Chapter 2

Pesticides Based on Plant Essential Oils:

Phytochemical and Practical Considerations
Murray B. Isman*
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Faculty of Land and Food Systems, University of British Columbia,

Vancouver, British Columbia V6T1Z4, Canada
*E-mail: murray.isman@ubc.ca.

Although plant essential oils have long been recognized

to possess insecticidal and/or insect repellent actions,
commercialization of pesticides based on common plant
essential oils dates back less than two decades. In large
part commercialization of such pesticides in the U.S.A.
was facilitated by exemption of certain oils from regulatory
requirements, but other pesticides based on essential oils are
beginning to reach the marketplace in the European Union,
India and China. Unlike conventional pesticides based on
synthetic chemicals, bioactivity of an essential oil in a pest
insect cannot always be attributable to the major constituent(s);
in some well-documented cases there is internal synergy
among constituents of a particular essential oil, with putatively
non (or less)-toxic constituents facilitating or enhancing the
putatively toxic (active) principles. In addition to chemical
considerations, there are a number of practical considerations
in commercialization of pesticides based on plant essential oils.
These include regulatory requirements and costs thereof (in
some jurisdictions), commodity prices of oils used as active
ingredients, ongoing availability of oils in large volumes,
and chemical consistency of oils. Commercial challenges
for essential oil-based pesticides include stability of active
ingredient oils in storage and transport, residual action of active
ingredients after application, and phytotoxicity on crop and
ornamental plants. These considerations and challenges are
addressed in this chapter.

© 2016 American Chemical Society

Jeliazkov (Zheljazkov) and Cantrell; Medicinal and Aromatic Crops: Production, Phytochemistry, and Utilization
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
 Recent History of Essential Oils as Pesticides
Plant essential oils have a long history of use in the fragrance and flavor
industries. More recently, the rise of their use in aromatherapy has expanded
markets for essential oil producers. And while there has been documented
traditional use of many plants and preparations thereof to repel insects and other
pests, there have been hardly any commercially successful repellents (with the
possible exception of citronella), let alone insecticides, based on plant essential
oils prior to the late 1990s (1, 2).
Commercialization of such pesticides in the United States was greatly
facilitated by recognition of a formerly little-regarded provision of the Federal
Insecticide, Fungicide and Rodenticide Act (FIFRA), namely “List 25b –
Exempted Products”. Items found on the list, mostly food ingredients or food
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additives and all “generally regarded as safe” (GRAS), can be used as active
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ingredients in pesticide formulations and sold without scrutiny and approval by

the Environmental Protection Agency (EPA), saving manufacturers months or
years normally required for review by the regulatory authority, and the millions
of dollars needed to generate toxicological and environmental data supporting
the safe use of such products as pesticides. The list, the exact genesis of which
remains obscure, includes half a dozen plant oils commonly used as flavoring
agents in foods and beverages (3). It is these specific oils and their inclusion
in List 25b that have been exploited to produce a wide range of EPA-exempt
insecticides, fungicides and herbicides used in agriculture, professional pest
control, and consumer (home and garden) markets. EcoSMART Technologies
(USA) set the precedent for this movement with its introduction of insecticides
for pest control professionals in 1998, followed by the introduction of products
for the retail consumer market and agriculture in 2001. The company continues
to be the market leader in essential oil-based pesticides to date.
As pesticides, essential oils enjoy a broad spectrum of action against
arthropods, including pests on crops and ornamental plants, public health pests
and disease vectors, and ectoparasites of farm and companion animals (4). Owing
to their lack of persistence in the environment, they tend to be compatible with
classical biocontrol agents and natural enemies, and generally safe for most
nontarget organisms such as fish and wildlife. Their familiarity to most people
and long history of safe use in humans is also a factor in their favor. Conversely,
they are far less effective than most conventional pesticides, requiring higher
rates of application, and their lack of environmental persistence can necessitate
frequent reapplication in some contexts.

Essential Oils Used in Pesticides and Commercial Pesticides

Containing Essential Oils
FIFRA List 25b includes a dozen plant oils, all of which, excluding soybean
oil, are normally considered essential oils (Table 1). It also includes three specific
compounds, eugenol from clove oil, geraniol from geranium oil, and 2-phenethyl
propionate from peanut oil. Curiously missing from the list is orange oil, a large
volume commodity (as a byproduct of the citrus industry) with a wide range of uses
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 as a cleaning agent and degreaser, and eucalyptus oil, widely used as a flavoring
agent and in medicines. Both are used outside of the U.S. as insecticides (5).

Table 1. Plant Oils on FIFRA List 25b – Exempted Products

Plant oil or derivative Botanical Source(s)a Plant Family
Cedar oil Juniperus spp. Cupressaceae
Cinnamon oil Cinnamomum spp. Lauraceae
Citronella oil Cymbopogon winterianus Poaceae
Clove oil, eugenol Syzygium aromaticum Myrtaceae
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Garlic oil Allium sativum Amaryllidaceae

Geranium oil, geraniol Pelargonium graveolens Geraniaceae
Lemongrass oil Cymbopogon citratus Poaceae
Mint oil Mentha spp. Lamiaceae
Peppermint oil Mentha piperita Lamicaeae
2-phenethyl propionate Arachis hypogaea Fabaceae
Rosemary oil Rosmarinus officinalis Lamiaceae
Soybean oil Glycine max Fabaceae
Thyme oil Thymus vulgaris Lamiaceae
a List 25b includes the common names shown in the lefthand column, but provides no
strict botanical definitions for these. The botanical names shown in the middle column
are representative but not inclusive. For some of these, multiple species are known by a
single common name.

Agricultural insecticides developed by EcoSMART and currently sold

under the EcotrolR and EcotekR brand names contain rosemary and peppermint
oils and geraniol as active ingredients. Consumer insecticides sold under
the EcoSMARTR brand all include rosemary oil, with different products also
containing various mixtures of peppermint, cinnamon, thyme and clove oils and
2-phenethyl propionate. Professional pest control products originally developed
by EcoSMART but now sold under the EssentriaTM brand are mostly based on
rosemary and peppermint oils and 2-phenethyl propionate. TyraTech recently
registered two insecticides in Canada containing thyme oil and wintergreen oil
(methyl salicylate; from Gaultheria species) as active ingredients. Other minor
brands in the U.S. use cedar or geranium oils as active ingredients.
An important exception to these EPA-exempt products is RequiemR, the
first EPA-registered insecticide based on a plant essential oil. This product,
containing an extract from a variety of wormwood (Dysphania [=Chenopodium]
ambrosioides nr. ambrrosioides) was first registered in 2011 by AgraQuest but
is currently marketed by Bayer CropScience. It was approved for use by the
European Commission in 2015.

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 In South Africa, Prev-AMR is an insecticide/fungicide containing 50%
orange oil as an active ingredient; a similar product containing 60% orange oil
is sold in France and the Netherlands under the same brand. In the European
Union, orange oil is one of only two plant oils approved for use as insecticides,
although clove, spearmint, citronella and rape seed oils (and geraniol) are
approved for use as insect repellents. In China there are two registered
insecticides containing eucalyptol (= 1,8-cineole, from Eucalyptus globulus and
related species), five insecticides containing camphor (from camphor wood oil,
Cinnamomum camphora), plus fungicides based on eugenol (from clove oil,
Syzygium aromaticum) and carvacrol (from oregano oil, Origanum sativum).
In India, eucalyptus leaf extract (rich in 1,8-cineole) is approved for use as an
insecticide while in Australia an insecticide/miticide has recently been approved
containing both eucalyptus and tea tree (Melaleuca alternifolia) oils as active
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ingredients. Garlic oil can be found as a major active ingredient in insecticides

in the U.S., Mexico and Colombia (5).

Phytochemical Considerations: Relationships Between

Chemistry of Essential Oils and Toxicity to Insects
Commercial botanical insecticides often state a single natural product as the
active ingredient, when in fact most plant defensive chemistry consists of suites of
natural products derived from a common biosynthetic pathway. Examples include
azadirachtin from neem, Azadirachta indica (azadirachtin and a seies of closely-
related limonoid triterpenes), rotenone from Derris and Lonchocarpus species
(rotenone and a series of related isoflavonoids), and pyrethrum from Tanacetum
cinerariaefolium (pyrethrins and related esters of chyrsanthemic acids) (6). Within
a plant essential oil, the major constituents, monoterpenoids and sesquiterpenoids,
can be more diverse and complex. Many plant essential oils comprise up to 80
or more such compounds. In some common essential oils a single constituent
can dominate, for example eugenol in clove oil (typically ≥ 80% by weight),
cinnamaldehyde in cinnamon oil (≥ 80% by weight), or d-limonene in orange
oil (≥ 90% by weight). In others, two constituents can dominate, for example
menthol and menthone in peppermint oil (together, 65-85% by weight) or thymol
and p-cymene in thyme oil (together 65-80% by weight). In yet other oils, e.g.,
rosemary oil, 3-5 constituents (or more) collectively make up the majority of the
oil by weight. Major constituents of some common essential oils used in pesticides
are shown in Table 2.
It should not be surprising that in the latter situations, attributing insect
toxicity to one or more constituents of an essential oil is anything but
straightforward. In an earlier study we attempted to correlate toxicity of 10
commercial rosemary oils to the cabbage looper (Trichoplusia ni) and the true
armyworm (Pseudaletia unipuncta) with their chemical compositions (7). We
observed slight but significant correlation between two minor constituents
(d-limonene and α-terpineol) and toxicity to the cabbage looper, but no significant
correlations between constituents and toxicity to the armyworm. These results,
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 and earlier results testing rosemary oil constituents against the twospotted
spider mite (Tetranychus urticae) (8) suggested synergistic interactions among
constituents in the oil with respect to toxicity. Other investigators have also
reported this phenomenon (9–11). We later confirmed this ‘internal’ synergy
among essential oil constituents in a study of the toxicity of the essential oil
of Litsea pungens to the cabbage looper (12). More recently we observed in
this same insect that most of the toxicity produced by topical administration of
rosemary oil can be mimicked or reproduced by a simple binary mixture (in their
proportions naturally occurring in the oil) of 1,8-cineole and camphor, two major
constituents of the oil (13) Figure 1. Most recently we provided evidence for the
mechanism underlying the synergistic interaction between these two compounds:
1,8-cineole facilitates the entry of camphor through the insect’s integument into
the bloodstream, where the latter compound is more toxic than the former (14)
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Figure 2. It is conceivable that other examples of such synergy will be found to

be a consequence of enhanced penetration of the putatively toxic constituents by
other constituents that, when tested individually, appear to be themselves inactive.

Table 2. Major Constituents of Some Common Plant Essential Oils

Plant essential oil Major constituent(s) (% by weight)a
Rosemary 1,8-cineole (52), α-pinene (10), camphor (9), β-pinene (8)
Peppermint Menthol (45), menthone (30)
Clove Eugenol (80)
Cinnamon Cinnamaldehyde (85)
Thyme Thymol (58), p-cymene (20), γ-terpinene (8)
Lemongrass Geranial (48), neral (38)
Eucalyptus 1,8-cineole (85)
Orange d-limonene (98)
a unpublished data, Berjé Inc. (Carteret, NJ, U.S.A.) and EcoSafe Natural Products Inc.

(Saanichton, BC, Canada)

Exacerbating this complex relationship between chemical composition of

essential oils and their toxicity to pests is natural chemical variation in composition
of the oils that can be a consequence of genetic, geographic, seasonal, climatic
or other influences. For example, seasonal variation in chemical content and
composition of essential oils has been reported for rosemary grown in southern
Spain (15) and basil (Ocimum basilicum) grown in Pakistan (16). Essential
oil composition of clove oils varied with country of origin (17). Chemical
composition of citronella (Cymbopogon winterianus) varied with time of harvest
after transplantation (18), and with daytime temperature. Temperature was also
found to be the strongest bioclimatic factor influencing chemical composition

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 of rosemary oil in the Balkan Peninsula (19). Even significant diural changes
in chemical composition have been observed in the essential oil of Ocimum
gratissimum growing in Benin (20).
Certain species of essential oil-producing plants exist as distinct chemotypes
or races that can differ markedly in chemical composition (e.g., wormwood,
Artemsia absinthium) (21). To a large extent this variation is managed or
mitigated by major producers of plant essential oils who rely on well established
supply chains starting with plant biomass that is propagated, grown and harvested
consistently following good agricultural practices. Nonetheless essential oils
as pesticides constitute a conundrum for regulatory authorities owing to their
potential chemical variation, the likelihood that toxicity cannot be attributed to
a single, major constituent, and the fact that – at least for use as pesticide active
ingredients – there is no strict chemical definition for a particular essential oil.
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Even the botanical definition of an essential oil can be subject to question; the
taxonomic boundries of some of the most common essential oils remain unclear
or controversial at best. Faced with this dilemma, a regulatory agency could
either recognize a major (and presumably toxic) constituent of the essential oil as
the active ingredient of a pesticide product, or alternatively, recognize the intact
oil itself as the active ingredient, the lack of definition of the oil noted above
notwithstanding.

Figure 1. Toxicity of rosemary oil and its major constituents to 3rd instar cabbage
looper (Trichoplusia ni) via topical administration. Based on data from reference
(14).

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Figure 2. Penetration of topically applied 1,8-cineole and camphor, administered

individually and as a binary mixture, in the cabbage looper, Trichoplusia ni. I =
applied individually; M = applied as a mixture. Data from reference (14).

Practical Considerations
Regulatory Concerns

In the developed world, regulatory approval remains the final, and often
most difficult, barrier to overcome in commercializaing a pesticide. Without such
approval, no product can be sold and no revenue realized. The only obvious
exception to this is the exempt active ingredient status afforded to certain essential
oils in the USA as noted above (Table 1). In other jurisdictions, approval for
essential oil-based pesticides has been problematic because pesticide regulatory
guidelines developed historically to evaluate synthetic pesticides where there is
a single active ingredient with no ambiguity. The EU is only now preparing to
publish criteria for “low risk active substance” that some essential oils may meet,
possibly clearing a path for approval of more pesticidal products based on such
oils (22).
Regulatory approval is based on review of data on product chemistry,
environmental fate, and toxicology to laboratory animals and nontarget organisms
including fish, wildlife and pollinators. Some regulatory agencies require efficacy
data while others do not. For essential oils used as flavoring agents in foods and
beverages, as fragrances in consumer products and cosmetics, and medicinally in
aromatherapy, product chemistry and laboratory animal toxicology are often well
established and documented, although such data is usually considered proprietary
and therefore not freely accessible. Less well documented is the environmental
fate of plant essential oils, although published studies consistently indicate
that these materials are minimally persistent in the environment owing to their
volatility and consequential evaporative loss (23), except in closed containers
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 where fumigation is the goal. Fewer still are investigations of the effects of
plant essential oils on nontarget organisms, although there is some evidence that
they can be used with a margin of safety towards biocontrol agents and fish (24,
25). Essential oils have been evaluated and sometimes used to manage Varroa
devastator, an ectoparasitic mite in honeybee colonies, but within the closed
confines of a hive the margin of safety to bees is rather narrow (26).
Given the widespread use of essential oils in foods, beverages and consumer
products, it is not surprising that most of the commonly used oils have minimal
or low toxicity to lab animals, typically with rat, oral acute LD50 values >2000
mg kg-1. One notably exception is pennyroyal (from the mint Mentha pulegium)
with a rat LD50 of 400 mg kg-1. The major constituent, pulegone, has a rat LD50
of 470 mg kg-1. Most importantly, there are reports that pennyroyal is a potential
abortifacent in humans (27). Among the more common essential oils, carvacrol,
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a major constituent of oregano (Origanum vulgare) oil and a minor constituent

of thyme (Thymus vulgaris) oil, is a strong corrosive and skin sensitizer. A more
thorough review of the toxicology of essential oils can be found elsewhere (28).

Cost and Availability

The agrochemical business is extremely competitive. Even a pesticide with

the least environmental and health impacts, or any other desirable traits, will not
be successful in the marketplace if it is not cost competitive with other pesticide
products available to the user. This is especially the case for pesticides used in
agriculture or by pest control professionals, where volumes used are greater and
costs of application are significant. What makes the material costs of certain
plant essential oils low enough to be attractive for use in pesticides is the large
scale international trade in those oils as commodities for use in the flavoring and
fragrance industries. It is these latter, well established uses and supply chains that
dictate prices; their use in pesticides thus far has been a minor alternative market
for producers that has yet to grow large enough to influence prices.
Prices for the major essential oils tend to be relatively stable owing to these
well developed supply chains. The greatest source of perturbations in price are
occasional crop failures in a principal supply region as a result of abnormal
weather events. On the other hand, some oils have seen a recent trend toward
price reduction as production has moved to geographic regions where land and
labor are less expensive, viz. China, India and Brazil. In contrast, the production
of certain oils remains largely restricted to regions where the source crops were
first successfully cultivated, for example clove and patchouli oils in Indonesia.
Overall it must be said that posted prices for any particular essential oil can vary
widely depending on the quality, source and volume of the oil in question.
Among the least expensive of essential oils is orange oil, in part because the
biomass (fruit peels) used for extraction is effectively a waste product of another,
very large, industry (orange juice), and in part because the oil can be obtained by
cold pressing of the fruit peels rather than via hydrodistillation. Recent commodity
prices for the most highly traded essential oils, including most of those use in
pesticides, are listed elsewhere in this volume (29).

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 Commerical Challenges
Apart from the obvious issues of cost, availability and consistency, there are
a number of challenges for those producing pesticides based on plant essential
oils. The first of these is long term stability of a formulation containing essential
oils, in storage and transport. Typically an agrochemical product is expected
to remain stable for up to two years in storage; short term stability trials at
elevated temperatures (e.g., 50°C for 90 days) attempt to simulate this. Though
relatively stable, some oils are susceptible to oxidation in the absence of any
antioxidants, even though certain oils themselves have been reported to have
antioxidant properties. Given the volatility of many constituents of essential oils,
the packaging material (bottles) used can be a factor in maintaining chemical
consistency and stability of a product containing an essential oil, with the least
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porous and most chemically inert materials preferable.

Another challenge is persistence of an essential oil pesticide, i.e., how long
the product remains biologically active against target pests after application to the
target area. Often the direct insecticidal action of an essential oil-based pesticide
is lost within hours of application, but field trials on horticultural crops suggest
that a single application can provide crop protection for up to three weeks (1).
Presumably this is because residual concentrations of the oils that are too low to
kill insects are sufficient to deter/repel pests for a much longer period of time.
Laboratory studies on the behavioral effects of essential oils in insects provide
some evidence for this, but direct observations of behavioral effects on pests in the
field are lacking. Nonetheless it is desirable to extend the residual life of essential
oil-based pesticides, at least in outdoor contexts where efficacy is clearly not based
on fumigant activity. Recent advances in pesticide formulation, especially the
use of microencapsulation and nanoformulation, appear to provide avenues to
solve this problem, possibly extending the residual activity of essential oil-based
pesticides from hours to days (or even weeks) in the field (30).
A particular challenge for the use of some essential oil-based pesticides
in agriculture or for home and garden use is phytotoxicity when application is
made directly onto plants. Almost any oil, whether from a natural source or from
petrochemicals, can be phytotoxic if applied at concentrations exceeding 2%
(as an aqueous emulsion), and in some cases at a concentration as low as 1%.
Most of the essential oil-based pesticides in current use are recommended to be
used at concentrations in the 0.5-1.0% range, depending on the crop and pest. At
higher concentrations (e.g. ≥ 5%), clove oil is sufficiently phytotoxic to be used
as an herbicide (31). As the margin of error for certain plants can be quite small,
empirical testing of any product on the intended crop under realistic conditions
is highly recommended. Formulation is again an avenue to mitigate or eliminate
phytotoxicity where the risk to a target crop is considerable.
Finally, in agricultural applications it is becoming common practice to tank
mix different pesticides, or to use tanks and spray equipment sequentially for
different pesticides with limited cleaning. For these reasons it is important to
establish the chemical compatibility of an essential oil-based pesticide with other
products that growers also use or have a high probability of use in tank mixtures.

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 Future Sources
Research interest in the insecticidal and repellent effects of plant essential
oils has grown dramatically since 2000. By 2011, 23% of all published papers
on botanical insecticides focused on essential oils, representing almost 5% of all
published papers on insecticides (32). Between 2004 and 2014, over 3,600 papers
were published on essential oils associated with insects and arthropods, according
to the Web of Science. The vast majority of these reported on the screening
and bioactivity of relatively exotic essential oils to insects, so the ‘discovery’
end of the R&D spectrum is well represented in the literature. Unfortunately
there is a relative dearth of papers toward the ‘development’ end of the spectrum,
although to be fair, a high proportion of the research effort in that regard is expected
to be protected information (i.e., intellectual property) that might only reach the
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scientific literature after patent protection has been secured. But it is easy to
observe that only a handful of essential oil-based pesticides have seen successful
commercialization, relative to the expansive scientific literature devoted to the
area.
That being said, and noting the practical considerations and challenges
described above, what are the prospects for the introduction of new pesticides
based on plant essential oils not currently in wide use in other industries? As
of this writing, even the most successful essential oil-based pesticides occupy
only a paper-thin share of the global insecticide market, although all indications
are that they are at a very earlier stage in that market and are poised for faster
market growth over the next decade than conventional pest management products.
Perhaps if these predictions have any accuracy, essential oil-based pesticides will
become significant participants in the rapidly expanding biopesticide market and
in so doing make the prospects for the introduction of pesticides based on exotic
oils more economically attractive.
One such example that has been subject to an extensive research effort
in recent years is the essential oil from wormwood, Artemisia absinthium
(Asteraceae) growing in Spain. This aromatic plant with a long history of
medicinal use is also the botanical source of absinthe, a bitter liqueur banned for
many years owing to its human toxicity, attributable to its major constituents, α-
and β-thujone. Thujone-rich oils have also been demonstrated to be insecticidal.
Although commercial samples of wormwood oil are often rich in thujones, there
are numerous chemotypes of the species, some of which lack these compounds
entirely (21). A series of thorough investigations of domesticated plants collected
from two locations in Spain and grown under both field conditions and controlled
conditions (in a growth chamber, greenhouse and in aeroponic culture) have
documented chemical variations in their essential oils (33). The major constituents
of essential oils produced from these cultivated plants, which lack thujones, are
cis-epoxycimene, chrysanthenol and chrysanthenyl acetate. Though less active
than thujones as antifeedants to the green peach aphid (Myzus persicae), bird
cherry oat aphid (Rhopalosiphum padi) and the cotton leafworm (Spodoptera
littoralis), oils containing the above noted compounds are effective antifeedants.
Interestingly, bioactivity to insects was not well correlated to concentrations
of any of the three compounds, providing another example of internal synergy

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 amongst constituents of an essential oil. These oils and extracts also have valuable
bioactivity against the human parasites causing leshmaniasis and trypanosomiasis
(33, 34). Rather striking quantitative year-to-year differences (up to 10-fold
for individual constituents) in oil composition were found in cultivated plants
from the two populations, and these in turn differed from plants grown under
controlled conditions and from wild conspecifics (33, 34). However, supercritical
fluid extraction of these plants gave much higher yields of the three compounds
relative to hydrodistillation or organic solvent extraction, and the SF extracts
were significantly more bioactive against all three pests (11, 35). Thujone-free
cultivated A. absinthium appears to have good potential for the production of
essential oils and extracts that can be formulated as biopesticides and for use
as antiparasitic agents, but production practices will require standardization to
achieve the consistency seen in other essential oils produced commercially over
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many decades (29).

Prospectus and Conclusions

As pesticides, plant essential oils should continue to make inroads into the
marketplace, especially as the arsenal of conventional pesticide products becomes
increasingly constrained, and consumers become ever more discerning about
pesticide residues in the food supply, the workplace and the outdoor environment.
They should find increasing use in organic production of high-value fruits and
vegetables, and with increasing global urbanization, in professional pest control,
consumer products and for vector control. Jurisidictions where pesticides are
highly regulated may in the near future take a more favorable view of products
based on essential oils, in particular those oils with a long history of human use
and safety. Economics of production, driven by much larger markets (the flavor,
fragrance and aromatherapy industries), will continue to dictate which essential
oils are likely to be formulated as pesticides. It will indeed be interesting to see
if a botanical source like wormwood can overcome the barriers and meet the
challenges to become a new crop based on extracts and oils whose main purpose
are for use as biopesticides and medicinal products.
Apart from purely descriptive biology and toxicology, our understanding of
the pesticidal properties of essential oils and their constituents in insects, fungi
and plants (as herbicides) remains somewhat rudimentary. As such, there is
tremendous scope for selecting and tailoring plants to produce essential oils with
enhanced efficacy as pesticides, for blending essential oils and/or constituents
to achieve higher pesticidal efficacy or a broader spectrum of action, and in
formulation to prolong residual action where desirable.

23
Jeliazkov (Zheljazkov) and Cantrell; Medicinal and Aromatic Crops: Production, Phytochemistry, and Utilization
ACS Symposium Series; American Chemical Society: Washington, DC, 2016.
 Acknowledgments
David Herbst (Berjé Inc.) generously provided valuable insight on the
essential oil industry to the author, as did Rod Bradbury (EcoSafe Natural Proucts
Inc.) on formulation chemistry. Dr. Rita Seffrin assisted with literature review.
Supported in part by grants from the Natural Sciences and Engineering Research
Council of Canada (NSERC).

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ACS Symposium Series; American Chemical Society: Washington, DC, 2016.