent activity (Davis, 1985).
Current research in insect repellents
Over the past several years, our laboratory has conducted
research investigating insect repellents of natural origin.
Insect repellents for protection of humans from biting
arthropods, principally mosquitoes, make up the lion’s share
of insect repellents sold in the United States. As mentioned
earlier, we believe that many applications of insect repellent
technology are under-utilized at this time. The use of
repellent barrier strips to prevent entry of insects into
sensitive areas is a largely untried approach. Pyrethroid
insecticides are sometimes used in this manner, but the acute
toxicity of these compounds to the insects is the principal
mode of action of these compounds. Also, impregnation of
repellents into packaging to prevent insect infestation of
stored or shipped products is also not commonly used. Our
work addresses some of the methods and materials that may
be employed in screening potential new active repellents in
novel applications.
Our work has focussed on insect repellents derived from
two plant species, the Osage orange (hedgeapple) (Maclura
pomifera) and catnip (Nepeta cataria).
Osage orange
The fruit of the osage orange has been utilized as an insect
repellent for many years. Pioneers in the American West
placed the ripe fruit of this tree in cupboards to repel
cockroaches and other insects (Sand, 1991). The scientific
validity of this well-popularized practice has been little
studied. Karr and Coats (1991) found that fragments of
Osage orange fruit, as well as its hexane and methanol
extracts, were significantly repellent to the German
cockroach Blattella germanica. Later research in our
laboratory demonstrated that the dichloromethane extracts
of Osage orange fruit were also repellent to the maize weevil
Sitophilus zeamais. We examined the extracts and found
that they contained two isoflavones, osajin and pomiferin
(Figure 2) (Peterson et al., 2000).
The previous study made no attempt to determine volatile
components of the Osage orange extracts. Volatility is
viewed by many as being essential to repellent activity,
although a compound irritating to the feet of an insect will
cause that insect to spend less time in a treated area. Our
next study employed gas chromatography and mass spectro-
scopy (GC-MS) to identify volatile components of Osage
orange essential oil and test the oil and its constituents in
repellency trials. Numerous sesquiterpenoids were deter-
mined to be present in the oil, and many of them were
repellent to the German cockroach (Figure 3) (Peterson et
al., accepted). To our knowledge, this was the first
examination of volatile components of Osage orange oil.
Because all of the compounds identified are well-known and
some are available from other sources, and because there is
only a small quantity of essential oil in an Osage orange, it
may be more economical to extract active compounds from
other sources. Whether these compounds are synergistically
enhanced in mixture or if the compounds would be effective
singly is currently under investigation.
Catnip has been noted for many years for its intoxicating
effect on cats. Nepetalactone has been isolated as the active
component of catnip, with two isomers being present in the
plant’s essential oil: Z,E (cis, trans) and E,Z (trans, cis), with
Z,E-nepetalactone predominating (Figure 4). Modern
nomenclature denotes the cis, trans isomer as Z,E and the
trans-cis isomer as E,Z. Catnip has folk uses as an insect
repellent, some of which have been confirmed scientifically.
Hot water extracts of catnip deterred flea beetles in one
study, and fresh catnip repelled black ants (Riotte, 1975),
and it was found to be repellent to members of 13 families
of insects (Eisner, 1964).
Nepetalactone is also an important component of the
defensive secretions of the coconut stick insect (Smith et al.,
1979) and the lubber grasshopper (Snook et al., 1993). We
isolated and purified the individual isomers of nepatalactone
and compared their activities to DEET. It was found that the
E,Z- isomer was more active than the Z,E- isomer and
DEET at both concentrations tested (Figure 5) (Peterson et
156 Pesticide Outlook – August 2001
Figure 2. Chemical structures of osajin (R = H) and pomiferin
(R = OH).
al., submitted). The structures of the nepetalactone isomers
(Figure 4) differ only in the orientation of a single chemical
bond. Why this difference results in higher repellency is
unknown. Obviously the E,Z- isomer has greater action
than the Z,E- isomer at some receptor. Very little is known,
however, about the receptors responsible for the repellent
response in cockroaches; it is not known if receptors specific
for repellents even exist. In all likelihood, the receptors
involved are specific for other compounds, and the action of
repellents at these receptors is secondary (such as the
proposed mode of action of DEET mentioned in this article).
Future outlook
Much more work needs to be done before it can confidently
be stated if insect repellents work in integrated pest
management systems. The safety of many of these
compounds still needs to be evaluated and field efficacy
trials are also required. It is hoped that repellent compounds
may be applied at levels lower than those compounds that
are acutely toxic, thereby lowering the pesticide load on the
urban environment, but this hope is purely conjectural at
this point.
The use of repellents by travellers (civilian and military)
may reduce the occurrence of local disease incidences in
temperate areas. In countries such as Kenya, where tourism
is a major source of national income, the use of repellents
can increase the pleasure and comfort of tourists. In military
operations, they may reduce the incidence of illness and
reduce annoyance to personnel, who can then complete their
operations more efficiently. Repellents can therefore be
viewed as a tool with a specific role in protecting people
from insect-borne illnesses. More traditional pest
management operations (larval control treatments for
mosquitoes, poisoned baits for cockroaches etc.) need to be
used in conjunction with repellent technology. Repellents
may have an increasingly important role in eliminating
insects from certain environments (such as schools, hospitals
and food preparation areas), and we believe that natural
products, such as essential oils, could play a major role in
new repellent technology.
Pesticide Outlook – August 2001 157
Figure 3. Repellency of Osage orange constitutents to the
German cockroach.
Figure 4. Structures of nepetalactone isomers from catnip.
Figure 5. Repellency of Z,E- and E,Z-nepetalactone isomers
compared to DEET.
Osage orange (hedgeapple) (left) and catnip (right), two plant species from which insect repellents have been extracted.
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158 Pesticide Outlook – August 2001
... 12,13 The use of insect repellents dates to ancient times, when substances such as plant oils, smokes, and tars were used to kill or repel insects. 14,15 Citronella oil, dimethyl phthalate, Indalone, and Rutgers 612 were the common insect repellents before World War II. 15 However, these products failed to provide the desired protection for military personnel, which led to the screening of 20,000 potential mosquito repellent compounds by the U.S. government and the discovery of N, N-diethyl-m-toluamide (DEET). ...
... 14,15 Citronella oil, dimethyl phthalate, Indalone, and Rutgers 612 were the common insect repellents before World War II. 15 However, these products failed to provide the desired protection for military personnel, which led to the screening of 20,000 potential mosquito repellent compounds by the U.S. government and the discovery of N, N-diethyl-m-toluamide (DEET). 15 DEET was first introduced into the market in 1956 and serves as an effective broad-spectrum insect repellent with a long-lasting effect on mosquitoes, ticks, chiggers, and fleas. ...
... 15 However, these products failed to provide the desired protection for military personnel, which led to the screening of 20,000 potential mosquito repellent compounds by the U.S. government and the discovery of N, N-diethyl-m-toluamide (DEET). 15 DEET was first introduced into the market in 1956 and serves as an effective broad-spectrum insect repellent with a long-lasting effect on mosquitoes, ticks, chiggers, and fleas. 15,16 DEET is available in a variety of formulations, including aerosols, creams, lotions, and sprays, and in concentration ranging from 5% to 100%, although most products contain less than 40%. ...
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Mosquito repellents are important for personal protection against nuisance and potentially infectious mosquito bites. Repellent activity of Australian blue cypress essential oil (EO) and a commercially formulated skin lotion containing blue cypress EO (topical formulation) were compared with 20% DEET (N, N-diethyl-3 toluamide) against mosquitoes under laboratory and field conditions in North Queensland, Australia. On a volunteer’s forearm, 1 mL of candidate material was applied to approximately 600 cm ² of exposed skin. When blue cypress EO was applied at various concentrations (0.5%–10.5%), it did not fully prevent mosquito landing or biting. However, a dose–dependent increase, approaching 80% protection, was observed at high EO concentrations. On the basis of these results, three concentrations (5%, 10%, and 20%) of blue cypress EO were selected for complete protection time (CPT) experiments. Topical formulation (undiluted) was also included in CPT experiments. Although some protection was afforded, mosquito landing/probing were still recorded immediately after application for both blue cypress EO and its topical formulation. Specifically, protection declined for blue cypress EO from 80% to 70% (laboratory) and from 93% to 50% (field) within 1 hour. For topical formulation, protection declined from 85% to 75% in the laboratory and from 63% to 50% in the field. In comparison, DEET maintained a 100% protection throughout the testing period of up to 1 h, and there was no landing/probing observed in volunteers who had applied DEET. To conclude, both blue cypress products provided some protection against mosquito bites, which decreased soon after application.
... belongs to the Laminaceae family and has approximately 300 species with high phenotypic plasticity and it originates from South-West Asia [21][22][23]. Nepeta racemosa Lam. is characterized by a high content of nepetalactone, which are secondary metabolites with a wide range of uses [21][22][23][24]. The beneficial effects can be divided into several categories depending on the bioactivity: the antiseptic, astringent, and antiasthma properties are used in medicine, the antibacterial and preservative properties are put to use in the food industry, the bio-herbicidal and pheromonal properties for aphides abilities are used in plant protection [21][22][23][24][25][26][27]. ...
... Nepeta racemosa Lam. is characterized by a high content of nepetalactone, which are secondary metabolites with a wide range of uses [21][22][23][24]. The beneficial effects can be divided into several categories depending on the bioactivity: the antiseptic, astringent, and antiasthma properties are used in medicine, the antibacterial and preservative properties are put to use in the food industry, the bio-herbicidal and pheromonal properties for aphides abilities are used in plant protection [21][22][23][24][25][26][27]. ...
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In this work, the effects of salt stress on Nepeta racemosa Lam. were studied to analyze the possibility of using it as a potential culture for salinity-affected soils. A total of nine concentrations of salts—NaCl (18, 39, and 60 mg/100 g soil), Na2SO4 (50, 85, and 120 mg/100 g soil), and a mixture (9 g NaCl + 25 g Na2SO4, 19 g NaCl + 43 g Na2SO4, and 30 g NaCl + 60 g Na2SO4/100 g soil)—simulated real salinity conditions. Environmental electron microscopy offered information about the size and distribution of glandular trichomes, which are very important structures that contain bioactive compounds. The chlorophyll pigments, polyphenols, flavonoids, and antioxidant activity were determined based on spectrophotometric protocols. The results have shown a different impact of salinity depending on the salt type, with an increase in bioactive compound concentrations in some cases. The highest polyphenol concentrations were obtained for Na2SO4 variants (47.05 and 46.48 mg GA/g dw for the highest salt concentration in the first and second year, respectively), while the highest flavonoid content was found for the salt mixtures (42.77 and 39.89 mg QE/g dw for the highest concentrations of salt in the first and, respectively, the second year), approximately 100% higher than control. From the Pearson analysis, strong correlations were found between chlorophyll pigments (up to 0.93), antioxidant activity and yield for the first harvest (up to 0.38), and antioxidant activity and flavonoid content for the second harvest (up to 0.95). The results indicate the possibility of growing the studied plants in salt-stress soils, obtaining higher concentrations of bioactive compounds.
... A credible alternative to DEET (N, N-diethyl-m-toluamide) for personal protection against mosquitoes and biting insects is the holy grail for many chemists. Despite five decades of research, no molecule has been discovered that offers the same level of protection against biting mosquitos or skin persistence as DEET (Peterson and Coats, 2001). Citronella, eucalyptus, and cedar wood oils are active ingredients in several personal repellents on the market in the United States; 2-phenethylpropionate, a component of peanut oil, and p-menthane-3,8-diol (derived from a specific type of mint) are also utilised in consumer products. ...
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Pest management is economic and ecological challenge worldwide due to human and environmental hazards caused by majority of the synthetic pesticide chemicals. Identification of novel effective insecticidal compounds is essential to combat increasing resistance rates. Botanical pesticides have long been touted as attractive alternatives to synthetic chemical pesticides for pest management because botanicals reputedly pose little threat to the environment or to human health. Academic interest in plant natural products with insecticidal properties has continued to grow in the past 20 years, while commercialization of new botanical insecticides and market expansion of existing botanicals has lagged considerably behind. Insecticides based on pyrethrum and neem (azadirachtin) continue to be standard bearers in this class of pesticides, but globally, their increased presence is largely a consequence of introduction into new jurisdictions. Insecticides based on plant essential oils are just beginning to emerge as useful plant protectants. Botanicals are likely to remain niche products in many agricultural regions and may have the greatest impact in developing countries in tropical regions where the source plants are readily available and conventional products are both expensive and dangerous to users.
... Most of the plant oils and extracts have a repellent effect against mosquitoes that can last from several minutes to several hours (Maia and Moore, 2011). A 2% formulation of A. indica oil in coconut oil provided complete protection from Anopheles mosquitoes for 12 hours (Peterson and Coats, 2001). Azadirachta indica oil emulsion in water has been proven effective in preventing the breeding of Aedes aegypti, Culex quinquefasciatus, and Anopheles stephensi in tanks, coolers, and swimming pools for a period of three weeks (Dua et al., 2009). ...
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Mosquitoes (Diptera: Culicidae) pose a serious threat to humans worldwide, known to transmit various pathogens that cause infectious diseases and arboviruses, which are viral diseases such as chikungunya, dengue, Rift Valley fever, yellow fever, malaria, elephantiasis, Murray Valley encephalitis, Japanese encephalitis, Saint Louis encephalitis virus, West Nile virus, Eastern equine encephalomyelitis virus, Highlands J virus, Everglades virus, and crosse encephalitis virus. The emergence of widespread insecticide resistance and the potential adverse environmental problems associated with synthetic insecticides have highlighted the need for alternative methods to control the spread of mosquito populations, making it an important research priority. Safe and innovative tools, such as plant-based repellents, have recently been implemented to enhance mosquito management strategies. Plant-based repellents play a crucial role in the development of natural products as alternatives to chemical control methods. Plant extracts and essential oils, which are biodegradable, target-specific, eco-friendly, and have potent effects against mosquitoes, are reviewed in this article. These plant-based repellents offer promising potential for effective mosquito management, providing a safer and environmentally friendly approach to control mosquito populations and reduce the spread of mosquito-borne diseases. Properly formulated and used in combination with other integrated vector management strategies, plant-based repellents can contribute to sustainable and effective mosquito control efforts.
... Therefore, it is now quite simple to locate chemical compounds that exhibit features of repulsion and to employ these compounds as the active components of a product that acts as a repellent. However, the creation of natural active substances requires a significant amount of time and financial investment, which often results in the finished product being more costly than its artificial counterparts [3]. In the most recent few years, in response to a rise in public concern over the safety of several chemical items that were once used as insecticides or insect repellents, several institutions and researchers have begun the creation of natural active components, with a particular focus on plant sources [4] . ...
... Over 3,500 known cockroach species have survived on the earth for more than 300 million years, almost without change. Four of them generally live in human habitations: the American cockroach (Periplaneta americana), the German cockroach (Blattella germanica), the brown-banded cockroach (Supella longipalpa), and the Oriental cockroach (Blatta orientalis) (Peterson & Coats 2001;Tatfeng et al. 2005). The American cockroach, Linnaeus, 1758, in reddish-brown and light-colored edges to the body with about 30 mm, is the largest species of common cockroaches (Mirzayans 1986). ...
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Cockroaches are known as mechanical vectors of some pathogens that can infect humans. The present study aims to rapidly identify Periplaneta americana fungal pathogens from sewer systems of public hospitals in Esfahan using the polymerase chain reaction (PCR) technique. A total of 55 P. americana cockroaches were randomly collected by direct trapping from sewer systems of seven hospitals and screened for fungal infectious agents using standard morphological methods and the PCR sequencing. From the American cockroach, we isolated 62 yeasts and 31 molds from the surface, hemocoel, and digestive tract of P. americana. Based on DNA sequence comparisons and other taxonomic characteristics, they were identified as more than four species of yeast and four species of mold. Yeast species including Pichia kudriavzevii, Candida glabrata, Pichia kluyveri, and Candida viswanathii, and molds such as Aspergillus niger, Penicillium italicum, Mucor plumbeus, and Rhizopus oryzae were isolated repeatedly from the surface, hemocoel, and digestive tract of P. americana. Our results show that the use of a combination of morphological, molecular techniques, and phylogenetic analysis can lead to the identification of pathogenic fungal agents in American cockroaches and also knowledge of fungal pathogens-arthropod host relationships. HIGHLIGHTS Periplaneta americana acts as a potential mechanical vector of medically important fungal pathogens from inside sewer systems to hospitals and conversely.; Pichia kudriavzevii, Candida glabrata, Pichia kluyveri, Candida viswanathii, and molds species such as Aspergillus niger, Penicillium italicum, Mucor plumbeus, and Rhizopus oryzae were isolated from the surface, hemocoel, and digestive tract of P. americana cockroaches.;
... On the other side, chemical repellents as alternatives to insecticides are now playing a significant role in pest control [102,103]. Some terpene-derived chemicals that are both effective and eco-friendly for insect control have been used extensively to interrupt the host-seeking process of the blood-feeding arthropods [104,105]. Harraca et al. [85] tested the olfactory responses of C. lectularius to nearly 30 chemicals including five chemical repellents. Liu et al. [106] conducted a systematic study characterizing the electrophysiological responses of olfactory sensillum in the common bed bug to 52 chemicals reported as repellents for different insects. ...
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The recent decades’ resurgence of bed bugs as a public health concern in industrialized countries has driven an increased interest on new sustainable insecticide-free methods to monitor and control these ectoparasites. Current methods of detection rely mainly on visual inspection or canine scent detection, which are methods that are time-consuming, require experience, are non-specific or require costly mission repetitions. Volatile organic compounds (VOCs) are considered an environmentally friendly alternative and a promising approach for bed bug detection. An overview of the released literature on VOCs, their chemical characteristics and their role in bed bugs’ intra- and inter-species communications allowed us to highlight the identification of 49 VOCs in Cimex lectularius (23 molecules) and C. hemipterus (26), which are emitted by both sexes during diverse compartments including aggregation (46), mating (11), defense (4), etc., and all life stages including exuviae or dead bed bugs as a principal indicator of infestation. The latter has a great importance for application of these semiochemicals in successful detection and control management of bed bugs and to prevent their further dispersion. This approach has the advantage of more reliability compared to conventional detection methods with no need for repeated inspections, household furniture moving or resident rehousing for bed bugs’ VOC detection, which are commonly performed by active or passive sampling with absorbing tubes and analyzed by gas chromatography-based analytical platforms.
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West Nile Virus (WNV) has afflicted different countries around the world, affecting not only humans but also animals such as horses and birds. It is an arbovirus that is transmitted to humans by mosquito bites. Initially, the epidemic was localized to Africa, Asia, Europe, and the Middle East. A recent outbreak of WNV has been currently transpiring in the USA. Our article aims to unriddle this ongoing outbreak in the United States of America (USA) to help annihilate this year-round pitfall infection. As of November 15, 2022, Centers for Disease Control and Prevention (CDC) has reported 913 cases of WNV in humans in the United States of America, out of which 639 (70%) were categorized as neuroinvasive and 274 (30%) were categorized as a non-neuroinvasive disease. Concerned authorities should swiftly act before it reaches to an alarming level, to prevent aggravation of the existing challenges amidst COVID-19 and Monkeypox pandemics in the United States. Decreasing breeding habitats, sustainable surveillance of mosquito larvae, biological and microbial larval control methods (fish and copepods), chemical control methods (larvicides), controlling adult mosquito vector population (hot or cold aerosols), and active practice of community based preventive measures would bring deliverance to the United States from WNV. This brief article discusses the ongoing outbreak of WNV in the USA and also highlights epidemiology and preventive measures related to WNV infection.
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Problems that are often encountered in increasing the production of large chili plants are pests and diseases. Some important pests that generally attack chili plants are armyworms, aphids, fruit flies, and mites. The study aimed to obtain citronella biopesticides that were effective in controlling fruit fly pests on large chili plants, using a randomized block design (RBD) with 5 levels of treatment and 5 repetitions. Biopesticide treatment consisted of citronella ash biopesticide (Ts4), citronella extract (Ts3), citronella oil (Ts2), existing (Ts1), and without biopesticide (Ts0). The results showed that citronella oil biopesticides (Ts2) had better potency than other biopesticides and controls. All citronella biopesticide treatments have low effectiveness against fruit fly pests (<40%). The main weather factor is high-intensity rain which greatly affects the effectiveness of biopesticide in the process of controlling fruit flies. Economically, the application of citronella biopesticides technology and existing biopesticides is beneficial for businesses. The value of income per hectare from large chili farming starts from the highest to the lowest respectively: treatment Ts2 (income Rp. 60,977,000 with a B/C ratio = 2.640), Ts3 (income Rp. 57,852,000 with a B/C ratio = 2.516), Ts1 (income Rp. 57,527,000 with a B/C ratio = 2.504), Ts4 (income Rp. 53,952,000 with a B/C ratio = 2.346) and Ts0 (income Rp. 46,852,000 with a B/C ratio = 2.171). With an average B/C ratio of > 1, it means that the citronella biopesticide technology is feasible to be developed to control fruit fly pests on large chili plants.
Mosquito repellents are important for personal protection against nuisance and potentially infectious mosquito bites. Repellent activity of Australian Blue Cypress (ABC) essential oil and a commercially formulated skin lotion containing ABC oil were compared with 20% DEET and evaluated against mosquitoes under laboratory and field conditions in North Queensland, Australia. Using the arm-in-cage method, the following cumulative doses of ABC oil in ethanol were tested; 0.5%, 1.5%, 3%, 5%, 7.5% and 10.5% against female Aedes aegypti. In the field, 2.5%, 5% and 10% of diluted ethanolic ABC oil were tested using the human landing catch method. We observed a dose-dependent increase in protection with diluted ABC oil approaching 80% at high concentrations. While some protection was afforded, mosquito landing and probing was still recorded immediately after application (laboratory) for both ABC essential oil and skin lotion. Protection declined from 80-70% and 93-50% for 20% ABC oil (laboratory) and 10% ABC oil (highest dose, field), respectively. For the formulated product, protection declined from 85-75% in the laboratory and from 63-50% in the field. To conclude, both ABC essential oil and the formulated skin lotion provided moderate protection against mosquito bites, which decreased soon after application.
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A trial was conducted to assess the repellent properties of three materials and of crude hexane and methanol extracts of the fruit of the osage orange (extracts were tested individually and in combination). Pyrethrins were used as a standard for comparison. Topical toxicity of the osage orange extracts was also examined by applying 0.1, 1.0, 10, or 100 μg of the extracts, dissolved in acetone, to the abdominal venters of adult male cockroaches. The extracts were prepared by shaking 200 g masticated osage orange fruit with 200 ml hexane or methanol for 30 min. The extract and solvent were then filtered through Na2S04. Shaking and filtering were repeated three times. The solvent was evaporated from the resultant extracts via rotary evaporation. To evaluate repellency, a choice-box method was used. The choice box consisted of two clear, plastic chambers (9 × 8.5 × 2 cm), connected via 20 cm of 1-cm-diameter Tygon® tubing. Five adult male cockroaches (2 wk post-molt, wild strain maintained in the laboratory for 5 yr) were placed in each of the two chambers of each choice box for 24 h prior to the start of the experiment. Filter paper (5 cm, Whatman no. 5) bearing small fragments (< 0.5 cm2) of the materials, or treated with the extracts or pyrethrins, was then placed in one randomly chosen chamber of the choice box and untreated filter paper was placed in the other. Treatment concentrations were expressed as parts per million (ppm) based on μg of material added per unit (cm3) of the treated chamber. Treatments were replicated six (for bay leaves, chewing gum, osage orange fruit, and pyrethrins) or seven (for the hexane and methanol extracts) times. Locations of the cockroaches with respect to the treated chambers were then noted at 1, 4, 24, and 48 h following exposure. No food or water was supplied during the experiment and choice boxes were held under 12:12 L:D. Data were expressed as mean % repelled from treated chamber; these data were transformed prior to analysis to arcsin %. Analysis of variance (ANOVA) and Duncan's multiple range test were used to detect and delineate treatment differences.
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The fruit of the osage orange tree, Maclura pomifera (Raf.) Schneid (Moraceae), has long been thought to be repellent to insects. A preliminary study reported here confirmed repellency of fruit extracts to the maize weevil, Sitophilus zeamais Motschulsky. Two isoflavones, osajin and pomiferin, were isolated from the mature fruit of M. pomifera in high purity (≥95%). Testing of purified osajin and pomiferin failed to show repellency. Repellency is likely caused by factors other than isoflavones in the fruit.
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The fruit of the Osage orange tree (Maclura pomifera (Raf.) Schnied.) was extracted by several methods: solid phase microextraction (SPME) volatile trapping of the headspace, solvent extraction with hexane, soxhlet extraction with hexane or methylene chloride and steam distillation. The isolates from each technique were subjected to GC/MS to compare extract components. Ripe and unripe fruits were compared using SPME. Several compounds of terpenoid structure, mostly sesquiterpenoids, were determined as present in the isolates. Among these were elemol/hedycaryol, α-copaene, α-cubebene, δ-cadinene, β-elemene, β-caryophyllene, α-ylangene/valencene, (Z,E)-farnesol and the green volatile hexyl hexanoate. The behavioral response of German cockroaches [Blattella germanica (L.)] to the oil and extracts was examined in a choice arena, and the extracts were found to be repellent. Individual compounds, including the isoflavones osajin and pomiferin, were purchased or isolated and tested directly, and several were found to be repellent to the cockroaches.
Nineteen novel Af-acetyI-2,2-dialkyloxazolidines (2) and Af-acetyl-2-alkyl-4,4-dimethyloxazolidines (3) were synthesized from commercially available carbonyl compounds and ethanolamine or 2-amino-2-methyl-l-propanol. Their bioactivity against laboratory-reared mosquitoes was compared in patch tests to known N-acetyl-2-alkyloxazolidines (1) and N,N-diethyl-m-toluamide (deet insect repellent). Isomeric composition measurements by [13C]NMR spectroscopy favoured the Z rotational isomer for samples of 2 (91-96% Z) and the £rotational isomer for samples of 3 (66-71% £), in agreement with molecular mechanics calculations on rotational isomers of model oxazolidines. Samples of 1 were previously shown to exist in solution mostly as the Z isomer (60-70% Z). Within the optimal molecular weight range for these experimental chemicals, the duration of repellency against Aedes aegypti (L.), Anopheles quadrimaculatus Say and Anopheles albimanus Wiedemann generally followed the order: 1 > 2 > deet > 3. Bioassay data are discussed in relation to the equilibrium populations of rotational isomers for substituted JV-acetyloxazoIidines.
Adults of the lubber grasshopper (Romalea guttata) secrete increased amounts of catechol from their defensive glands when fed diets containing only catnip leaves (Nepeta cataria). Model compound bioassays showed that these insects were able to sequester and biomagnify simple phenols, such as catechol and hydroquinone, in their defense gland secretions. Excessive catechol secretions from caffeic acid-fortified diets indicated metabolic pathways exist to perform efficiently more complex biochemical conversions. Reverse-phase HPLC of methanol extracts of catnip revealed only one major caffeoyl-polyphenol as a possible precursor for the observed elevated catechol secretions, when this plant is fed to lubbers. The compound was shown to be caffeoyltartronic acid (CTA). During analysis of CTA by probe-MS or gas chromatography (of its silylated derivative), CTA decomposed by loss of carbon dioxide to form caffeoylglycolic acid (CGA), making identification by these methods ambiguous. Only fast atom bombardment mass spectrometry (FAB-MS, negative mode) gave a true molecular weight. Groundivy (Glecoma hederacea), a relative of catnip, was also shown to contain CTA. The mung bean (Phaseolus radiatus=Vigna radiata), a species totally unrelated to catnip, is the only other reported plant source of CTA. Catnip leaves were found to contain about twice as much CTA as mung bean leaves.
Catnip (nepetalactone) is closely related chemically to certain cyclopentanoid monoterpenes recently isolated from insects, and it shares with some of these terpenes an ability to repel insects. It is suggested that the adaptive function of catnip is to protect the plants that produce it against phytophagous insects.
Spatial statistical analysis was used to compare and quantify the distribution of German cockroaches among harborages before and after application of a repellent solution to those encompassing at least 85% of the cumulative distribution. Trials consisted of 16 yellow laminated Plexiglas harborages (7.5 by 7.5 cm) in (1.2 by 1.2 m) arenas, and concurrent studies involving 49 harborages in a room 6 by 8 m. Results in arena and room trials were similar. In rooms under a photoperiod or continuous lighting conditions, harborages cumulatively encompassing 89-95% of the population (18 or 19 of 49 harborages) each were treated with a formulation containing 2% n-methyl neodecanamide (MNDA) repellent. All other harborages received an equal volume of water. Subsequent spatial analysis revealed a dramatic shift of 96-98% of the reintroduced cockroach populations to nonrepellent treated harborages; patterns persisted for the duration of the study (28 d (12:12) and 20 days (continuous)). Spatial analysis also was used to quantify the areas of emigration and immigration in experimental rooms resulting from the repellent; 89% of the population was redistributed into harborages occupying 16.7 m2 of the room, leaving 11% of the population in harborages within the remaining 28.5 m2. Only 2-4% of the population remained in the 16.1 m2 that originally contained 89% of the cockroach population. This approach allows researchers to quantify the impact of an intervention that changes distribution rather than survivorship. These studies indicated that this formulation clearly precluded populations from re-establishing in previously inhabited harborages under either lighting condition. Implications of these spatial measuring procedures, and the repellent, to a reduced-risk integrated management strategy are discussed, including the concept of herding cockroaches toward areas strategically baited with toxicants.
Ethanol extracts from the bodies of male or female American cockroaches, Periplaneta americana (L.), repel conspecifics of all ages and sexes from shelters during the photophase. Full repellency is obtained above a dosage of 1.6 cockroach equivalents per shelter. The repellent is endogenously produced, is distributed throughout the bodies of individuals of both sexes, and is effective against at least four other species of cockroaches of diverse phylogenetic relationship, including the German cockroach, Blattella germanica (L.). There was no evidence that the repellent is released by living insects as an alarm pheromone. The active materials (identified elsewhere as unsaturated fatty acids) differ from the proteinaceous dispersion-inducing substance produced by living German cockroaches. There was no evidence that the repellent reported here was released from living cockroaches, even at very high population densities. Cockroaches were repelled, however, by intact and ruptured corpses. The repellent may function as a cue for avoiding areas where other cockroaches have died. A literature review suggests that unsaturated fatty acids may elicit avoidance of dead conspecifics across wide phylogenies of invertebrates.
Repellency and toxicity of milled aromatic eastern red cedar, Juniperus virginiana L., flake board were evaluated against the German cockroach, Blattella germanica (L.) (Dictyoptera: Blattellidae), the American cockroach, Periplaneta americana (L.) (Dictyoptera: Blattidae), and the smokybrown cockroach, Periplaneta fuliginosa (Serville) (Dictyoptera: Blattidae). Cedar flake board was repellent to B. germanica in Ebeling choice-box tests but was not repellent to either P. americana or P. fuliginosa. The degree of repellency forB. germanica increased linearly (P < 0.05) with surface area of cedar in the choice box, but in no case were >63% of the cockroaches repelled. Cedar boards did not cause cockroach mortality in continuous-exposure tests. Cedar flake boards may be useful as a repellent in indoor cockroach integrated pest management.
Nineteen novel N-acetyl-2,2-dialkyloxazolidines (2) and N-acetyl-2-alkyl-4,4-dimethyloxazolidines (3) were synthesized from commercially available carbonyl compounds and ethanolamine or 2-amino-2-methyl-1-propanol. Their bioactivity against laboratory-reared mosquitoes was compared in patch tests to known N-acetyl-2-alkyloxazolidines (1) and N,N-diethyl-m-toluamide (deet insect repellent). Isomeric composition measurements by [13C]NMR spectroscopy favoured the Z rotational isomer for samples of 2 (91–96% Z) and the E rotational isomer for samples of 3 (66–71% E), in agreement with molecular mechanics calculations on rotational isomers of model oxazolidines. Samples of 1 were previously shown to exist in solution mostly as the Z isomer (60–70% Z). Within the optimal molecular weight range for these experimental chemicals, the duration of repellency against Aedes aegypti (L.), Anopheles quadrimaculatus Say and Anopheles albimanus Wiedemann generally followed the order: 1>2>deet>3. Bioassay data are discussed in relation to the equilibrium populations of rotational isomers for substituted N-acetyloxazolidines.