Lesson Notes By Weeks and Term - Senior Secondary School 2

Pests of crops

Date: 6th-17th of February 2023

Class: SSS 2

Term: 2nd Term

Week: 5&6

Subject: Agricultural Science

Topic: Pests of crops

Duration:45 minutes

Teaching Aid: A chart

Reference Book: 1. Essential Agricultural Science for Senior Secondary Schools by O.A Iwena(page241-243)

  1. Comprehensive Certificate Agricultural Science For Senior Secondary Schools by L.A Are et al (page340-346)

Behavioural Objectives: By the end of this topic, students should be able to

  1. Define pests
  2. Mention the types of crop pests and classify insect pests
  3. Discuss prevention of pests


Step 1: Teacher revises last topics

Step 2: Teacher introduces and explains new topic

Step 3: Teacher dictates note

Step 4: Teacher evaluates students

Step 5: Teacher marks students' notes and give assignment

Previous knowledge: Students have been taught Pasture and forage



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:

(i) insect; (ii) birds; (iii) rodents; (iv) monkeys; (v) man; (vi) nematodes


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

  1. Bitting and chewing insects;
  2. Piercing and sucking insects;
  3. Boring insects.
  4. Biting and Chewing Insects: These insect (mouth-parts) which enable them to bite and chew plant parts. Examples include: termites, grasshoppers, leaf worms, army worms, mantids, locust, beetles, etc.
  5. Piercing and sucking insects: These insect pests posses strong mouthparts called proboscis stuck liquid from materials from plants’ tissues. Examples include aphids, cotton strainers, mealy bugs, scale insects, capsids or mirids, white flies, etc.
  6. 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 include: bean beetles, stem burrowers, maize weevils and rice weevils.


Insect Pest

Crops Attacked

Nature of Damage and Economic Importance

Prevention and Control Measure

Stem burrower

Cereals e.g. rice, maize, guinea corn

    i.     Larvae bore holes into stems.

  ii.     They eat up the plant

iii.     They weaken the plant

iv.     Reduced growth and yield

    i.     Uproot and burn infected plant.

  ii.     Spray with insecticides e.g. Gammlin 20.

iii.     Early planting

iv.     Crop rotation.

Army Worm

Cereals e.g. maize

    i.     Larvae invade and eat up leaves and stem

  ii.     Reduce photosynthesis

iii.     Retarded growth

iv.     Reduced yield

    i.     Hand picking

  ii.     Spray with insecticides e.g. DDT.


Pod Burrower

Legumes e.g. cowpea, soyabeans

    i.     Larvae bore into the pod.

  ii.     They eat up the seeds.

iii.     Reduced yield

iv.     Introduce disease

    i.     Crop rotation

  ii.     Early harvesting

iii.     Spray with insecticides


Legumes e.g cowpea, soyabeans

    i.     Stunted growth

  ii.     Galls on leaves

iii.     Vectors of disease e.g. rosette, mosaic disease of cowpea

    i.     Spray with insecticides to kill vector

  ii.     Uproot and burn infected plant


Leaf beetle

Legume e.g. cowpea soyabeans

    i.     They eat up the leaves

  ii.     Reduce photosynthesis

iii.     Reduced yield

    i.     Spray with insecticides

  ii.     Use resistant varieties


Cocoa mirids (capsids)

Beverages e.g. cocoa

    i.     They inject toxic saliva into plant

  ii.     Transmit fungal diseases

iii.     Reduced yield

iv.     Stunted growth

    i.     Spray with insecticide e.g. Gammalin 20

  ii.     Regular weeding

Yam beetles

Tubers e.g. yam

    i.     Bore holes into yam tubers

  ii.     Reduction in yield

iii.     Reduction in quality and market value

    i.     Dust yam sets with Adrin dust before planting

  ii.     Crop rotation

Cassava mealybugs

Tubers e.g. cassava

    i.     Twisting of stem and reduce internodes

  ii.     Swelling of shoots

iii.     Reduced yield

    i.     Early planting

  ii.     Use resistant varieties

iii.     Cutting treatment

iv.     Spray with insecticides

Green spidermite

Tuber e.g. cassava

    i.     They feed on the leaves

  ii.     Reduce rate of photo synthesis

iii.     Reduction in yield

    i.     Use biological control

  ii.     Spray with insecticides.

Variegated grasshopper

Tubers e.g. cassava, yam

    i.     Adults and larvae eat up the leaves and stem

  ii.     Reduce the rate of photosynthesis

iii.     Reduced growth

iv.     Reduced yield

    i.     Hand picking

  ii.     Spray with insecticides e.g. Adrex 40.

Cotton stainer


    i.     They pierce and suck sap from plants.

  ii.     Produce toxic saliva

iii.     Transmit diseases.

iv.     Reduce quality of boll

  v.     Leaf distortion

    i.     Hand picking

  ii.     Spray with insecticides.

Cotton bollworm


    i.     Larvae feed on the seeds of cotton

  ii.     Crop rotation

iii.     Destroy the lint and reduce its quality

iv.     Premature fall of cotton boll.

    i.     Spray with insecticides to kill insects.

  ii.     Burn cotton plant debris after harvesting.


Vegetables e.g. onion, tomato

    i.     Browning of leaves

  ii.     Wilting of plant

iii.     Reduced yield

    i.     Spray with insecticides.

Leaf rollers


Leaf beetle



Vegetables e.g. pepper, okro, tomato

    i.     Rolling and twisting of leaves.

  ii.     Reduction in rate of photosynthesis.

iii.     Reduce yield

iv.     They eat up the leaves and stems

  v.     Reduced photosynthesis

vi.     Reduction in yield and quality

Spray with insecticides e.g. Vetox 85.


Spray with appropriate insecticides e.g. Vetox 85

Bean beetle, grain weevils

Stored produce e.g. rice, cowpea, maize

    i.     Bore holes into grainsand eat them up.

  ii.     Reduce the quality of stored produce

iii.     Reduce quality of grains to powder

iv.     Reduce farmer’s income

  v.     It reduces the market value of grains

vi.     It reduces viability of infested grains.

    i.     Early harvesting

  ii.     Proper storage of produce

iii.     Proper cleaning and fumigation of store with phostoxin tablets or with lindane dust

iv.     Store grains over fire places

  v.     Proper drying of seeds to reduce moisture content and kill the eggs and larva of pest.


Rice, maize, millets, sorghum

    i.     Feed on grains in the field

  ii.     Reduction in quality and yield

iii.     Reduction in income of farmer

    i.     Use of bird scarer or scare cow.

  ii.     Use of cage traps with baits

iii.     Drumming or noise making on the farm

iv.     Shooting with catapult

  v.     Use of explosive mechanism at regular intervals

vi.     Use of avicides

vii.     Fencing/screening farms in greenhouse.

Rodents e.g. bush rabbit, rats, squirrel

Rice, yam, cassava, fruits

    i.     They feed on crops

  ii.     Destroy whole plants

iii.     Reduction in yield

iv.     Increase in cost of production

    i.     Trapping with baits

  ii.     Use of rodenticides

iii.     Use of string/wire tapes

iv.     Use of predator e.g. dogs and cats

  v.     Clean weeding of farms

vi.     Shooting and fencing

vii.     Use of pit traps.


Cocoa, mango, banana, orange.

    i.     They eat up the fruits

  ii.     Reduce the quality of fruits

iii.     Losses to the farmer

    i.     Use traps

  ii.     Shooting with gun where possible



  1. Insects pest 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 insets may predispose crops to disease attact.
  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:

(1) Physical control; (2) Cultural Control (3) Biological control; (4) chemical control.

  1. Physical Control: This involves the physical removal of pests by:
  2. Handpicking of insects and larvae,
  3. Setting traps to catch rodents.
  4. Shooting rodents with gun.
  5. Fencing round the farm with wire nets.
  6. Cultural Control: This method involves the use of farm practise to prevent or control pest especially on the field. Examples of cultural control include:
  7. Practicing crop rotation
  8. Use of pest resistant varieties of crops
  • Appropriate tillage operations
  1. Use of insect traps
  2. Handpicking and destruction of insects,
  3. Burning crop residues,
  4. Timely planting of crops
  5. Proper weeding or sanitation
  6. Timely harvesting.
  7. Close season practices, especially in cotton
  1. Biological Control: This involves the introduction of the natural enemies of pest to control or the pests population under control. Such enemies eat up or feed on these pests thereby reducing the population of the pest.
  2. Chemical Control: This involves the use of chemical called insecticides or pesticides to control pests or crop plants.

Definition of Insecticides

An insecticide is a chemical preparation used to control insect pest.

Forms of 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                       mode of action

(i)        Powder                        (i)        Contact

(ii)       Liquid                          (ii)       Systemic

(iii)      Granules                      (iii)      Stomach

(iv)      Gas (eous)                   (iv)      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:

  • Pesticides -           chemicals to control pests
  • Insecticides -           chemicals to control insect, e.g. Grasshopper
  • Rodenticides -           Chemicals to control rodents, e.g. Rats
  • Avicides -           Chemicals to control birds, e.g. weaver birds
  • Nematicides -           Chemicals to control nematodes, e.g. Eel worms.


The use of various control methods of disease and pests has some side effect. These side effect are follows:

(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
  • It may leave undesirable residue in the environment
  1. Pests and diseases may develop resistance to chemicals
  2. Some are washed out of soil to rivers and streams where they can endanger aquatic life and cause pollution
  3. Empty containers could be a source of poisoning when used as container for consumables.

(b)       Biological Methods of Control

  1. The new organism introduced may start attacking crops which were originally free from attack
  2. The predators expected to control other may rather feed on other beneficial insects
  • 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 organism
  2. Resistant varieties may become adapted to the environment so that the resistance in short-lived where fire is used.
  • It care is not taken, fire may spread to other farms.
  1. The use of fire may cause the destruction and loss of organic matter from the soil
  2. It may also lead to the destruction of soil structure and cause soil erosion.

Evaluation: describe the classes of insect pests

Assignment: draw one insect pests in each classes(alternative to practical)

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