LECTURE NOTES ON PEST MANAGEMENT

PESTS: Pests are harmful species, whose population size or population density goes beyond the damage threshold level, either throughout the year or during specific seasons, adversely affecting the availability, quality and value of human resources.
NATURAL PEST CONTROL: This involves the operation of natural factors, without much human influence. Includes Climatic, Topographic and Biological Factors.
Climatic Factors:
a)  Temperature:  Temperature is the most effective and most important factor in insect control. Each insect requires an optimum range of temperature for each stage of its life cycle. If the temperature goes above or below the optimum range, it will have a damaging effect on insect population and even kill the insects.
b) Rain: Too much or too little rain fall can control the growth of insects. Eg:- Red hairy caterpillar of Cut worms has to burrow in to the soft soil for pupation and moderate rain enables this. Absence of rain makes the soil hard and caterpillar find it difficult to enter in to the soil for pupation.
c) Humidity:  High humidity helps the developments of certain fungi which attacks the insects and thereby control insect population.  Eg:- In Nilgiri area, during October to January,  when  humidity goes high, resulting  in the growth of a fungi, Cephalosporium lecanii  on Green Scale Insect of Coffee and controls it.
Topographic Factors:
Geographical barriers like large mountain ranges, large water bodies, vast deserts, dense forests etc limits or restrict the dispersal of insects. The nature of lakes and rivers like the larva of some insects survive only in stagnant or slow moving waters, while the larva of black flies and caddis flies live only in swift flowing streams.
Biological Factors:
For any insect there are natural enemies. They may be parasites or predators. Predators include other insects, mites, spiders, birds, reptiles, fishes and mammals. Parasites include insects, mites and disease causing viruses, bacteria and fungi. These keep the insect population in an optimal size. Birds are very effective in controlling insect population as they feed on grass hoppers, caterpillars, wood-boring insects and scale insects. Many larvivorous fishes feed on the larvae of insects.

CULTURAL  PEST CONTROL:
     Cultural pest control is the deliberate modification of agricultural practices so as to destroy the insect pests or to prevent them from destroying the crop. Pests are either locally eliminated or are reduced to well below the damage threshold level. This method is the cheapest of all control measures, has no toxicity and minimal harm to non targeted organisms. This include
a)  Crop Rotation: This is the practice of growing a different crop in a field every year in a 2-6 year cycle. It keeps the pest population from building up. This is most effective to control soil- inhabiting pests. If the same crop is grown continuously for many years, the pest of that crop will get a regular and continuous source of food and breeding sites, which will result in an uncontrolled increase of that pest. Eg:- A soya bean  Corn crop rotation is effective and economical against some weevils because the host plant  of the insect will be altered and  is deprived of food supply.
b) Trap Cropping or Companion Cropping:  In this method, small ‘trap plots (Plots where more susceptible or preferred crops are grown) are maintained near the major crop. Trap crop act as a trap’ and attracts the pest. After the pest had established on the host in the trap plot, the plot is either ploughed or treated with pesticide. Eg:- Castor plants are often planted near chilly cultivation and Tomatoes in Citrus orchards.
c) Mixed Cropping: In this method 2 or more crops are grown simultaneously in the same plot. Even if one crop suffers from pest attack, the others grow up well.
d) Tillage Operation:- Thorough ploughing helps to burry and kill soil  inhabiting insects and their eggs, larvae and pupae. This is also helpful in exposing hiding and hibernating stages of pests to hot sun, desiccation and bird predation.

MECHANICAL PEST CONTROL:
These are procedures by which pest species are trapped or killed by mechanical means, or are prevented from gaining access to the host plants by making barriers. It is very effective in the initial stages of infestation of some insect pests, such as aphids, jassids, scale insects etc. The commonly used mechanical pest control procedures are the following.
1) Killing of the eggs, Larvae and other inactive stages of pests by hand picking, net collection etc.
2) Collection and destruction of pests using Traps and Trenches like Cricket-traps, Light-traps, Suction- traps, Electric traps etc.
3) Sieving and winnowing for stored products.
4) Mechanical exclusion using barriers, which will prevent the pests from reaching the crop.
5) Destruction of affected plants and plant parts together with the pest.
6) Spiking of stem- borers in their bore holes.
7) Banding of fruit trees with grease or other banding materials to stop or entangle & kill crawling pests.
8) Shaking of trees & shrubs to dislodge and kill pests.
9) Flooding of the infested fields after harvest to kill the soil- inhabiting larvae, pupae, and adult pests.
10) Pest- proof packing of stored products.
11) Covering of fruits and vegetables.

PHYSICAL PEST CONTROL:
This involves the deliberate modification of some physical factors to slow down the growth or minimise or prevent pest infestation. They include,
a) Use of Drie- die:   Drie die is a material formed of highly porous silica gel. Its application causes the excessive loss of moisture from the body of insects, result in their death. This method is effectively used against the pests of stored grains in USA.
b) Use of high and low lethal temperatures:  High frequency radio waves generate a temperature of about 80*C and is used to kill granary weevils and flour beetles.
c) Use of ionizing radiations to kill insect pests or to induce sterility; male insects can be made sterile by exposing them to gamma radiation.
d) Blowing of refrigerated air through stored grains to maintain a very low temperature and to kill the pests.
e) Use of light traps to attract, catch and kill nocturnal insects.
f) Use of colour traps to attract, catch and kill some diurnal insects.

LEGAL OR REGULATORY PEST CONTROL:
Legal or legislative pest control is the control of pests through the enactment of laws and regulations. This prevents the entry of pest species from one country to another so that living things could not be freely imported or exported between countries. The legal measures, now in force in different countries are
1) Legislation for foreign quarantine to prevent the introduction of new pests, diseases and weeds from foreign countries.
2) Legislation for domestic quarantine to prevent the spread of established pests, diseases and weeds from one part of the country to another.
3) Legislation to ensure the application of effective control measures to prevent the damage by established pests, diseases and weeds.
4) Legislation to fix the permissible level of pesticide residues in food stuffs and also to prevent the adulteration and misbranding of pesticides.
5) Legislation to regulate pest- control activities and operations and also to regulate the applications of hazardous pesticides.
In India presently there are 2 kinds of regulatory measures for pest control. They are
1) Legislative measures through plant quarantine - This deals with the prevention of introduction of exotic pests and diseases in to the country and their spread from one state or union territory to another.
2) Legislative measures through State Agricultural Pests and Diseases Act.  This deals with the prevention of spread of pests and diseases in areas within a state or union territory.
CHEMCALCONTROL:
ORGANIC INSECTICIDES:  Organic insecticides are different types and are widely used in modern agricultural practices. The major categories are 1) Hydrocarbon oils, 2) Organic compounds of animal origin, 3) Organic compounds of plant origin, 4) Synthetic organic insecticides.
HYDROCARBON OILS:- These are the insecticides, formed of Hydrogen and Carbon. Mineral (petroleum) oils and coal tar are example. The insecticidal property of these oils is due to the presence of a heterogeneous mixture of cyclic and saturated as well as unsaturated hydrocarbons in them.
Hydrocarbon oils are widely used as insecticides mainly because they are cheap, have good spreading capacity, are less toxic to animals, are easy to mix, and insect develop no resistance against them. The disadvantages of hydrocarbon oils include, they are more toxic to plants and less toxic to insects, and are unstable to store. Often they damage the rubber parts of the spraying instruments.
ORGANIC INSECTICIDES OF ANIMAL ORIGIN:- There are only very few insecticides of animal origin. The most important of this type is the toxic substance extracted from the marine Annelids Lumbrineris heteropoda and Lumbrineris brevicirra. This extract is called Neristoxin (Dimethylamino dithiolane) and is very effective.
ORGANIC INSECTICIDES OF PLANT ORIGIN:- These are generally called botanicals . They are extracted from plants. The following are examples.
Nicotine :- Nicotine is the main alkaloid present in tobacco, is well known for its insecticidal property.  It is present in the leaves of Nicotiana tabacum. Nicotine is neurotoxic and it can enter into the body of insect pests through cuticle, spiracles and ingested food. It can be sprayed as a solution with soap, lime or ammonium hydroxide. The solution can be prepared by boiling 1 kg of tobacco waste in 10 litres of water for 30 minutes and then by diluting it into 30 litres and adding 90 gm of soap. This solution is an effective insecticide.
Pyrethroids:- Pyrethroids are extracts of the plant Chrysanthemum coccineum. The insecticidal property of pyrethroids is due to the presence of esters. The flowers of Chrysanthemum are powdered and a mixture of this power and talc or clay is used as an insecticidal dust. This is a contact poison. When this powder is dusted on a pest, it knocks down the pest immediately. Usage of increased concentration of this pesticide ensures the death of the pest and prevents recovery of the pest due to enzymatic degradation of pyrethroids. They have broad insecticidal property and low mammalian toxicity.
Rotenoids:-  Rotenone is a  compound present in the roots of plants Derris and Lonchocarpus. It was first extracted in 1848, and used against leaf-eating caterpillars.  Insects, poisoned with rotenone , show a decline in oxygen consumption, leading paralysis and death. On exposure to light and air, rotenone may get oxidized to a non-insecticidal compound.
Neem products:- The comounds extracted from Neem plant, Azadirachta indica are of high inscecticidal usage. From neem tree compounds such as Nimbecidine and from the kernels of neem tree Azadirachtin is extracted.
SYNTHETIC ORGANIC INSECTICIDES:-
These include organochlorines, organophosphorus compounds, carbamates, synthetic pyrethroids, insect growth regulators, organic thiocyanates and dinitrophenols.
Organochlorines :- They are also called Chlorinated hydrocarbons. They consists of an aliphatic or aromatic hydrocarbon nucleus and varying number of chlorine atoms attached to it. DDT, BHC (more correctly termed HCH- Hexachlorocyclic hexane.), Chlordane, Lindane, Heptachlor, Toxaphene, Aldrin, Dieldrin,Endrin, Endosulfan  are some of the examples.
Organochlorines are hard or persistent pesticides, because they are not easily bio-degradable. They persist in the soil up to 15 years, get biologically magnified and are stored in the fatty tissues of a variety of organisms. This causes severe problems with environmental contamination and residues in soil and harvested food products.
Chlorinated hydrocarbons are quick acting and highly toxic to most of the organisms. They are neurotoxins, which inhibit iron transport across nerve membrane and interfere with the transmission of nerve impulses. Some of them have hormone-like growth regulating properties. Most organochlorines act by contact, some by ingestion and others by vapour action. The toxicity to human beings varies with their kind and there is no effective remedy for mammalian poisoning.
DDT (dichloro diphenyl trichloro ethane) is the most important organochlorine compound. In India, the use of DDT in agriculture is banned. It was first synthesized by Othnar Zeidlar in 1874 and insecticidal properties were discovered by Paul Muller in 1934. DDT is a stomach poison and a contact insecticide of high persistence. It affects sense organs and nervous system. Many insects developed resistance to DDT due to irrational use.
Endosulfan is a chlorinated hydrocarbon and an organic sulphate. It was using since 1956 as an insecticide. It acts as a contact poison and also a stomach poison. It is effective against insects which sucks plant juice. Endosulfan is discussed widely now a days because of the toxicity caused to human beings and other organisms due to the over and irrational usage in the cashew plantations of Kasaragod District. Thousands of people are affected due to environmental contamination in soil, water and air and residues in soil and harvested food.
ORGANOPHOSPHORUS COMPOUNDS:- These are organic pesticides, with a invariable phosphorus- containing central core and variable remaining part. This group includes some of the most toxic insecticides such as parathion, malathion, diacinon, trithion, ethion, fenthion, dichlorvos, etc.
These are nerve poisons, extremely toxic to not only insects, but also to fishes, birds and mammals including human beings. They inhibit the action of choline esterase enzyme, which degrades the excess of the neurotransmitter and thereby prevents persistent post-synaptic depolarization. They are bio-degradable and hence are not persistent, which remain in the atmosphere only for few hours or days. Most of them are contact poisons, while demeton-S-methyl is systemic poison and dichlorvos is a fumigant.
CARBAMATES or URETHANES:- They are derivatives of carbamic acid and have a carbamic acid nucleus. They are inhibitors of choline esterase. Carbaryl (sevin), isolan, pyrolan, aldicarb (temik), aminocab (zeneb), carbosulfan, carbofuran (baygon), etc are examples.  Carbaates like carbaryl are less toxic , mostly used for horticultural purposes, while others are highly poisonous.
SYNTHETIC PYRETHROIDS:-   Synthetic pyrethriods can over come the draw backs of natural pyrethrum since they are more stable and more toxic and are effective against a wide range of insect pests. Eg:- Permethrin, Cypermethrin, Allethrin, Cyfluthrin, Fenvalerate.
INSECT GROWTH REGULATORS (IGRs) :-  These are chemicals with the properties of moulting and growth hormones of insects, and also with the potentiality to kill insects. They interfere with the action of insect growth hormone systems and thereby inhibit moulting and growth , eventually killing the insects. Eg:- Dimilin, Penfluron, Juvabione, Methoprene, Ecdysoid etc.