Sustainable crop disease management using natural products.pdf

Sustainable Crop Disease Management
using Natural Products

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Sustainable Crop Disease Management
using Natural Products
Edited by
Sangeetha Ganesan
Department of Plant Pathology, Annamalai University, Chidambaram, India
Kurucheve Vadivel
Department of Plant Pathology, Annamalai University, Chidambaram, India
Jayaraj Jayaraman
Department of Life Sciences, The University of the West Indies, St. Augustine,
Trinidad and Tobago

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Library of Congress Cataloging-in-Publication Data
Names: Sangeetha, G. (Ganesan), editor.
Title: Sustainable crop disease management using natural products / edited by G. Sangeetha, V.
Kurucheve and J. Jayaraj.
Description: Boston, MA : CAB International, [2015] | Includes bibliographical references and index.
Identifiers: LCCN 2015036412 | ISBN 9781780643236 (hbk : alk. paper)
Subjects: LCSH: Phytopathogenic microorganisms--Biological control. | Plant diseases. |
Natural pesticides.
Classification: LCC SB732.6 .S94 2015 | DDC 632/.3--dc23
LC record available at http://lccn.loc.gov/2015036412
ISBN-13: 978 1 78064 323 6
Commissioning editor: Rachael Russell
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Production editor: Tim Kapp
Typeset by AMA DataSet Ltd, Preston, UK
Printed and bound in the UK by CPI Group (UK) Ltd, Croydon, CR0 4YY

v
Contents
Contributors vii
PART I: CROP DISEASE MANAGEMENT BY COMPOUNDS OF PLANT ORIGIN
1 Characterization of Bioactive Compounds from Botanicals for the
Management of Plant Diseases 1
Duraisamy Saravanakumar, Loganathan Karthiba, Rajendran Ramjegathesh, Kuppusami
Prabakar and Thiruvengadam Raguchander
2 Potential Use of Essential Oils, Plant Fats and Plant Extracts as Botanical
Fungicides 19
Pramila Tripathi and A.K. Shukla
3 Use of Natural Plant Compounds Against Fungal Diseases of Grains 35
Gustavo Dal Bello and Marina Sisterna
4 Natural Products and Elicitors of Natural Origin for the Postharvest
Management of Diseases of Fruits and Vegetables 49
G. Sangeetha, A. Anandan and V. Kurucheve
5 Plant Isothiocyanates as an Alternative for Sustainable Disease Control of
Horticultural Crops 74
Rosalba Troncoso-Rojas and Martín Ernesto Tiznado-Hernández
6 Antifungal Substances from Wild Plants for Development of Natural
Fungicides 95
J.C. Pretorius and E. Van der Watt
7 Botanical Pesticides: The Novel Chemotherapeutics for Managing Plant
Viruses 114
C. Jeyalakshmi, D. Dinakaran and C. Rettinassababady
8 Role of Medicinal Plants and their Metabolites for the Management of Plant
Pathogens 131
Rashmi Thakare, Dnyaneshwar Rathod and Mahendra Rai
9 Role of Natural Products in Disease Management of Rice 144
D. Krishnaveni, D. Ladhalakshmi, G.S. Laha, V. Prakasam, Asma Jabeen, S.K. Mangrauthia
and M. Srinivas Prasad

vi Contents
PART II: CROP DISEASE MANAGEMENT BY SOURCES FROM MARINE AND MICROBES
10 Use of Seaweed Extracts for Disease Management of Vegetable Crops 160
Jayaraj Jayaraman and Nerissa Ali
11 Managing Plant Diseases with By-products of the Fish Processing Industry 184
Pervaiz A. Abbasi
12 Chitosan for Plant Disease Management – Prospects and Problems 198
Rajendran Ramjegathesh and Jayaraj Jayaraman
13 Biocontrol Agent Formulations for Sustainable Disease Control of Plants 213
Jayaraj Jayaraman and Angela T. Alleyne
PART III: OTHER ALTERNATIVE ECOFRIENDLY APPROACHES
14 Effect of Compost Tea on Plant Growth and Plant Disease Management 234
Francisco Marín, Fernando Diánez, Francisco J. Gea, María J. Navarro and Mila Santos
15 Ecofriendly Management of Mycotoxigenic Fungi and Mycotoxin
Contamination 265
M. Surekha, V. Krishna Reddy and S.M. Reddy
16 Use of Silicon Amendments Against Foliar and Vascular Diseases of Vegetables
Grown Soil-less 293
Maria Lodovica Gullino, Massimo Pugliese and Angelo Garibaldi
17 Bioactive Natural Products for Managing Peronosporomycete
Phytopathogens 307
M. Tofazzal Islam, M. Motaher Hossain and M. Mahfuzur Rahman
18 Potential of Compost for Suppressing Plant Diseases 345
Chaney C.G. St. Martin and Adash Ramsubhag
19 Biofumigation in Crop Disease Management 389
D. Ladhalakshmi, R. Madhubala, S. Sundravadana, G.S. Laha, D. Krishnaveni,, G. Sangeetha
and G. Ragothuman
Index 403

vii
Contributors
P.A. Abbasi, Agriculture and Agri-Food Canada, Southern Crop Protection and Food Research Cen-
tre, 1391 Sandford St. London, Ontario, Canada N5V 4T3. E-mail: pervaiz.abbasi@agr.gc.ca
N. Ali, Department of Life Sciences, The University of the West Indies, St. Augustine, Trinidad and
Tobago
A.T. Alleyne, Department of Biological and Chemical Sciences, Faculty of Science And Technology,
The University of the West Indies, Cave Hill, Barbados
A. Anandan, Crop Improvement Division, Central Rice Research Institute, Cuttack, Odisha, India
E.E. Cogliati, Agroinnova, Centre of Competence for Innovation in the Agro.Environmental Sector,
University of Torino, 44 10095 Grugliasco, Italy
G. Dal Bello, Comisión de Investigaciones Cientíﬁcas de la Provincia de Buenos Aires, Centro de
Investigaciones de Fitopatología (CIDEFI) – Facultad de Ciencias Agrarias y Forestales, Universi-
dad Nacional de La Plata, 60 y 119, (1900) La Plata, Argentina. E-mail: dalbello@speedy.
com.ar
F. Diánez, Departamento de Producción Vegetal, Escuela Superior de Ingeniería, Universidad de
Almería, 04120 Almería, Spain
D. Dinakaran, Horticultural College and Research Institute for Women, Navalur Kuttappattu,
Tiruchirappalli 620 009, Tamil Nadu, India. E-mail: ddkaranpat@gmail.com
A. Garibaldi, Agroinnova, Centre of Competence for Innovation in the Agro.Environmental Sector,
University of Torino, 44 10095 Grugliasco, Italy. E-mail angelo.garibaldi@unito.it
F.J. Gea, Centro de Investigación, Experimentación y Servicios del Champiñón (Cies), Quintanar del
Rey, 16220 Cuenca, Spain.
M. Lodovica Gullino, Agroinnova, Centre of Competence for Innovation in the Agro.Environmen-
tal Sector, University of Torino, 44 10095 Grugliasco, Italy. E-mail: marialodovica.gullino@
unito.it
A. Jabeen, Directorate of Rice Research, Hyderabad 500 030, India
J. Jayaraj, Department of Life Sciences, The University of the West Indies, St. Augustine, Trinidad
and Tobago. E-mail: jaya1965@hotmail.com
C. Jeyalakshmi, Department of Plant Pathology, Pandit Jawaharlal Nehru College of Agriculture
and Research Institute, Karaikal, U.T. of Puducherry 609 603, India. E-mail: csjayal@yahoo.
co.in
L. Karthiba, Department of Plant Pathology, Centre for Plant Protection Studies, Tamil Nadu Agri-
cultural University, Coimbatore 641 003, India. E mail: karthiba@gmail.com

viii Contributors
V. Krishna Reddy, Toxicology Laboratory, Department of Botany, Kakatiya University, Warangal
506 009, India
D. Krishnaveni, ICAR – Indian Institute of Rice Research, Rajendranagar, Hyderabad, Telangana
500 030, India. E-mail: krishnavenid4@gmail.com
V. Kurucheve, Department of Plant Pathology, Annamalai University, Chidambaram, India.
D. Ladhalakshmi, ICAR – Indian Institute of Rice Research, Rajendranagar, Hyderabad,Telangana
500 030, India. Email: lathasavitha@gmail.com
G.S. Laha, ICAR – Indian Institute of Rice Research, Rajendranagar, Hyderabad, Telangana 500
030, India. E-mail: lahags@yahoo.co.in
R. Madhubala, National Institute for Plant Health Management, Hyderabad, India. E-mail: rvmad-
hubala@yahoo.co.in
M. Mahfuzur Rahman, WVU Extension Service, West Virginia University, Morgantown, WV
26506-6108, USA. E-mail: mahfuz81@hotmail.com
S.K. Mangrauthia, Directorate of Rice Research, Hyderabad 500 030, India
F. Marín, Departamento de Producción Vegetal, Escuela Superior de Ingeniería, Universidad de Alm-
ería, 04120 Almería, Spain
M. Motaher Hossain, Department of Plant Pathology, Bangabandhu Sheikh Mujibur Rahman
Agricultural University, Gazipur 1706, Bangladesh
M.J. Navarro, Centro de Investigación, Experimentación y Servicios del Champiñón (Cies), Quin-
tanar del Rey, 16220 Cuenca, Spain
K. Prabakar, Department of Plant Pathology, Centre for Plant Protection Studies,Tamil Nadu Agri-
cultural University, Coimbatore 641 003, India. E-mail: sidhukavi@yahoo.com
V. Prakasam, Directorate of Rice Research, Hyderabad 500 030, India
J.C. Pretorius, Department of Soil, Crop and Climate Sciences, University of the Free State, Bloem-
fontein 9300, South Africa. E-mail: pretorjc@ufs.ac.za
M. Pugliese, Agroinnova, Centre of Competence for Innovation in the Agro.Environmental Sector,
University of Torino, 44 10095 Grugliasco, Italy. E-mail Massimo.pugliese@unito.it
G. Ragothuman, Coconut Development Board, Abhayapuri, Bongaigaon, Assam 783 384, India.
E-mail: rg71kashyap@gmail.com
T. Raguchander, Department of Plant Pathology, Centre for Plant Protection Studies, Tamil Nadu
Agricultural University, Coimbatore 641 003, India. E-mail: traguchander@rediffmail.com
M. Rai, Department of Biotechnology, SGB Amravati University, Amravati 444 602, Maharashtra
State, India. E-mail: mkrai123@rediffmail.com
R. Ramjegathesh, Department of Life Sciences, Faculty of Science and Technology, The University
of the West Indies, St. Augustine, Trinidad and Tobago. E-mail: ramjegathesh@gmail.com
A. Ramsubhag, Department of Life Sciences, Faculty of Science and Technology, The University of
the West Indies, St. Augustine, Republic of Trinidad and Tobago. E-mail: adesh.ramsubhag@
sta.uwi.edu
D. Rathod, Department of Biotechnology, SGB Amravati University, Amravati 444 602, Maharash-
tra State, India
S.M. Reddy, Toxicology Laboratory, Department of Botany, Kakatiya University, Warangal 506 009,
India
C. Rettinassababady, Department of Plant Pathology, Pandit Jawaharlal Nehru College of Agricul-
ture and Research Institute, Karaikal, U.T. of Puducherry 609 603, India. E-mail: crsvaisu@
yahoo.co.in
C.C.G. St. Martin, Department of Life Sciences, Faculty of Science and Technology, The University
of the West Indies, St. Augustine, Republic of Trinidad andTobago. E-mail: cstmartin@hotmail.
com
G. Sangeetha, Department of Plant Pathology, Annamalai University, Chidambaram, India. E-mail:
sangeethaau@hotmail.com. Present Address: Central Horticultural Experiment Station (IIHR),
Bhubaneswar 751019, Odisha, India

Contributors ix
M. Santos, Departamento de Producción Vegetal, Escuela Superior de Ingeniería, Universidad de
Almería, 04120 Almería, Spain. E-mail: msantos@ual.es
D. Saravanakumar, Department of Food Production, Faculty of Food and Agriculture, The Univer-
sity of the West Indies, St. Augustine, Trinidad. E-mail: agrisara@rediffmail.com
A.K. Shukla, Department of Botany, Indira Gandhi National Tribal University, Amarkantak 484
886, India. E-mail: ashukla@rediffmail.com
M. Sisterna, Comisión de Investigaciones Cientíﬁcas de la Provincia de Buenos Aires, Centro de
Investigaciones de Fitopatología (CIDEFI) – Facultad de Ciencias Agrarias y Forestales, Universi-
dad Nacional de La Plata, 60 y 119, (1900) La Plata, Argentina. E-mail: mnsisterna@gmail.
com
M. Srinivas Prasad, Directorate of Rice Research, Hyderabad 500 030, India
S. Sundravadana, Coconut Research Station, Tamil Nadu Agricultural University, Coimbatore,
India. E-mail: sundravadana@rediffmail.com
M. Surekha, Toxicology Laboratory, Department of Botany, Kakatiya University, Warangal 506
009, India. E-mail: magantirekha@gmail.com
R. Thakare, Wageningen University and Research Centre, Wageningen, the Netherlands. E-mail:
rashu.biotech@gmail.com
M.E. Tiznado-Hernández, Coordinación de Tecnología de Alimentos de Origen Vegetal, Centro de
Investigación en Alimentación y Desarrollo, A.C. Apartado Postal 1735, Hermosillo, Sonora
83000, México. E-mail: tiznado@ciad.mx
M. Tofazzal Islam, Department of Biotechnology, Bangabandhu Sheikh Mujibur Rahman Agricul-
tural University, Gazipur 1706, Bangladesh.E-mail: tofazzalislam@yahoo.com
P. Tripathi, Department of Botany, DAV College, Kanpur 208 001, India. E-mail: pramilatripathi_
bhu@rediffmail.com
R. Troncoso-Rojas, Coordinación de Tecnología de Alimentos de Origen Vegetal, Centro de Inves-
tigación en Alimentación y Desarrollo, A.C. Apartado Postal 1735, Hermosillo, Sonora, 83000,
México. E-mail: rtroncoso@ciad.mx
E. Van der Watt, Department of Soil, Crop and Climate Sciences, University of the Free State,
Bloemfontein 9300, South Africa.

© CAB International 2015. Sustainable Crop Disease Management using Natural Products
(eds Sangeetha Ganesan, Kurucheve Vadivel and Jayaraj Jayaraman) 1
1.1 Introduction
Plant diseases cause significant damage and eco-
nomic losses in agricultural and horticultural
crops every year. Global losses caused by plant
pathogens are estimated to be 12% of the poten-
tial crop production, despite the continuous
release of new resistant cultivars. As a conse-
quence, management strategies including the
use of chemical pesticides are often employed
inappropriately and indiscriminately. Further-
more, fungi are continually becoming resistant
to fungicides and they are at risk of being with-
drawn from the market. In addition to reducing
crop yield, fungal pathogens often lower crop
quality by producing toxins that affect human
health. Thus, the replacement of synthetic
fungicides by natural products that are non-
toxic and specific in their action is gaining con-
siderable attention. In tandem, the higher plants
contain a wide spectrum of secondary sub-
stances having antimicrobial activity. Plant bio-
chemicals and crude extracts have also been
reported to have antimicrobial properties against
plant pathogens including viruses, fungi, bacte-
ria, nematodes and insects in vitro as well as in
vivo. Further, the use of botanicals is regarded as
the best suited ecofriendly measure as they are
easily biodegradable and safer.
Nevertheless, the use of botanicals for the
management of plant diseases has not achieved
its full potential due to lack of standardization of
extraction methods and difficulties in identifica-
tion and characterization of antifungal com-
pounds. Thus, the characterization of bioactive
compounds has potential for the management
of plant diseases using botanicals. In this chap-
ter, the use of botanicals in plant disease man-
agement and methods of extraction of bioactive
compounds are discussed in detail.
1 Characterization of Bioactive
Compounds from Botanicals for the
Management of Plant Diseases
Duraisamy Saravanakumar,1,3* Loganathan Karthiba,3
Rajendran Ramjegathesh,2 Kuppusami Prabakar3
and Thiruvengadam Raguchander3
1Department of Food Production, Faculty of Food and Agriculture, The University
of the West Indies, St. Augustine, Trinidad; 2Department of Life Sciences, Faculty of
Science and Technology, The University of the West Indies, St. Augustine, Trinidad;
3Department of Plant Pathology, Centre for Plant Protection Studies, Tamil Nadu
Agricultural University, Coimbatore, India
* E-mail: agrisara@rediffmail.com

2 D. Saravanakumar, L. Karthiba et al.
1.2 Botanicals in Plant Disease
Management
Plants have been known for their medicinal and
antimicrobial properties since ancient times.
Approximately 2400 plant species are known to
possess biologically active compounds that con-
trol various pests and pathogens effectively.
Conspicuously there are more than 10,000 sec-
ondary metabolites that have been found to
have a role in plant defence out of 400,000
plant chemicals (Hamburger and Hostettmann,
1991). The antimicrobial activities of different
plant extracts against plant disease have also
been observed by several researchers (Mishra
and Tewari, 1990; Ali et al., 1992; Akhtar et al.,
1997; Suberu, 2004). For example, different
parts of neem have been found to have insecti-
cidal and fungicidal properties. Bansal and
Sobti in the early 1990s demonstrated the anti-
fungal activity of neem extracts against Asper-
gillus niger infection in groundnut (Bansal and
Sobti, 1990). After a series of phytochemical
studies the antifungal principle was identified as
a combination of triterpenoids called Nimbidin
(Govindachari et al., 1998). During the same
period, Anila and his coworkers found that oil
cakes of Pongamia glabra, P. pinnata and Azadi-
rachta indica were effective in reducing the inci-
dence of powdery mildew (Erysiphe polygoni) in
opium poppy (Anila et al., 1991). Since then
much research has been carried out to evaluate
the efficacy of botanicals against various plant
diseases.
The antifungal activities of Allium cepa,
Eucalpytus rostrata and Capsicum frutescens
extracts were noticed against spore germination
and vegetative growth of Alternaria solani and
Saprolegnia parasitica (Khalil, 2001). Rawal and
Thakore (2003) have observed similar inhibi-
tory effect of leaf extracts (20%) of Datura stra-
monium against mycelial growth of Fusarium
solani, which causes Fusarium rot of sponge
gourd. In addition to in vitro studies, foliar appli-
cation of Datura metel leaf extract was effective
against foliar diseases namely, late leaf spot (Cer-
cospora arachidicola) and rust (Puccinia arachidi)
of groundnut up to 95 days after sowing, in
addition to an increase in the pod yield of 91%
over the untreated control (Kishore and Pande,
2005). Similarly, application of hot water
extracts of Xylopia aethiopica and Zingiber offici-
nale was found to be effective in controlling the
postharvest tuber rot of yam caused by Fusarium
oxysporum, Aspergillus niger and A. flavus (Okigbo
and Nmeka, 2005). Some researchers have also
demonstrated the antifungal activity of plant
extracts under laboratory and field conditions.
Harish and his coworkers (2008) have shown
the inhibitory property of Nerium oleander and
Pithecolobium dulce leaf extracts against mycelial
growth (77.4%, 75.1% reduction, respectively)
and spore germination (80.3%, 80.0% reduc-
tion, respectively) of Bipolaris oryzae in vitro. The
same authors have observed greater inhibitory
action of neem oil cake extracts against mycelial
growth (80.18%) and spore germination
(81.13%) of B. oryzae under in vitro conditions.
In addition to laboratory studies, application of
two rounds of neem cake extract and N. oleander
leaf extract upon the initial appearance of field
disease had 15 days later significantly reduced
the brown spot incidence (70% and 53% disease
reduction, respectively) and increased the yield
by 23% and 18%, respectively (Harish et al.,
2008). More recently, Aswini et al. (2010) have
demonstrated that leaf extracts of garlic creeper
(Adenocalymma alliaceum) were effective in
reducing the postharvest anthracnose (Colleto-
tricum gloeosporioides) and stem end rot (Botryo-
diplodia theobromae) disease incidence in mango
fruits.
In addition to aqueous plant extracts, the
essential oils extracted from Chenopodium
amboinicus were fungistatic to fruit infecting
pathogens including Aspergillus flavus and A.
niger (Samuel et al., 1995). During the same
period, Chaudhary et al. (1995) screened the
essential oils from 11 higher plants for their
antifungal activity against different fungal
pathogens. It was also demonstrated by Dubey
et al. (1983) that the essential oils of Ocimum
canum and Citrus medica act as volatile fungitoxi-
cants in protecting postharvest fungal patho-
gens Aspergillus flavus and A. versicolor. The
essential oils of Cymbopogon citratus, Caesulia
axillaris and Mentha arvensis have shown fumi-
gant activity against storage fungi in wheat, spe-
cifically Aspergillus flavus and the insect pests,
Sitophilus oryzae and Tribolium castaneum (Varma
and Dubey, 2001). Later, Tripathi and Dubey
(2004) and Holley and Patel (2005) have found
volatile compounds to be effective in the control

Characterization of Bioactive Compounds from Botanicals 3
of mould infestations and for enhanced shelf life
of food commodities during storage. The same
authors have demonstrated that the oil extracted
from the leaves of Chenopodium ambrosioides, at a
concentration of 3000ppm was completely
inhibitory to mycelial growth of Colletotrichum
falcatum, Fusarium moniliforme, Rhizoctonia
solani, Ceratocystis paradoxa, C. lunata, C.
pallescens, Periconia atropurpurea and Epicoccum
nigrum. Similarly, Sahayarani (2003) reported
that wintergreen oil at a concentration of 0.05%
effectively inhibited the spore germination of a
powdery mildew pathogen of Phyllanthus niruri.
The combination of essential oils extracted from
leaves of Cinnamomum camphora and the rhi-
zome of Alpinia galangal significantly arrested
the production of aflatoxin B by Aspergillus flavus
(Srivastava et al., 2008). Similarly, essential oils
obtained from aerial parts of aromatic plants
such as oregano (Origanum syriacum var. beva-
nii), thyme (Thymbra spicata ssp. spicata), laven-
der (Lavandula stoechas ssp. stoechas), rosemary
(Rosmarinus officinalis), fennel (Foeniculum vul-
gare) and laurel (Laurus nobilis) were found to be
effective in reducing the mycelial growth of Phy-
tophthora infestans isolated from late blight dis-
ease of potato (Soylu et al., 2006). It was also
demonstrated that a low concentration of oils
extracted from Mentha arvensis, Ocimum canum
and Zingiber officinale was better able to inhibit
the postharvest rotting of citrus fruits (Penicil-
lium italicum) than synthetic fungicides (Tripa-
thi et al., 2004).
Plant extracts from Datura metel and Cur-
cuma longa have been observed to have antibac-
terial activities (Kagale et al., 2004; Jabeen et al.,
2011). In addition to antifungal and antibacte-
rial activities, most of the plant products are
reported to possess antiviral principles. The
plant extracts of Lentinus edodes exhibited antivi-
ral effects against human herpes simplex virus
(Cradock et al., 2001). Similarly, Lavanya et al.
(2009) have demonstrated the antiviral activity
of Bougainvillea spectabilis and Prosopis chilinesis
extracts in cowpea and sunflower plants. It has
also been widely reported that methods of
extraction and the type of active compounds
present play a major role in determining anti-
fungal activity (Sen and Batra, 2012). The anti-
microbial activity of different plants and their
extracts against various pathogens are listed in
Table 1.1.
1.3 Extraction of Bioactive
Compounds
Plants are known to produce a wide variety
of bioactive compounds and substances
characterized as natural defence molecules,
namely, flavonoids, phenolic acids, lignans,
salicylates, stanols, sterols and glucosinolates
(Hooper and Cassidy, 2006). The concentration
of each compound in the plant is influenced by
several factors including plant physiology, grow-
ing conditions, geographic location, genotype
and evolutionary process (Figueiredo et al.,
2008). Nevertheless, the large biodiversity of
plants provides a great exploration field for
research on bioactive compounds and their bio-
logical properties (Yesil-Celiktas et al., 2009). To
characterize the desired chemical compounds,
the extraction of bioactive compounds without
the loss of their properties is considered as the
most significant step in the study of bioactive
compounds. It has also been widely reported
that methods of extraction and the type of active
compounds play a major role in determining the
antifungal activity (Sen and Batra, 2012). The
extraction includes pre-washing, drying and
grinding of plant materials to obtain a homoge-
nous sample.
1.3.1 Choice of solvents
Success in the identification of bioactive com-
pounds from a wide variety of plants is highly
reliant on the type of solvent used in the extrac-
tion protocol. Furthermore, the choice of sol-
vent depends on the specific nature of the
biologically activity compound that is being tar-
geted. A good solvent should have high evapora-
tion at low heat and low binding affinity to an
extract so as to avoid the formation of new com-
plex substances and preservative action as
described in Hughes (2002). In addition, the sol-
vent should be free from toxicity and should not
interfere with the assessment of the efficacy of
plant extracts (Ncube et al., 2008). Different sol-
vent systems have been studied for extraction of
biologically active compounds from plants. Of
these, water is considered as the universal sol-
vent for extraction of antimicrobial plant prod-
ucts. Though traditionally water is used, use of

4
D.
Saravanakumar,
L.
Karthiba
et
al.
Table 1.1. Plant antimicrobial compounds against different plant pathogens.
Plant product Extracts Target pathogens (disease) Crop
Compounds
identified Reference
Neem
Azadirachta indica
Seed Gaeumannomyces graminis var. tritici (take-all disease)
Microdochium nivale (snow mould disease)
Sphaerotheca fuliginea (powdery mildew)
Wheat
Cucurbits
- Coventry and
Allan, 2001
Datura metel Leaves Rhizoctonia solani (sheath blight)
Xanthomonas oryzae pv. Oryzae (bacterial blight)
Rice Daturilin Kagale et al., 2004
Garlic creeper
Adenocalymma alliaceum
Leaves Colletotricum gloeosporioides (Anthracnose)
Botryodiplodia theobromae (Stem end rot)
Mango fruits Tannic acid
Resorcinol
Aswini et al., 2010
Cinnamomum camphora Leaves Aspergillus flavus and Aflatoxin B1 Peanuts Aflatoxigenic Srivastava et al.,
2008
Alpinia galanga Rhizome Aspergillus flavus and Aflatoxin B1 Peanuts – Srivastava et al.,
2008
Oregano
Thyme
Lavender
Rosemary
Leaves Phytophthora infestans (late blight) Potato Carvacrol,
CamphorBorneol
1,8-cineole
Anethole
Soylu et al., 2006
Fennel Seeds Phytopathora infestans (late blight) Potato – Soylu et al., 2006
Acacia nilotica
Achras zapota
Datura stramonium
Emblica officinalis
Eucalyptus globules
Lawsonia inermis
Mimus opselengi
Peltophorum pterocarpum
Polyalthia longifolia
Prosopis juliflora
Punica granatum
Sygigium cumini
Leaves Aspergilluscandidus
A. columnaris
A.flavipes
A. flavus
A. fumigatus
A. niger
A. ochraceus
A. tamarii
Sorghum
Maize
Paddy seed
samples
(storage
fungi)
– Satish et al., 2007

Characterization
of
Bioactive
Compounds
from
Botanicals
5
Cedrus deodara
Trachyspermum ammi
Essential oil Aspergillus niger
Curvularia ovoidea
Black gram – Singh and Tripathi,
1999
Thyme
Thymus vulgaris
Essential oil (vapour
and direct contact)
Penicillium digitatum (green mould) Citrus fruits Eugenol
β-caryophyllene
Yahyazadeh et al.,
2008
Clove
Eugenia caryophyllata
Essential oil (vapour
and direct contact)
Penicillium digitatum (green mould) Citrus fruits Thymol
p-cymene
δ-terpinene
Yahyazadeh et al.,
2008
Mentha arvensis
Ocimum canum
Oil extraction from
leaves
Penicillium italicum (blue mould rot) Oranges and
lime fruits
Phenols Tripathi et al., 2004
Zingiber officinale Oil extraction from
rhizome
Penicillium italicum
Aspergillus niger
Fusarium oxysporium
Pythium aphanidermatum
Storage fungi Phenols Tripathi et al., 2004
Azardiachta indica
Artemessia annua
Eucalyptus globulus
Ocimum sanctum
Rheum emodi
Root and leaves Fusarium solani f. sp. melongenae (Wilt) Brinjal – Joseph et al., 2008
Ocimum gratissimum
Aframomum melegueta
Leaves Aspergillus niger
A. flavus
Fusarium oxysporium
Rhizopus stolonifer
Botryodiplodia theobromae
Penicillium chrysogenum
Yam – Okigbo and
Ogbonnaya,
2006
continued

6
D.
Saravanakumar,
L.
Karthiba
et
al.
Table 1.1. continued.
Plant product Extracts Target pathogens (disease) Crop
Compounds
identified Reference
Citrus sinensis Essential oil from
epicarp
Aspergillus niger
Botryodiplodia
Theobromae
Mango Limonene
Linalool
Myrcene
Sharma and
Tripathi, 2006
Cladosporium
Fulvum
Botrytis cinerea
Alternaria alternata
Tomato
Penicillium expansum
Ulocladium chartarum
Alternaria mali
Apple
Penicillium chrysogenum
Cladosporium cladosporioides
Grapes
Myrothecium roridum
Ulocladium sp.
Bitter gourd
Thompson seedless grape
Flame seedless grape
Zizyphus
Pomegranate
Fig
Methanolic leaf
extract
Alternaria solani
Botrytis cinerea
Botrytis fabae
Tomato Polyphenols and
flavonoids
El-Khateeb et al.,
2013
Tamarindus indica
Manilkara zapota
Methanolic extracts
seeds
Salmonella paratyphi A
Vibrio cholerae
– Antibacterial,
antioxidant
activity
Kothari and
Seshadri, 2010b
Datura stramonium
D. innoxia
D. metal
D. ferox
Leaf extracts Alternaria solani
Fusarium oxysporum f. sp. udum
Tomato
Pea
Alkaloids Jalander and
Gachande, 2012
Aloe vera Aqueous leaf extracts Rhizopus stolonifer Papaya Antifungal Abirami et al., 2013
Curcuma longa Rhizome Xanthomonas oryzae pv. oryzae Rice Curcumin Jabeen et al., 2011

organic solvents is reported to be more effica-
cious in extraction of antimicrobial compounds
when compared to water extracts (Parekh et al.,
2005). It is also evident from the findings of
Nang et al. (2007) that flavonoids solubilized by
water do not show any antimicrobial activity.
Similarly, phenolic compounds extracted using a
water solvent system exhibited only the antioxi-
dant activity (Nang et al., 2007). To solubilize
the hydrophilic compounds, polar solvents,
namely, methanol, ethanol or ethyl-acetate are
required. In some cases, use of dichloromethane
and or a combination of methanol and dichloro-
methane (1:1v) is required for extraction of the
more lipophilic compounds. Similarly, Cos et al.
(2006) have used hexane to remove chlorophyll
during plant extractions. Thus, it is understood
from several studies that testing of plants for the
presence of antimicrobial compounds critically
begins with alcohol or crude extractions fol-
lowed by the use of different organic solvent
extraction techniques.
1.3.2 Aqueous extracts
The use of water to extract compounds from
plant samples is considered to be the simplest
method. There are several reports demonstrat-
ing antimicrobial properties of plant extracts in
the field of medicine. In the case of agriculture,
though the reports on the use of water as extrac-
tion medium are encouraging, organic solvents
have been found to play a major role in the
isolation of bioactive compounds. So far several
aqueous plant extracts have been tested for their
antifungal activity against plant pathogens.
Aqueous extracts of Acacia nilotica, Achras
zapota, Datura stramonium, Emblica officinalis,
Eucalyptus globules, Lawsoniai nermis, Mimus
opselengi, Peltophorum pterocarpum, Polyalthia
longifolia, Prosopis juliflora, Punica granatum and
Sygigium cumini have shown significant activity
against Aspergillus candidus, A. columnaris, A. fla-
vipes, A. flavus, A. fumigatus, A. niger, A. ochraceus
and A. tamari isolated from paddy, maize and
sorghum seed samples. Of several species of
Aspergillus tested, A. flavus showed the highest
sensitivity to the aqueous extracts of the plant
products. The aqueous extracts of Allium sati-
vum, Terminalia arjuna, Curcuma longa and Tama-
rindus indica showed maximum efficacy against
bacterial leaf blight infection of rice when evalu-
ated through detached leaf, glasshouse and field
assays (Jabeen et al., 2011).
1.4 Non-aqueous Extracts
1.4.1 Organic solvent extract
The use of organic solvent systems is popularly
known as effective extraction methodology to
isolate the bioactive compounds. The solvents,
namely, petroleum ether, benzene, chloroform,
methanol, ethanol, acetone and ethyl acetate are
commonly used chemicals for the extraction of
antifungal compounds.The individual extraction
methods using organic solvents have been stan-
dardized. Chloroform extract of Azadirachta indica
seeds and fruit, methanolic extract of Terminalia
chebule (fruits), alcoholic extract of Phyllanihus
emblica (fruits), acetone extract of Phyllanihus
emblica and Mangifera indica, ethanol extract of
Thuja orientalis and ethyl acetate extract of Termi-
nalia chebule all showed maximum antimicrobial
activity against Xanthmonas oryazae pv. Oryzae,
which causes bacterial leaf blight (BLB) in rice
plants (Jabeen et al., 2011). Similarly, Dahot et al.
(1997) isolated seven and 14 peptides from Mor-
inga oleifera seeds using gel filtration techniques
from samples prepared using acetone and etha-
nol, respectively. The ethanol fractions showed
good inhibitory action against pathogenic bacte-
ria, while the samples did not show inhibition of
fungi. In contrast, it was demonstrated by Kagale
et al. (2004) that Datura metel plant extract
derived from a methanolic solvent system showed
higher antifungal and antibacterial activity
against sheath blight (Rhizoctonia solani) and BLB
(Xanthomonas oryzae pv. oryzae) diseases of rice
under in vitro and greenhouse conditions.
Aswini et al. (2010) used different solvents to
extract antifungal compounds from the garlic
creeper. Among the various organic solvents
used for extraction, chloroform extract was found
to be highly effective in inhibiting the spore ger-
mination of Colletotrichum gloeosporioides by
84.62%andBotrydiploideatheobromaeby84.50%
followed by methanol extract. Similarly, the
extracts from leaves of Thompson seedless grape,
flame seedless grape, zizyphus, pomegranate and
fig using the methanolic extraction system

exhibited higher inhibition of phytopathogenic
fungi, namely, Alternaria solani, Botrytis cinerea
and B. fabae in vitro (El-Khateeb et al., 2013). The
highest antioxidant activity and phenol content
were registered by chloroform:methanol extract
of Carica papaya seeds against bacterial growth.
Interestingly, the maximum radical scavenging
activity was exerted by a water extract of Annona
squamosa seeds, whereas an acetone extract of C.
papaya registered the highest flavonoid contents.
Polar extracts were found to be better for free
radical scavengers compared with less polar
extracts. Acetone was proved to be an efficient
solvent in extracting flavonoids, whereas phenols
were best extracted in a combination of chloro-
form and methanol (Kothari and Seshadri,
2010a).
1.4.2 Choice of extraction methods
Thesuitabilityof plantextractionmethodsshould
be considered as a major factor in the extraction
of target bioactive compounds as they possess
various degrees of polarity and are thermally
labile. In addition to the use of water or organic
solvent systems to macerate fresh plants or dried
powered plant material, physical forces and prin-
ciples, namely, sonification, soxhlet extraction
andheatingunderrefluxarecommonlyemployed
to extract the bioactive compounds from plant
samples. In addition to conventional classical
methods of plant extraction, modern methods
have also been developed for efficient and quick
extraction of organic compounds from plants.
These methods include supercritical-fluid extrac-
tion, solid-phase micro-extraction, microwave-
assisted extraction, pressurized-liquid extraction,
surfactant-mediated techniques and solid-phase
extraction (Huie, 2002).
1.5 Bioassay Techniques for
Antimicrobial Activity
Bioassay methods are commonly used to detect a
specific biological activity of the compound that
leads to the development of a new therapeutic
drug or industrial product. Selection of an appro-
priate bioassay is crucial and critically acknowl-
edged. The detection of antifungal compounds
from plant extracts depends on the sensitivity
and reliability of the bioassay methods used. The
complete set of fractions derived from the whole
extraction must be screened for antimicrobial
activity and, once antimicrobial activity is found,
the fractions should be characterized to identify
the bioactivity compounds with further isolation
and purification processes. In most cases, the bio-
assays demand specific requirements to pick out
the effective plant extracts. Furthermore, the bio-
assays should be inexpensive, simple and fast
enough to process a large number of samples.
Apart from these requirements, the technique
should be sensitive enough to detect the bioactive
compounds as their concentration in crude plant
extracts will be very meagre.
The following are some of the common
methods used to evaluate the efficacy of bioac-
tive compounds isolated from plants.
1. Disc diffusion method/agar well method: In
general, the antimicrobial screening of the iso-
lated product can be performed by disc diffusion
and/or agar well methods. These methods are
considered to be highly effective for testing fast-
growing microorganisms including bacteria and
fungi. The effect of test compounds is expressed
by measuring the zone of inhibition under in
vitro conditions. The method is a qualitative test
indicating the sensitivity or resistance of the
microorganisms to the plant compounds to be
tested (Hammer et al., 1999).
2. Poisoned food technique: The principle
involved in this technique is to poison the nutri-
ent with a plant product to be tested and then
allow a test fungus to grow on the medium. With
this technique, either a solid agar or a liquid
medium can be used.
3. Spore germination assay: The assay is used
specifically against the fungal pathogens. The
fungal spore suspension and the plant product
of desired concentration are prepared and mixed
on cavity slides in order to observe the conidial
germination at different time intervals under the
microscope (Dubey, 1991).
1.6 Mechanism of Action
Phytochemical studies are considered as an
important step in the understanding of antimi-
crobial compounds isolated from plant products.

Phytochemicals are non-nutritive plant chemi-
cals that have protective or disease preventive
properties. The plant produces these chemicals
to protect itself but recent research demon-
strates that many phytochemicals can protect
plants against diseases. There are a number of
‘families’ of phytochemicals in fruits and botani-
cals. In accordance with Trease and Evans
(1989) and Harborne (1998), the extracts were
subjected to phytochemical tests for plant sec-
ondary metabolites, tannins, saponins, steroid,
alkaloids and glycolsides.The woody plants were
also reported to synthesize and accumulate a
range of phytochemicals, e.g. alkaloids, cyano-
genic glycosides, flavonoids, lignins, lignans,
phenolic compounds, saponins and tannins in
their cells (Shetty, 1997).
In general, the longer chain (C6–C10) mole-
cules in plant extracts have been observed to
have greater antifungal properties (Ultee et al.,
2002; Holley and Patel, 2005). The mechanism
of action of plant products on fungal cells is
thought to be: (i) granulation of cytoplasm; (ii)
membrane rupture in cytoplasm; (iii) inhibition
and inactivation of intracellular and extracellu-
lar enzyme synthesis. These actions can occur in
an isolated or in a concomitant manner and cul-
minate with mycelium germination inhibition
(Cowan, 1999). Chromatographic techniques
are commonly used to characterize such com-
pounds and they have different properties
against the plant pathogens.The chromatogram
characterization of Allium sativam (garlic) has
revealed the presence of the compound, Ajoene.
Ajoene has been successfully used for the man-
agement of powdery mildew (Erysiphe pisi) of
pea in field conditions (Singh et al., 1995; Prithi-
viraj et al., 1998).
The characterization of antiaflatoxigenic
properties of C. camphora and A. galanga oils
using gas chromatography-mass spectrometry
[GC-MS] revealed the presence of antifungal
compounds like α-pinene, fenchone, cam-
phene, pentadecanol, γ-terpinene, β-asarone,
β-terpinene, α-phellandrene and trans-
caryophyllene (Srivastava et al., 2008). Simi-
larly, the antifungal activity of essential oils of
thyme, oregano, rosemary, lavender, fennel and
laurel against Phytophthora infestans was mainly
attributed to the presence of major compounds
such as carvacrol, borneol, camphor, anethole
and 1,8-cineole. These compounds also led to
morphological alterations in fungal hyphae
such as cytoplasmic coagulation, vacuolations,
hyphal shrivelling and protoplast leakage and
inhibition to sporangial production (Soylu et al.,
2006). The grouping and characterization of
secondary compounds present in the plant
extracts via chromatogram techniques has
resulted in the identification of active principles.
1.6.1 Phenolics and polyphenols
Phenols are aromatic chemical compounds,
which have weakly acidic properties and are
characterized by an attachment of one or more
hydroxyl groups to a benzene ring. The presence
of phenols in plant product is considered to be
potentially toxic to the growth and development
of fungal pathogens and thereby reduces plant
diseases (Okwu and Okwu, 2004). The struc-
tural classes of phenolic compounds include the
polyphenolic (hydrolysable and condensed tan-
nins) and monomers such as ferulic and cate-
chol (Okwu, 2005). These phenolic metabolites
function to protect the plants from biological
and environmental stresses and, therefore, they
are synthesized in response to pathogenic attack
such as by a fungal or bacterial infection or high
energy radiation exposure, e.g. prolonged UV
exposure (Vattem and Shetty, 2003). Girijashan-
kar and Thayumanavan (2005) characterized
the phenolic compounds using reversed-phase
high pressure liquid chromatography (RP-
HPLC) from the aqueous extracts of Lawsonia
inermis. The phenolic compounds were observed
to have an antifungal effect on the mycelial
growth of economically important soil-borne
pathogens (Macrophomina phaseolina, Pythium
aphanidermatum and Rhizoctonia solani). Simi-
larly, eugenol is a phenol series well character-
ized in clove oil, and has bacteriostatic properties
against pathogenic fungi and bacteria (Thom-
son, 1978). The fungitoxic action of essential
oils from Thymbra spictata, Sathureja thymbra,
Salvia fruticosa, Laurus nobilis, Inula viscose, Euca-
lyptus camaldulensis and Origanum minutiflorum
was identified to be due to the presence of phe-
nolic fractions by Mueller-Riebau et al. (1995).
El-Khateeb et al. (2013) has recently reported
the characterization of 12 antifungal poly-
phenolic compounds (catechin, gallic acid,

pyrogallic acid, protocatechuic, ο-coumaric
acid, ρ-hydroxy benzoic acid, ρ-coumaric acid,
phenol, salicylic acid, coumarin, quercetin and
cinnamic acid) from the leaf extracts of flame
seedless grape, Thompson seedless grape, fig,
pomegranate and zizyphus. Mason and Wasser-
man (1987) suggest the possible mechanism of
action of phenolic compounds on various
microbes could be the inhibition of essential
enzymes by oxidation and specific interaction
with sulfhydryl groups and non-specific inter-
actions with other proteins. Furthermore, the
antimicrobial activity of the phenol compounds
in essential oils is determined by the presence of
a C3 side chain at a lower level of oxidation and
in the absence of oxygen. Many plant phenolic
compounds function as precursors to structural
polymers such as lignin or serve as signal mole-
cules to induce the defence systems of the plant
(Nicholson and Hammerschmidt, 1992).
1.6.2 Quinones
Quinones are structurally aromatic rings with
double ketone substitutions. They are ubiqui-
tous in nature and characterized as being highly
reactive. In most biological systems the presence
of the redox potential of the quinone–
hydroquinone couple is vital. At the same time,
the quinones are derived from the hydroxylated
amino acids in the presence of enzyme polyphe-
noloxidase. As well as being the source for stable
free radicals, quinones have the ability to form
irreversible complexes with nucleophilic amino
acids present in proteins, which leads to inacti-
vation and functional loss in said proteins (Stern
et al., 1996). This factor is considered to be the
critical and potential contributor to the antimi-
crobial activity of the quinone compounds in
plant extracts. Thus, the cell wall peptides, sur-
face exposed adhesins and membrane bound
enzymes in the microbial cells are considered to
be the potential targets for the quinone com-
pounds isolated from plant parts. In accordance
with this point, an anthraquinone compound
isolated from Cassia italica plants exhibited bac-
teriostatic activity to Corynebacterium pseudo-
diphthericum, Bacillus anthracis and Pseudomonas
aeruginosa and bactericidal activity against P.
pseudomalliae (Kazmi et al., 1994).
1.6.3 Flavones, flavonoids and flavonols
Flavonoids are 15-carbon compounds generally
distributed throughout the plant kingdom. They
have been studied as one of the plant defence
responses to pathogenic infection and have
shown antimicrobial activity against a range of
microorganisms in vitro (Harborne, 1973).
Cotoras et al. (2001) have isolated flavones from
the resinous exudates of Pseudognaphalium spp.
that showed antifungal activity against B. cine-
rea.The characterization revealed the flavones to
be 5,7-dihydroxy-3,8-dimethoxy flavone and
5,8-dihydroxy-3,6,7-trimethoxy flavone. Two of
these compounds have reduced the mycelial
growth of B. cinerea by 32.1% and 14.9%,
respectively, at 40μgml−1 concentration. Based
on the molecular and fragmentation ions derived
from electrospray ionization (ESI)-LC-MS, Akila
et al. (2011) have recently identified two flavone
antifungal compounds, namely, 5,40-dihydroxy,
7-O-glycosyl 30-methoxy flavone, 5,40-dihy-
droxy, 7-O-pentosyl, 30-methoxy flavone from
Datura metel and these compounds were demon-
strated to show antifungal activity against
Fusarium wilt pathogen (Fusarium oxysporum f.
sp. cubense) in banana plantations.
1.6.4 Alkaloids
Alkaloids are usually colourless, but often opti-
cally active substances. Most are crystalline but
a few are liquid at room temperature. Alkaloids
are basic natural products occurring primarily
in many plants. Alkaloids rank among the most
efficient and therapeutically significant plant
substances (Okwu, 2005). Approximately 5500
alkaloids are known and they comprise the larg-
est single class of secondary plant substances,
containing one or more nitrogen atoms, usually
in combination as part of a cyclic structure
(Harborne, 1973). The characterization of
plants belonging to the Ranunculaceae family
showed the presence of antimicrobial diterpe-
noid alkaloids (Omulokoli et al., 1997). Similarly,
plants like Datura fastuosa have been reported to
contain nematicidal alkaloid compounds, tigloi-
dine (3B-tigloyloxytropane), 6B-tigloxytropane-
a-ol, tropine (3a-hydroxy tropane), apoatropine,
hyoscyamine and scopolamine (Shahwar et al.,

1995). Liu et al. (2009) isolated four alkaloids,
sanguinarine, chelerythrine, protopine and
alpha-allocryptopine, from the whole plant of
Macleaya cordata and demonstrated their anti-
fungal activity against Rhizoctonia solani. Alka-
loids such as ent-norsecurinine, norsecurinine
and allosecurinine isolated from Phyllanthus
amarus plants were also effective in reducing the
mycelia growth of Alternaria alternata, A. brassi-
cae, A. brassicicola, Curvularia lunata, C. maculans,
C. pallenscens, Colletotrichum musae, Erysiphe pisi,
Helminthosporium echinoclova and H. spiciferum
(Goel et al., 2002; Sahni et al., 2005). Further-
more, the alkaloids have been demonstrated to
strongly inhibit the spore germination and
mycelial growth of the above tested fungi (Singh
et al., 2008).
1.6.5 Other antimicrobial compounds
Plant compounds such as tannins and lectins
also possess antimicrobial activity. Tannins are
water-soluble polyphenols and have been char-
acterized in a number of plants. They have been
found to inhibit the growth and development of
microbes by protein precipitation and by restrict-
ing the availability of nutritional proteins to
microbes (Sodipo et al., 1991). The tannins have
been reported to arrest the growth of several
microorganisms including bacteria, yeasts,
fungi and viruses (Chung et al., 1998).Thus, the
characterization and study of tannins from
plant extracts could also be a potential option for
the management of plant diseases.
1.7 Botanical Formulations
The botanicals in general are characterized as
possessing target specificity, biodegradability
and low mammalian toxicity. They also contain
several active compounds in low concentrations,
which makes them viable options for the man-
agement of several insect pests and pathogens
(Kalaycioglu et al., 1997; Harish et al., 2008;
Akila et al., 2011). However, the botanicals will
reach the end users only when the bioactive
compounds are made available as commercial
formulations. To derive the formulations, suit-
able carrier materials, adhesives and stabilizers
should be standardized so as to enhance or to
maintain the property of the bioactive com-
pound as such. In this context, aqueous formu-
lations are made for commercial purposes by the
EC. Narasimhan et al. (1998) have developed oil
formulations, NO 60 EC (citric acid), NO EC (ace-
tic acid) and NO+PO 60 EC (citric acid), against
sheath rot and for grain discoloration disease
management in rice (Rajappan et al., 2001).
Similarly, Veerasamy (1997) has developed EC
formulation ETCCA-60EC (A) combining Euca-
lyptus tereticornis, Trianthema portulacastrum, cit-
ronella oil and CaCl2 to fight Alternaria leaf
blight in aubergine. Use of ETCCA-60EC (A) for-
mulation has resulted in lower blight incidence
with maximum aubergine yield. Another EC for-
mulation (60EC) prepared from Lantana camera
at 2% and 4% has proven effectiveness against
sheath blight disease in rice plants (Anusha,
2003).
An aqueous formulation of concentrated
extracts of giant knotweed (Reynoutria sachalin-
ensis) at 20% effectively controlled powdery mil-
dew (Sphaerotheca fuliginea) in cucumber as well
as the fungicide, benomyl. Similarly, various
concentrations of aqueous emulsions (1%, 5%
and 10%) of formulations possessing clove oil,
pepper extract and mustard oil, neem oil, syn-
thetic cinnamon oil and cassia extract were eval-
uatedformanagementof Phytophthoranicotianae
infection in periwinkle by Bowers and Locke
(2000). The results showed that formulations of
clove oil, pepper extract–mustard oil combina-
tion, two cassia extracts and synthetic cinna-
mon oil reduced the Phytophthora nicotianae
populations by between 98.4 and 99.9% after
21 days compared with the non-treated control
soil under glasshouse conditions. Similarly, Pari-
mala Devi and Marimuthu (2011) have carried
out partial purification of bioactive compounds
from leaf extracts of Polygonum minus using
chloroform extraction and developed the emulsi-
fiable concentrates. The formulation was devel-
oped by adding emulsifying agent (Unitox 30X
and Unitox 60Y), stabilizing agent (epichlorohy-
drin) and solvent (cyclohexanone). The authors
named the combined formulation ‘Polymin’.
The 2% Polymin-40 was effective in the man-
agement of early blight disease in tomato caused
by Alternaria solani. Similarly, the formulation
ADENOCAL 60 EC was developed from the
extracts of garlic creeper for the management of

postharvest diseases of mango fruits (Aswini
et al., 2010). Vanitha (2010) developed new EC
formulations of wintergreen oil and lemongrass
oil, which showed higher efficacy than the con-
trol against Alternaria chlamydospora-causing
leaf blight in Solanum nigrum. The 30 and 40 EC
formulations were effective in registering 100
per cent inhibition to mycelial growth and spore
germination of A. chlamydospora. The EC formu-
lations stored at room temperature for different
periods showed antifungal effect for up to 60
days. Similarly, the commercial product Wanis
40 EC (v/v) [commercial botanical fungicide
developed and marketed by Southern Petro-
chemical Industries (SPIC) Ltd, India] showed
antifungal activity against Fusarium solani, F.
equiseti, F. oxysporum, Phytophthora capsici, Scler-
otinia sclerotiorum, Pyricularia oryzae, Drechslera
oryzae and R. solani (Narasimhan et al., 1998;
Narasimhan et al., 1999). Similarly, the essential
oil of Carum carvi was marketed as TALENT in
the Netherlands and is known to inhibit sprout-
ing of potato tubers during storage and protects
them from bacterial rotting. The commercially
marketed botanical formulations are listed in
Table 1.2.
1.8 Problems with Efficacy, Stability
and Quality Control
The efficacy, safety and quality of botanicals and
products depend on extraction, processing,
transport and storage practices. Inadvertent
contamination by microbial or chemical agents
during any of the production stages can also
lead to deterioration in safety and quality. The
time of harvest or field collection of plants can
also have an influence on the quality of the for-
mulation. Nevertheless, the extraction methods
are not standardized for most of the bioactive
compounds. The compounds present in biofor-
mulations are found to degrade rapidly, making
shelf life of the bioformulation very short.
Hence, they cannot be stored for long periods as
a minimum shelf life period is required for com-
mercializing the products in the pesticides mar-
ket. Furthermore, most studies are confined only
to in vitro efficacy and sustained research efforts
have not been put forth to examine formulations
under field conditions. Sometimes the chemical
compounds from the plants are harmful to
humans and animals, which means that they
may not form suitable formulations for the man-
agement of plant diseases. The inconsistent per-
formance of the plant extracts and botanical
formulations is also considered as the major
drawback in the development of biopesticides.
1.9 Fortification of Botanical
Formulations
The inconsistent performance of biopesticides is
a major concern in the management of plant
diseases. Thus, the use of botanicals and biocon-
trol agents (beneficial microorganisms) could be
a viable and integrated strategy for the effective
control of various plant diseases. There are
reports on the combined use of biocontrol agents
and botanicals, which requires compatibility
studies of the two different formulations or bio-
active compounds. The compatibility of the
newly developed lemongrass oil and winter-
green oil EC formulation with biocontrol agents,
namely, Trichoderma viride, Pseudomonas fluore-
scens and Bacillus subtilis, showed that these for-
mulations did not inhibit the growth of
biocontrol agents. This will pave the way for
integrated or combined use of botanicals and
biocontrol agents. Recently, Akila et al. (2011)
used two botanical fungicides, namely, Damet
50 EC and Wanis 20 EC, along with selected
plant growth promoting rhizobacteria (PGPR)
strains (Pseudomonas fluorescens Pf1 and Bacillus
subtilis TRC 54) with known biocontrol activity
for the management of Fusarium wilt disease in
banana plants under greenhouse and field con-
ditions. The application of botanical formula-
tion and biocontrol agents in combination
significantly reduced the incidence of wilt dis-
ease in banana plants under greenhouse (64%
disease reduction) and field conditions (75% dis-
ease reduction). The combined use of bioformu-
lations also induced the production of the
defence-related enzymes peroxidase (PO) and
polyphenol oxidase (PPO) in host plants. Similar
research in future to fortify the bioformulations

Table 1.2. Commercial botanical formulations.
Commercial name Active ingredient Target pathogens Company
AgrisponTM Plant and mineral
extracts
Cercospora beticola (leaf spot in
sugarbeet)
Agricultural Sciences,
Dallas
SincocinTM Plant extracts Cercospora beticola (leaf spot in
sugarbeet)
Meloidogyne incognita (nematode
infection in cowpea)
Agricultural Sciences,
Dallas
Timorex Gold® Plant extracts from
Melalueca
alternifolia
Erysiphae necator (powdery mildew in
grapevine)
Plasmopara viticola (downy mildew in
grapevine)
Oidium neolycopersicum (powdery
mildew in tomato)
Sphaerotheca fuliginea (powdery
mildew in cucumber)
Leivellula taurica (powdery mildew in
pepper)
Stockton Ltd, Israel
FICHA TECNICA
BC-1000 (dust and
liquid formulation)
Bioflavonoid of seed
extracts and
grapefruit pulp
Botrytis cinerea IMO Chile S.A.
EcoSMART
OrganicTM
Rosemary oil Botrytis sp. (mould on flower crops)
Diplocarpon sp. (black spot on roses)
Alternaria sp. (blight on flower crops)
EcoSmart Technolo-
gies, USA
Eco SafeTM Combination of
pongamia and tulsi
and Ricinus
communis oil
Pythium aphanidermatum (damping
off in chilli and vegetables)
Rhizoctonia solani (sheath blight in
rice)
Xanthomonas campestris (bacterial
blight in pomegranate)
S. K. Bio Extracts and
Applications, India
Biostin Castor oil Pythium aphanidermatum (damping
off in vegetables like chilli, tomato,
brinjal)
Colletotrichum capsici (fruit rot in chilli)
Cercospora arachidicola (leaf spot in
groundnut)
S.K. Bio Extracts and
Applications, India
Influence WP Garlic Oidium neolycopersici (powdery
mildew of tomato)
Phytophtora infestans (late blight in
tomato)
Podosphaera xanthii (powdery mildew
in cucumber)
Pseudoperonospora cubensis (downy
mildew in cucumber)
Pythium spp. (damping off in
cucumber)
Rhizoctonia solani (root rot in
cucumber)
Erysiphe cichoracearum (powdery
mildew in squash)
AEF, Global Inc.,
Canada

by adding beneficial microbes to the botanical
formulations or vice versa could provide effec-
tive biopesticides for the management of plant
diseases.
1.10 Conclusion
Plants are valued as great sources for new and
biologically active compounds possessing anti-
microbial activity for the ecofriendly manage-
ment of plant diseases. At present, lots of
research is taking place across the globe to iso-
late, characterize and identify the plant products
that have antimicrobial properties. To accom-
plish better characterization and identification
of antimicrobial compounds it is necessary to
develop and to standardize the extraction meth-
ods, as well as designing a systematic approach
to testing the antimicrobial compounds against
a wide range of pathogens in vitro. It is unfortu-
nate that several potential bioactive compounds
which have shown efficacy under in vitro condi-
tions have not passed this stage for several
academic and non-academic reasons. Plant
compounds that have shown inhibitory effects
against various microorganisms in vitro should
be tested further in vivo to assess their real poten-
tial under applied conditions. In most cases the
application of botanicals results in inconsistent
performance under field conditions. In such
cases, possible combinations of two or more
botanicals with antimicrobial compounds
should be tested in future for the consistent and
effective management of plant diseases. Crop
production practices for the application of
botanicals possessing antifungal compounds
have to be developed in the context of soil- and
air-borne pathogens, and viable technologies
should be standardized for large-scale isolation
of bioactive compounds. The use of botanicals
has huge potential for replacing chemical fungi-
cides and fumigants in agriculture, maybe not in
the immediate future but in the long run for the
sustainable management of plant diseases.
Thus, an efficient collaboration among plant
pathologists, agronomists, biochemists and
agro-based industries is highly warranted in
order to develop target antimicrobial compounds
from botanicals into a marketable commercial
product. In addition, the specific mode of action
of botanical compounds against different phyto-
pathogens should be studied so as to have better
application strategies.
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© CAB International 2015. Sustainable Crop Disease Management using Natural Products
(eds Sangeetha Ganesan, Kurucheve Vadivel and Jayaraj Jayaraman) 19
2.1 Introduction
Plant diseases are caused by a diverse group of
microbes including fungi, bacteria, viruses,
viroids and nematodes. Plant pathogens create
challenging problems in the cultivation of crops
and pose real economic threats to farming sys-
tems because they are constantly mutating,
resulting in new strains and new challenges to
growers. There is a multiplicity of methods cur-
rently being employed for the management of
plant pathogens such as physical, chemical, bio-
logical and cultural methods. One effective
method to control plant pathogens has been the
application of artificial pesticides (Kiran et al.,
2006) as they are toxic or inhibitory to the
pathogens, dependable in terms of activity and
also justifiable in terms of benefits compared to
cost. Application of artificial pesticides has been
successful overall in combatting phytopatho-
gens. It has contributed to increased crop yields
and enhanced stability of crop production and
has maintained the market quality of the pro-
duce (Froyd, 1997). However, indiscriminate
utilization of artificial pesticides for control of
plant pathogens has caused an imbalance
in environmental equilibrium and potential
human health problems. The widespread
application of synthetic pesticides has led to
serious side effects for humans and animals,
such as carcinogenicity, oncogenicity and other
genotoxic problems (Basilico and Basilico,
1999). Further, their continuous use has led to
development of resistance among pathogens
(Brent, 1995; Yamaguchi and Fujimura, 2005).
Accumulation of fungicide residues in the food
chain above safe limits is another serious
problem (El-Nahhal, 2004). Use of artificial
fungicides has been criticized by environmental-
ists and they are known to be one of the most
detrimental man-made pollutants (Khoshoo,
1980).
This has led to exploration of environmen-
tally friendly alternative methods for the control
of plant pathogens (Parveen and Kumar, 2004).
Plant-based natural substances for plant patho-
gen control have attracted the interest of
researchers around the world (Hadacek and
Greger, 2000; Dixon, 2001; Gimenez et al.,
2007; Zhou et al., 2007; Yen et al., 2008).
Chemical substances isolated from plant materi-
als for control of pathogens have different modes
of action and are known to be better than
synthetic pesticides. Much interest has been
2 Potential Use of Essential Oils,
Plant Fats and Plant Extracts as
Botanical Fungicides
Pramila Tripathi1 and A.K. Shukla2
1Department of Botany, DAV College, Kanpur, India; 2Department of Botany, Indira
Gandhi National Tribal University, Amarkantak, India
* E-mail: pramilatripathi_bhu@rediffmail.com

20 P. Tripathi and A.K. Shukla
generated recently in generally regarded as safe
(GRAS) compounds. Plant-based natural sub-
stances are examples of GRAS compounds.
Plant-derived compounds including essen-
tial oils, plant fats and plant extracts represent a
vast and rapidly progressing resource as crop
protectors (Kishore and Pande, 2004). A num-
ber of studies have been carried out to test the
ability of essential oils extracted from aromatic
plants to control plant pathogens (Soliman and
Badeaa, 2002; Valero and Salmeron, 2003).
Essential oils consist of a number of compounds
that help to create resistance to plant pathogens
as well as chemical substances that have been
found to play important roles in the ecological
fitness and developmental processes of plants
(Wink, 2003; Gershenzon and Dudareva,
2007). It is very well established that plant-
derived essential oils consist of numerous com-
pounds such as terpene hydrocarbons and their
oxygenated derivatives such as aldehydes, alco-
hols, ketones, esters and acids (Tzortazakis et al.,
2007). The chemical constituents of essential
oils have been evaluated by many workers for
antimicrobial properties (Preuss et al., 2005;
Nostro et al., 2007; Ćavar et al., 2008). In addi-
tion, studies have been carried out to test the
antimycotic, antioxygenic, antiviral and insecti-
cidal properties of essential oils (Bishop, 1995;
Lamiri et al., 2001; Juglal et al., 2002; Moon
et al., 2006; Michaelakis et al., 2007).
The advantages of using essential oils
against fungal pathogens are their natural pro-
duction and the low chance of resistance devel-
opment by pathogens. Essential oils may replace
synthetic fungicides because oils possess a num-
ber of bioactive substances and are in general
used as fragrances and flavouring agents for
foods and beverages (Isman, 2000). Plant parts
extracted either in water (Singh and Tripathi,
1993; Bhat et al., 1994) or in organic solvents
(Hiremath et al., 1994; Jain et al., 1998; Madhu-
mati et al., 1999) have also proved their potency
as botanical pesticides.
This chapter reviews the recent literature
on the exploitation of essential oils and plant
extracts for the management of plant fungal dis-
eases of foliage, roots and seeds, postharvest and
stored product commodities, and other classes of
pathogens, including bacteria and viral patho-
gens and plant parasitic nematodes.
2.2 Mode of Action of Plant Essential
oils on Fungal Cells
Essential oils are basically plant originated prod-
ucts with hydrophobic properties and contain-
ing volatile aromatic compounds. These are
mixtures of different terpenoid chemicals and
their oxygenated derivatives (Wijesekara et al.,
1997).These oils are not only used as fragrance
and flavouring agents in the food and beverages
industries (Lahlou, 2004), but also may provide
potential alternatives for use as plant fungal
pathogenic control agents (Isman, 2000; Tripa-
thi and Dubey, 2004).
The antifungal properties of essential oils
include suppression of spore germination, germ
tubeelongationandreductionof hyphalgrowth.
Application of essential oils induces cytoplasmic
vacuolations and lysis in fungi (Fiori et al.,
2000). Ultrastructural observation through a
scanning electron microscope (SEM) indicated
that essential oils bring about changes in fungal
hyphae such as hyphal shrivelling, vacuolations,
cytoplasmic coagulation, protoplast leakage and
loss of conidiation. The growth inhibition effects
of essential oils is known to be caused by, vari-
ously, modification of cell wall composition
(Ghfir et al., 1997), plasma membrane disorien-
tation, mitochondrial structure disorganization
(de Billerbeck et al., 2001) and hindrance of
enzymatic reactions on the membranes of mito-
chondria, such as proton transport, respiratory
electron transport and coupled phosphorylation
steps (Knobloch et al., 1989). For instance, the
effects of thyme oil and thymol on the hyphae
cytomorphology of Fusarium solani, Rhizoctonia
solani and Colletotrichum lindemuthianum were
found to be due to accumulation of lipid bodies,
increased vacuolization of the cytoplasm and
undulations of the plasmalemma, and modifica-
tions of the mitochondria and endoplasmic
reticulum (Zambonelli et al., 2004).
2.2.1 Activity of essential oils, plant fats
and plant extracts against fungal plant
pathogens
Fungal pathogens are accountable for loss in
yield of a number of cultivated crops (Pedras,

Essential Oils, Plant Fats and Plant Extracts as Fungicides 21
2004). In overall world crop production, damage
in field conditions due to fungal pathogens is
about 12% in developing countries (Lee et al.,
2001). Compounds with broad-spectrum activ-
ity are expected to provide protection against a
range of pathogenic fungi that attack the plant
at the same or subsequent growth stages follow-
ing their application. Essential oils are a rich
source of broad-spectrum antifungal plant-
derived metabolites that inhibit both fungal
growth and production of toxic metabolites
(Kishore and Pande, 2004). The essential oils
and their ingredients have been reported to have
antifungal properties (Sridhar et al., 2003). A
number of researchers throughout the world
have reported the antifungal nature of plant
essential oils (Paster et al., 1995; Bouchra et al.,
2003; Daferera et al., 2003). The antifungal
properties of an essential oil may be down to the
synergistic activity of a number of compounds
rather than an individual compound (Daferera
et al., 2003).
Kazmi et al. (1995) studied the impact of
neem oil on root pathogens under in vitro condi-
tions. Ramezani et al. (2002) found there to be
fungicidal activity of Eucalyptus citriodora oil
against pathogenic fungi and bacteria. Antifun-
gal compounds such as cinnamaldehyde and
eugenol have been reported from essential oils of
Cinnamomum zeylanicum and Syzygium aromati-
cum (Paranagama, 1991; Beg and Ahmad,
2002). These were found to be active against
crown rot and anthracnose pathogens of
banana (Ranasinghe et al., 2002). Clove, cedar
wood, lemongrass, peppermint, citronella and
nutmeg oils were evaluated in vitro against Pho-
mopsis azadirachtae, the causative agent of die
back diseases of neem, and these oils showed sig-
nificant activity against the pathogen (Nagendra
et al., 2010).The chemical compounds β-pinene,
γ-terpinene and cuminaldehyde have been
established as the main constituents of essential
oil of Cuminum cyminum (Iocobelli et al., 2005).
Both β-pinene and γ-terpinene, the two main
components of C. cyminum oil, have antifungal
properties against a number of fungi. The main
constituents of Ocimum vulgare oil are carvacrol,
p-cymene and thymol (Bozin et al., 2006). The
volatile terpenes such as carvacrol, p-cymene
and thymol are considered to be the antifungal
constituents of O. vulgare oil (Holly and Patel,
2005). p-Cymene, a constituent of O. vulgare oil
showed synergistic activity with thymol against
fungi (Pina-Vaz et al., 2004). Rahman et al.
(1999) reported that the essential oil applied
into medium at a concentration of 200μg ml−1
inhibited the mycelial growth of Pseudoallesche-
ria boydii by 88% and F. oxysporum f. sp. lycoper-
sici by 19%.
2.2.2 Essential oils, plant fats and plant
extracts against foliar fungal pathogens
Plant oils and fats also have potential antifungal
activity. For example, oil from seeds of Azadirac-
tha indica has been shown to be equally effective
as chemical fungicides in control of foliar fungal
diseases (Amadioha, 2000). Enikuomehin
(2005) found leaf extracts of Chromolaena
odorata, Musa paradisiaca, Aspilia africana and
Tithonia diversifolia to be effective in controlling
Cercospora leaf spot on two sesame cultivars
(530–6–1 and Pbtil No. 1). Sesame plant disease
was reported to be controlled by application of
7.5% leaf extracts at an interval of two weeks. In
particular, extracts of C. odorata and A. africana
were found to be effective in inhibiting the
growth of fungal pathogen on foliar parts, which
in turn, protected the flowers and capsules.
Seeds produced by plants treated with extracts
of A. africana, C. odorata and T. diversifolia were
found to have less infection. Overall, leaf extracts
of A. africana, C. odorata or T. diversifolia were
found to be on a par with Bentex T (20% Ben-
late+20% Thiram) in terms of suppressing Cer-
cospora leaf spot disease in gingelly cultivars.
Reynoutria extracts and olive oil were found
to be efficient in controlling powdery mildew of
squash caused by Sphaerotheca fuliginea (Cheah
and Cox, 1995). Since olive oil is used in cook-
ing, food additives and medicines, it is unlikely to
cause any human health or environmental
problems. Blumeria graminis f. sp. hordei is one of
the barley powdery mildew pathogens and is a
widespread biotrophic fungi that colonizes plant
epidermal tissue, causing severe yield loss (Zhou
et al., 2001). Tea tree oil solution at concentra-
tions of 1% and 0.5% inhibited the formation of
mildew colonies on leaf surface completely (Tezi
et al., 2007).

22 P. Tripathi and A.K. Shukla
2.2.3 Essential oils, plant fats and plant
extracts against soil-borne fungal
pathogens
There have been few reports on the potential role
of essential oils and essential oil components as
protectants against soil-borne fungi when
applied as a seed treatment. Soil amendment
with cinnamon oil and clove oils and essential oil
components effectively reduced the occurrence
of pre-emergence rotting as well as post-emer-
gence wilting of peanut seedlings in infested soil.
Cinnamon oil and clove oil were more effective
than the essential oil components in the control
of post-emergence wilting of peanut seedlings
(Kishore and Pande, 2004). Reduced plant dis-
ease incidence through reduction in soil fungal
populations with the use of oils has been
reported. Bowers and Locke (2004) found that
treatment with 5% and 10% clove oil and syn-
thetic cinnamon oil reduced soil populations of
Phytophthora nicotianae by 98% after 21 days
compared with unprotected soil. Soil fumigation
with clove oil (70%) can control almost 97.5%
population density of F. oxysporum f. sp. chrysan-
thimi after 3 days of treatment (Bowers and
Locke, 2000). Essential oil of Chenopodium
ambrosioides and Lippia alba showed strong fungi-
toxicity against Pythium aphanidermatum and P.
debaryanum at 1000μg/ml and they were found
to have a broad range of fungitoxicity without
exhibiting phytotoxicity (Kishore and Dubey,
2002). These oils were more effective than syn-
thetic fungicides like Agrosan GN, Captan and
Ceresan. When seeds are soaked in the above-
mentioned oils, damping-off disease of tomato is
reduced in soil infested wtih P. aphanidermatum
or P. debaryanum pathogens. Singh et al. (1980)
reported that neem extract effectively inhibited
soil-borne fungal pathogens of Cicer arietinum.
Plant extracts have been used successfully for
management of Fusarium wilts of crops. Plant
extracts of Prosopis juliflora (Raghavendra et al.,
2002) and a number of plants from around 12
families (Russel and Mussa, 1977) were found to
control Fusarium in both in vitro and in vivo
conditions. Plant extracts, namely, Eucalyptus
globulus, Ocimum sanctum, Azardiachta indica,
Artemessia annua and Rheum emodi have been
reported to control brinjal wilt disease under in
vitro conditions. Growth of the pathogen was
signiﬁcantly reduced by all the plant extracts.
Among these, a 20% concentration of A. indica
was found to be the most effective followed by
R. emodi, E. globulus, A. annua and O. sanctum
(Babu et al., 2008). The formulations derived
from these plants might be potentially appropri-
ate for seed and foliar treatments for the control
of Fusarium and other soil-borne fungi.
2.2.4 Essential oils against seed-borne
fungi
Essential oils extracted from seeds of neem (A.
indica, asafoetida (Ferula asafoetida), mustard
(Brassica campestris) and black cumin (Nigella
sativa) exhibited antifungal activity at concen-
trations of 0.5%, 0.1% and 0.15% and were
found to inhibit notably the growth of eight
seed-borne fungi, namely, Aspergillus niger, A.
flavus, Fusarium oxysporum, F. moniliforme, F.
nivale, F. semitectum, Alternaria alternata and
Drechslera hawiinesis. Of these oils, asafoetida oil
at concentrations of 0.1% and 0.15% apprecia-
bly inhibited the growth of all test pathogens
except A. flavus, and N. sativa oil at a concentra-
tion of 0.15% was also effective against tested
fungi but showed a slight fungicidal activity
against A. niger (Uzma et al., 2008).The antifun-
gal activity of Eucalyptus citriodora oil was attrib-
uted to citronellal, the volatile compound which
is the major constituent of the oil. The antifun-
gal activity of citronellal against several species
of Aspergillus, Penicillium and Eurotium was also
reported using the vapour–agar contact method
(Nakahara et al., 2003). Locke (1995) reported
that under ﬁeld conditions A. niger, F. oxysporum
and Alternaria alternata were completely con-
trolled through fumigation by applying 2–10%
neem oil. It has been observed that mustard seed
oil also exhibited antifungal activity against Pen-
icillium commune, P. roqueforti, Aspergillus flavus
and Endomyces fibuliger (Nielsen and Rios, 2000;
Dhingra et al., 2004).
2.3 Essential Oils and Plant Extracts
Against Bacterial Plant Pathogens
Management of diseases caused by bacteria is a
severe problem in agriculture practice. Antibi-
otics are banned in many countries. Copper

Essential Oils, Plant Fats and Plant Extracts as Fungicides 23
compounds, because of their general toxicity,
exert a negative impact on both yield and the
environment and their use is restricted in the
European Union (Iacobellis and Cantore,
2005). Natural biologically active compounds
produced in plants are being tested for their
antibacterial activity. Plants are rich in second-
ary metabolites like alkaloids, flavonoids, glu-
cosinolates, etc., which could be potentially
bacteriostatic or bactericidal (Cowan, 1999). A
number of chemical substances from different
plants have been investigated for their antimi-
crobial properties against plant pathogenic
bacteria (Martyniuk et al., 1999; Krupinski and
Sobiczewski,2001;Smolinska,2004;Kokoškov
and Roman, 2005; Lojkowska et al., 2005;
Bahraminejad et al., 2008). Daferera et al.
(2003) and Soylu et al. (2005) reported inhibi-
tory effects of oregano, thyme and dictamnus
plant essential oils on the colony growth of Cla-
vibacter michiganensis ssp. michiganensis. Vasin-
auskiene et al. (2006) established toxic activity
of essential oils towards bacterial pathogens,
namely, Xanthomonas vesicatoria, Pseudomonas
syringae, P. marginalis pv. marginalis and Bacillus
sp. Extracts from shoots of the medicinal plant
Ziziphora clinopodioides have a strong and wide
spectrum of antibacterial activity against many
bacteria and also against Pectobacterium caroto-
vorum ssp. carotovorum and Erwinia chrysan-
themi (Ozturk and Ercisli, 2007). Extracts from
Allium sativum have the prospective to inhibit
the common genera of phytopathogenic bacte-
ria, for example, Pectobacterium carotovorum,
Pseudomonas syringae and Xanthomonas campes-
tris (Curtis et al., 2004). Coventry and Allan
(2001) found antibacterial properties in neem-
based botanicals against a number of bacterial
species, for example, P. syringae pv. phaseolicola,
Pectobacterium carotovorum ssp. carotovorum, X.
campestris, A. tumefaciens, B. subtilis, Staphyllo-
coccus aureus, Corynebacterium bovis and Esche-
richia coli. Neem extracts assayed using the agar
diffusion method showed good results against
bacteria like B. subtilis, S. aureus, C. bovis and E.
coli. Antimicrobial properties of Nigella sativa
oil under in vitro and in vivo conditions has been
reported against S. aureus, Candida albicans and
P. aeroginosa (Hanafy and Hatem, 1991; Mash-
hadian and Rakshandeh, 2005). Aqueous
extracts of Nigella sativa seeds have also been
reported to have inhibitory effects against C.
albicans under in vivo conditions (Khan et al.,
2003).
Paret et al. (2010) evaluated the impact of
Palmarosa (Cymbopogon martini), lemongrass
(C. citratus) and eucalyptus (Eucalyptus globulus)
oils in management of bacterial wilt disease of
edible ginger (Zingiber officinale) caused by Ral-
stonia solanacearum.They observed that essential
oils significantly reduced the bacterial wilt inci-
dence of ginger without affecting the growth
and yield of plants.
Members of the Brassicaceae family contain
a class of chemicals known as glucosinolates
(Gardiner et al., 1999). Glucosinolates are
thought to be biologically active after the inci-
dent of tissue damage. These molecules are fur-
ther cleaved by thioglucosidase, producing
several active compounds including thiocya-
nates, isothiocyanates, nitriles, etc. (Horbowicz,
2003). The analysis of glucosinolates in Brassi-
caceae plants showed that B. juncea contains a
very high concentration of 2-propenyl ITC, for
example, 648μgg−1 in dry plant tissues (Smo-
linska and Horbowicz, 1999). Plants belonging
to the Solanaceae family generally contain gly-
coalkaloids, which have a synergistic toxic effect
on pathogens (Lachman et al., 2001). A number
of glycoalkaloids are found in potato but achaco-
nine and α-solanine constitute 95% of the total
amount (Friedman and McDonald, 1997);
α-chaconine is found in lower amounts than
α-solanine but α-chaconine possesses compara-
tively greater toxicity (Lachman et al., 2001).
2.4 Essential Oils and Plant Extracts
Against Nematodes
It is difficult to estimate yield suppression caused
by plant pathogenic nematodes because often
damage is not limited to a single nematode spe-
cies. Root-knot nematodes are major contribu-
tors to economic losses. Nematicidal activity of
phytochemicals and plant essential oil is very
well reported (Chitwood, 2002). Nematicidal
compounds like carvacrol and thyme have been
found in aromatic plants and culinary herbs.
Root-knot nematodes Meloidogyne spp. are capa-
ble of severely damaging a wide range of crops,
causing dramatic yield losses (Kiewnick and
Sikora, 2006). Extracts of certain ornamental

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