Classwork Series and Exercises {Biology – SS1}: Pest Of Agricultural Importance

Biology, SS 1 Week: 3

Topic: Pests of Agricultural Importance

Introduction

A pest is an organism with characteristics that people see as damaging or unwanted, as it harms agriculture through feeding on crops or parasitizing livestock. An animal can also be a pest when it causes damage to a wild ecosystem or carries germs. The term pest is used to refer specifically to harmful animals but it also relates to all other harmful organisms, including fungi and viruses.

Definition of Pests

Pests are living organisms that cause physical damage to man, animals and crops. In other words, pests can be described as any organism capable of causing damage to crop plant.

Types of Crop Pest

Important pests of crop plants are grouped into the following classes:

• Insects
• Birds
• Rodents
• Monkeys
• Man
• Nematodes

Classification of Insect Pests

These can be classified into various groups based on their mode of feeding. These groups of insect pests include:

1. Biting and chewing insects
2. Piercing and sucking insects
3. Boring insects

Biting and Chewing Insects: These insects pests possess strong mandible and maxillae (mouth-parts) which enable them to bite and chew plant parts. Examples include: termites, grasshoppers, leaf worms, army worms, mantid, locusts, beetles, etc.

Piercing and Sucking Insects: These insect pests possess strong mouth-parts called proboscis which enable them to pierce through plants and suck liquid materials from plants tissues. Examples include: aphids, cotton strainers, mealy bugs, scale insects, capsids, white flies, etc.

Boring Insects: These insects, including their larvae, are capable of boring into plant parts and destroy the tissues of the plants, fruits or seeds. Examples include: bean beetles, stem borers, maize weevils and rice weevils

Crops and Major pests

Crop	Pests
Beans	Beans weevils (Callosobronchus maculatus)
Rice	Rice weevil (Sitophilus oryzae), stem borers, army worms and leaf rollers
Maize	Maize weevils (sitophilus zea), stem borers and army worms
Yam	Yam beetles and rodents
Cocoa	Stem borers, root mealy bug, aphids, black tea thrips, and scales
Groundnut	Leaf worm aphids, boll worms, snail and hoppers
Cotton	Cotton strainers and boll worms
Sorghum	Weevils, boll worms, aphids and sorghum midge
Stored grains	Weevils

Effects or Economic Importance of Insect Pests in Crop Production

1. Insect pests destroy crops in the field through their biting, chewing, boring, sucking and defoliation activities
2. They cause reduction in the viability of stored produce
3. Site of injuries by insects may predispose crops to disease attack
4. They increase the cost of production during the course of controlling them
5. They render vegetables and fruits unattractive and unmarketable
6. Some are carriers or vectors of diseases
7. The profits of farmers are reduced
8. They reduce the quality of produce either in the store or in the field
9. They generally reduce the yield of crops
10. They can also cause total death of crop plants

Prevention and Control of pests

Pests of crops can be prevented or controlled through the following methods:

• Physical control
• Cultural control  

• Biological control
• Chemical control

Physical control: This involves the physical removal of pests by:

1. Hand-picking of insects and larvae
2. Setting traps to catch rodents
3. Shooting rodents with gun
4. Fencing round the farm with wire nets

Cultural control: This method involves the use of farm practices to prevent or control pests especially on the field. Examples of cultural control include:

1. Bush fallowing
2. Crop rotation change in the time of planting
3. Regular weeding
4. Proper timing of planting
5. Use of resistant varieties
6. Bush burning
7. Proper time of harvesting

Biological control: This involves the introduction of the natural enemies of pests to control or keep the pests population under control. Such enemies eat up or feed on these pests thereby reducing the population of the pests

Chemical control: chemical control involves the use of chemicals called pesticides to control pests of crop plants. These chemicals which are in form of powder, liquid, granules and tablets are used on the insects by various methods like spraying or dustings seeds or plants to check pests. Examples of such chemicals include:

• Pesticides – chemicals to control pests
• Insecticides – chemicals to control insects
• Rodenticides – chemicals to control rodents
• Avicides – chemicals to control birds
• Nematicides – chemicals to control nematodes

Diseases of Crop

A plant disease may be defined as a departure or deviation of the plant from the normal state of health, presenting marked symptoms or outward visible signs. In other word, diseases are defined as visible changes or disorder noticed in an organism due to physical, chemical or biological factors.

Classification of Plants disease

The disease spreads through seed, soil, or through wind. Plant disease may be grouped as

1. Seed – borne,
2. Soil borne,
3. Air borne

Causes of Crop Diseases

Diseases of crops are caused by the following agents:

1. Viruses
2. Bacteria
3. Fungi
4. Nematodes
5. Nutrient deficiency

Diseases of Farm Animals

Animal Diseases	Symptoms	Animal Affected	Control
Food & mouth (Virus)	Blisters in mucous lining of mouth, skin, hoofs and teats	Cattle	Isolation, killing, burying chronic animals and vaccination
Rinderpest (Virus)	High fever, weakness, choking of breath, diarrhea, formation of lesions with discharge	Cattle, sheep & goat	Regular vaccination, allowing only healthy animals in the herd. Restriction of animals
Newcastle (Virus)	Sneezing, coughing, diarrhoea, paralysis and muscular tremor	Fowl	Vaccination, good sanitation and disinfection of houses
Anthrax (Bacteria)	High fever, stupor staggering and sudden death	Cattle, sheep, goats and pigs	Isolation of sick animals, proper sanitation and giving of clean water
Brucellosis (Bacteria)	High fever, diarrhea, wobbling gait, arthritis and death	Swine	Isolation of sick animals, proper sanitation and giving of clean water
Tuberculosis (Bacteria)	Constant coughing, loss of weight and sudden death	Cattle, poultry and pigs	Good sanitation, isolation, and vaccination
Aspergilosis (Fungi)	Mouldy appearance, feeds on food saprophytically	Farm animals and man	Good sanitation and use of fungal spray
Trypanosomiasis (Protozoa)	Intermittent fever, anaemia and loss of weight	Domestic animals and man	Drugs like trypanosomide, clearing of bush around livestock

General Effects of Diseases on Crop Production

Diseases cause lots of damage to crop and their effects are as follow:

1. It generally reduce the yield or productivity of crops
2. Damage of crops