📖 Lesson 4: Life Cycles of Pests and Parasites

👩🏽‍🏫 Introduction

Hello, science defender! 🛡️
Have you ever seen a weevil in stored rice or a tick on a goat’s skin? These tiny creatures might look harmless—but they can destroy crops, spread disease, and hurt farm animals. In this lesson, we’ll explore how pests and parasites affect farming—and more importantly, how we can interrupt their life cycles to stop the damage.

By the end, you’ll be able to explain what these organisms are, how they develop, and how to control them using smart, science-based strategies.

Let’s dive into this miniature battlefield! 🔬

🔍 Core Concepts

🔹 1. What Are Pests and Parasites?

• Pests often damage crops or farm animals.

• Parasites can be internal (endoparasites) or external (ectoparasites).

🔹 2. Classification of Pests and Parasites

🔹 3. Life Cycle of a Pest or Parasite

Understanding the life cycle helps us target weak points for control.

Let’s look at four examples:

🦟 A. Anopheles Mosquito (Carrier of Malaria)

Life Cycle:

1. Egg (laid on water)

2. Larva (wriggler – aquatic)

3. Pupa (inactive stage)

4. Adult mosquito (bites and spreads Plasmodium)

🌍 Control: Eliminate stagnant water, use mosquito nets and insecticides.

🐛 B. Weevil (Grain pest)

Life Cycle:

1. Egg (laid in a grain)

2. Larva (feeds inside grain)

3. Pupa

4. Adult weevil (bores exit hole)

🌾 Control: Sun-drying grains, storing in airtight containers, insecticide dust.

🪱 C. Tapeworm (Endoparasite in humans)

Life Cycle:

1. Eggs passed in feces

2. Ingested by pigs or cattle

3. Larvae form cysts in muscles

4. Humans eat undercooked meat → larvae grow into adult worms in intestines

⚠️ Control: Proper cooking of meat, good sanitation, deworming.

🐐 D. Tick (Ectoparasite on animals)

Life Cycle:

1. Egg (on ground or in cracks)

2. Larva (six-legged stage)

3. Nymph

4. Adult tick (feeds on host blood)

🐄 Control: Regular dipping or spraying, pasture management, clean housing.

🔹 4. Economic and Health Effects

🔹 5. Methods of Control

✅ WASSCE Tip: Use Integrated Pest Management (IPM)—a mix of methods for safer and more effective control.

🧠 Sample Problem Walkthrough

🌾 Problem:

Your teacher asks you to explain how to control mosquito infestation around your school.

✅ Step-by-Step Solution:

1. Identify breeding site: Mosquitoes lay eggs in stagnant water.

2. Break life cycle:

   • Remove or cover water containers.

   • Drain puddles and gutters.

   • Use larvicides in water bodies.

3. Protect people:

   • Install mosquito nets.

   • Spray rooms with insecticide.

   • Encourage use of repellents.

✔️ Answer: Remove stagnant water, apply larvicides, and use protective methods like nets and sprays to interrupt mosquito development.

✍🏽 Practice Exercises

1. Multiple Choice

Which of these is an endoparasite?
A. Tick
B. Rice weevil
C. Tapeworm
D. Tsetse fly

Answer: C. Tapeworm
Explanation: It lives inside the intestines of its host.

2. Fill in the Blanks

(a) The mosquito stage that lives in water and moves like a wriggler is the _______.
(b) Weevils damage grains mostly during the _______ stage.

Answers:
(a) larva
(b) larva

3. Match the Pest to Its Effect

Answers:
(i) → B
(ii) → A
(iii) → C

4. Short Answer

Q: Why is it important to understand the life cycle of pests and parasites when planning control methods?
A: Because each stage may require a different control method. Interrupting the life cycle prevents reproduction and future infestation.

🌀 Recap

In this lesson, you’ve learned:

• Pests and parasites harm crops, animals, and humans.

• They have different types: internal, external, crop-based, and human-based.

• Life cycles include egg, larva, pupa, and adult stages—or more.

• Controlling them requires knowing their weak points.

• Integrated Pest Management is a safe and effective strategy.

💭 Reflection Prompt

Look around your home or community. Can you spot any pests or parasites (like mosquitoes, ants, or grain weevils)? Choose one and describe:

1. Where it breeds or lives

2. Its life cycle stage you observed

3. One method you could use to control it