This document discusses essential oils as biopesticides for insect pest management. It provides an overview of the chemistry and extraction of essential oils, which are secondary metabolites produced by plants that contain mixtures of hundreds of compounds. Essential oils have insecticidal, repellent, and antifeeding properties and can be an alternative to synthetic pesticides. Their mechanisms of action include inhibiting the enzymes acetylcholinesterase and octopamine, interfering with insect neurotransmission. Structure-activity relationships show that functional groups and positions of compounds in essential oils impact their activity. Essential oils have potential as natural, less toxic biopesticides.
2. Overview of the Seminar
Introduction
Chemistry of Essential Oil(EO)
Extraction Technique
Technique applied for analysis
Essential Oil as Bioinsecticide
Mechanism of Action
SAR
Conclusion
3. Introduction
Known as essences, volatile oils.
Secondary by product of plant metabolism.
EOs have densities less than water.
Contain hundreds of individual compounds and their mixture.
Alternative to synthetic insecticides, less persistent.
Play important role in plant defence system against
microorganisms, insects etc.
Commercially used for pharmaceutical drugs, cosmetic and
perfume industries beside pesticides.
4. Constituents of EO
Terpenes, benzene derivatives, hydrocarbons another
miscellaneous compounds.
Monoterpenoids (represented by 90% of EOs)
Monoterpenes and their related chemical structure compounds
have 10-carbon hydrocarbon such as:
Acyclic alcohols Cyclic alcohol Phenols
eg linalool terpineol thymol
6. Extraction Technique
Clevenger Apparatus
(Clevenger, 1928)
Yield varies from plant
to plant ,species to
species and even
depends on the isolation
method.
Most common method is
Hydrodistillation using a
Clevenger type
apparatus.
7. Techniques applied for analysis
Depends on the number of molecular species and
the method used for extraction.
Most method rely on chromatographic techniques.
Gas Chromatography, detectors such as FID, TCD
and others can be used for EO analysis.
Most common and simple technique is GC-MS for
identification by comparison of the required
unknown mass spectra with those of identified in
ref. MS library.
8. Antifeeding activity: Antifeeding are compounds that reduce
insect feeding by modifying the insect behavior, through a direct
action on peripheral sensilla of insects.
Repellant activity: compounds which discourages insect from
landing or climbing on that area.
Fumigant activity: EOs being volatile in nature, therefore they are
frequently used as a fumigant. Linalool and limonene against
Sitophilus oryzae (kim et al.,2003)
Insecticidal activity: substances used to kill insects. They include
ovicides and larvicides used against insect eggs and larvae,
respectively.
Insecticidal properties of EOs
9. Insecticidal properties of EOs
Compounds Plant used Biological activity Insect used References
1. d-limonene Ostericum grosseserratum Insecticidal Sitophilus zeamais Chu et al., 2013
2. linalool Myrtus communis L. Insecticidal Acanthoscelides obtectus Ayvaz et al., 2010
3. carvacrol Satureja khuzistanica Antifeeding Leptinotarsa decemlineata Saroukolai et al., 2014
4. thymol Thymus daenensis Antifeeding Leptinotarsa decemlineata Saroukolai et al., 2014
5. α-pinene Juniperus formosana Repellent Tribolium casteneum Guo et al., 2016
6. methyl chavicol Tagetes lucida Repellent Tribolium casteneum Gallardo et al., 2011
1
2
3
4 5 6
11. Octopamine:neuromodulator,
neurotransmitter and neurohormone.
• Irreversible blocking of
octopamine receptor leads to
complete knock-down effect.
ACh acts as messenger to transmit nerve impulse.
EO components inhibits AChE, prevents the cleavage of ACh,
Accumulation of ACh leads to tremors,
• convulsions, paralysis and death.
•
12. Structure Activity Relationships
The activities of EOs and their constituents are dependent on
the functional group (nature and position)
13. Chemical structures of L-menthyl and its derivatives isolated from EO of
Mentha arvensis
14. Conclusion
EOs shows broad spectrum activity against a wide range of
pest (agricultural and stored grain)
Various MoA such as fumigation, granular application or in the
form of direct spray causes various physiological changes in
the insect physiology.
Low toxic, ecofriendly and less persistent (high volatility),
have short residual half-life on plants.
15. References:
Abdel-Tawab H. Mossa, 2016. Green pesticides: Essential oils
as biopesticides in insect-pest management. J. Environ. Sci.
Technol., 9: 354-378.
Tripathi, A. K., Upadhyay, S., Bhuiyan, M., & Bhattacharya, P.
R. (2009). A review on prospects of essential oils as
biopesticide in insect-pest management. Journal of
Pharmacognosy and Phytotherapy, 1(5), 052-063.
Dhaliwal, G. S., & Koul, O. (2011). Biopesticides and pest
management: conventional and biotechnological approaches.
Kalyani Publishers.
