Pest Of Crops SS2 Agricultural Science Lesson Note

MEANING OF CROP PEST

A crop pest can be defined as any organism capable of causing damage to the crop.

TYPES OF CROP PEST

Important crop pests are grouped into the following classes;

1. Insects
2. Birds
3. Rodents
4. Monkeys
5. Man
6. Nematodes

CLASSIFICATION OF INSECT PEST

1. Biting and Chewing Insects: They possess strong mandible and maxilla (mouth parts) which enable them to bite and chew plant parts e.g. termites, grasshoppers, leafworms, mantids, locusts and beetles.

2. Piercing and Sucking Insects: They possess strong mouthparts called proboscis which enable them to pierce through plants and suck liquid materials from them. Examples are aphids, cotton strainers, mealy bugs, scale insects, capsids, mirids and white flies.

3. Burrowing Insects: They and their larva stage are capable of burrowing the tissue of the plant parts or fruits or seeds. Examples are bean beetles, stem borers, maize weevils and rice weevils.

IMPORTANT PESTS OF MAJOR CROPS

ECONOMIC IMPORTANCE OF INSECT PESTS IN CROP PRODUCTION

1. They destroy crops in the fields through their biting, chewing, boring, sucking and defoliation activities.

2. They cause a reduction in the viability of stored produce.

3. Spot injuries by insect pests predispose crops to pathogen attack.

4. They increase the cost of production as they are being controlled.

5. They render vegetables and fruits unattractive and unmarketable.

6. Some are vectors of disease.

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 the total death of crop plants.

METHODS OF PEST CONTROL

Crop pests can be prevented or controlled through the following methods:

1. Physical control
2. Cultural control
3. Biological control
4. Chemical control

Physical Control

This involves the physical removal of pests by:

• Hand-picking of insects and larvae
• Setting traps to catch rodents
• Shooting rodents with a gun
• Fencing around the farm with wire nets.
• Use of scarecrows.

2. Cultural Control

This method involves the use of farm practices to prevent or control pests, examples of cultural control are:

• Practicing crop rotation
• Use of pest-resistant varieties of crops
• Appropriate tillage operations
• Burning crop residues
• Timely planting of crops
• Proper weeding or sanitation
• Timely harvesting
•  Close season practices (no living plant is allowed for a certain period).

3. Biological Control

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

4. Chemical Control

This involves the use of chemicals called pesticides to control pests of crop plants. Examples of pesticides are insecticides, rodenticides, avicides etc. 

Examples of chemicals used to control pests are:

1. Insecticides: for controlling insect pests e.g grasshopper
2. Rodenticides: chemical control for rodents such as rats
3. Avicides: for controlling bird pest
4. Nematicides: a chemical used to control nematodes. E.g worms

FORMS OR GROUPS OF INSECTICIDES

The four groups and the mode of action are:

SIDE EFFECTS OF THE VARIOUS PREVENTIVE AND CONTROL METHOD OF DISEASE AND PEST OF CROPS

The use of these control methods have their effect, these effects include:

1. Death of some beneficial insect and soil organism, toxic exposure to animals and man, chemical residue in the environment, washing away of chemicals into aquatic life e.t.c when chemical control method is employed.
2. Organisms introduced may attack cultivated crops or stored grains, predators might not feed on targeted pests and deviate to feeding on beneficial organisms, and the activities of new organisms might cause an ecosystem imbalance when a biological control method is employed.
3. When a cultural control method is employed, the use of the bush burning method might get out of hand thereby destroying soil structure, spreading to other farms, loss of organic matter and leading to the death of beneficial microbes.