2. REVIEW OF LITERATURE - Information and Library ...shodhganga.inflibnet.ac.in/bitstream/10603/29762/9/09...2. REVIEW OF LITERATURE Allelochemicals from essential oil bearing plants

2. REVIEW OF LITERATURE

Allelochemicals from essential oil bearing plants have started to make

commercial impact recently and have been categorized as green pesticides (Koul et al.,

2008). With an aim to reduce the use of synthetic insecticides, they represent one of the

most promising approaches for their eco-chemical control. With very few exceptions,

botanical insecticides in commercial use have been used in traditional practices dating

back at least 150 years and often much longer (Jacobson and Crosby, 1971; Philogene et

al., 2005).

The aim of the present work has been to study the efficacy of essential oil

compounds against lepidopteran larvae to demonstrate their potential specifically against

maize borer, Chilo partellus Swinhoe, very difficult insect to control otherwise, and

Asian armyworm, Spodoptera litura Fabricius, which is becoming resistant to synthetic

insecticides. Such compounds will be useful if used in IPM programmes that would

reduce the selection pressure and should allow for the reversion of resistant populations.

Accordingly, the literature was scanned to obtain the details about the bioefficacy of

various essential oils and their constituents, against various pest species.

2.1 EFFICACY OF ESSENTIAL OILS AND THEIR CONSTITUENTS AS

INSECTICIDES AND GROWTH INHIBITORS

Essential oils are complex mixtures of natural organic compounds which are

predominantly composed of terpenes (hydrocarbons) such as myrecene, pinene,

terpinene, limonene, p-cymene, α- and β-phellandrene etc.; and terpenoids (oxygen

containing hydrocarbons) such as acyclic monoterpene alcohols (geraniol, linalool),

monocyclic alcohols (menthol, 4-carvomenthenol, α-terpineol, carveol, borneol),

aliphatic aldehydes (citral, citronellal, perillaldehyde), aromatic phenols (carvacrol,

thymol, safrol, eugenol), bicyclic alcohol (verbenol), monocyclic ketones (menthone,

pulegone, carvone), bicyclic monoterpenic ketones (thujone, verbenone, fenchone), acids

(citronellic acid, cinnamic acid) and esters (linalyl acetate). Some essential oils may also

contain oxides (1,8-cineole), sulphur containing constituents, methyl anthranilate,

coumarins, etc. Zingiberene, curcumene, farnesol, sesquiphellandrene, termerone,

Review of Literature

10

nerolidol, etc. are examples of sesquiterpenes (C15

) isolated from essential oils. Mono and

sesquiterpenoidal essential oil constituents are formed by the condensation of isopentenyl

pyrophosphate units. Diterpenes usually do not occur in essential oils but are sometimes

encountered as by-products (Koul et al., 2008).

Traditionally essential oil compounds have been used for protection of stored

commodities, especially in the Mediterranean region and in Southern Asia, but interest in

the oils was renewed with emerging demonstration of their fumigant and contact

insecticidal activities to a wide range of pests in the 1990s (Isman, 2000). The rapid

action against some pests is indicative of a neurotoxic mode of action, and there is

evidence for interference with the neuromodulator octopamine that regulate the

movement, heart rate, behavior, metabolism and pupation of insects (Enan, 2001;

Kostyukovsky et al., 2002; Enan, 2005a,b) by some oils and with GABA-gated chloride

channels by others (Priestley et al., 2003). The purified terpenoid constituents of essential

oils are moderately toxic to mammals, but with few exceptions, the oils themselves or

products based on oils are mostly nontoxic to mammals (Roe, 1965; Cockayne and

Gawkrodger, 1997; Hjorther et al., 1997), birds (Wager-Page and Mason, 1997; Kumar et

al., 2000), and fish (Stroh et al., 1998). The oils are safe for natural enemies for instance,

a rosemary oil based insecticide/acaricide was significantly less toxic to predatory mite

(Phytoseiulus persimilis Athias-Henriot) than to their spider mite prey, two spotted spider

mite (Tetranychus urticae Koch), although the whitefly parasitoid, Encarsia formosa

Gahan, was more susceptible than its hosts (Gorski, 2004). Owing to their volatility,

essential oils also have limited persistence under field conditions; therefore, although

natural enemies are susceptible via direct contact, predators and parasitoids reinvading a

treated crop one or more days after treatment are unlikely to be poisoned by residue

contact as often occurs with conventional insecticides. Recent evidence for an

octopaminergic mode-of-action for certain monoterpenoids (Kostyukovsky et al., 2002;

Bischof and Enan, 2004), combined with their relative chemical simplicity may yet find

these natural products useful as lead structures for the discovery of new neurotoxic

insecticides with good mammalian selectivity.

Essential oils like that of rose (Rosa damascene), patchouli (Pogostemon

patchouli), sandalwood (Santalum album), lavender (Lavendula officinalis) and geranium


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(Pelargonium graveolens), etc., are well known in perfumery and fragrance industry

(Koul et al., 2008). Other essential oils such as pine, lemon grass (Cimbopogon

winteriana), Eucalyptus globulus, rosemary (Rosemarinus officinalis), vetiver (Vetiveria

zizanoides), clove (Eugenia caryophyllus) and thyme (Thymus vulgaris) are known for

their pest control properties; like peppermint (Mentha piperita), pennyroyal (Mentha

pulegium), spearmint (Mentha spicata) and basil (Ocimum basilicum) are effective in

warding off ants, flies, fleas and lice (Koul et al., 2008). Similarly, essential oil bearing

plants like Artemesia vulgaris, Melaleuca leucadendron, Pelargonium roseum,

Lavandula angustifolia, M. piperita, Juniperus virginiana and Backhousia citriodora, are

also effective against various insects (Kumar and Dutta, 1987; Adams et al., 1988;

Cavanagh and Wilkinson, 2002; Wilkinson et al., 2003; Kordali et al., 2005). Essential

oils from Abelmoschus moschatus, Acorus calamus, Bunium persicum, Cedrus spp.,

Cinnamomum zeylanicum, Cuminum cymium, Cymbopogon citratus, C. martini,

Eucalyptus spp., Eugenia caryophyllata, Foeniculum vulgare, Gaultheria procumbens,

Inula racemosa, Lippia turbinate, L. polystachya, Melinis minutiflora, Ocimum

kilimandscharicum, O. kenyense, Piper spp., Rabdosia melissoides, Saussurea lappa

Securidaca longepedunculata, Tanacetum vulgare, Thujopsis dolabrata var. hondai

Sawdust, Trachyspermum ammi and Xylopia aethiopica have been demonstrated in

various studies to show toxic and growth inhibitory effects (Smith, 1965; Nijholt et al.,

1981; Chatterjee et al., 1982; Barton et al., 1989; Steven et al., 1990; Bathal et al., 1993;

Regnault-Roger and Hamraoui, 1994; Weaver et al., 1994; Lindsay et al., 1996; Laurent

et al., 1997; Lee et al., 1997b; Marimuth et al., 1997; Park et al., 1997; Prates et al.,

1998; Zollo et al., 1998; Landolt et al., 1999; Larocque et al., 1999; Pandey et al., 2000;

Bekele and Hassanali, 2001; Moretti et al., 2002; Thacker, 2002; Chansung et al., 2005;

Jayasekara et al., 2005; Kathuria and Kaushik, 2005a; Kathuria and Kaushik, 2005b;

Oyedeji et al., 2005; Adewoyin et al., 2006; Amer and Mehlhorn, 2006a; Choochote et

al., 2006; Kumar et al., 2007; Omar et al., 2007; VanTol et al., 2007a; Kembro et al.,

2008; Koul et al., 2008; Autran et al., 2009; Palacios et al., 2009).

Some essential oils are known to control S. litura. Essential oil of Ocimum

sanctum caused mortality to 3rd instar S. litura larvae (Sharma et al., 2001) and O. canum

and Rhinacanthus nasutus oils could kill 4th instar S. litura larvae (LC50 = 36.46 and


12

68.08 ppm, respectively) (Kamaraj et al., 2008a). These oils also caused mortality of

gram pod borer, Helicoverpa armigera Hubner (Kamaraj et al., 2008b). In a topical mode

of application oils from Satoreja hortensis, Thymus serpyllum and Origanum creticum

(Isman et al., 2001), Aegle marmelos (Tripathi et al., 2003b), and Ageratum conyzoides

(Sharda et al., 2000) have also been shown to induce toxicity against S. litura larvae

though at various levels of treatment. Essential oils from I. racemosa and S. lappa are

also biologically active against S. litura (Bathal et al., 1993). Such biological activities

like growth inhibition by Lippia alba against same species is also on record (GI50

=

6.9−11.0 mg/g diet) (Tripathi et al., 2003b). Laboratory bioassays of the essential oil of

Chloroxylon swietenia and its isolates geijerene, pregeijerene, germacrene D and β-

ocimene show significant toxicity by topical application against S. litura and pure oil,

geijerene and pregeijerene were more toxic with LD50 values of 28.6, 35.4 and 40.7

µg/larva, respectively (Kiran et al., 2006a). Pavela (2005) has reported the study of 23

essential oils against the 3rd instar larvae of Egyptian cotton leafworm, Spodoptera

littoralis (Boisdnval), via topical application, where eight essential oils from M. citrata,

N. cataria, Salvia sclarea, O. vulgare, O. compactum, Melissa officinalis, Thymus

mastichina and L. angustifolia were highly toxic with LD50 ≤ 50 µl/larva.

Topical application of O. onites essential oil against Pine processionary moth,

Thaumetopoea wilkinsoni Tams, also caused larvicidal activity and the activity has been

attributed to carvacrol and thymol, though γ-terpinene and terpinen-4-ol, were also

moderately active (Cetin et al., 2007). The essential oils from wood terpentine, thyme

herb, juniper berry, laurel leaf, lavender (flower and leaf), eucalyptus leaf and cypress

berry are also toxic to these moths (Kanat and Alma, 2003).

Some oils are also known to cause toxicity by contact. Buchu leaf, niaouli,

rosemary, armoise, cypress, galbanum and mace oils have been reported active against

almond moth, Cadra cautella (Walker) (Sim et al., 2006) in contact application. Essential

oil of Origanum onites was evaluated against cattle tick, Rhipicephalus turanicus

(Pomerantsev) and found effective in causing mortality against ticks with LC50 and LC90

values of 2.34 and 7.12, respectively after 24 h post treatment, proving this oil to be

utilized at reasonable concentrations to control tick infestation (Coskum et al., 2008).

Caraway seed, clove leaf, eucalyptus, pennyroyal, peppermint, rose wood, spearmint and


13

tea tree essential oils are effective against whitefly, Trialeurodes vaporariorum

Westwood adults, nymphs and eggs at very low concentrations (Choi et al., 2003). Jojoba

oil extracted from seeds of Simmondsia californica and S. chinensis is effective against

whiteflies, Bemisia tabaci (Gennadius) and T. vaporariorum in contact application

(Copping, 2004). Choi et al. (2003) evaluated 53 plant essential oils against T.

vaporariorum in Korea, where it is reported as an important pest of various greenhouse

vegetables and recorded insecticidal action for these oils. Similarly, insecticidal activity

of essential oils from 23 plant species studied against turnip aphid, Lipaphis

pseudobrassicae Davis showed that Bifora radians and Satureja wiedemaniana essential

oils as toxic (Sampson et al., 2005). Some Mediterranean plant essential oils are also

aphicidal against A. pisum and M. persicae (Digilio et al., 2008) and mustard aphid,

Brevicoryne brassicae Linn. (Mustafa and Gazi, 2009).

In volatile toxicity bioassays, rosemary oil was significantly toxic against elaterid

beetle, Agriotes obscurus Linn. At LC50 = 15.9 µg/cm3, (Waliwitiya et al., 2005a).

Rosemary oil is also toxic to armyworm, Pseudaletia unipuncta Haworth and cabbage

looper, Trichoplusia ni Hubner and toxicity has been attributed to camphor (LD50 = 189.4

µg/larva) against P. unipuncta and α-terpineol (LD50 = 128.5 µg/larva) against T. ni

(Isman et al., 2008). The essential oil obtained from roots of L. mutellina (containing

dillapiole, ligustilide and myristicin as major constituents) has been evaluated and found

toxic against 3rd instars of P. unipuncta (Passreiter et al., 2005).

The turmeric rhizome (C. longa), contains pungent, odoriferous oil and oleoresin

and is well known for its biological activity against insects (Sivananda, 1958; Raghunath

and Mitra, 1982; Srimal, 1997; Rath et al., 1998). The turmeric leaves, (the unutilized

part of turmeric plant) on hydrodistillation yield oil rich in α-phellandrene (70%). This oil

induces growth inhibition and larval mortality in Bihar hairy caterpillar, Spilosoma

obliqua Walker (Agarwal et al., 1999, Walia, 2005) and diamond back moth, Plutella

xylostella (Linnaeus) (Govindaraddi, 2005). This oil is also ovicidal and nymphicidal

against red cotton bug, Dysdercus koenigii (Fabricius) (Agarwal et al., 2001). Essential

oil of turmeric also possess contact toxicity against lesser grain borer, Rhyzopertha

dominica Fabricius adults with an LD50 value of 36.7 µg/mg body weight (Tripathi et al.,

2002). Garlic oil is larvicidal against many insects, like house fly, Musca domestica


14

Linnaeus and khapra beetle, Trogoderma granarium Everts, (Bhatnagar-Thomas and Pal,

1974); S. litura, Euproctis spp., and Foul water mosquito, Culex peus Speiser (Deb-

Kirataniya et al., 1980); Yellow fever mosquito, Aedes aegypti (Linn.) larvae (Amonkar

and Reeves, 1969) and green peach aphid, Myzus persicae (Sulzer) (Hori, 1996).

The essential oil from roots of sweet flag, A. calamus is well known for its

insecticidal and antigonadal actions, and activity has been attributed to its major

compound β-asarone (Koul et al., 1990; Schmidt and Streloke, 1994; Koul, 1995). A.

calamus has also been shown to be toxic to 3rd instar larvae of hairy caterpillar, Spilarctia

obliqua (Walker) in both laboratory and field conditions (Dubey et al., 2004).

Essential oils or their constituents are also effective against termites. Japanese

termite, Reticulitermes speratus Kolbe are killed by Orixa japonica essential oil at a

concentration of 3.5 µl/l air, whereas Eucalyptus radiate, Cinnamomum cassia, Allium

cepa, Illicium verum, Schizonepeta tenuifolia, Cacalia roborowskii and clove bud oils

induce 100% mortality within 2 days of treatment at 2.0 µl/l of fumigation (Park and

Shin, 2005). According to Raina et al. (2007) orange oil extracted from citrus peel caused

96 and 68% mortality to formosan subterranean termite, Coptotermes formosanus Shiraki

within 5 days, and there was significant reduction in feeding as compared to controls at 5

ppm concentration (v/v); also the termites did not tunnel through glass tubes fitted with

sand treated with 0.2–0.4% orange oil extract. Similar activity was observed with vetiver

oil and nootkatone, which act as soil barriers against termites (Maistrello et al., 2001a,b;

Zhu et al., 2001a,b; Maistrello et al., 2002). Catnip oil derived from Nepeta cataria and

its two major components E, Z-nepetalactone and Z, E-nepetalactone cause 100%

mortality at 40 mg/cm2 in formosan subterranean termite, C. formosanus after one day,

and 97% mortality at 20 mg/cm2 within 7 days, respectively. Repellent action was also

obvious as tunneling by termites was prevented (Chauhan and Raina, 2006).

Bruchids have been reported as highly susceptible to various essential oils. They

are insecticidal and also deter fecundity and fertility. For example, varied type of actions

have been demonstrated against bean weevil, Acanthoscelides obtectus (Say) (Regnault-

Roger and Hamraoui, 1994,1995a,b; Papachristos and Stamopoulos, 2003; Regnault-

Roger et al., 2004). In choice and no-choice bioassays against A. obtectus, geranium oil

had a strong repellent action, whereas eucalyptus oil strongly reduced fecundity,


15

decreased egg hatchability and increased neonate larval mortality (Stamopoulos, 1991).

Bioefficacies of mixture of essential oil of Clausena anisata and aromatized clay powder

were evaluated against, A. obtectus for their insecticidal activity and their effects on

progeny production. Contact toxicity assayed by coating on bean grains has shown

significant mortality by oil and clay (when applied individually) after 2 days with LD50

values of 0.069 and 0.081 µl/g grains, respectively and considerable reduction in the F1

progeny was observed. Mixtures, however, were less toxic than individual oils (Ndomo et

al., 2008). Essential oils from Luvandula hybrida, R. officinalis and Eucalyptus globules,

are also toxic to, A. obtectus with LC50 values ranging from 0.8 to 47.1 mg/l air

(Papachristos and Stamopoulos, 2002a,b; Papachristos et al., 2004).

Dill oil obtained from dill plant (Anethum sowa), a by-product of dill industry is

also a rich source of carvone and dillapiole. These are well known for their insecticide-

synergistic properties (Koul et al., 2008). Contact toxicity and repellency of essential oils

from the seeds of umbelliferous plants like dill, Peucedanum verticillare, Prangos

asperula, and coriander against granary weevil, Sitophilus granarius (Linn.) is well

known (Zuelsdorff and Burkholder, 1978).

Vector control is also an important component of pest management. It has been

observed that many essential oils are quite promising in repelling mosquitoes or act as

larvicides. For instance, Cymbopogon spp., Ocimum spp., Eucalyptus spp., Tagetes

patula, Dalbergia sisso, Mentha piperita, Cinnamomum osmophloeum, Dendropanax

morbifera, Thymus capitatus and Piper essential oils are significantly active (Writz et al.,

1980; Perich et al., 1994; Chantraine et al., 1998; Ansari et al., 2000a,b; Mansur et al.,

2000; Sosan et al., 2001; Cheng et al., 2003; Xue et al., 2003; Cheng et al., 2004;

Burfield and Reekie, 2005; Dharmagadda et al., 2005; Morais et al., 2006; Choochote et

al., 2007; Morais et al., 2007; Nathan, 2007; Gillij et al., 2008; Kimbaris et al., 2008;

Silva et al., 2008; Autran et al., 2009; Cheng et al., 2009c; Chung et al., 2009; Lucia et

al., 2009; Pavela, 2009). Essential oils extracted from Myrtus communis were found to be

most toxic against 4th instar larvae of Northern house mosquito, Culex pipiens Linn.,

followed by those of Origanum syriacum, Mentha microcorphylla, Pistacia lentiscus and

Lavandula stoechas with LC50 values of 16, 36, 39, 70 and 89 mg/l, respectively

(Traboulsi et al., 2002). The essential oils extracted from O. onites and O. minutiflorum


16

had a high toxicity against 3rd and 4

th instar larvae of C. pipiens (Cetin and Yanikoglu,

2006), whereas Foeniculum vulgare, Ferula hermonis, Citrus sinensis, Pinus pinea,

Laurus nobilis and Eucalyptus spp. oils were effective with LC50 values in the range of

24.5−120 mg/l (Traboulsi et al., 2005). Alpine thyme oil, parsley seed oil, aniseed oil and

coriander fruit oil are larvicidal against seaside mosquito, Ochlerotatus caspius Knowlet

4th instar with LC50 in the range of 15−156 ppm (Knio et al., 2008). Similarly, essential

oil of Pimpinella anisum is larvicidal against 4th instars of malaria mosquito, Anopheles

stephensi Liston and Southern house mosquito, Culex quinquefasciatus Say with LC50

values of 115.7 and 149.7 µg/ml, respectively (Prajapati et al., 2005). Essential oil from

Trachyspermum sp. is also larvicidal against A. aegypti and C. quinquefasciatus, (LC50 =

93.19−150.0 ppm) (Vrushali et al., 2001), however, Vanillosmopsis arborea oil (LC50 =

15.9 ppm) apparently is more toxic against this mosquito spp. (Furtado et al., 2005).

Lemongrass oil and geranium (Pelargonium radula) oils are also effective against A.

aegypti 2nd

instar larvae, in the range of 40−100 ppm. Linaloe (Bursera delpechiana) oil

is toxic and also produces malformed adults (60−100%) which ultimately die due to

failure in pupal ecdysis (Osmani and Sighamony, 1980). Leaf and twig essential oils of

Clausena excavate, are toxic to 4th instar A. aegypti and Asian tiger mosquito, Aedes

albopictus Skuse larvae in the range of 37.1−40.1 and 41.1−41.2 µg/ml, respectively. The

effective constituents, limonene, γ-terpinene, terpinolene, β-myrcene, 3-carene and p-

cymene have been identified from these oils. Limonene has been the most active with

LC50 value of 19.4 and 15.0 µg/ml, respectively against both species of mosquitoes

(Cheng et al., 2009a). Similarly, mosquito larvicidal activity of essential oils and their

constituents from E. camaldulensis and E. urophylla is also on record (Cheng et al.,

2009b). The larvicidal activity of C. swietenia is well known against mosquitoes, A.

aegypti and A. stephensi (Kiran et al., 2006b).

Many pure compounds from essential oils are also toxic and growth inhibitors

against various pests of economic importance. Eugenol shows variable LD50

values

which are purely species specific. Cornelius et al. (1997) evaluated toxicity of various

monoterpenoids against subterranean termite, C. formosanus of which eugenol was found

most effective as termiticide, fumigant and as feeding deterrent. Eugenol is also reported

as toxic against S. litura, S. granarius, M. domestica and Western corn root worm,


17

Diabrotica virgifera virgifera LeConte, (LD50 = 2.5–157.6 µg/insect) (Lee et al., 1997a;

Obeng-Ofori and Reichmuth, 1997; Hummelbrunner and Isman, 2001); its activity

against Fruit fly, Drosophila melanogaster Meigen, yellow fever mosquito, A. aegypti

and American cockroach, Periplanata americana (Linnaeus) is well known (Bhatnagar et

al., 1993; Ngoh et al., 1998). Contact toxicity (LD50 = 516.5 µg/larva) and volatile

toxicity (LC50 = 20.9 µg/cm

3) of eugenol has been reported against elaterid beetle, A.

obscurus (Waliwitiya et al., 2005b) as well.

Thymol seems to be potential compound for insect control. Its toxicity against M.

domestica and S. litura (LD50 = 25.4–29.0 µg/insect) (Lee et al., 1997a; Hummelbrunner

and Isman, 2001), D. melanogaster and Northern house mosquito, C. pipiens, (LC50 =

36−49 mg/l) (Franzios et al., 1997; Traboulsi et al., 2002) and contact toxicity (LD50 =

196.0 µg/larva) and volatile toxicity (LC50 = 17.1 µg/cm

3) against A. obscurus

(Waliwitiya et al., 2005b) has been reported.

Citronellal is toxic against S. litura and M. domestica (LD50 = 66.0–111.2

µg/insect) (Lee et al., 1997a; Hummelbrunner and Isman, 2001), cowpea weevil,

Callosobruchus maculatus (Fabricius) and D. melanogaster (Don-Pedro, 1996a,b).

Contact toxicity (LD50 = 404.9 µg/larva) and volatile toxicity (LC

50 = 6.3 µg/cm3) by

citronellal against elaterid beetle, A. obscurus is also reported (Waliwitiya et al., 2005b).

Hierro et al. (2004) showed monoterpenic compounds active against herring worm,

Anisakis simplex Karl larvae and found that geraniol, citronellol, citral, carvacrol and

cuminaldehyde were active at 12.5 µg/ml concentration.

Carvacrol and 1,8-cineole have been evaluated against M. domestica to show

their toxicity at LD50 = 92 and 281 µg/insect, respectively 24 h after topical application

(Lee et al., 1997a). Carvacrol is also biocidal against ticks, fleas, and mosquitoes with

LC50

values of 0.0068, 0.0059, and 0.0051% (w/v), respectively after 24 h (Panella et al.,

2005). 1,8-Cineole is toxic to D. virgifera virgifera (LD50 = 224 µg/insect) (Lee et al.,

1997a). Insecticidal activity of 1, 8-cineole from lavender (Clemente et al., 2007) and

some essential oil formulations (Passino et al., 1999) have been evaluated against

Mediterranean fruit fly, Ceratitis capitata Wied. Similarly, 1,8-cineole from A. annua is

toxic to rust red flour beetle, Tribolium castaneum (Herbst) adults with LD50 values of


18

108.4 µg/mg body weight (Tripathi et al., 2001). 1,8-Cineole also acts as growth inhibitor

against various post harvest and house hold pests (Jacobson and Halber, 1947; Klocke et

al., 1989; Obeng-Ofori and Reichmuth, 1997).

Limonene found in the essential oil of various citrus leaves and fruit peels have

exhibited significant insect control properties against cat flea, Ctenocephalides felis

(Bouche) (Taylor and Vickery, 1974; Hink and Fee, 1986), scale insects and mealybugs

(Hollingsworth, 2005). Limonene in the range of 50–273.7 µg/insect is toxic to M.

domestica, D. virgifera virgifera, S. litura (Lee et al., 1997a; Hummelbrunner and Isman,

2001) and some stored grain pests and cockroaches (Coats et al., 1991; Don- Pedro,

1996b; Lee et al., 2001). Limonene, linalool, α-myrcene and α-terpineol significantly

increased the nymphal duration in German cockroach, Blattella germanica (Linnaeus)

when fed through artificial diet (Karr and Coats, 1992). Limonene, linalool and α-

terpineol were also observed to have toxic properties against several insects damaging

stored grains and considered as alternative insecticides to protect stored products

(Weaver et al., 1991; Weaver et al., 1995). Other monoterpenoids like carveol,

carvomenthenol, geraniol, isopulegol, linalool, l-menthol, α-terpineol, verbenol, d-

carvone, l-carvone, l-fenchone, menthone, thujone and verbenone have been reported to

be active against M. domestica (LD50 = 73−247 µg/insect), and D. virgifera virgifera

(LD50 = 12−224 µg/insect) 24 h after topical application (Lee et al., 1997a). These

compounds also reduce growth of 1st instars European corn borer, Ostrinia nubilalis

(Hubner) larvae at (0.02−20.0 mg/g diet) (Lee et al., 1999). In another study, Tarelli et al.

(2009) have shown that M. domestica is very sensitive to limonene and many other

compounds by topical application methods and the LD50 values (µg/insect) determined

were 0.07 (geranium), 0.09 (mint), 0.13 (lavender), 0.14 (eucalyptus), 0.04 (linalool),

0.10 (limonene), 0.11 (menthone) and 0.13 (eucalyptol), suggesting significant potential

of this compound in controlling M. domestica.

Menthone, trans-anethole and cinnamaldehyde are well known anti-insect

compounds that have been studied against variety of insects with wide range of dosage

required to kill 50% population (65–1735 µg/insect) (Harwood et al., 1990; Franzios et

al., 1997; Huang and Ho, 1998; Chang and Ahn, 2001; Hummelbrunner and Isman, 2001;

Lee et al., 2001; Chang and Cheng, 2002). trans-Anethole is insecticidal against M.


19

domestica with LD50 value of 75.0 µg/fly, whereas anisaldehyde, estragole, anisyl

alcohol, anisic acid, p-cresol and eugenol are moderately toxic against the house fly. It

has also been observed that trans-anethole and anisaldehyde increased the toxicity to flies

when applied simultaneously with parathion, paraoxon, carbaryl, carbofuran insecticides.

This resulted from an increased penetration of the insecticides into the insect body and

retardation to non-toxic, water-soluble metabolites (Marcus and Lichtenstein, 1979).

Pulegone is a very potential compound and shown to be effective against M.

domestica, D. virgifera virgifera, P. saucia and S. litura in the range of LD50 = 38–753.9

µg/insect (Harwood et al., 1990; Lee et al., 1997a; Hummelbrunner and Isman, 2001).

Pulegone and menthol also inhibit growth and reproduction of Southern armyworm,

Spodoptera eridania (Cramer) (Gunderson et al., 1985) and variegated cutworm,

Peridroma saucia (Hubner) (Harwood et al., 1990). Pulegone has also been observed to

be more toxic than menthol against European corn borer, O. nubilalis 1st instar, whereas

reverse toxicity was observed against 2nd

instar (Lee et al., 1999). In another study,

pulegone was most toxic, followed by menthone and limonene with LC50 values of 1.21,

6.03 and 15.42 µg/ml, respectively against sciarid fly, Lycoriella ingenua (Dufour) (Park

et al., 2006b).

Camphor, a major component of O. kilimandscharicum, when either impregnated

on filter paper (100 mg/filter paper) or applied topically (100 µg/insect), was highly toxic

to granary weevil, S. granarius, maize weevil, Sitophilus zeamais Motschulsky, and

larger grain borer, Prostephanus truncatus (Horn) causing over 93 and 100% mortalities,

respectively, whereas 70 and 100% mortality was observed against T. castaneum adults.

Also, when impregnated on surface of whole wheat grains, the development of immature

stages within grain kernels, as well as progeny emergence, was completely inhibited in

camphor treated grains (Obeng-Ofori et al., 1998).

Carvone isolated from aerial parts of dill plants (Anethum graveolus) reported

earlier as insecticidal (Lichtenstein et al., 1974), also inhibits larval growth and adult

survival (Ouden et al., 1993) in Drosophilla and Aedes spp. Carvones have been reported

to be toxic against termites (Odontotermes brunneus Hagen) and adults of Leucaena

psyllid, Heteropsylla cubana Linn., (Sharma et al., 1992; Sharma and Raina, 1998) and

oviposition deterrent against adults of cabbage root fly, Phorbia brassicae Bche (Ouden


20

et al., 1993). Carvones have also been reported to act as feeding deterrents of adult desert

locust, Schistocerca gregaria Forskall. (Saxena, 1980) and pales weevil, Hylobius pales

Herbst (Saloman et al., 1994).

Perillaldehyde (LC50 = 3 µg/g) in soil bioassay, was only 1/3 as toxic as

carbofuran, a commercial soil insecticide (LC50 = 1 µg/g) against pine needle gall midge,

Thecodiplosis japonensis Uchida and Inouye (Lee et al., 1997b). Meepagala et al. (2006)

found that apiol (at 1%, w/w) isolated from Ligusticum hultenii exhibited absolute

termiticidal activity within 11 days after treatment whereas cnicin isolated from

Centaurea maculosa showed 81% mortality within 15 days after treatment when applied

at 1.0% (w/w) concentration to these termites.

In another study, methyl allyl disulfide significantly decreased the growth rate,

food consumption and food utilization with feeding deterrence indices of 44% at 6.08

mg/g food for S. zeamais and 1.52 mg/g food for T. castaneum, respectively (Huang et

al., 2000a). Similarly, diallyl trisulfide (LD50 values of 1.02 and 5.54 µg/mg insect)

(Huang et al., 2000a) and cinnamaldehyde (LC50 value of 0.70 and 0.66 mg/cm2) (Huang

and Ho, 1998) were reported to cause mortality, among T. castaneum and S. zeamais

adults, respectively. The growth inhibitory activity of gingerol, curcumene and ginger

oleoresin (constituents of ginger oil) against 3rd instar S. obliqua larvae, were lower (EC50

values ranging from 9.6 to 9.8 mg/ml) than dehydroshogaol, zingerone dihydrozingerone

and dehydrozingerone (EC50 values ranging from 3.5 to 5.5 mg/ml) (Agarwal et al.,

2001). Beninger et al. (1993) observed that a diterpene 3-epicaryotin reduced growth of

European corn borer larvae when incorporated into artificial diet, and pupal deformities

and time to pupation also increased. Survival of onion thrips, Thrips tabaci Lindeman on

leaf disc surface was significantly decreased when treated with terpinen-4-ol at 1.0%

concentration (Koschier et al., 2002).

2.2 ACARICIDAL EFFECTS

Acaricidal activities of various essential oils or pure constituents offer an

attractive alternative to synthetic acaricides and have been assessed and found toxic

against honey bee mite, Acarapis woodi (Rennie), (Cox et al., 1989; Calderone et al.,

1991; Ellis and Baxendale, 1997), varroa mite, Varroa jacobsoni Oudemans (Frediani


21

and Pinzauti, 1988; Colin, 1990; Colin, 1991; Calderone and Spivak, 1995; Sammataro et

al., 1998; Calderone, 1999; Elllis, 2001; Noel et al., 2002), Northern fowl mite,

Ornithonyssus sylviarum (Canestrini and Fanzago) (Carroll, 1994), storage grain mites,

Tyrophagus longior Gervais, (Perrucci, 1995) and Tyrophagus putrescentiae (Schrank)

(Ramos and Castanera, 2001; Kwon and Ahn, 2002a; Kim et al., 2003a; Kim et al.,

2004a; Lee et al., 2006), spruce spider mite, Oligonychus ununguis (Jacobi) (Cook,

1992), scab mite, Psoroptes cuniculi (Delafond) (Perrucci et al., 1995), two spotted

spider mite, T. urticae (Larson and Berry, 1984; Sawires et al., 1988; Amer et al., 1989;

Dimetry et al., 1990; EI-Gengaihi et al., 1992; Ibrahim and Amer, 1992; Amer et al.,

1993; Ibrahim et al., 1993; EI-Gengaihi et al., 1996; Lee et al., 1997a; Chiasson et al.,

2001; Aslan et al., 2004; Calmasur et al., 2006; Cavalcanti et al., 2009), carminr spider

mite, Tetranychus cinnabarinus Boisduval (Mansour et al., 1986), American house dust

mites, Dermatophagoides pteronyssinus (Trouessart) and Dermatophagoides farinae

Huges, (Yatagi, 1997; Kwon and Ahn, 2002b; Kim et al., 2003b; Kim et al., 2004b,c;

Rim and Jee, 2006; Kim et al., 2007; Williamson et al., 2007) and scrub typhus mite,

Leptotrombidium akamushi (Brumpt) (Eamsobhana et al., 2009).

The emulsifiable concentrate UDA-245 (25% EC, v/v), based on essential oil

extract from Chenopodium ambrosioides at 0.5% concentration is more effective than

0.7% (a.i.) of neem oil and as effective as 0.006% (a.i.) of abamectin against T. urticae

and European red mite, Panonychus ulmi (Koch) (Chiasson et al., 2004). Several oils and

their constituents are effective against the phytophagous spider mites, as commercial

miticides based on rosemary or cinnamon oils attest (Isman, 2000; Miresmailli et al.,

2006). Rosemary oil is also toxic against predaceous mites Amblyseius barkeri Hughes,

A. zaheri and Typhlodromus athiasae Porath (Momen and Amer, 1999). The toxicity of

cassia essential oil, Cinnamomum cassia, formulations against adult American house dust

mites, D. farinae and D. pteronyssinus has been examined using contact toxicity bioassay

(sprays containing 20−50 g/l cassia oil) and found effective when applied to fabric, glass,

paper, plastic, tin or wood substrates with different space volumes and surface areas and

significantly comparable in activity with that of commercial acaricide benzyl benzoate,

but higher in activity than that of dibutyl phthalate and diethyl-m-toluamide (DEET),


22

proving cassia oil to be an effective tool to provide protection to humans from house dust

mites (Kim et al., 2006).

Approximately 150 essential oils have been evaluated against varroa mite,

Varroa destructor Anderso & Trueman with various results (Calderone and Spivak,

1995; Imdorf et al., 1999; Floris et al., 2004; Ruffinengo et al., 2005). Many of the tested

oils have been effective against V. destructor in laboratory experiments and field trials

(Colin, 1990; Calderone et al., 1991; Colin, 1991; Calderone and Spivak, 1995; Kraus

and Page, 1995; Calderone et al., 1997; LeConte et al., 1998; Lindberg et al., 2000;

Melathopoulus et al., 2000; Ruffinengo et al., 2001; Ardeshir et al., 2002; Ruffinengo et

al., 2002). Bioactivity of various essential oils isolated from Acantholippia seriphioides,

Aloysia polystachya, Eupatorium buniifolium, Lippia turbinate, Loppia junelliana

Minthostachys mollis, Schinus molle, Tagetes minuta and Wedelia glauca are known to

be effective against V. destructor (Rickli et al., 1991). Pellets of Apilife VARR

(containing thymol, eucalyptol, menthol and camphor) when placed above the brood

combs of colonies infested with V. jacobsoni and replaced after 14 days, 100% mortality

of mite was observed when used for 79 days (Rickli et al., 1991). Colin (1990)

demonstrated that essential oils of thyme, Thymus vulgaris, and sage, Salvia officinalis,

can effectively control V. jacobsoni.

George et al. (2009b) have suggested that certain essential oils may be of use as

an alternative to synthetic acaricides in the management of poultry red mite,

Dermanyssus gallinae (DeGeer). At a level of 0.21 mg/cm2, the essential oil of

Eucalyptus citriodora, controlled 85% of D. gallinae over a 24 h exposure period in

contact toxicity tests (George et al., 2009a). Choi et al. (2004) evaluated 53 plant

essential oils against T. urticae and predatory mite, P. persimilis as a fumigant, out of

which caraway seed, citronella, lemon, eucalyptus, pennyroyal and peppermint oils were

found to be highly toxic.

Turmeric oil at 0.01% concentration (v/w), when evaluated in stored wheat grains

against storage mites, T. putrescentiae and Suidasia nesbitti Hughes, the average count

was 54.8 and 70.2, respectively, as compared to 125.2 and 144.2 in untreated control,

whereas 100% mortality of mites was observed at 0.5% concentration (Gulati, 2002).


23

Eugenol from cloves, Eugenia cryophyllus; 1,8-cineole from Eucalyptus globules

and R. officinalis; citronellal from lemon grass, Cymbopogon nardus; pulegone from

Mentha pulegium, and thymol and carvacrol from Thymus vulgaris are the most active

constituents which have significantly repellent and toxic action against two spotted spider

mite, T. urticae (EI-Gengaihi et al., 1996; Miresmailli et al., 2006). Linalool, thymol and

1,8-cineole alone or blended with other essential oils or pure compounds caused mortality

in V. jacobsoni and are important component of integrated pest management programme

for the control of varroa mite (Chiesa, 1991; Gal et al., 1992; Calderone et al., 1997;

Imdorf et al., 1999; Nasr and Kevan, 1999; Rice et al., 2004; Liang et al., 2005).

Over the past few years the worldwide trend has been to use natural substances

against varroa mites particularly thymol which has been tested in powdered form with

different quantities and application intervals (Imdorf et al., 1999; Whittington et al.,

2000), impregnated in porous ceramic carrier (Apilife VARR) (Imdorf et al., 1995) or

included in a gel (Apiguard) (Colombo and Spreafico, 1999; Arculeo, 2002). Aerosol

sprays 4 times and with 4 days of intervals, with mixture of thyme (0.5%) and sage oil

(0.25%), 92−98% mortality of V. jacobsoni has been observed (Colin, 1990). Citronellal,

eugenol, menthol, pulegone, and thymol seem to be moderately active against varroa and

scab mites (Calderone and Spivak, 1995; Perrucci et al., 1995; Ellis and Baxendale,

1997). The pronounced acaricidal activity has been reported in case of menthol, α-

terpineol and thymol (with LD50 values 70.8−234.3 mg/m2) than dibutyl phthalate (LD50

= 285.1 mg/m2) against American house dust mites, whereas menthol and citral have

been reported toxic against tracheal mites (Ellis and Baxendale, 1997). In residual contact

and vapour-phase toxicity bioassays, Kim et al. (2008) have reported that

cinnamaldehyde and salicylaldehyde are 2.5 and 1.7 times more toxic than benzyl

benzoate against D. farinae and D. pteronyssinus (based on 24 h LD50 values). These

studies indicate that such compounds can make substantial impact as commercial

products, if suitable delivery systems are developed.

2.3 FUMIGANT EFFECTS

Monoterpenes being volatile are more useful as insect fumigants. Several studies

have been undertaken in the past to explore the potential of essential oils and their


24

constituents as insect fumigants (Regnault-Roger, 1997; Rajendran and Sriranjini, 2008).

In vapor phase toxicity bioassays against C. cautella larvae, rosemary and niaouli

oils were effective with LC50 values (after 24 h) from 64.6−64.7 mg/l air (Sim et al.,

2006). The fumigant toxicity of 66 plant essential oils to P. xylostella using vapour-phase

toxicity bioassay has been demonstrated where pennyroyal oil (10.77 mg/filter paper of

4.25 cm diameter) was most toxic fumigant, followed by rosemary and sage oils (15.15

mg/paper). Similarly, potent fumigant toxicity has also been reported from armoise,

buchu leaf, cedarleaf, coriander, eucalyptus, howood, lavender, myrtle, niaouli,

peppermint and rosewood oils (LC50 = 21.29−27.31 mg/paper) (Chang et al., 2007).

Essential oils of N. cataria and Thuja occidentalis are also toxic against 3rd instar S.

littoralis larvae with LC50 ≤ 10.0 ml/m3, whereas Salvia sclarea, Thymus mastichina, O.

majorana, Pogostemon cablin and M. pulegium are less toxic (LC50 = 10.1−20.01 ml/m3)

(Pavela, 2005).

Dipteran larvae of sciarid fly, Lycoriella ingenue Dufour, have been controlled by

fumigation method using essential oils of Chenopodium ambrosioides, Eucalyptus

globules, E. smithii, horseradish oil (Armoracia rusticana), anise oil, (Pimpinella anisum)

and garlic oil (Allium sativum) at concentrations of 5−10 µl/l air (Park et al., 2006a).

Essential oils of Acorus gramineus, Schizonepeta tenuifolia and Zanthoxylum piperitum,

are active at 25 µg/ml air concentration against L. ingenue (Park et al., 2006b). In a

similar study, essential oils of caraway seed (Carum carvi), lemongrass (C. citrates),

mandarine (Citrus reticulate), nutmeg (Myristica fragrans), cade (Juniperus oxycedrus),

cumin (Cuminum cyminum) and thyme red (Thymus vulgaris) are shown to be active

against L. ingenue at 30x103 mg/ml air concentration (Park et al., 2008). Tarelli et al.

(2009) have recently evaluated fumigant toxicity against M. domestica by exposing them

to vapors delivered by filter paper treated with 200 µl of essential oils and monoterpenes,

respectively and suggest their knockdown property. Knockdown times (KT50) were 17.7

(geranium), 10.4 (mint), 10.9 (lavender), 3.3 (eucalyptus), 7.6 (linalool), 7.5 (limonene),

19.0 (menthone) and 2.3 (eucalyptol) minutes.

Insecticidal activity has also been reported against hemipterans. Tunc and

Sahinkaya (1998) found that essential oils of cumin (Cuminum cyminum), anise

(Pimpinella anisium) oregano (Origanum syriacum var. bevanii) and eucalyptus


25

(Eucalyptus camaldulensis) are effective as fumigants against the cotton aphid (Aphis

gossypii Glover). Fumigant assays of the essential oil of Vitex pseudonegundo on mustard

aphid, B. brassicae showed concentration dependent nymphal mortality in the range of

1.6 to 12 µl/l of air space from 3 to 24 h (Moharramipour and Sahaf, 2006).

Use of essential oils have shown substantial potential to control pests of stored

products (Shaaya et al., 1997; Buchbauer, 2000; Isman, 2000; Kim and Ahn, 2001;

Bazzoni et al., 2002; Lee et al., 2002b; Kim et al., 2003c; Isman, 2005; Mondal and

Khalequzzaman, 2006; Kouminki et al., 2007; Ngamo et al., 2007; Hubert et al., 2008).

Toxic effects of essential oils from Artemisia vulgaris, Baccharis sagittalis, Elletaria

cardamomum, Evodia rutaecarpa, Junellia aspera, Laurus nobilis, Ocimum gratissimum

and garlic oil against T. Castaneum and S. zeamais have been extensively studied (Saim

and Meloan, 1986; Sarac and Tunc, 1995; Chiam et al., 1999; Liu and Ho, 1999; Huang

et al., 2000a,b; Cifuente et al., 2002; Andronikashvili and Reichmuth, 2003; Pungitore et

al., 2003; Wang et al., 2006). Insecticidal activity of Ageratum conyzoides essential oil in

diet assays at 0.01−0.1 mg/g of diet (Bouda et al., 2001), and Dennettia tripetala powder

mixed with maize grains at 1.5 g/25 g grains killed all adults of S. zeamais in 24 h and

also suppressed the emergence of F1 offsprings and gave protection for up to 4 months of

storage. This oil was as effective as primiphos-methyl (10 ppm) (Okonkwo and Okoye,

1996).

Cowpea weevil, Callosobruchus maculatus (Fabricius), T. castaneum, cigarette

beetle, Lasioderma serricorne (Fabricius), rice weevil, Sitophilus oryzae (Linn.) and

Angoumois grain moth, Sitotroga cerealla (Oliver) are also susceptible to essential oil

treatments (Krishnarajah et al., 1985; Ivbijaro and Agbaje, 1986; Saxena et al., 1992;

Rice and Coats, 1994a,b; Ndungu et al., 1995; Bekele et al., 1996; Huang et al., 1997;

Onu and Sulyman, 1997; Huang and Ho, 1998; Huang et al., 1999; Kimani and Sum,

1999; Liu and Ho, 1999; Obeng-Ofori and Reichmuth, 1999; Keita et al., 2000; Lee et

al., 2000; Ketia et al., 2001; Ketoh et al., 2002; Tapondjou et al., 2002; Hori, 2003;

Pascual-Villalobos and Ballesta-Acosta, 2003; Boeke et al., 2004; Lee et al., 2004;

Umoetok and Ukeh, 2004; Aslan, et al., 2005; Tapondjou et al., 2005; Garcia et al.,

2005; Negahban et al., 2006; Negahban et al., 2007; Lopez et al., 2008; Ogendo et al.,

2008 ; Sahaf et al., 2008; Cosimi et al., 2009; Nerio et al., 2009a,b).


26

Ketoh et al. (2005) have studied the insecticidal activity of essential oil of

Cymbopogon schoenanthus against C. maculatus and observed 100% mortality at 33.3

µl/l concentration within 24 h exposure period and the development of newly laid eggs

and neonate larvae was significantly inhibited sulethal concentrations. However the oil

has variable efficacy against bruchid instars developing inside the seeds, without

affecting the efficacy of natural enemy of bruchid, solitary parasitic wasp, Dinarmus

basalis Rodani. Lippia rugosa essential oil has been found most persistent toxic for S.

zeamais, S. oryzae, C. maculatus and T. castaneum though the toxicity was variable from

50 to 100% (Ngamo et al., 2007). Nagassoum et al. (2007) has studied the insecticidal

activity of essential oils of Vepris heterophylla, Ocimum canum and Hyptis spicigera

plants against S. oryzae where O. canum oil was most active with LD50 value of 42.9

ppm. Chenopodium oil is highly toxic against adults of C. maculatus (100% mortality at

40 µg/insect), L. serricorne (92.5% mortality at 50 µg/insect) and moderately toxic to S.

oryzae (52.5% mortality at 50 µg/insect), when applied topically. However, when applied

to wheat and cowpea seeds, the oil reduced infestation of S. oryzae and C. maculatus at

2000 and 1000 ppm, respectively (Su, 1991). The essential oils of Eucalyptus intertexta,

E. sargentii and E. camaldulensis, have potent fumigant toxicity against 1 to 6 day old

adult stored product beetles with LC50 values in the range of 2.55−3.97 µl/l air of C.

maculatus, 6.93−12.91 µl/l air for S. oryzae and 11.59−33.50 µl/l air against T.

castaneum, (Negahban and Moharramipour, 2007). In fumigant toxicity tests, the

insecticidal activity of essential oil of Carum copticum, has been observed against S.

oryzae and T. castaneum adults with LC50 values of 0.91 and 33.14 µl/l, respectively,

showing S. oryzae susceptible than T. castaneum (Sahaf et al., 2007), however, S. oryzae

(LC50 = 18.75 µl/l) seem to be resistant than T. castaneum (LC50 = 11.39 µl/l) when

essential oil of Perovskia abrotanoides was used in the treatments (Arabi et al., 2008). At

12.0 µg/ml concentration of essential oil of Coriandrum sativum, mortality of T.

castaneum adults was 95%. The treatment at larval stage showed that the percentage of

larvae reaching to pupal and to adult stages decreased significantly with increasing

concentration. Absolute mortality (100%) of eggs was observed with oil fumigation at 20

µg/ml and 96 h exposure period (Islam et al., 2009). The activity of essential oils of


27

sweet flag, A. calamus and clove, Syzygium aromaticum as fumigant against S. oryzae

inhibited F1 progeny after 14 days post-treatment (Sharma and Meshram, 2006).

Essential oils from lime, navel orange, grapefruit and lemon are highly toxic to T.

castaneum and S. granarius. These studies have also shown that non-toxic dosages of

these oils have synergistic action when combined with pyrethroid cypermethrin and

pirimiphos-methyl (Abbassy et al., 1979).

The fumigant toxicity of 28 essential oils extracted from various spice and herb

plants and some of their major constituents have been evaluated against adult

coleopterans, R. dominica, sawtoothed grain beetle, Oryzaephilus surinamensis (Linn.)

and T. castaneum. The compounds terpinen 4-ol, 1,8-cineole and essential oils of sage,

three-lobed sage, baylaurel, rosemary and lavender are most active against R. dominica;

the compounds linalool, α-terpineol, carvacrol and essential oils of oregano, basil, syrian

marjoram and thyme are most active against O. surinamensis, whereas anise and

peppermint are active against T. castaneum (Shaaya et al., 1991). The essential oil of

Clausena anisata however, is moderate repellent with high fumigant toxicity (LC50 =

0.093 µl/cm3) against adults of A. obtectus (Ndomo et al., 2008).

Number of compounds has been evaluated as fumigants against M. domestica and

T. castaneum and their LC50

(µg/l) values have been determined for carvacrol, carveol,

geraniol, linalool, menthol, α-terpineol, thymol, verbenol, carvones, fenchone, menthone,

pulegone, thujone, verbenone, cinnamaldehyde, citral, citronellal, and cinnamic acid

(Rice and Coats, 1994a,b). Toxic effects of many monoterpenes like d-limonene,

linalool and α-terpineol have been observed in several insects damaging stored products

and considered as alternative insecticides to protect stored products (Sy et al., 1972; Don-

Pedro, 1985; Weaver et al., 1991; Weaver et al., 1995). Pulegone, linalool and limonene

are known effective fumigants against rice weevil, S. oryzae (Singh et al., 1989). Linalool

and limonene are active with LC50 values of 14 and 19 µl/l air space, respectively,

whereas LC50 values for myrcene and α-terpineol are > 100 µl/l air space against S.

oryzae (Coats et al., 1991). Menthone is toxic (LC50 = 12.7 µl/l air) followed by

linalool (LC50 = 39.2 µl/l air) and α-pinene (LC50 = 54.9 µl/l air) against S. oryzae (Lee et

al., 2001). A relationship between fumigant toxicity and inhibition of

acetylcholinesterase activity has also been studied (Gracza, 1985; Grundy and Still, 1985;


28

De-Oliveira et al., 1997; Jukic et al., 2007). Studies on inhibition of acetylcholinesterase

activity of S. oryzae showed menthone to have a 9-fold lower enzyme inhibitory effect

than menthol, despite menthone being 8-fold more toxic than menthol to the rice weevil

(Lee et al., 2001).

α-Pinene (LD50 = 9.85 µl/l air) is toxic fumigant followed by β-pinene (LD50 =

11.85 µl/l air) and linalool (LD50 = 21.15 µl/l air), also the mixture of α- and β-pinene

exhibited stronger fumigant toxicity than individual compounds against the mushroom

sciarid fly, Lycoriella mali (Fitch), adults, suggesting potent fumigant activity during

mushroom cultivation (Choi et al., 2006). Using fumigation bioassay, citronella (LD50 =

2.3 µl/l air) seem to be highly potent against spring tail, Proisotoma minuta (Tullberg)

(Lee et al., 2002a).

Carvone has been reported to cause 24 times more fumigant toxicity than contact

toxicity against lesser grain borer, R. dominica (Tripathi et al., 2003a). Carvone causes

contact toxicity while menthol causes fumigant toxicity against T. castaneum and C.

maculatus, whereas 1,8-cineole exhibits both contact and fumigant toxicity against T.

castaneum (Tripathi et al., 2001).

trans-Anethole, thymol, 1,8-cineole, carvacrol, α-terpineol, and linalool have

been evaluated as fumigants against T. castaneum. Only compound to show significant

effect against this insect species was trans-anethole and red flour beetles seemed to be

least susceptible to most of the other compounds up to 300 µl/l fumigation. Anethole has

shown significant effect on population from 20 µl/l concentration (66% reduction in

population), which touched to 98% at 80 µl/l level and beyond this there was absolute

control of population generation. For improving the mortality effect of anethole,

minimum heat treatment (45°C) device was used that enhanced the toxicity of adults by

2-fold at 50 µl/l and 100 µl/5l treatment, respectively. Among various combinations of

compounds used anethole combined with 1,8-cineole (1:1) was the best. This

combination reduced the population by 100% at 50 µl/l concentration and at the same

time was toxic to adults as well. As T. castaneum was resistant to most of the

compounds, a workable gelatin capsule formulation (IBRC-TACT) based on combination

of four compounds has been developed, which reduced the progeny by 100%. A

significant observation has been that when treatment was continued for larvae in 5-litre


29

jars (with feeding medium) and insects were allowed to complete life cycle under treated

conditions the freshly emerged adults coming to the surface of the feeding medium were

dead within 12 h. This suggests that freshly emerged adults were highly susceptible to the

treatment of anethole or IBRC-TACT and could not withstand the effect of compounds.

One of the plausible explanations for such an effect has been attributed to the interference

during the sclerotization immediately after the emergence from pupae, which ultimately

leads to the death of beetles within 12 h of their emergence (Koul et al., 2007).

2.4 ANTIFEEDANT EFFECTS

Antifeedant chemicals may be defined as being either repellent without making

direct contact to insect, or suppressant or deterrent from feeding once contact has been

made with insects. Essential oil constituents such as thymol, citronellal and α-terpineol

are effective as feeding deterrent against tobacco cutworm, S. litura and synergism or

additive effects of combination of monoterpenoids from essential oils have been reported

against S. litura larvae (Hummelbrunner and Isman, 2001). Bioefficacy of Eucalyptus

camaldulensis var. obtusa and Luvanga scandans essential oils has also been determined

against S. litura larvae. 1,8-Cineole from E. camaldulensis var. obtusa and linalool from

L. scandans species are shown to be most active isolates from these plants via topical

application. Linalool was more active (LD50 = 85.5 µg/larva) than 1, 8-cineole (LD50

=

126.6 µg/larva) (Singh et al., 2008). Maximum feeding deterrence has been observed for

geijerene, pregeijerene from the essential oil of Chloroxylon swietenia against S. litura

with DC50 values of 82.5 and 95.1 µg/cm2, respectively (Kiran et al., 2006a).

Considerable feeding inhibition (70.21–80.21%) has been recorded against 3rd

instar larvae of S. obliqua when treated with 0.4% concentration of Artemisia nilagarica

and Juglans regia var. kumaonica oils, while at 0.3% these oils induced feeding

deterrence of 63.12–83.76% among 5th instar larvae of S. litura (Chowdhury et al., 2000).

Essential oils from Elsholtzia densa, E. incise and E. piulosa also showed significant

antifeedant activity against 3rd instar larvae of S. litura (Shishir et al., 2004). Oil of M.

pulegium significantly inhibits the feeding of fall armyworm, Spodoptera frugiperda (J. E

Smith) (Zalkow et al., 1979). Highest feeding deterrence of 76.4% has been observed

against H. armigera using essential oil of Aegle marmelos (Tripathi et al., 2003b). The


30

essential oils of Artemisia tridentata, Purshia tridentata and Crysothamnus nauseosus

deter feeding in Colorado potato beetle, Leptinotarsa decemlineata (Say) and A. calamus

oil in variegated cutworm, P. saucia (Jermy et al., 1981; Koul et al., 1990). Ginger oil

and its constituent curcumene at 10 g/l caused 48 and 54% feeding inhibition against 3rd

instar S. obliqua larvae, whereas ginger oleoresin exhibited pronounced feeding

inhibition causing 82 and 74% feeding inhibition at 10 and 7 g/l, respectively (EC50 = 3.1

mg/ml). The enhanced activity of ginger oleoresin has been attributed to the possible

synergistic action of its various constituents (Agarwal et al., 2001). Dose dependent

antifeedant effect of various essential oils like citronella, palmarosa, geranium,

wintergreen, patchouli, citriodora and camphor oils has been determined against 3rd instar

larvae of darth meal moth, Pericallia ricini (Fab.) when applied at concentrations from

2.5−10% on castor leaves (Dale and Saradamma, 1981). In a study, Guerra et al. (2007)

observed that when potato tubers were covered with dried chopped leaves and flowers of

Minthostachys spicata and M. glabrescens, significant reduction in tuber damage as

compared to controls by potato tuber moth, Phthorimaea operculella (Zeller) was

recorded.

Feeding deterrence activities of leaf essential oil of C. longa against adult and

larvae of grain borer, R. domestica; rice weevil, S. oryzae; and red flour beetle, T.

castaneum has been attributed to the presence of monoterpenes, carvone and

dihydrocarvone (Tripathi et al., 2003a). Products isolated/derived from C. longa

(turmeric) and Zingiber officinale (ginger) have also been found effective as insect

antifeedant and insect growth regulators (Agarwal et al., 2001; Agarwal and Walia,

2003). Diallyl trisulfide significantly reduced nutritional indices, as feeding deterrence

indices of 27 and 51% has been obtained in S. zeamais adults and T. castaneum larvae,

respectively at the concentration of 2.98 mg/g food. Feeding deterrence of 85% has been

achieved in T. castaneum adults at a much lower concentration of 0.75 mg/g food as

copmpared to 90% feeding deterrence with azadirachtin (@ 1.66 mg/g of aza.) (Huang et

al., 2000a). In another study, a terpenoid lactone exhibited antifeedant activity against

granary weevil (S. granarium), khapra beetle (T. granarium) and confused flour beetle

(Tribolium confusum Duval) (Paruch et al., 2000) and the activity was comparable to

neem biopesticide.


31

The antifeedant effect of essential oils and their constituents from majoram,

rosemary, mint, sage and lavender, using leaf disc bioassays against onion thrip, T. tabaci

after 24 h at 0.01–1.0% concentration has been recorded. In no-choice bioassays,

oviposition rate of thrips has been significantly reduced by about 45–60% as compared to

untreated control after application of majoram, mint and lavender oils at 0.1–1%

concentration (Koschier and Sedy, 2001). Similar studies of feeding deterrence against T.

tabaci has been reported by Koschier et al. (2002) and Koschier and Sedy (2003).

Citronellal (800 µg/seed), thymol (400 µg/seed) and eugenol (1600 µg/seed) have been

shown to protect corn seeds from elaterid beetle, A. obscurus feeding (Waliwitiya et al.,

2005a,b).

2.5 REPELLENT EFFECTS

It has long been observed that certain essential oils repel insects of stored

products and households (Osmani, 1971; Osmani, 1974; Collart and Hink, 1986; Ahmad

et al., 1995; Ho et al., 1997; Regnault-Roger, 1997; Thorsell et al., 1998; Lwande et al.,

1999; Adler et al., 2000; Omolo et al., 2004; Dietrich et al., 2006; Stamopoulos et al.,

2007; Yoon et al., 2007; Regnault-Roger and Philogene, 2008).

Citronella (Cymbopogon nardus), essential oil has been used for over fifty years

both as an insect repellent and toxicant (Wong et al.., 2005). Combining few drops each

of citronella, lemon (Citrus limon), rose, lavender and basil essential oils with one litre of

distilled water is effective to ward off indoor insect pests (Zaridah et al., 2003) and the

larvicidal activity of citronella oil has been mainly attributed to its major monoterpenic

constituent citronellal. Citronellal is also good repellent when used to protect clothes and

other valuable materials from insect attack in closets, drawers, and chests (Ray et al.,

2000; Plarre et al., 1997). Vetiver oil consists of more than 300 compounds, among

which α- and β-vetivone, khusimone, khusistone, zizanal and epizizanal have been

reported to be repellents to cockroaches and house flies (Jain et al., 1982). There are

numerous reports on the insecticidal, fumigant and repellent activities of oregano

essential oils from Origanum spp. (Karpouhtsis et al., 1998; Tunc et al., 2000; Erler,

2005a,b; Erler and Tunc, 2005). The repellent property of sweet majoram, Origanum

majorana and clove basil, Ocimun gratissimum essential oils in the range of 87 and 71%,


32

respectively as compared to controls has been observed against T. tabaci (VanTol et al.,

2007a).

Plants whose essential oils have been reported to have repellent activity against

various insects include citronella, cedar, verbena, pennyroyal, geranium, lavender, pine,

cinnamon, rosemary, basil, thyme, black pepper oil and peppermint. Most of these

essential oils provided short-lasting protection usually lasting less than 2 h. Repellent

properties of rosemary oil against onion aphid, Neotoxoptera formosana (Takahashi)

(Masatoshi and Hiroaki, 1997) and the green peach aphid, M. persicae (Masatoshi, 1998)

is well known. Bruce et al. (2005) studied the repellent effect of Hemizygia petiolata

essential oil against M. persicae, grain aphid, Sitobion avenae Fab., and pea aphid,

Acyrthosiphon pisum (Harr.). This essential oil contains germacrene, bicyclogermacrene

and high levels (> 70%) of the sesquiterpene β-farnesene which acts as an alarm

pheromone for many economically important aphid species.

Essential oil of lavender, L. angustifolia has been identified as a potential

repellent for pollen beetle, Meligethes aeneus (Fab.), a major pest of oilseed rape, without

effecting behaviour of its parasitoids, Phradis interstitialis (Thomson) and Phradis

morionellus (Holmgren) (Cook et al., 2007). The budding strips impregnated with

essential oil of lavender and α-terpineol decreased the infestation of red bud borer,

Resseliella oculiperda (Rubs.) from grafted apple trees by 95 and 80%, respectively as

compared to controls, whereas moderate repellent action was recorded using essential oils

of Juniperus virginiana, Cinnamomum camphora and their constituents citronellal, r-

carvone, linalool and r-fenchone (VanTol et al., 2007b). In a field study with potatoes,

wormwood (Artemisia mariatinia) and lavender oils at 0.5−1.0% concentration have

repellent effect against L. decemlineata larvae and adults and are as effective as

deltamethrin (Mateeva, 1998).

Since oxygenated essential oil constituents are more active, efforts have been

made to improve bioefficacy of one such oxygenated essential oil constituent fenchone

(LC50

= 3.8 mg/l for house flies and 14.2 mg/l for red flour beetles) (Rice and Coats,

1994a) by its chemical modification and structure-activity relationship studies. In binary

choice bioassays with M. domestica, feeding on 20 µl of watery honey solutions mixed

with 10 µl of pine oil completely suppressed feeding and remained inhibitory after 24 h


33

and 95% of flies have been repelled at a distance > 6 mm from the source (Maganga et

al., 1996). Volatile compounds and olfaction play a major role in long-range orientation

by the Japanese beetle (Ahmad, 1982; Loughrin et al., 1997, 1998). Earlier studies with

essential oils derived from pine (Pinus spp.) cade (Juniperus spp.), hyssop (Hyssop spp.),

cajuput (Melaleuca spp.) and cascarilla (Croton spp.) have demonstrated repellent action

against Japanese beetles from attractant-baited traps and host trees (Metzger, 1930;

Metzger and Grant, 1932). Similarly, Youssef et al. (2004) has found wintergreen and

peppermint oils reduce Japanese beetle response to traps baited with an attractant.

Repellency of mint (Appel et al., 2004; Chen, 2009) and citrus oil (Vogt and Appel,

1996; Vogt et al., 2002) has been evaluated against red imported fire ants, Solenopsis

invicta Buren.

Several monoterpenoids are repellent to insects. Linalool, nerol, carvone, pulegol,

pulegone and isopulegol are most effective space repellents, others like Japanese mint

and spearmint have been found effective as olfactory repellents against B. germanica

(Inazuka, 1982; 1983; Karr and Coats, 1988; Appel and Mack, 1989; Coats et al., 1991;

Scheffler and Dombrowski, 1992; Appel et al., 2001). The active constituents in Schinus

molle having repellent effect are thymol, citronellyl acetate and β-caryophyllene with

repellency index of 95, 86 and 85%, respectively against B. germanica (Guardiola et al.,

1990; Chopa et al., 2006). S. molle is also effective against many Mediterranean insects

(Ferrero et al., 2006).

Catnip and cedar oils are repellent to German cockroach (Appel and Mack, 1989;

Peterson et al., 2002) and house fly (Peterson, 2001). Recent work has shown that catnip

oil is repellent to the Eastern subterranean termite, Reticulitermes flavipes (Kollar) in

laboratory experiments (Haenke et al., 2002) and citral, citronellal, eugenol, geraniol and

nerol are both toxic and repellent to termites (Lu et al., 1987; Cornelius et al., 1997).

Repellency of oils of lemon, eucalyptus, geranium, and lavender have also been

recorded against sheep tick, Ixodes ricinus Linnaeus (Acari: Ixodidae) in the laboratory

and field (Jaenson et al., 2006). Similarly, laboratory bioassays with 15 natural products

isolated from essential oil from heartwood of Alaska yellow cedar, Chamaecyparis

nootkatensis have demonstrated that camphor, 1,8-cineole, thymol, myncene, limonene

and methyl eugenol are repellents against deer tick, Ixodes scapularis Say nymphs,


34

oriental rat flea, Xenopsylla cheopis (Rothchild), and A. aegypti adults (Kalemba et al.,

1993).

Vector-borne diseases caused by mosquitoes have become global health

problems. Many essential oils and their monoterpenic constituents are known for their

mosquito repellent activity against Culex species (Choi et al., 2002; Traboulsi et al.,

2002). The mosquito repellent activity of 38 essential oils against A. aegypti under

laboratory conditions using human subjects have shown that Cymbopogon nardus

(citronella), Pogostemon cablin (patchuli), Syzygium aromaticum (clove) and

Zanthoxylum limonella are the most effective and provided complete repellency for 2

hours (Trongtokit et al., 2005). Some other essential oil bearing plants, like

Acantholippia seriphioides, Achyrocline satureioides, Aloysia citriodora, Anemia

tomentosa, Baccharis spartioides, Chenopodium ambrosioides, Eucalyptus saligna,

Hyptis mutabilis, Minthostachys mollis, Rosmarinus officinalis, Tagetes minuta, T.

pusillalemon and Piper marginatum Jacqare also repellent to A. aegypti (Lima, 1998;

Cavalcanti et al., 2004; Gillij et al., 2008; Autran et al., 2009).

Some Kenyan plants produce oils that repel African malaria mosquito, Anopheles

gambiae Giles (Barasa et al., 2002; Omolo et al., 2004; Odalo et al., 2005; Omolo et al.,

2005). Lemon grass oil ointment containing 15% v/w citral exhibited 50% repellency

against mosquitoes which lasted for 2−3 h (Oyedela et al., 2002). Volatile oils extracted

by steam distillation from four plant species, turmeric (C. longa), Kaffir lime (Citrus

hystrix), citronella grass (Cymbopogon winterianus) and hairy basil (Ocimum

americanum) have been evaluated against mosquitoes and significant repellent activity

has been observed for eight hours (Tawatsin et al., 2001). Similarly, repellent properties

of essential oils derived from Zanthoxylum piperitum and Apium graveolens both in

laboratory and field do repel mosquitoes significantly as compared to commercial

products (Choochote et al., 2004; Tuetun et al., 2005; Kamsuk et al., 2007). Though

thousands of plants have been tested as potential sources of insect repellents, only a few

plant-derived chemicals tested to date demonstrate the broad effectiveness and duration

as good as DEET (Trigg, 1996; Cockcroft et al., 1998; Sfara et al., 2009). Catnip (Nepeta

cateria), is a perennial herb known for its intoxicating effect on cats. The essential oil of

catnip is highly effective for repelling mosquitoes, bees, ants and other flying insects. The


35

most active constituent in catnip has been identified as nepetalactone which repels

mosquitoes ten times more than DEET and is particularly effective against A. aegypti

mosquito, a vector for yellow fever virus, with similar effect against black fly, Simulium

decorum Walker (Velasco et al., 1989). Essential oils of Z. officinale, R. officinalis and

Cinnamomum zeylanicum were found to be repellent to three mosquito species, A.

stephensi, A. aegypti and C. quinquefasciatus; C. zeylanicum being most active as

repellent (RD95 = 49.6, 53.9 and 44.2 mg/mat, against three mosquitoes, respectively)

(Prajapati et al., 2005). Similarly, litsea oil (Litsea cubeda), cajeput oil (Melaleuca

leucadendron), niaouli oil (M. quinquenervia) and violet oil (Viola odorata) have been

found effective with a protection rate of 8 h for 100% repellency against A. aegypti.

These oils are also effective against malaria vector, A. stephensi and filariasis and

encephalitis vector, C. quinquefasciatus (Amer and Mehlhorn, 2006b; Tawatsin et al.,

2006).

Turmerone and ar-turmerone (dehydroturmerone), the major constituents of

turmeric rhizome powder oil are strong repellents to stored grain pests (Su et al., 1982;

Jilani et al., 1988; Jilani and Saxena, 1990; Saju et al., 1998). The turmeric oil and

essential oil of Cyperus articulatus has been reported to provide protection to wheat

grains against red flour beetle, T. castaneum (Herbst) (Abubakar et al., 2000; Chahal et

al., 2005). Oils from Hyptis spicigera, Ocimum sauve and Lippia sp. show repellent

properties against S. zeamais and C. maculatus (Hassanali and Lwande, 1989; Sanon et

al., 2006). The fruit oil of Piper retrofractum has also shown high repellency (52−90%)

against T. castaneum at 0.5−2% concentration (Chansang et al., 2005). Ndungu et al.

(1995) reported that the repellent action of Cleome monophylla essential oil against S.

zeamais is higher than commercial arthropod repellent N, N-diethyl toluamide (DEET).

The repellent activity of the essential oil of Ocimum kilimandscharicum against S.

zeamais, R. dominica and the Angoumois grain moth, S. cerealella has also been

documented (Bekele et al., 1995). Similar results have been reported by Ukeh et al.,

(2009) suggesting repellent activity of essential oils of Aframomum melegueta and Z.

officinale against S. zeamais and Adhatoda vasica essential oil against S. oryzae and

Callosobruchus chinensis (Linnaeus) (Kokate et al., 1985). O. suave oil repelled S.

zeamais (Hassanali and Lwande, 1989); Lippia spp. oil from Kenya (Mwangi et al.,


36

1992) and A. calamus essential oil repelled T. castaneum and C. maculatus beetles (Jilani

et al., 1988; EI-Nahal et al., 1989; Jilani and Saxena, 1990; Rahman and Schmidt, 1999;

Park et al., 2003). Absinthium essential oil is both toxic and repellent to S. granarius

(Kalemba et al., 1993). S. aromaticum and Melaleuca alternifolia essential oils caused

100% repellency against S. oryzae at 5 and 40% concentrations, respectively

(Eamsobhana et al., 2009). Tripathi et al., (2000) observed that adult beetles of T.

castaneum are repelled significantly by Artemisia annua oil at 1.0% concentration (v/v).

Methyl salicylate, the major component of Securidaca longepedunculata has been

reported to exhibit a dose dependent repellent effect against S. zeamais, R. dominica and

larger grain borer, P. truncatus (Jayasekara et al., 2005). Repellent properties of

isoalantolactone, a natural product isolated from traditional Chinese medicinal herb, Inula

racemosa against S. oryzae (Liu et al., 2006), propionic acid (occurs in the blends of

volatile compounds emitted by barley grains) against S. granarius and S. oryzae

(Germinara et al., 2007) and zimtaldehyde, eugenol and thymol against T. confusum

(Ojimelukwe and Adler, 1999) have been reported. Eugenol is highly repellent against S.

granarius, S zeamais, T. castaneum and P. truncatus with overall repellency in the range

of 80−100% (Obeng-Ofori and Reichmuth, 1997). 1,8-Cineole, borneol and thymol are

effective against S. oryzae at a dose of 0.1 µl/720 ml, while camphor and linalool are

effective against R. dominica at similar concentrations (Rozman et al., 2007). Osajin and

pomiferin, two isoflavones purified from osage orange fruits are found to be significantly

repellent against maize weevil (Peterson et al., 2000).

2.6 OVIPOSITION INHIBITION AND OVICIDAL ACTION

Various essential oils and their constituents have ovicidal and oviposition

deterrent activity against insects. Essential oil of Chloroxylon swietenia and its

constituents geijerene and pregeijerene deter oviposition in S. litura (Kiran et al., 2006a).

The ovicidal effects of volatiles from garlic oil on eggs of four cotton insect pests, spotted

bollworm, Earias vitella (Fab.), D. koenigii, S. litura and H. armigera have also been

reported (Gurusubramanian and Krishna, 1996). Garlic oil which is also an oviposition

deterrent has been found to be highly toxic to eggs of P. xylostella (Govindaraddi, 2005)

and 99.5% reduction in egg hatching has been recorded in S. obliqua at 250 mg oil/50


37

eggs using essential oil of Aegle marmelos (Tripathi et al., 2003b).

Tomova et al. (2005) has reported biological activity of essential oil of Tagetes

minuta against pea aphid, A. pisum, green peach aphid, M. persicae and fox glove aphid,

Aulacorthum solani (Kaltenbach) and demonstrated that this oil significantly reduced the

reproduction potential of the tested species. Gorur et al. (2008) has demonstrated adverse

effects of thymus, veronica and agrimonia essential oils on cabbage aphid as they

significantly decreased fecundity rate. In binary choice bioassay with M. domestica,

feeding on watery honey solution (20 µl) mixed with linalool (1µl) significant reduction

in oviposition has been observed, as the females avoid oviposition sites that are treated

with linalool (Maganga et al., 1996). Application of 1, 8-cineole and majoram reduced

ovipopsition rate of thrips, T. tabaci by 30–50% at concentration of 1.0%, as compared to

untreated controls (Koschier and Sedy, 2001).

A. calamus oil at 0.1% prevents oviposition of C. maculatus (Dimetry et al.,

2003) and similar activity has been reported against melon fly, Bactrocera cucurbitae

Coquillett (Nair and Thomas, 2001). Rahman and Talukder (2006) reported bio-

insecticidal activity of different plant oils and showed that plant oils suppressed the

oviposition ability of C. maculatus adults and thus reduced the damage significantly.

Essential oils of citronella and palmarosa give total protection to groundnut pods by

inhibiting oviposition by the groundnut bruchid, Caryedon serratus Olivier, each at a

dose of 15 ml/kg pods for 6 months with an efficacy equal to that of malathion dust

(Kumari, et al., 1998). Treated groundnut seeds with the essential oils obtained from

clove and ginger reduced egg laying in C. serratus by 51.2−69.6% and 40−45%,

respectively, as compared to untreated seeds, thus suppressed development of progeny in

groundnut seeds (Lale and Maina, 2002).

Sanon et al. (2006) studied that powder and essential oil from Hyptis spicigera

reduced oviposition by 20 and 75%, respectively when tested in stored cowpeas against

T. castaneum, also the egg viability decreased with increasing doses in the range of

40−75% and 25−86%, respectively. Essential oils extracted from leaves of C. longa

reduced the oviposition and hatching of T. castaneum (Tripathi et al., 2002) and A.

obtectus (Papachristos and Stamopoulos, 2002a). Oviposition deterrent activity with

various degrees ranging from 16.6 to 94.7% of various essential oils, from thai plants


38

against A. aegypti has also been reported (Tawatsin et al., 2006).

The emulsifiable concentrate UDA-245 (25% EC, v/v), based on essential oil

extract from Chenopodium ambrosioides at 0.5% concentration significantly reduced egg

hatching 5−9 and 6 days after treatment against two spotted spider mite, T. urticae and

European red mite, P. ulmi, respectively (Chiasson et al., 2004). There is complete

cessation of oviposition by females of storage mites, T. putrescentiae and S. nesbitti when

0.2% concentration (v/w) of turmeric oil was evaluated in stored wheat grains. T.

putrescentiae is more susceptible against turmeric oil treatment than S. nesbitti (Gulati,

2002).

Fumigant toxicity of the essential oils from Lavandula hybrida, R. officinalis and

E. globules against eggs of A. obtectus show LD50 values ranging between 1.3 and 35.1

µl/l air, depending on egg age, as young eggs (≤ 3-day-old) were more tolerant than older

ones (> 4-day-old) and apart from inhibition of hatching, the exposure of eggs to essential

oil vapours increased the subsequent mortality of hatched larvae (Papachristos and

Stamopoulos, 2004). Essential oils of Z. officinale, Juniperus macropoda, Pimpinella

anisum and R. officinalis have also been found as ovicidal against three mosquito species,

A. stephensi, A. aegypti and C. quinquefasciatus (Prajapati et al., 2005).

Essential oil of waya (Plectranthus grandifolius) has been reported to be repellent

(84%) against adults and toxic to both adults and eggs of C. maculatus with LC50 values

of 3.1 and 2.6 µl/l, respectively (Mikolo et al., 2009). Diallyl trisulfide totally suppressed

egg hatching of T. castaneum at 0.32 mg/cm2 (Huang et al., 2000a). Similar activity has

been reported for the essential oils of garlic (Ho et al., 1997), nutmeg and cardamom

(Huang et al., 1997) and for diallyl disulfide (Chiam et al., 1999) against T. castaneum.

Carvone also suppresses the egg hatching in the range of 33−100% of T. castaneum at

7.22 mg/cm2 surface treatment (Tripathi et al., 2003a). These studies demonstrate that

monoterpenoid ketones are significantly more effective than structurally similar alcohols

(like menthone versus menthol; verbenone versus verbenol, etc.). Carvacrol, carveol,

geraniol, linalool, menthol, α-terpineol, thymol, verbenol, carvones, fenchone, menthone,

pulegone, thujone, verbenone, cinnamaldehyde, citral, citronellal, and cinnamic acid have

been evaluated as ovicides against M. domestica eggs (Rice and Coats, 1994a).


39

2.7 ATTRACTANTS

Some essential oils or the components there in do attract insects. Attraction of

Banana weevil, Cosmopolites sordidus (Linn.) (Ndieqie et al., 1996), cudweed

grasshopper, Hypochlora alba (Dodge) (Blust and Hopkins, 1987a,b) and Mexican fruit

fly, Anastrepha ludens (Loew) (Robacker, 1991) to 1,8-cineole has been determined.

Methyl eugenol has been used to trap oriental fruit fly, Dacus dorsalis Hendel, whereas

eraniol and eugenol are attractants and are used as lures in traps (Vargas et al., 2000).

Investigations on constituents of A. calamus root oil as attractant to B. cucurbitae and D.

dorsalis is also on record (Singh and Sehgal, 2001). Youssef et al. (2009) identified

several plant essential oils that act as semiochemical disruptants against the Japanese

beetle, Popillia japonica Newman. Cinnamyl alcohol, 4-methoxy-cinnamaldehyde,

cinnamaldehyde, gerany-lacetone and α-terpineol do attractive to adult corn rootworm

beetles, Diabrotica sp. (Hammack, 1996; Petroski and Hammack, 1998; Copping and

Duke, 2007). The essential oil and a number of extracts of R. officinalis in solvents of

increasing polarity, specifically ethanol and acetone extracts attract grape berry moth,

Lobesia botrana (Denis and Schiffermuller). However, none of the extracts had a

significant effect on western flower thrips, Frankliniella occidentalis (Pergande), which

is attracted by 1,8-cineole, a major essential oil component (Katerinopoulos et al., 2005).

Lemon essential oil is distilled from the peels of Citrus limonum and this oil

contains several terpenes and geraniol, which have all been shown to attract thrips,

fungus gnats, mealybugs, scale and Japanese beetles. Adding this oil to the insect-a-peel,

thrips/leafminer blue trap, or the yellow aphid/whitefly sticky trap attracts unwanted pests

and are captured in the traps (http://www.arbicoorganics.com/1610075.html).

Compositions of cis-jasmone has been found to effectively attract adult

lepidopterans. The cis-jasmone may be used alone or in combination with one or more

other volatiles of the Japanese honeysuckle flower, particularly linalool and/or

phenylacetaldehyde. By attracting the moths to attracticidal baits and/or field traps, the

attractants are useful for the control and monitoring of these agricultural pests (Pair and

Horvat, 1997). Similarly, natural essential oils have shown a high attractiveness for

greenhouse whitefly, T. vaporariorum. Greenhouse whitefly particularly react intensively

to sandalwood oil, basil oil, and grapefruit oil. After the application of aromatic


40

substances on yellow sticky traps, the number of insects caught do increase significantly

(Gorski, 2004). Thus, natural essential oils or their constituents could be useful in the

monitoring of pests, at least under greenhouse conditions.

2.8 ANTIFUNGAL EFFECTS

Many plant essential oils and their major constituents have demonstrated

antifungal activity against a range of plant pathogenic fungi including those responsible

for both pre and post harvest diseases (Garg, 1974; Zutschi et al., 1975; Benijilali et al.,

1984; Deshmukh et al., 1986; Singh et al., 1986; Yadav and Saini, 1990; Adam et al.,

1998; Rai and Acharya, 2000; Burt, 2004; Wilkinson and Cavanagh, 2005; Cavalcanti et

al., 2006; Nikos, 2007; Yang and Clausen, 2007; Regnier et al., 2008; Khongkhunthian et

al., 2009). Antifungal activities of certain effective essential oils or their components like

palmarosa oil, red thyme, clove bud oil, ginger oil (Z. officinale), Salvia officinalis,

Melissa officinalis, Cymbopogon spp. oils, oregano oil, peppermint oil, lavender oil,

dictamus oil, mint oil, cinnamon, cinnamaldehyde, oregano, basil, marjoram, citronellal

and eugenol are effective against Botrytis cinerea (Wilson et al., 1997; Moretti et al.,

1998), Monilinia fructicola (Okoko et al., 1999; Tsao and Zhou, 2000), Rhizoctonia

solani, Fusarium moniliforme and Sclerotinia sclerotiorum (Mishra, 1990; Muller et al.,

1995; Agarwal et al., 2001; Edris and Farrag, 2003; Mimica et al., 2004; Omidbeygi et

al., 2007), F. oxysporum (Rai et al., 1999; Bowers and Locke, 2000), Cymbopogon

nardus (De-Billerbeck et al., 2001), Aspergillus niger, A. flavus (Singh et al., 1988;

Paster et al., 1995; Montser and Carvajal, 1998; Paranagama et al., 2003; Klaric et al.,

2007; Dikbas et al., 2008), Penicillium digitatum (Daferera et al., 2000; Arras et al.,

2006), P. citrinum (Vazquez et al., 2001), F. solani, R. solani, Pythium ultimum and

Colletotrichum lindemuthianum (Zambonelli et al., 1996), Alternaria padwickii,

Bipolaris oryzae, and peanut fungi (Krishna et al., 2007; Nguefack et al., 2007),

Rhizopus stolonifer, Mucor sp. (Thompson, 1989; Edris and Farrag. 2003; Kalemba and

Kunicka, 2003), Macrophomina phaseolina (Dubey and Dwivedi, 1988);

Helminthosporium oryzae (Singh et al., 1980; Endo et al., 1990) and Candida albicans

(Sarac and Ugur, 2009).


41

Unlike insects, different fungal species show more consistent results. Thymus spp.

showed strong antifungal activity, however higher than Mentha sp., whereas both oils

have much higher antifungal activity than commercial fungicide, bifonazole, therefore,

used as natural preservatives and fungicides (Sokovic et al., 2009).

The oregano and thyme oils completely inhibit mycelial growth and fungal spore

germination of A. flavus, A. niger and A. ochraceus at 400 to 700 µg/ml, whereas under

aerobic conditions, these oils at 250 to 350 µg/ml concentration inhibit growth of

Staphylococcus aureus and Salmonella typhimurium pathogens (Paster et al., 1990). At

800 µl/l, essential oil of Seseli indicum inhibits growth of A. flavus and F. oxysporum

infecting pigeon pea seeds and protect these seeds in storage up to 12 months (Chaturvedi

and Tripathi, 1989).

Similarly, 15 essential oil constituents have been evaluated for antifungal activity

against A. niger, F. oxysporum and P. digitatum out of which citral, cinnamic aldehyde

and citronellal, geraniol are most inhibitory with their minimal inhibitory concentrations

(MIC) at 100 µg/ml (Moleyar and Narasimhan, 1986). Similar activity has been observed

with essential oils from Thymus rariflorus and T. serpyllum (Akgul and Kvanc, 1989;

Kandil et al., 1994; Arras and Usai, 2001).Various greenhouse experiments have been

conducted to determine the effectiveness of plant essential oils as soil fumigants to

manage bacterial wilt (caused by Ralstonia solanacearum) in tomato. Pottin-gmixture

(“soil”) infested with R. solanacearum has been treated with the essential oils at 400 mg

and 700 mg per liter of soil in greenhouse experiments. Populations decline to

undetectable levels in thymol, palmarosa oil, and lemongrass oil treatments at both

concentrations, whereas tea tree oil had no effect. Tomato seedlings transplanted in soil

treated with 700 mg/l each of thymol, palmarosa oil, and lemongrass oil remain free from

bacterial wilt and 100% of plants in thymol treatments have been seen free of R.

solanacearum infection (Pradhanang et al., 2003). Antibacterial activities of essential oils

of Thymus persicus, T. eriocalyx, Taxandria fragrans and Lavandula stoechas are well

studied (Talei and Meshkatalsadat, 2007; Hammer et al., 2008; Kirmizibekmez et al.,

2009). Manuka and phoebe essential oils (extracted from Leptospermum scoparium and

Phoebe porosa, respectively), which contains high proportions of α-copaene and

calamenene, are good trap baits for monitoring red bay ambrosia beetle, Xyleborus


42

glabratus Eichhoff (vector of wilt causing fungus, Raffaelea sp.) distribution and

population trends (Hanula and Sullivan, 2008). Essential oil of Ocimum basilicum var.

pilosum, which contains linalool (29.68%) and cinnamic acid methyl ester (21.49%) has

shown significant antifungal activity against some plant pathogenic fungi (Zhang et al.,

2009). Lavendula oil (extracted from Lavendula angustifolia), rich in linalool (49.2%),

linalyl acetate (12.3%), lavendul acetate (6.5%), and 4-terpineol (5.9%) have exhibited

complete inhibition of post-harvest phytopathogens (R. stolonifer and A. niger) at 1000

ppm concentration (Behnam et al., 2006). Essential oils extracted by hydrodistillation

from fruits of Cuminum cyminum and Carum carvi are active against the genera

Clavibacter, Curtobacterium, Rhodococcus, Erwinia, Xanthomonas, Ralstonia and

Agrobacterium, which are responsible for plant and mushroom diseases (Iacobellis et al.,

2005).

Essential oils from sage (Salvia officinalis) leaves, rosemary leaves, caraway (C.

carvi) fruits, cumin (Cuminum cyminum) fruits, clove flower buds and thyme leaves have

been tested for their inhibitory effect against gram-negative bacteria (Pseudomonas

fluorescens, Escherichia coli and Serratia marcescens) and gram-positive bacteria

(Staphylococcus aureus, Micrococcus spp., Sarcina spp. and Bacillus subtilis) at very

low concentrations of 0.25−12.0 mg/ml to prevent microbial growth. It has been observed

that gram-positive bacteria are more sensitive to antimicrobial compounds than gram-

negative bacteria (Farag et al., 1989). Significant antifungal and antibacterial activities by

essential oil of Schinus molle var. areira have also been reported (Dikshit, 1986;

Gundidza, 1993).

Antifungal activity of oils extracted from fruit peels of pummelo (Citrus maxima)

and grapefruit (C. paradisi) using poisoned food technique against Phaeoramularia

angolensis has been demonstrated where sporulation is reduced from 45.93 to 100% and

radial growth from 87 to 100% at 1000 to 2000 ppm concentration (Kuate et al., 2006).

The essential oil of Eupatorium cannabinum is fungitoxic in nature against stem

rot causing organisms, Botryodiplodia theobromae and Colletotrichum gloeosporioides

in mango. This helps in enhancing the shelf life of mangoes (Dubey et al., 2007). The

volatile oil of Hyptis suaveolens is strongly fungitoxic against H. oryzae at its minimum

inhibitory concentration of 0.4% without being toxic to seed and seedlings (Pandey et al.,


43

1982). During screening the essential oils isolated from leaves of Chenopodium

ambrosioides, Cinnamomum zeylanicum, Citrus medica, Melaleuca leucadendron, O.

canum and O. grattissimum fungitoxicity against A. flavus at 2000 ppm concentration has

been recorded and most of the oils are more efficacious than synthetic fungicides (Mishra

et al., 1989). In a study by Chaturvedi et al. (1988) Areca catechu when treated with

5000 ppm (w/v) of the essential oil of Trachyspermum ammi and stored in polythene

containers could prevent fungal growth up to 8 months. Exposure of this oil at 1000 ppm

(for 120 min) to seeds of radish and Vigna mungo eliminate seed mycoflora and has no

effect on germination (Sandhya et al., 1989). Seeds of chilli treated with essential oil of

Ocimum adscendens give better control of fungal development than synthetic fungicides

like Bavistin, Blitox and Dithane M-45, when stored in jute bags and tin containers for 12

months (Asthana et al., 1989). The oil of C. citratus (lemon grass) inhibits completely the

mycelial growth of F. solani sp. phaseoli, S. sclerotiorum and R. solani and field

experiments have also shown reduction of disease development, when soil was treated

with 5% aqueous suspension or 0.5% seed dressing (Valarini et al., 1996). When

inoculated fruits of guava infested with fruit rotting fungi, Pestalotiopsis versicolor and

R. solani are dipped in essential oils of eucalyptus and clove, they completely checked

rotting and also preserved the keeping quality of guava (Madhukar and Reddy, 1989).

Curcumene and ginger oil at 0.2% concentration induces 86% inhibition of the mycelial

growth of the test fungus R. solani (Agarwal et al., 2001).

Essential oil of Hyptis suaveolens, at 0.6 µl/cm3 of oil is sufficient to completely

inhibit the fungal growth of F. oxysporum f. sp. gladioli, whereas 0.4 µl/cm3 completely

inhibit conidial germination during storage in vitro. In vivo, studies suggest that essential

oils when used in combination with hot water (55oC for 30 min) and UV-C (3.63 kJ/m

2)

significantly reduce the pathogen population and prolong the storage period from 2 to 4

weeks (Sharma and Tripathi, 2008). Essential oils of citronella, lemongrass

(Cymbopogon citratus), palmarosa (C. martinii) and karanj (Pongamia pinnata) at 0.20%

significantly reduce the development of the pathogen, Mycosphaerella musicola causing

“sigatoka” disease of banana (Misra et al., 2007).

In field tests, honey bee colonies were fed with sugar candy containing oil of

Satureia montana (1 ml/colony) and 75 days later there were significantly fewer chalk


44

brood mummies caused by Ascosphaera apis at the entrances of treated hives than in

colonies fed with sugar candy only (Colin et al., 1989). In other experiment by Okabe

and Saito, (1991), chalk brood was prevented by spraying hiba oil extracted from

Thujopsis dolabrata. Hiba oil and hinokitiol were found to inhibit the growth of A. apis at

concentrations of 1600 and 2500 ppm, respectively.

The essential oil of Caesulia axillaries and M. arvensis acts as potent fumigants

for the management of biodeterioration of stored wheat by A. flavus (Varma et al., 2002).

These oils also control the blue mould rot of oranges caused by Penicillium italicum and

enhance the market life of the oranges for a considerable period (Varma and Dubey,

2001).

Thymol and carvacrol are very active against most fungal species tested (Kurita et

al., 1981; Muller et al., 1995; Ulthee et al., 1999; Tsao and Zhou, 2000; Si et al., 2006;

Krist et al., 2007). Combined effect of thymol and cymene to control the growth of

Bacillus cereus vegetative cells is also on record (Delgado et al., 2004). The synthetic

alkyl derivatives (ethers) of thymol showed significantly improved antifungal activity

over acyl derivatives (esters) and pure compound against the test fungi (Kumbhar and

Dewang, 2001). The mechanism of action of these compounds against fungi is unknown

but may be related to their general ability to dissolve or otherwise disrupt the integrity of

cell walls and membranes (Isman and Machial, 2006). Carvones are also toxic to fungi

(Caccioni, 1992; Srivastava et al., 1994; Smid et al., 1995).

Cinnamaldehyde a major component of oil found in fresh seeds of cassia plants,

Cassia tora is used in mushrooms, row crops, horticultural crops, turf and pine forests to

control diseases such as dry bubble, (Verticillium fungicola), dollar spot (Sclerotinia

homeocarpa) and pitch canker disease (Fusarium moniliforme var. subglutinans). The

combined effects of cinnamaldehyde with catechin, quercetin and eugenol against wood

decay fungi, Laetiporus sulphurrus show that combination with eugenol is highly

synergistic and interrupts the fungal cell wall synthesis thereby inducing cell wall

destruction (Yen and Chang, 2008). In a study, strong antifungal activity of

cinnamaldehyde, α-methyl cinnamaldehyde, eugenol, isoeugenol and (E)-2-

methylcinnamic acid, has been reported against white rot fungus, Lenzaes betulina

(Wang et al., 2004; Cheng et al., 2007). Significant growth inhibitory effects of carvacrol


45

and cinnamaldehyde compounds against food-born bacteria has been determined at

concentrations ranging from 50 to 100 ppm when added to growth media and these

compounds, when used in combination with sodium chloride and ascorbic acid, exhibit

an enhanced effects (Kvanc and Akgul, 1988).

2.9 ANTIVIRAL EFFECTS

Plant essential oils and pure isolates have been mentioned as containing

substances which interfere with or inhibit infection of viruses. Essential oils of A.

conyzoides, Callistemon lanceolatus, Carum copticum, O. sanctum and Peperomia

pellucida have been evaluated for inhibitory activity against cowpea mosaic virus

(CPMV), mung bean mosaic virus (MBMV), bean commonil mosaic virus (BCMV) and

Southern bean mosaic virus (SBMV). O. sanctum at 3000 ppm gave the best inhibition of

89.6, 90, 92.7, and 88.2% against CMV, MBMV, BCMV, and SBMV, respectively.

Other oils also showed inhibitory activity against other viruses (Rao et al., 1986). The

essential oil of Melaleuca alternifolia in concentrations of 100, 250, 500 ppm has been

found to be effective in decreasing local lesions of TMV on host plant Nicotiana

glutinosa (Bishop, 1995). Another report has shown 62% inhibition against tobacco

mosaic virus. The fresh hydrodistilled carrot leaves yielded 0.07% essential oil and

twenty nine compounds have been identified and the major constituents are sabinene

(10.93%), linalool (14.90%), linalyl acetate (8.35%), and carvone (8.77%) which are

active against viral agents (Khanna et al., 1990).

Tagetes minuta oil has been found to be active against carnation ring spot

(CaRSV) and carnation vein mottle viruses (CaVMV). The ingredients present in the oil

namely dihydrotagetone and ocimene when tested individually in pure form, were found

to have enhanced antiviral activity against two carnation viruses (US Patent 6444458,

2002). The oil as such and the bioactive consitituent present in oil can be commercially

used as natural and eco-friendly antiviral products.

Thrips-vectored Tomato spotted wilt virus is one of the most devastating pest

complexes affecting tomato. Field trials were conducted over 2 years to determine the

effects of volatile plant essential oils and kaolin-based particle films on the incidence of

tomato spotted wilt and population dynamics of Frankliniella thrips. The essential oil


46

compound, geraniol, lemongrass (Cymbopogon flexuosus) oil, and tea tree (Melaleuca

alternifolii) oil, have been compared with a standard insecticide treatment and an

untreated control. All treatments were applied with and without kaolin, in a 5 × 2

factorial design. When combined with kaolin, the three essential oils reduced tomato

spotted wilt virus incidence by 32 to 51% in 2005 and by 6 to 25% in 2006 compared

with the control. When applied with kaolin, the three essential oils produced yields

similar to the insecticide standard (Reitz et al., 2008). Therefore, naturally occurring

products, such as essential oils and kaolin, could be used successfully to control viruses

and reduce insecticide use on tomatoes.

In view of the substantial work done on use of essential oils for insect pest

management, the emphasis on lepidopterans has been scanty. The aim of the present

work, therefore, was to identify reduced risk compounds from essential oils specifically

for borer lepidopterans and compare the efficacy with surface feeding insects.

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2. REVIEW OF LITERATURE - Information and Library ...shodhganga.inflibnet.ac.in/bitstream/10603/29762/9/09...2. REVIEW OF LITERATURE Allelochemicals from essential oil bearing plants