RECENT METHODS OF PEST CONTROL

MD.MAHTAB RASHIDBPSAC/21/2012-2013B.Sc.(Ag) 4th Semester

Recent methods of pest control includes following agents

A. Anti-feedantsB. Insect AttractantsC. Insect RepellantsD. Genetic Control/Autocidal ControlE. Insect Growth Regulators

A. ANTIFEEDANTS These are the chemical substances that

inhibit feeding of insects when applied on the foliage without impairing their appetite and gustatory receptors or driving them away from the food.

They are also called Gustatory repellants/ Feeding deterrents / Rejectants.

Since insects do not feed on treated surface, they die due to starvation.

MODE OF ACTION

They inhibit gustatory (taste) receptors of the mouth parts

GROUPS OF ANTIFEEDANTSA. Triazines eg:- AcetanilideB. Organotins :- Compounds having tin eg:-Triphenyl tin acetateC. Carbamates :- Sub-lethal doses of thiocarbamates eg:- BaygonD. Botanicals :- Anti-feedants from non-host plants ∙Pyrethrum- From C. cinerarifolium .Neem .Apple factor .Solanum alkaoids- Leptine, Tomatine & Solanine

ADVANTAGES DISAADVANTAGES

Affects plant feeders but safe to N.E.

Pests are not killed immediately so N.E. can feed on them

No phytotoxicity No pollution

Not effective for sucking pests

Not effective as sole control measure

B. INSECTS REPELLENTS Chemicals which cause insects to move

away from their source are referred to as repellents (or) Chemically that prevent insect damage to plants (or) animals by rendering them unattractive, unpalatable (or) offensive are called repellents.

Mode of Action:- Influences both gustatory & olfactory receptors.

TYPES OF REPELLENTSPhysical repellents

Contact stimulus repellents eg:- Wax or Oil

Auditory repellents amplified sounds

Barrier repellants eg:-Tar bands or Mosquito nets

Visual repellents eg:- Yellow light

Feeing repellants eg:-Antifeedants

Chemical repellents

Plant origin eg:-Oils from Citronella, Camphor, Cedarwood & Lemon-grass

Synthetic repellents eg:-Dimethyl pthalate, Napthalene, Bordeaux mixture & Smoke

C. INSECTS ATTARACTANTS

Chemicals that cause insects to make oriented movements towards their source are called insect attractants.

Mode of Action:- It influences both gustatory and olfactory receptors

TYPES OF ATTARACTANTS1. Pheromones:-Chemical that is secreted into the external

environment by an animal and that elicits a specific response in a receiving individual of the same species.

2. Food Lures:-These are Chemicals present in plant and animal hosts that attract (lure) insects for feeding. They stimulate olfactory receptors.

3. Oviposition Lures:-These are chemicals that govern the selection of suitable sites for oviposition by the adult female eg:-Corn attaractants for H. armigera

4. Poison Baits:-Poison baits are a mixture of food lures and insecticides. The effort is made to make the bait more attractive to insects than their natural food and also a smaller quantity should be able to attract the largest number of insects.

ADVANTAGES DISADVANTAGES

Target specific Doesn’t disrupt

eco-system Can be used for

mass trapping Do not cause

environmental pollution

Insects can always find untreated hosts

It is not a sole source of insect control

PHEROMONES Semiochemicals:- They are chemicals that

mediate communication between organisms.

It is classified into two groups:- i. Pheromones:- Intra-specific ii. Allelo-chemicals:- Inter-specific--Pheromones are also called Ectohormones.--The term “pheromone” was given by Karlson and Butenandt in 1959 when they identified it in Silkworm moth.

CLASSIFICATION OF PHEROMONES Primer pheromones:- A chain of physiological

changes is triggered off in the receiving animal. They act on gustatory receptors. eg:-Caste discrimination & reproduction in social insects.

Releaser pheromone:-An immediate and reversible behavioural change is produced in the receiving animal.

i. Sex Pheromone ii. Aggregation Pheromones iii. Trail Pheromones iv. Alarm Pheromones

Aphrodisiacs:- These are substances that aid in courtship of the insects after two sexes are brought together. In many cases, male produce aphrodisiacs.

Calling position:- The posture shown by the female during the pheromone release.

Mono-component pheromone system:- If a pheromone consists of only one chemical compound.

Multi-component pheromone system:- If a pheromone consists of more than one chemical compounds.

Use of Sex pheromones in Pest management i. Monitoring ii. Mass trapping iii. Confusion or Decoy method

D. GENETIC INSECT CONTROL/AUTOCIDAL CONTROL

A) Induced Sterility i) Sterile male release technique: When a sterile male mates with normal female there will be no progeny. -This theory of Male Sterile Technique was conceived by E.F. Knipling as early as 1937. ii) Aspermia: Inactivation of sperms. iii) Infecundity: Sterile eggs by dominant lethal mutation.B) Cytoplasmic Incompatiblity: Sterility is due to a cytoplasmic factor transmitted through the egg, which kills the sperm of incompatible male after its entry into the egg.

C) Hybrid Sterility: In some insect cross-types or races which produce fertile females but sterile males among progeny.D) Population replacement: The ability of disease transmission of vectors i.e. replacement of specific vector populations can as well be changed by genetic methods. E) Autosterilization: Sterilization of native insects in their natural environment by using chemosterilants along with the species specific attatractants / lures/ bait traps. -Bonus effect: The sterile males mates with the normal females thus reduces reproductivity.

METHODS OF STERILIZATIONA. Chemosterilants i. Alkalyting agents: They inhibit nucleic acid synthesis, inhibits gonad development & produce mutagenic effects. Eg:- TEPA, Chloro ethylamine etc. ii. Antimetabolites: Chemicals with structural similarity with biological substances. Eg:- 5-Fluororacil, Amethopterin etc.B. Irradiations: It is done by exposing the insects to X- rays or neutrons emitted from Cobalt.

E. INSECT GROWTH REGULATORS

IGRs are compounds which interfares with the growth, development and metamorphosis of insects.

TYPES1.Ecdysone or Moulting Hormone (MH):Synthetic analogues of ecdysones are called ecdysoids - It causes defective cuticle formation.2. Juvenoids: The possibility that JH analogs may have potential as insect control was first recognized by Williams & Slama (1966). The compounds showing JH activity, ‘Juvenoids’. -They found it in paper made of Balsam fir tree.

3.Anti JH or Precocenes: Precocenes are the compounds which would antagonize the JH activity and de-arrange the insect development. These compounds induce the precocious metamorphosis of immature insects. Precocenes affect insect diapause, reproduction and behaviour. These compounds first extracted from the plant Ageratum houstonium.4.Chitin synthesis inhibitors: Chitin synthesis inhibitors disrupt molting by blocking the formation of chitin, the building block of insect exoskeleton. Without the ability to synthesize chitin, molting is incomplete, resulting in malformed insects that soon die. It suppresses egg-laying and causes egg sterility in treated adults through secondary hormonal activity Eg:-Diflubenzuron, Flufenoxuron etc.

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