Subject – Biological Insect-pests Management, Semiochemicals in IPM, Semiochemicals M. Sc. Ag. Thesis.

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Index

S. N.	Topocs
1.	Introduction
1.1	What is semiochemical?
1.2	Why use semiochemicals?
2.	Importance of semiochemicals
2.1	Pest surveillance
2.2	Application of semiochemicals in pest management
3.	Classification of Semiochemicals
3.1	Pheromones
3.2	Allomones
3.3	Kairomones
3.4	Synomones

1. Introduction

1.1 What is semiochemical?

Semiochemicals are a class of chemicals that can change or modify the behaviour of receiving living organisms. It is derived from the Greek word ‘simeone‘, which means ‘a signal’.

1.2 Why use semiochemicals?

Semiochemical can be used in crop field for multi-purposes. It is a replacement for lethal pesticides and very important aspect of sustainable agriculture.

2. Importance of semiochemicals

Semiochemicals are eco-friendly pest control tool. The way it works is totally different from the traditional approaches. It can be included as an integral part of IPM. Semiochemicals are best suited for sustainable agriculture.

Importance of semiochemicals are:

2.1 Pest Surveillance

Pest surveillance for a species- Some semiochemicals work as an attractant. These types of chemicals are released by the female insect to attract the male counterparts. Certain species of pests are detected by the application of these chemicals.

Decision making– It helps in decision making. Some most dangerous pests are detected using semiochemicals. These are seasonal insect-pests. Presence of the insect can be detected at right time. A management program is scheduled according to the pest surveillance.

Monitoring for insecticide resistance– survived population of pests after the application of insecticides can be estimated and the degree of resistance of insect’s against a particular insecticide can be determined.

2.2 Application of semiochemicals in pest management

• In pollination.
• Making attractant-bait traps.
• Mating disruption.
• Use as deterrent.

3. Classification of Semiochemicals

Semiochemicals

1. Naturally Secreted
   • Pheromones.
     • Releaser.
     • Primary.
   • Allelochemicals.
     • Allomones.
     • Kairomones.
2. Synthetics
   • Attractants.
   • Disruptants.
   • Repellents.
   • Other parapheromones.

Semiochemicals are also classified in interspecific and interspecific.

Interaspecific Semiochemical– This type of chemical changes the behaviour of the pest of same species.

Interspecific Semiochemical– This type of chemical modify the behaviour of other species.

3.1 Pheromones

Origin of the word– From Greek word ‘pherin’ means ‘to transfer’.

Pheromones are interspecific.

List of some pheromones

S. N.	Name of pheromones	Targeted pest
1.	Hellilure	Helicoverpa armigera
2.	Gossylure	Pectinophera gosypiella
3.	Disparlure	Lymantriya dispar
4.	Grandlure	Cotton grey weevil

Also read– Entomology multiple choice questions and answers.

Application of pheromones

1. Pest surveillance.
2. Mass trapping.
3. Mating disruption.

Pheromone trap is the best tool for applying pheromones against the pests in standing field.

3.2 Allomones

What is allomones– Allomones are a class of semiochemicals. It is released by one organism and received by the others.

Mode of action– The chemical is favourable to emmiter. It is non favourable to receiver. It acts as repellents and deterrents.

Example– Pentadecanal in rice has allomonal properties against brown plant hopper.

3.3 Kairomones

It is released by one species and received by others. The chemical compound is beneficial to receiver but not to emmiter.

Mode of action– Attractants, arrestants, proposition and feeding stimulants.

Example– Cosmopolitan parasitoid wasp, Diaeretiella rapae is attracted by the allylisothiocyanate which is released by the cruciferous plants. Mainly Brevicoryne brassicae is parasititised by this wasp.

3.4 Synomones

These chemical compounds are beneficial to both the emmiters and the receivers.

Mode of action– Attractants to insect’s natural enemies.

Example– Terpenoid volatile released by the spider mite attract the predators of plant herbivores.

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