A review of Cannabis sativa-based insecticides, Miticides, and repellents

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Journal of Entomology and Zoology Studies 2018; 6(6): 1288-1299
E-ISSN: 2320-7078
P-ISSN: 2349-6800
JEZS 2018; 6(6): 1288-1299
© 2018 JEZS
Received: 07-09-2018
Accepted: 13-10-2018
John M McPartland
Department of Family Medicine,
University of Vermont,
Burlington VT, USA
Zahra Sheikh
Department of Medical
Entomology and Vector Control,
School of Public Health, Tehran
University of Medical Science,
Tehran, Iran
Correspondence
John M McPartland
Department of Family Medicine,
University of Vermont,
Burlington VT, USA
A review of Cannabis sativa-based insecticides,
Miticides, and repellents
John M McPartland and Zahra Sheikh
Abstract
Plant-based pesticides are gaining attention as safe, effective, eco-friendly alternatives to synthetic
pesticides. We conducted a literature search regarding the use of hemp (Cannabis sativa) as a plant-based
insecticide, miticide, or repellent. The search yielded 88 publications, which we grouped into five types
of applications: companion planting (17 articles), the use of harvested plant material without any
extraction (25 publications), aqueous extracts (20 publications), essential oil extracts (EOs, nine
publications), and solvent extracts (17 publications). Few studies chemically analyzed the contents of
their extracts, and most studies lacked control comparisons. EO studies were the most rigorous, and
yielded the best results. Results with solvent extracts showed moderate efficacy, but little better than
aqueous extracts, which lacked tetrahydrocannabinol (THC). Collectively, the studies suggest that EOs
(terpenoids) are the primary Cannabis constituents responsible for arthropod deterrence. THC exerts
nominal deterrence, but is toxic to insects. Mechanisms of action are discussed.
Keywords: Cannabis sativa, plant extracts, botanical pesticides, essential oils, tetrahydrocannabinol
1. Introduction
Many arthropods are disease vectors. Mosquitoes (Culex, Anopheles, Aedes spp.) vector the
causes of malaria, yellow fever, dengue fever, West Nile virus, Zika virus, Chikungunya, and
filariasis. Fleas (Pulex irritans, Xenopsylla cheopis) vector murine typhus and bubonic plague.
Lice (Pediculus and Pthirus pubis spp.) vector epidemic typhus. Ticks (Ixodes, Amblyomma,
Dermacentor, Rhipicephalus spp.) spread Lyme disease, babesiosis, anaplasmosis,
ehrlichiosis, Rocky Mountain spotted fever, and Q fever. Kissing bugs (Rhodnius and
Triatoma spp.) vector Chagas disease, and sand flies (Phlebotomus and Lutzomyia spp.) vector
leishmaniasis. Arthropod-borne diseases as malaria, Chagas disease, and leishmaniasis account
for more than 17% of all infectious diseases, causing more than 700,000 deaths annually [1].
Arthropod pests destroy an estimated 18-26% of annual crop production worldwide. Most of
this occurs in the field (13-16%), and the rest is due to post-harvest losses [2]. Household
arthropod pests include termites, carpenter ants, fire ants, clothes moths, and cockroaches.
Many of these arthropod pests and disease vectors are preventable through informed protective
measures.
Prior to synthetic pesticides, plant-based biopesticides were the principal means of repelling
arthropods. Plants produce powerful chemicals for defense against phytophagous arthropods.
Ancient people used indigenous plants to repel phytophagous arthropods, as well as blood-
feeding arthropods and household pests. A century ago synthetics came to dominate the
market, because of their greater efficacy, longer duration of action, and more stable shelf life
than plant-based products. While this may be true, the widespread use of synthetic pesticides
has resulted considerable damage to worldwide ecosystems, and polluted air, water and soil.
They may be harmful to non-target species, and directly toxic to users. Widespread usage has
led to the development of resistance among the target species.
Plant-based biopesticides can be produced in a sustainable manner, inexpensive to extract,
nonirritating to skin, and considered natural. They are culturally acceptable in communities
with a tradition of plant use, and they are gaining popularity as substitutes for synthetic
pesticides. Spatial repellents derived from Cannabis sativa were traditionally deployed against
human pests. Targets included mosquitoes, fleas, lice, ticks, bedbugs (Cimex lectularius), and
scabies mites (Sarcoptes scabiei). Cannabis-based insecticides and repellents were also
traditionally employed to protect crops from phytophagous arthropods [3].
The active ingredient in Cannabis that deters arthropods has not been confidently ascertained.

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In human medicine, the focus has been on Phytocannabinoids,
a class of natural products unique to Cannabis. The two best-
studied phytocannabinoids are tetrahydrocannabinol (THC)
and cannabidiol (CBD). Cannabis does not actually
biosynthesize THC and CBD. It produces precursor
molecules, tetrahydrocannabinol acid (THCA) and
cannabidiolic acid (CBDA). These molecules decarboxylate
into THC and CBD upon heating (boiling, baking, smoking).
The bioactivities of THCA and CBDA are poorly understood,
and they differ from THC and CBD. For example, THCA is
not psychoactive; it does not bind to the human CB1 receptor
[4].
Terpenoids refer to a class of compounds that includes both
hydrocarbon terpenes and their oxygenated derivatives.
Terpenoids from other plants are well-known insecticides,
such as ryania, azadirachtin, and pyrethrins. Three terpenoids
produced by Cannabis-limonene, linalool, and pinene—are
marketed as insecticides. Cannabis biosynthesizes about 140
terpenoids, mostly monoterpenoids (C10H16 templates) and
sesquiterpenoids (C15 H24 templates). Collectively, terpenoids
constitute the plant’s essential oil (EO, also known as volatile
oil).
Several other classes of natural products are minor
constituents of Cannabis, such as flavonoids (quercetin,
apigenin, orientin, kaempferol, canniflavone, cannflavin),
phenols (eugenol, cannabispiradienone), polyphenols
(cannabispirone, canniprene, tannins), phytosterols
(camesterol, stigmasterol, β-sitosterol), amines (piperidine),
lignanamides (cannabisin A-G), and fatty acids in seeds.
Many of these compounds show insect repellency [5].
Cannabis produces terpenoids and phytocannabinoids in
glandular trichomes, of which there are two main types:
sessile glandular trichomes arise on all aerial surfaces
throughout the plant’s lifespan, except for cotyledons. Their
gland heads are 40-50 µm in diameter. Stalked glandular
trichomes are largely limited to the flowering tops (perigonal
bracts and subtending leaves) of female plants. Their gland
heads are at least 70-100 µm in diameter, atop a multicellular
stalk usually over 200 µm tall. Potter [6] measured a
monoterpenoid-to-sesquiterpenoid ratio of 4:1 in stalked
glandular trichomes on flowering tops, and nearly the reverse
ratio in sessile glandular trichomes on leaves. The contents of
gland heads consist of 90% phytocannabinoids and 10%
terpenoids [6, 7].
Gland heads on living plants are “touch-sensitive,” burst
easily, and release terpenoids and phytocannabinoids. These
fluids oxidize and polymerize into a resin on the trichome
stalk and leaf surface. The gummy resin physically disables
small insects, thereby exerting mechanical control as well as
chemical control. Potter [6] photographed cotton melon aphids
(Aphis gossypii) snared by stalked glandular trichomes. The
aphids struggled for a while and then died.
2. Methods
We used three search engines to obtain literature, CAB Direct
(https://www.cabdirect.org), PubMed
(www.ncbi.nlm.nih.gov/pubmed), and Google Scholar
(https://scholar.google.com), using the following boolean
search string: (cannabis) AND (insecticide OR aracacide OR
pest repellent OR antifeedant). Retrieved articles were
screened for supporting citations, and antecedent sources were
retrieved.
Publications selected for inclusion included all pre-20th
century reports of pesticidal or repellent activity against
blood-feeding arthropods and phytophagous arthropods.
Publications of the 20th and 21st centuries were limited to first-
person accounts in the primary literature. Secondary sources
(review articles and textbooks) were excluded, unless: 1. they
cited primary sources not available to us; 2. they included
experimental data (e.g., LC50, the concentration of a chemical
in air or water that kills 50% of arthropods; LD50, the amount
of a chemical, given all at once, that kills 50% of arthropods).
We also excluded ethnobotanical surveys, which were
second-person accounts and lacked experimental data.
Data extracted from publications included plant parts utilized
(leaves, flowering tops, seeds, or all aerial parts), targeted
arthropod, assay used to measure activity, and experimental
results. Activities included acute toxicity (LC50, LD50, or
percent killed), repellency, feeding inhibition, and oviposition
inhibition. Our narrative review was structured by product
application, segregated into five categories:
2.1 Cannabis as a companion plant
Companion planting or intercropping describes the sowing of
two or more plant species in close proximity. This mimics the
biodiversity of natural ecosystems, and enhances crop
production via pest control and other mechanisms.
Companion plants can be employed in an attract-and-kill
(A&K) strategy-pests are lured to an attractant (usually a
semiochemical and/or a visual cue), and then killed by a
pesticide.
2.2 Recently harvested or dried plants
This category includes the direct usage of plant material
without any extraction. In this manner Cannabis has found
use as a spatial repellent. Recently harvested plants (“fresh,”
“green”) emit volatile compounds—primarily terpenoids.
Phytocannabinoids are not volatile. They are present in the
fumes of burned plants.
2.3 Aqueous extracts
No studies analyzed the active ingredients in their aqueous
extracts. Here we infer their contents: Several classes of
Cannabis constituents are soluble or miscible in water,
including flavonoids, alkaloids, tannins, and amines.
Monoterpenes lack solubility. At 25ºC, only 5.0 mg of 𝛼-
pinene is soluble in a liter of water; limonene, 20.4 mg/L; and
myrcene, 29.9 mg/L [8]. Conversely, oxygenated
monoterpenoids show 60-fold greater soluble: linalool, 1559
mg/L; 𝛼-terpineol, 1889 mg/L; carveol, 2931 mg/L.
Sesquiterpenes are also hygrophobic: (E)-caryophyllene, 0.05
mg/L; trans-𝛼-bergamotene, 0.03 mg/L [9].
THC is not water soluble: 2.8 mg/L at 23ºC [10]. THCA’s
carboxylic acid likely makes it more water soluble, but its
solubility has not been measured. Aqueous extracts are either
infusions (plant material steeped in room-temperature water
or heated water) or decoctions (plant material boiled at
100ºC). The difference is an important consideration, because
decoctions have lost THCA (decarboxylated into THC) and
oxygenated monoterpenoids (which have boiled off).
2.4 Essential oils
EOs are extracted primarily by steam distillation or
hydrodistillation. Steam distillation passes steam through a
bed of plant material in a closed system. Volatile compounds
are carried away in the steam, condensed and separated.
Hydrodistillation is an older version of steam distillation,
where plant material is soaked in water, then boiled, and

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volatile compounds are carried away in the water-oil vapor,
condensed and separated.
Benelli [11] described hydrodistillation as “more aggressive”
than stem distillation, producing oxidative and hydrolytic
reactions. Hydrodistillation shifts the EO profile towards a
higher percentage of water soluble terpenoids. Bertoli [12] used
hydrodistillation to obtain an EO with an oxygenated
terpenoid fraction of 5.67% and 7.46% (cultivar ‘Felina 32’
grown in two sequential seasons). Benelli [11] steam distilled
the identical cultivar in the same region (central Italy), and
obtained only 1.6% oxygenated terpenoids.
Phytocannabinoids are not significantly present in steam-
distillates. Malingré [7] estimated that 3.3% of
phytocannabinoids in plants passed into a steam distillate,
whereas 75% of EO passed into a steam distillate.
Hydrodistillation is not as selective; Benelli [11] measured
0.1% CBD in steam-distilled ‘Felina 32’, they compared this
with Bertoli [12], who hydrodistilled 1.69% and 1.89% CBD
(two seasons).
2.5 Solvent extracts with phytocannabinoids
Phytocannabinoids are extracted with nonpolar solvents (e.g.,
hexane, chloroform, petroleum ether, supercritical CO2) or
polar solvents (methanol, ethanol, butanol, acetonitrile). The
extraction can be done at room temperature, or heated (often
using a Soxhlet extractor). Unfractionated (crude) extracts
contain phytocannabinoids as well as EOs. Fractionation
methods then separate THC, CBD, and other
phytocannabinoids.
3. Results and Discussion
The search strategy yielded 88 relevant publications: 17
regarding companion planting, 25 using harvested Cannabis
plant material without any extraction, 20 using aqueous
extracts, nine using EOs, and 17 using solvent extracts. Some
studies tested Cannabis extracts against phytophagous
arthropods known to feed on Cannabis, such as Tetranychus
urticae, T. cinnabarinus, Frankliniella occidentalis, Popillia
japonica, Arctia caja, Helicoverpa armigera, Spilosoma
obliqua, Spodoptera frugiperda, and Gryllotalpa gryllotalpa
[13].
3.1 Companion plants
Of the 17 publications that described companion planting with
Cannabis, 13 were observational reports, and four were
experimental studies. The observational reports were
universally positive, whereas the experimental studies
reported mixed results (two positive, two negative).
Eight of the observational reports concern hemp repelling
Pieris brassicae, the cabbage butterfly. In 1768, Pratje [14]
wrote a short article, “Remedy against the cabbage
caterpillars,” which likely refers to P. brassicae. “If one wants
to drive the cabbage to safety from the caterpillars, one should
sow hemp around the land on which one has been sowed. It
will be astonishing to realize that, although all the land lying
around is covered with caterpillars, [cabbage] on which hemp
is surrounded, not a single one will be seen.”
Willich [15] paraphrases Pratje without citing him, “the borders
of the ground, where it is intended to plant cabbages, be sown
with hemp; and, however the vicinity may be infested with
those insects, the ground enclosed will be found to be
perfectly free from them.” Hamm [16] suggests that the smell
of hemp repels egg-laying butterflies, so a ring of plants will
protect vegetables and brassicas. Jentink [17] says the
interplanting of hemp and cabbage is “a well known fact”
among peasants in the Netherlands. D’Arenberg [18] planted
hemp in and around cabbage plots to drive away Piérides du
Choux. He placed cabbage plants in a wire cage with a “tuft
of hemp” at one end, and Piérides du Choux in the cage
massed at the opposite end from the hemp.
Blanchard [19] recommends companion crops of hemp and
Jerusalem artichoke (Helianthus tuberous) to protect cabbage
fields. Linsbauer [20] observed the interplanting of hemp with
cabbage to drive away P. brassicae; he attributes this effect to
odors emitted by “the plant glands.” Beling [21] quotes Pratje
[14]. However, an actual experiment found no such protective
effect against P. brassicae [22]. Nevertheless, popular guides
still recommend planting hemp to drive off P. brassicae (e.g.,
[23]).
Foy [24] says Egyptian farmers sow Cannabis in onion fields.
This may have been companion planting; one of onion’s rare
pests is the onion thrips, Thrips tabaci. Potter [6] observed T.
tabaci becoming ensnared by stalked glandular trichomes in
C. sativa. Riley [25] “believed” that hemp, C. sativa, planted in
the midst of cotton reduced damage by the cottonworm,
Alabama argillacea, as did the neem tree (Melia azedarach),
pyrethrum plant (Chrysanthemum sp.), and dill (Anethum
graveolens).
Feldt [26] reports that hemp protects plants from the dock
aphid, Aphis rumicis, as does carrot (Daucus carota), parsley
(Petroselinum crispum), and coriander (Coriandrum sativum).
Pakhomov and Potushanskii [27] quantified the effects of hemp
on the wheat bulb fly, Delia coarctata. A control plot of
winter wheat showed 31% infestation by D. coarctata,
whereas a plot bordered by hemp plants showed only 9%
infestation.
Stratii [28] reports that when hemp was grown around a potato
plot, plants nearest to the hemp were free from infestation by
the Colorado potato beetle (Leptinotarsa decemlineata)
whereas other plants became heavily infested. However,
Mackiewicz [29] grew hemp around the edges of a potato field
and within the field, and found no effect on L. decemlineata.
Hemp also had no effect on black bean aphids (Aphis fabae)
in the beet fields.
3.2 Freshly harvested or dried plants
Of 25 reports that used Cannabis plant material without any
extraction, 12 reports concerned blood-feeding pests of
humans, six targeted storage insects (grain weevils, clothes
moths), four concerned phytophagous insects in the field, one
study mentioned both blood-feeding and phytophagous
insects, one study targeted the varroa mite in honeybee
colonies, and one cited nonspecific “bugs” (Table 1). Some of
these reports come down to us from secondary sources. The
majority (71%) predated the 20th century, and most of them
were observational reports. Only five were experimental
studies, and they lacked controls. One study compared the
efficacy of Cannabis to other plants.

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Table 1: Reports concerning freshly-cut plants or dried flowers and tops, listed chronologically
Target species, citation
Extracted data
Locusts
Rodgers [30]
Ibn Wahshīyah of Iraq fumigated crops infested by locusts with šāhdānaj (hemp) and sulfur. Ibn Wahshīyah
wrote Filāha an-Nabātiyya, the earliest agricultural book in Arabic, between 904 and 931 AD.
Mosquitoes
Beckh [31]
The anonymously-written Geoponika, ca. 904-959 AD, says “If you lay a flowering branch of καννάβεως (green
hemp) near you when you go to sleep, κώνωπες (mosquitos) will not touch you.” Five lines later: “Mosquitos
will not bother a person in bed if he puts καννάβια (hemp) under him.” Geoponika attributes this information to
Democritus (460-370 BC), whose writings are lost.
Mosquitoes
Needham [32]
A passage in Wù Lèi Xiāng Gǎn Zhì, written by Zànníng ca. 980 AD, recommends burning má yè (hemp leaves)
to repel mosquitoes.
Bed bugs
Ardoini [33]
According to Ardoini, “Hippocrates said: If herba canapis (hemp leaves) should be put under the bed, cimices
shall not come near to him.” Cimices likely refers to Cimex lectularius. To our knowledge, Hippocrates never
wrote anything about cannabis in any context.
Mosquitoes
Estienne [34]
Estinne translated Geoponika from Greek to Latin, but altered the text: florentes canabis surculi (flowering
cannabis shoots) control involatia culicum agmina (hordes of flying mosquitos).
Mosquitoes
Ruel [35]
Ruel quotes Democritus in a translation of Hippiatrica that includes some passages from Geoponika: cannabis
frutices (hemp flowers) repel infestis culicibus (troublesome mosquitoes) from around the bed.
Bed bugs
Teodosi [36]
Teodosi likely cribbed Ardoini: cimices (bugs) are repelled by the olent (smell) of canabis [sic] folia et caules
(hemp leaves and stems)
Fleas
Piemontese [37]
Girolamo Ruscelli wrote a “book of secrets” under the pseudonym of “Alessio Piemontese,” Spreading semenza
del canape (hemp seed) around the house will drive away pulici (fleas).
Mosquitoes
Wecker [38]
A posthumous compilation of writings by the Swiss alchemist states that mouscheros (mosquitoes) will not
annoy a person who places chanvre (hemp) under his bed
Bed bugs and caterpillars
Chomel and Bradley [39]
Bradley translated and revised Dictionnaire œconomique by Noël Chomel. His revision makes comments that do
not appear in Chomel’s original. “Take some ox-gall and hemp-oil, mix the whole together, rub the joints and
bedstead therein, and the bugs will never touch the places you have rubbed.” Regarding caterpillars in crops,
“Some burn hemp-sheaves, as they are called, being the stalk of the hemp, near their gardens, and it’s very good
to kill them.”
Grain weevils
Walpole [40]
A British diplomate in Munich reports that Bavarians repel “flying weevils” by mixing green hemp into piles of
stored grain.
Clothes moths
Anonymous [41]
“Moist [i.e., fresh] hemp and tobacco leaves preserves all sorts of cloaths from moths and worms.”
Mosquitoes
Darwin [42]
Erasmus Darwin, grandfather of Charles, says the “musquito, Culux pipiens… may be driven away by smoke,
especially… by that of cannabis, hemp.”
Bugs
Rafinesque [43]
“Bugs are killed by the smoke of the cayenne pepper, the infusion of the Acorus or sweet flag, and of the hemp
seeds.”
Bed bugs
King [44]
King recommends placing “green plants collected in the spring” around the bed to rid the room of bedbugs
Grain weevils
Riley and Howard [45]
Leaves gathered from wild-type Cannabis in South Africa were placed among bags and heaps of grain for
protection from “grain weevils.”
Fleas
Chopra and Badhwar [46]
“Hemp (Cannabis sativa L.), if spread under a bedsheet, affords ample protection against fleas which disturb
sleep at night in many of the hill stations of India.”
Ticks
Reznik and Imbs [47]
Larvae of Ixodes redikorzevi, Haemaphysalis punctate, Rhipicephalis rossicus, and Dermacentor marginatus
exposed to powdered leaf were killed in 10, 18, 8, and 21 minutes, respectively. Exposure to fresh whole leaf
killed larvae in 50, 68, 50, and 72 minutes, respectively.
Sitophilus oryzae
Khare [48]
300 adult weevils were placed into an olfactameter, with wheat mixed with powdered Cannabis, 1% w/w. After
24 hours, only 1.66% of weevils were found in the grain, the rest were repelled. Cannabis was more effective
than Acorus calamus or Physalis minima.
Leptinotarsa
decemlineata
Stratii [28]
When flowering hemp plants were torn up and waved over infested potato plants, adult beetles fell to the ground
paralyzed.
Spilosoma obliqua
Deshmukh [49]
When 6th instar larvae were fed a no-choice diet of freshly-harvested Cannabis leaves, 50% died after 24 days.
Arctia caja
Rothschild [50]
Larvae fed a no-choice diet high-THC Cannabis leaves did not survive beyond the third instar. Those fed high-
CBD leaves pupated successfully.
Sitophilus oryzae
Prakash [51]
Dried leaves mixed into rice, 2% w/w, gave 59% protection against adult weevils in the laboratory. This dose
failed to provide adequate protection under natural storage conditions (Prakash et al. 1982)
Varroa jacobsoni
Surina and Stolbov [52]
Honeybee mites were partially controlled by vapors from fresh leaves and stems, reduced to a powder. Inner
walls of the hive were rubbed with 10-12 g powder per bee family.
Phthorimaea operculella
Kashyap [53]
A 2 cm layer of dried, powdered leaves over piles of potatoes protected them from larvae of the tuber moth for
up to 120 days. Of eight plants tested, Cannabis tied for second place.
Cannabis may employ an A&K strategy: Deshmukh [49] gave
6th instar larvae of the jute hairy caterpillar, Spilosoma
obliqua, a choice of 16 plants from 12 plant families, and
Cannabis was among the six favorite. But when larvae were
fed a no-choice diet of fresh Cannabis leaves, 50% died after
24 days. Surviving larvae did not pupate. Rothschild [50] raised
larvae of the garden tiger moth, Arctia caja, on fresh leaves of
either high-CBD (Turkish) or high-THC (Mexican) landraces
of C. sativa. Larvae reared on high-THC leaves did not
survive beyond the third instar. Those fed high-CBD leaves
pupated successfully. But in a feeding choice experiment,
caterpillars showed a definite preference for high-THC leaves.
“Should these compounds exert a fatal fascination for tiger
caterpillars it suggests another subtle system of insect control

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by plants.” Larvae of Arctia caja fed C. sativa passed THC
into the frass (3.0 mg/g), or sequestrated THC in the
exoskeleton (1.4 mg/g). The exoskeleton accumulated up to
0.07 mg THC per caterpillar-enough to cause psychoactivity
in a caterpillar-eating mouse. This is analogous to larvae of
the monarch butterfly, Danaus plexippus, which accumulate
toxic glycosides in their exoskeleton.
3.3 Aqueous extracts
Studies on aqueous extracts (n=20) rarely described their
extraction techniques, whether infusions (either cold or
heated), or boiled decoctions. Three reports were
observational, the rest were experimental studies. Few
experimental studies had control arms, but several studies
compared Cannabis to other plants.
Only three reports predated the 20th century, and these were
the observational reports. Piemontese [54] boiled semenza del
canape (hemp seed) in seawater, and poured the decoction
around the house to get rid of pulici (fleas). Buc’hoz [55] killed
underground nests of courtillières (mole crickets, Gryllotalpa
spp.) by flooding them with water suffused with hemp seed
oil. This causes them to flee from their holes, blacken, and
die.
Culpeper [56] says “juice” squeezed from fresh leaves dropped
into the ears “draweth forth earwigs” which have gotten into
them. It is well-known that Culpeper revised information
regarding earlier authors without cited them. Regarding
earwigs, Culpeper likely revised Pliny (ca. 23-79 AD), who
says juice of hemp seed (semen cannabis) “drives out of the
ears the worms and any other creature that has entered them”
[57]. Pliny in turn plagiarized Dioscorides (ca. 20-70 AD), who
instilled “juice of

λωρός καρπόν” (fruit when green) to treat
ear aches (nothing about worms) [58].
Mackiewicz [59] sprayed potato plants in the laboratory with a
water extract of hemp, which had no repellent effect on
ovipositing potato beetles, Leptinotarsa decemlineata, and did
not affect larval development. In contrast, Stratii [28] sprayed a
decoction of boiled hemp flowers on infested potato plants,
and no living beetles or larvae of L. decemlineara remained
after 45 minutes. Kurilov and Kukhta [60] repeated the study in
laboratory and field tests. Aqueous extracts of neither leaves
nor flowering tops had any effect on larvae or adults of L.
decemlineara. Adding sunflower oil to the extract caused
young adults to drop to the ground, but they returned to plants
in 5-10 minutes and resumed feeding.
Fenili and Pegazzano [61] reported that leaf extracts of
Cannabis sativa (preparation details not given) were toxic to
all stages of the spider mite Tetranychus urticae. Bajpai and
Sharma [62] sprayed a 20% w/v cold water extract of bhang to
reduce oviposition by the spotted stalk borer, Chilo partellus.
Plants sprayed with the extract averaged 110 eggs, and control
plants averaged 765 eggs.
Rothschild and Fairbairn [63] evaluated the cabbage butterfly,
Pieris brassicae, in a free-choice test of oviposition
deterrence. Cabbage leaves were sprayed with either tap
water, aqueous extracts of Mexican (high-THC) Cannabis, or
Turkish (high-CBD) Cannabis. Extracts were prepared at
room temperature, 5 g leaves in 5 Imperial oz water (i.e.,
3.4% w/v). Given the choice of leaves sprayed with tap water
versus Mexican extract, butterflies laid 1418 eggs and 135
eggs, respectively, on the two choices. Offered tap water
versus Turkish extract, they laid 1421 eggs and 773 eggs,
respectively. Butterflies could also distinguish between the
two extracts: they laid 510 eggs on the Mexican extract versus
1691 eggs on the Turkish extract.
Then Rothschild and Fairbairn heated the extracts in a steam
bath for 30 minutes to remove volatiles. The loss of volatiles
resulted in a reduction in oviposition deterrence. Given the
choice of Mexican unsteamed versus Mexican steamed, they
laid 72 eggs and 683 eggs, respectively. Given the choice of
Turkish unsteamed versus Turkish steamed, they laid 319
eggs and 405 eggs.
Sharma [64] tested a 2% leaf extract (preparation details not
given) against the potato tuber moth, Phthorimaea
operculella. Dipping eggs in the extract for two minutes
extract reduced egg hatching by 13.7%. Potato leaves dipped
in the extract for 2 minutes deterred egg laying by 41.7%. Out
of ten plant species tested, Cannabis ranked 5th in oviposition
deterrence, and tied for 6th in ovicidal mortality.
Masih and Singh [65] tested a leaf extract (1% w/v) on three
lepidopteran borers, Chilo partellus on maize, Helicoverpa
armigera on gram, and Leucinodes orbonalis on eggplant.
They evaluated mortality on the 2nd, 4th and 6th days after
treatment: C. partellus (37.5, 17.5 and 7.5%, respectively), H.
armigera (55.0, 27.5 and 5.0%), and L. orbonalis (30.0, 20.0
and 7.5%).
Sharma et al. [66] tested ovicidal effects against eggs masses of
the diamondback moth, Plutella xylostella, using five
dilutions of an aqueous leaf extract. Egg hatch was 90.9%
(distilled water), 86.5% (1% extract), 79.9% (2.5% extract),
88.8% (5% extract), 84.4% (8% extract), and 82.2% (10%
extract). Extracts from all other plants showed greater
ovicidal effects (Melia azedarach, Lantana camara, Artemisia
annua). Kumar et al. [67] republished the data, with
clarifications regarding methods: The dilutions came from a
20% w/v stock solution of leaves that were air-dried for 6-7
days. Egg masses were on cauliflower leaves; they were
dipped for 10 seconds in each test solution.
Bhattacharyya et al. [68] collected ruderal plants in Bengal, and
prepared room-temperature aqueous extracts from dried
leaves. Extracts were sprayed on mustard (Brassica juncea) to
test repellency against the mustard aphid Lipaphis erysimi.
Three days later, control plants harbored a mean of 21.25
aphids, and plants sprayed with 6000 ppm cannabis extract
had a mean of 35.41 aphids (1.7-fold increase). In contrast,
plants sprayed with Parthenium hysterophorus extract showed
a 3.4-fold decrease.
Sharma et al. [69] tested oviposition deterrence in the tobacco
cutworm, Spodoptera litura. Leaves were dried in a 30ºC
oven for 24 hours (therefore likely devoid of monoterpenoids,
and THCA decarboxylated into THC, and possibly oxidized
into CBN). Four concentrations of aqueous extracts were
tested. Egg laying was reduced by 11.9% (1% extract), 15.5%
(2.5% extract), 18.5% (5% extract), and 18.1% (10% extract).
Extracts from all other plants showed greater oviposition
deterrence (M. azedarach, L. camara, Azadirachta indica,
Nerium indicum, Rininus communis, Solanum nigrum,
Eucalyptus sp.).
Sharma et al. [70] tested larvicidal effects against the tobacco
cutworm, Spodoptera litura, and the cabbage worm, Pieris
brassicae (extract preparation details not given). Second-
instar larvae were placed on leaves dipped in aqueous extracts
(castor leaves for S. litura, cabbage for P. brassicae).
Mortality assessed at 24 hours. For S. litura the results were
6.2% (1% extract), 23.8% (2.5% extract), 23.8% (5% extract),
and 9.5% (10% extract). Extracts from M. azedarach, A.
indica, N. indicum, R. communis, and S. nigrum caused
greater mortality, L. camara and Eucalyptus sp. caused less.

Journal of Entomology and Zoology Studies
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Sharma and Gupta [71] tested antifeedant and toxic effects on
second instar larvae of Pieris brassicae. They dipped cabbage
leaves in extracts prepared at room temperature from flowers,
fruits, and leaves (10% w/v), and recorded antifeedant effects
(percentage of leaf area not eaten) after 24 hours. Four
concentrations were tested (10, 5, 2.5, and 1%), with a mean
antifeedant effect of 25.8%-the least efficacy of eight plant
species tested. Mortality response, corrected for control
mortality, averaged 15.8%-Cannabis ranked third, after Melia
azedarach (19.6%), Nerium indicum (19.6%), and
Azadirachta indica (18.5%).
Zia et al. [72] tested the effects of ten plants on the stored
cowpea bruchid, Callosobruchus chinensis. Aqueous extracts
were prepared by boiling 1g dried leaf material in 100 mL of
water for 10 minutes. They placed ten pairs of C. chinensis in
a container (who mated and laid eggs) with 40 g cowpeas, and
a cotton swab injected with 1 mL of extract. Parameters
included: 1. number of days to 100% mortality, 2. feeding
damage (number of holes/cowpea), 3. feeding damage
(weight loss of cowpea) 4. extent of oviposition, 5. percent of
egg hatching, 6. mortality of F-1 generation. Four plants of
ten plants outperformed the Cannabis extract: Piper nigrum,
Syzygium aromaticum, Azadirachta indica, and Allium
sativum.
Sattar et al. [73] prepared aqueous extracts of leaves or seeds of
Cannabis, at three concentrations described as 50%, 33%, and
25%. Filter paper was injected with 0.2 mL of each
concentration, placed in a petri dish with 4th-5th instar termites
of Microtermes obesi and Odontotermes lokanandi. On days
1-3, the seed extract caused greater mortality than the leaf
extract for both species. After 11 days, 95-100% of M. obesi
died at all concentrations for both leaf and seed extracts. O.
lokanandi mortality was 80-100%, significantly higher at 50%
and 33% than 25%, but no difference between leaf and seed.
Yadav and Patel [74] tested five plant extracts on mortality of
third instar larvae of tobacco caterpillar (Spodoptera litura)
and mustard sawfly (Athalia proxima), feeding on leaves of
castor and mustard, respectively. Fresh leaves (250 g) were
added to 500 mL water, and boiled down to half the original
volume. Leaves of castor and mustard were dipped in three
extract concentrations (1, 3, and 5%). Mortality of S. litura at
72 h was 73.3%, 76.7%, and 86.7%, respectively. At 5%,
Cannabis tied for first with Solanum nigrum. Mortality of A.
proxima at 72 h was 73.3%, 73.3%, and 80.0%, respectively.
Cannabis ranked last.
3.4 Essential oils
We identified nine studies of EOs. Most authors described
their extraction technique (i.e., steam distillation or
hydrodistillation), but few analyzed the content of their EOs
(Table 2). All were experimental studies; few had control
arms, several compared Cannabis to EOs from other plants,
and in one case, a synthetic pesticide.
Table 2: Studies of Cannabis essential oils, listed chronologically
Target species, citation
EO extraction method, Analysis1
Assay, activity2
Culex tritaeniorhynchus, Aedes
aegypti, Anopheles stephensi,
Culex quinquefasciatus,
Thomas et al. [75]
hydrodistillation of ruderal plants in
Delhi, bioassay using WHO
protocol
Four concentrations of EO (0.06, 0.1, 0.12 and 0.2 ml/litre) added
to water with larvae of four mosquito species. Rank order of LC50:
C. tritaeniorhynchus (0.0101), A. aegypti (0.026), A. stephensi
(0.0273), C. quinquefasciatus (0.0919)
Mosquito
Culex quinquefasciatus
Pavela 2009 [76]
EO purchased in USA
Fourth instar larvae exposed 24 h to doses,
LC50 =127.3 𝜇g/mL. Out of 22 plant species, Cannabis ranked
10th (Thymus vulgaris best, 32.9 𝜇g/mL)
rosy apple aphid
Dysaphis plantaginea
Górski et al. [77]
steam distillation of Polish fiber
hemp cultivars, with water
emulsifier RO-1 (which caused no
mortality alone)
Mortality from two EO concentrations (0.05 and 0.1%) sprayed on
apple trees at rate of 750 L/ha.
After 24 hours, mortality 93.0% (with 0.05%) and 93.5% (with
0.1%). Mortality similar to Mospilan 20 SP insecticide at rate of
0.125 kg/ha
Spider mites
Tetranychus urticae
Tetranychus cinnabarinus
Fiedler et al. [78]
Same as above
(emulsifier Triton),
cucumber leaves naturally
colonized by spider mites
T. urticae: mortality after 14 days from spraying leaves with 0.5%
EO, nymphs 82%; adults 91%
T. cinnabarinus: mortality after 14 days from dipping leaves in
0.5% EO, nymphs 75%; adults 87%.
Spider mite Tetranychus urticae;
foxglove aphid Aulacothum solani
Górski et al. [79]
Same as above
(emulsifier RO-1)
S 50.9%, M 49.3%
T. urticae: mortality on bean leaves dipped in 0.02%, 0.05%, or
0.10% EO. After 24 hours, mortality 43.6%, 60.3%, and 71.1%
respectively. After 48 hours 66.6%, 71.4%, and 79.8%. After 72
hours 83.3%, 95.8%, and 98.7%.
A. solani: mortality on eggplant dipped in same three
concentrations. After 24 hours, mortality 22.3%, 27.5%, and
23.9%, respectively. After 48 hours 29.4%, 25.9%, and 57.3%.
After 72 hours 98.2%, 100%, and 100%.
Termite, Reticulitermes virginicus;
fruit fly, Drosophila melanogaster
Prabodh & Setzer 2014[80]
EO from leaves of a Nepali plant,
S 68.1%, M 11%, CBD 1.6%, THC
0.4%
R. virginicus: worker larvae mortality after 24 h exposure to filter
paper w/ 1% EO at three concentrations: LC50 =354 𝜇g/mL. D.
melanogaster mortality after 24 h exposure to 1% EO at 20 𝜇L or
150 20 𝜇L, LC50 =500 𝜇g/mL
Mosquito
Aedes albopictus,
Bedini et al. [81]
EO purchased in Italy,
M 58.6, S 39.0
Fourth instar larvae exposed 24 h to doses from 25 to 500 𝜇L/L,
LC50 =301.6 𝜇L/L
Mosquito, Culex quinquefasciatus;
House-fly, Musca domestica;
Tobacco cutworm
Spodoptera littoralis
Benelli et al. [82]
hydrodistillation of monoecious
‘Futura 75’, flowering tops (M
37.9, S 47.7, CBD 11.1) or
leaves (M 5.3, S 75.0, CBD 10.0)
C. quinquefasciatus: WHO protocol, larvae exposed 24 h to doses
from 30 to 500 𝜇L/L;
leaf LC50 =152.3 𝜇L/L, flower LC50 =124.5 𝜇L/L. M. domestica:
adult females, 2-5 days old, topical application of 1 𝜇L EO in
acetone, range of doses 0-90% EOs; leaf LD50 = 305.2 𝜇g/adult,
flower LD50 =122.1 𝜇g/adult.

Journal of Entomology and Zoology Studies
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S. littoralis: early 3rd instar larvae, topical application of 1 𝜇L EO
in acetone, range of doses 30-500 𝜇g/larvae; leaf LD50 =112.8
𝜇g/larvae, flower LD50 =65.8 𝜇g/larvae
Mosquito, Culex quinquefasciatus;
House-fly, Musca domestica;
Tobacco cutworm
Spodoptera littoralis
Green peach aphid
Myzus persicae
Benelli et al. [11]
steam distillation of flowering tops,
monoecious ‘Felina 32’ (M 54.2, S
45.6, CBD 0.1), protocols similar
Benelli et al.[82]
C. quinquefasciatus larvae: LC50 =252.5 mL/L
C. quinquefasciatus adults: LC50 =500 𝜇g/cm2
M. domestica adults: LD50 =43.3 𝜇g/adult
S. littoralis larvae: LD50 =152.3 𝜇g/larvae.
M. persicae: four concentrations sprayed on cabbage leaves,
adults placed on leaves and mortality at 48 h: LC50 =3.5 mL/L.
1. Analysis of EO, if performed: M, monoterpenoid percentage; S, sesquiterpenoid percentage
2. Assay: WHO, World Health Organization
In Table 2, note that Benelli et al. [82] found that a
monoterpenoid-dominant EO (from flowers) was more potent
than a sesquiterpenoid-dominant EO (from leaves) in three
different insect species. In addition to mosquitos, Bedini et al.
[81] tested a nontarget species, the mayfly Cloeon dipterum,
with a LC50 = 282.2 𝜇L/L. They also compared Cannabis EO
to Humulus lupulus EO, which was more toxic to C. dipterum
(LC50 = 219.8 𝜇L/L). Benelli et al. [82] tested two nontarget
species. They exposed the multicolored Asian lady beetle,
Harmonia axyridis, to various EO concentrations (0.6, 1.25,
2.5, and 5.5 mL/L sprayed on cabbage leaves). Adults showed
no mortality, and 3rd instar larvae showed only 3.3% mortality
at the highest concentration. In comparison, 0.005% 𝛼-
cypermethrin killed 100% of larvae and adults. They exposed
Eisenia fetida earthworms to various EO concentrations (50,
100, and 200 mg/kg of soil), with no mortality after a week,
whereas 𝛼-cypermethrin (250 𝜇L/kg soil) killed 100%.
3.5 Solvent extracts with phytocannabinoids
Seventeen studies used solvent extracts. All were
experimental studies; few had control arms, several compared
Cannabis to extracts from other plants. No studies chemically
analyzed the constituents in their solvent extracts, we assume
the presence of phytocannabinoids and terpenoids. Two
studies used purified cannabinoids (THC, CBD, or THCA).
Table 3: Studies of Cannabis solvent extractions, listed chronologically
Target species,
citation
extraction method,
Analysis1
Assay, activity2
Japanese beetle, Popillia japonica
Metzger and Grant [83]
Pharmaceutical (U.S.P.) EtOH
diluted to 1/64
Repelled adult beetles. They made extracts from 390 plant species,
and only 56 showed any repellency.
Mosquito Aedes aegypti Abrol and
Chopra [84]
EtOH of leaves, 20% solution
A spray repelled mosquitos but caused no toxicity
Cabbage butterfly
Pieris brassicae Rothschild and
Fairbairn [63]
Egg laying, free choice test,
spraying cabbage leaves with
water or EtOH solutions of
purified THC 1% or CBD 1%
Choice of THC, 1301 eggs; vs. CBD, 3261 eggs.
Choice of water, 2211 eggs; vs. THC, 1119 eggs.
Choice of water, 2739 eggs; vs. CBD, 3859 eggs.
Choice of Mexican extract, 0 eggs, vs. THC, 83 eggs.
Spotted stalk borer
Chilo partellus Bajpai and Sharma
[62]
PE extract of leaves, 20% w/v
Extract killed 40% of borers, and this toxicity persisted for four
days.
Anopheles stephensi, Culex
quinquefasciatus, Aedes aegypti
Jalees et al. [85]
EtOH of leaves,
4% solution
Extracts added to water in the laboratory killed all mosquito larvae
within 24 hours, LC50 = 1000 mg/L (A. stephensi), 1400 (C.
quinquefasciatus), 5000 (A. aegypti)
Termite Reticulitermes speratus
Lajide et al. [86]
MeOH extract from Xylopia
aethiopica, which contained
cannabisin B and D
Feeding deterrence at 10,000 ppm.
Potato tuber moth Phthorimaea
operculella Sharma et al. [64]
EtOH, PE, benzene, and acetone
extracts of leaves, 2%. Ovicidal
effects by dipping eggs in
extract for 2 min. Oviposition
deterrence on potato leaves
dipped in extract for 30 sec, 1
min, or 2 min
Reduction in egg hatching: Ethanol 13.7% > PE 13.3% > Benzene
10.4% > Acetone 6.7%. Mean of four extracts, Cannabis ranked
6th out of 10 tested plants.
Reduction in egg laying: Ethanol 35.7% w/30 sec, 42.7 w/1 min,
43.3% w/2 min, > Acetone 31.3% w/30 sec, 40.0% w/1 min,
41.9% w/2 min, > PE 30.0% w/30 sec, 35.5% w/1 min, 42.4% w/2
min. Mean of four extracts, Cannabis ranked 5th out of 10.
Asian blue tick
Rhipicephalus microplus
Mansingh and Williams [87]
EtOH of leaves, topical
application on engorged ticks
Acaricidal index (ranged from 50 to 100), Cannabis = 58, ranked
24th out of 29 plants tested
Swarming non-biting midge
Chironomus samoensis
Roy and Dutta [88]
EtOH of wild-type leaves in a
refluxing apparatus. Last-instar
larvae incubated in 200 mL
phosphate buffered saline (PBS)
PBS with 2 mL DSMO (1%), plus 5, 10, or 20 mg dried crude
extract per mL PBS. Paralysis and death in 82-100, 66-80, and 36-
48 minutes, respectively. Controls (DSMO only) moulted into
normal adults. Microscopy (SEM) showed damage to body cuticle,
especially sensilla trichoidea, suggestive of neurotoxicity
Mustard aphid
Lipaphis erysimi
Srivastava & Guleria [89]
PE extract, 200 g leaves in 500
ml PE, Soxhlet at 40-60ºC
Mustard leaf dipped in extract diluted to 1% extract, adult aphids
placed on leaves; 22.2% mortality. Cannabis tied 8th out of 34
tested plants
Fall armyworm Spodoptera
frugiperda Sirikantaramas et al. [90]
Insect cell culture, Sf9 cell line,
24 hour exposure to THCA at
50 𝜇M
THCA induced cell death via apoptosis as demonstrated by trypan
blue staining

Journal of Entomology and Zoology Studies
~ 1295 ~
Tobacco cutworm
Spodoptera litura
Singh et al. [91]
Acetone, EtAC, and EtOH
extracts
Antifeedant activity (preference index value) rank order: acetone
(0.46), EtAC (0.5), EtOH (0.5)
Tobacco cutworm
Spodoptera litura
Singh et al. [92]
Acetone, EtAC, and EtOH
extracts, assayed three
paramters
Shortened larval period: acetone 12.2 days, EtAC 13.8 days, EtOH
14.5 days. Percent pupation: acetone 73.3%, EtAC 83.3%, EtOH
83.3%. Adult emergence: acetone 23.3%, EtAC 30.0%, EtOH
23.3%. Rank order: Azadirachta indica > Datura alba > Cannabis
> seven other plants
Diamondback moth Plutella
xylostella
Sharma et al. [66] (method
clarifications in Kumar et al. [67]).
EtOH leaf extract, Soxhlet
apparatus. Ovicidal effects of
eggs on califlower leaves dipped
in test solutions for 10 sec.
Egg hatch 97.7% (distilled water), 81.1% (1% extract), 93.2%
(2.5% extract), 91.1% (5% extract), 77.8% (8% extract), and
75.5% (10% extract). Extracts made from Melia azedarach,
Lantana camara, and Artemisia annua showed greater ovicidal
effects.
Mosquito
Culex quinquefasciatus
Maurya et al. [93]
CT, PE, MeOH leaf extracts,
Soxhlet apparatus, WHO
protocol, 3rd instar larvae
LC50 (ppm) after 24 hours: CT (88.5) > MeOH (160.8) > PE
(294.4). After 48 hours: CT (68.7) > MeOH (71.1) > PE (73.32).
Extracts from Aloe barbadensis more effective
Two spotted spider mite,
Tetranychus urticae; Wheat aphid,
Schizaphis graminum;
Western flower thrips, Frankliniella
occidentalis
Taisiya et al. [94]
EtOH flower extract, 30 g in
300 EtOH for 3 days, sonicated,
evaporated. 1% emulsion made
with Tween. Leaf dipped in
emulsion, then pests introduced.
Adult female spider mites counted after seven days on bean leaves,
50–80% lethality.
Adult female aphids counted after 24 hours on wheat leaves, 50–
80% lethality.
Early 2nd instar thrips larvae counted after 5 days on bean leaves,
0–20% lethality
Pulse beetle, Callosobruchus
chinensis
Thakur and Devi [95]
Acetone and MeOH, room
temperature extraction of leaves,
assayed mortality, oviposition
deterrence, and F1 adult
emergence
Acetone 20% extract 100% mortality took 7 days, 10% extract
took 9 days, 5% extract took 10 days.
MeOH 20% extract 100% mortality took 8 days, 10% extract took
10 days, 5% extract took 11 days. Number of eggs laid: acetone
20% extract 4.1, control 36.0; methanol 20% extract 5.4, control
38.6. Number F1 adult emerged: acetone 20% extract 1.7, control
26.0; methanol 20% extract 2.3, control 27.5.
Extraction method: carbon tetrachloride, CT; ethanol, EtOH; ethyl acetate, EtAC; methanol, MeOH; petroleum ether, PE
Two studies compared aqueous extracts to solvent extracts.
They suggest little difference in efficacy. Sharma et al. [64]
assayed ovicidal activity and oviposition deterrence in the
potato tuber moth, Phthorimaea operculella. A 2% aqueous
extract reduced egg hatching by 13.7%, identical to a 2%
ethanol extract, and marginally superior to PE extract
(13.3%), benzene extract (10.4%), and acetone extract (6.7%).
Potato leaves dipped in a 2% aqueous extract for 2 minutes
deterred egg laying by 41.7%, marginally inferior to ethanol
extract (43.3%), PE extract (42.4%), and acetone extract
(41.9%).
Sharma et al. [66] assayed ovicidal activity in the diamondback
moth, Plutella xylostella, and compared extracts at several
dilutions. They reported ethanol extracts showing greater
ovicidal activity than aqueous extracts at 10%, 8%, and 1%
concentrations, but the reverse was found at 2.5% and 5%
(data repeated in Kumar et al. [67]). They did not run statistics;
our paired t test of their data showed no significant difference.
The study by Rothschild and Fairbairn [63] is particularly
instructive. Aqueous extracts with terpenoids (cold extracts)
were more effective than aqueous extracts lacking terpenoids
(heated extracts), and extracts made from pure THC or CBD
were even less effective. CBD was actually an oviposition
attractant. The authors summarized, “the butterfly is
sufficiently sensitive to differentiate between purified THC
and CBD-two substances which taste and smell alike to the
human observer.”
Thomas et al. [75] compared their EO results with those of
Jalees et al. [85], who used ethanol extracts. Both groups tested
the same insects, in the same laboratory (one co-author in
common). The EO extract was more effective than the ethanol
extract. They suggested that hydrodistillation retained an
active ingredient lost or reduced in the ethanol extract.
3.6 Mechanism of action
THC’s mechanism of action in arthropods is not mediated by
cannabinoid CB1 receptors-its primary target in vertebrates.
Arthropods do not express CB1 receptors [96]. The spectrum of
activity of THC is similar to that of rotenone: little or no
repellency, but notable toxicity. Rotenone and THC do not
share a mechanism of action. Rotenone potently inhibits the
mitochondrial Complex I electron transport system. This
inhibition has been measured in rat liver mitochondria and
Spodoptera frugiperda Sf9 cells, with an IC50 of 19.3 and
21.0 nmol/L, respectively [97]. THC only inhibited Complex I
activity 11% in pig brain mitochondria, at a thousand-fold
greater dose (50 𝜇mol/L) [98].
Organophosphate pesticides inhibit acetylcholinesterase
(AChE) activity, whereas THC does not inhibit AChE activity
[99]. AChE activity is inhibited by EOs extracted from
Azadirachtina, Mentha, and Lavendula [99]. Surprisingly, EOs
extracted from Cannabis show little AChE inhibition, with an
IC50 = 4.0 mg/mL [82]. Benelli and colleagues [82] noted that
individual terpenoids in Cannabis EO show potent AChE
inhibition, such as 𝛼-farnesene, β-pinene, terpinolene, and
(E)-caryophyllene. They concluded that the complex mixture
in Cannabis EO was competitive, rather than synergistic.
Rather than AChE inhibition, they suggest that Cannabis EO
targeted insect octopamine or GABA receptors.
Octopamine receptors in insects are equivalent to
norepinephrine receptors in vertebrates. Octopaminergic
toxicity is elicited by EOs extracted from Citronella, Pinus,
Cendrus, and Eucalyptus [100], as well as amitraz.
Octopaminergic activity by Cannabis EO or
phytocannabinoids has not been assayed.
The monoterpenoid thymol (present in the EO from Thymus
vulgaris) antagonizes the insect GABAergic system [100], as
does the insecticide fipronil. THC impacts the GABAergic
system in vertebrates, although its direct effects are difficult
to assess, because CB1 receptors are localized on GABAergic
neurons, where CB1 activation decreases GABAergic activity.
However, one study showed that THC decreased locomotion,

Journal of Entomology and Zoology Studies
~ 1296 ~
nociception, body temperature in knockout mice with a
deletion of CB1 in GABAergic neurons [101]. This suggests
that THC may be a mechanism imparting toxicity in insects.
GABAergic effects by Cannabis EO have not been measured.
Several pesticides target voltage-gated sodium channels in
nerve axons. Pyrethrins, sabadilla, and DDT depolarize axon
membranes. Indoxacarb and metaflumizone block sodium
channels [102]. THC also depresses voltage-gated sodium
channels [103], so THC may also affect insects via this
mechanism.
4. Conclusions
Companion planting showed the least robust evidence of the
five types of applications. Most publications were anecdotal.
The two experimental studies diverged: one showed efficacy,
the other did not. The use of harvested plant material, without
any extraction, has an ancient anecdotal history. Experiments
with this material successfully repelled or killed pests, at least
in under laboratory conditions.
Aqueous and solvent extracts showed similar efficacies. Both
extracts produced a wide range of outcomes, from no
repellency to total mortality. Ten studies with aqueous
extracts compared Cannabis with other pesticidal plants, and
Cannabis ranked in the top half four times. In seven studies
with solvent extracts, Cannabis ranked in the top half four
times.
Experiments with EO extracts were the most rigorous, and
yielded the best results. However, these studies evaluated
small arthropods with thin cuticles (mosquitos, aphids, spider
mites, termites). Studies with aqueous and solvent extracts
tested a greater percentage of Lepidoptera and Coleoptera.
The two EO studies with Lepidoptera showed only moderate
toxicity.
Collectively, the studies point to terpenoids as the primary
Cannabis constituents responsible for arthropod deterrence.
EO extracts-nearly pure terpenoids-worked the best. Aqueous
and solvent extracts have lesser amounts of terpenoids, and
lesser efficacies. Freshly harvested plant materials outgas
terpenoids, not cannabinoids, and they repelled or killed
arthropods, especially in closed laboratory conditions.
Terpenoids dissipate outdoors, and this may explain poor
results seen in companion plant experiments.
Cannabis-based pesticides show promise in repelling pests of
humans and crop plants. Surprisingly, some even showed
efficacy against arthropods that attack Cannabis crops. No
toxicity was seen in three non-target organisms, which is
remarkable, to say the least. The mechanisms of action of
Cannabis EO and THC remain to be elucidated.
5. References
1. World Health Organization, 2017. Vector-borne diseases.
Available at: http://www.who.int/news-room/fact-
sheets/detail/vector-borne-diseases. 17 October, 2017.
2. Culliney TW. Crop losses to arthropods, in Pimental D,
Peshin R, eds. Integrated Pest Management. Springer
Science, Dordrecht, 2014, 201-225.
3. McPartland JM. Cannabis as repellent and pesticide.
Journal of the International Hemp Association. 1997;
4(2):87-92.
4. McPartland JM, MacDonald C, Young M, Grant PS,
Furkert DP, Glass M. Affinity and efficacy studies of
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