A pest 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:

  1. insects
  2. birds;
  3. rodents;
  4. monkeys;
  5. man;
  6. nematodes.


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

  • biting and chewing insects;
  • piercing and sucking insects;
  • boring insects.


  1. Biting and Chewing Insects: These insect pests possess strong mandible and maxillae (mouthparts) which enable them to bite and chew plant parts. Examples are: termites, grasshoppers, leaf worms, army worms, mantids, locusts and beetles.
  2. Piercing and Sucking Insects: These insect pests possess strong mouthparts called proboscis which enable them to pierce through plants and suck liquid materials from plants’ tissues. Examples are: aphids, cotton stainers, mealy bugs, scale insects, capsids or mirids and white flies.
  3. Burrowing Insects: These insects including their larvae are capable of burrowing into plant parts and destroying the tissues of the plant or fruits or seeds. Examples are: bean beetles, stem burrowers, maize weevils and rice weevils.



  1. Insect pests destroy crops in the field through their biting, chewing, boring, sucking and defoliation activities.
  2. They cause reduction in viability of stored produce.
  3. Spot 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.


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

  • physical control;
  • cultural control;
  • biological control;
  • chemical control.


a) 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.


b) Cultural Control: This method involves the use of farm practices to prevent or control pests, especially on the field.

Examples of cultural control are:

  1. practising crop rotation;
  2. use of pest-resistant varieties of crops;
  3. appropriate tillage operations;
  4. use of insect traps;
  5. hand-picking and destruction of insects;
  6. burning crop residues;
  7. timely planting of crops;
  8. proper weeding or sanitation;
  9. timely harvesting;
  10. close-season practices, especially in cotton.


c) Biological Control: This involves the introduction of the natural enemies of pest 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.


d) Chemical Control: This involves the use of chemicals called insecticides or pesticides to control pests of crop plants.


Definition of Insecticide: An insecticide is a chemical preparation used to control insect pests.

Forms or Groups of Insecticides: There are four major forms or groups of insecticides used in the control of insect pests of crops. These forms or groups and their mode of action are:

Groups and Mode of action

  • powder – contact.
  • liquid – systemic.
  • granules – stomach.
  • Gas (eous) – fumigation.

These groups of insecticides can be used either directly on insects, seeds, plants and plant parts to check the activities of insects.


Examples of chemicals used to control pests are:

  1. pesticides – chemicals to control pests.
  2. insecticides – chemicals to control insects, e.g Grasshoppers.
  3. rodenticides – chemicals to control rodents, e.g rats.
  4. avicides – chemicals to control birds, e.g weaver birds.
  5. nematicides – chemicals to control nematodes, e.g. eel Worms.




The use of the various control methods of diseases and pests has some side effects .. These side effects include the following:

a) Chemical Method of Control

  1. Some beneficial insects and soil organisms may be destroyed.
  2. The chemical used may be toxic to man and domestic animals.
  3. It may leave undesirable residue in the environment.
  4. Pests and diseases may develop resistance to chemicals.
  5. Some are washed out of soil to rivers and streams where they can endanger aquatic life and cause pollution.
  6. Empty containers could be a source of poisoning when used as containers for consumables.


b) Biological Method of Control

  1. The new organism introduced may start attacking crops which were originally free from attack.
  2. The predators expected to control others may rather feed on other beneficial insects.
  3. The activities of the new organism introduced may cause serious imbalance in the ecosystem.


c) Cultural Method of Control

  1. The use of fire to kill harmful pests may also result in the destruction of other beneficial organisms.
  2. Resistant varieties may become adapted to the environment so that the resistance is short-lived where fire is used.
  3. If care is not taken, fire may spread to other farms.
  4. The use of fire may cause the destruction and loss of organic matter from the soil.
  5. It may also lead to the destruction of soil structure and cause soil erosion.

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