DISEASES OF CROPS
Subject:
Agricultural Science
Class:
SS 2
Term:
Second Term / 2nd Term
Week:
Week 6
WEEK SIX
Date:
TOPIC: DISEASES OF CROPS
CONTENT
- Meaning and causes of diseases
- Details of selected diseases
MEANING AND CAUSES OF DISEASE
A crop is a plant cultivated by man for a specific purpose. A plant disease is a deviation of the plant from the normal state of health, presenting outward visible signs. Diseases are caused by pathogens and enhanced by some physiological factors.
CAUSES OF DISEASE
Plant diseases are caused by pathogens. Pathogens are disease causing organism which passes through a regular cycle of development and reproduction. Examples of pathogens that cause plant disease are viruses, bacteria, fungi, parasitic worms and rarely protozoa. Some of these pathogens are carried by vectors and other agents.
Physiological factors such as nutrient deficiency in the soil, heat, presence of inorganic salts in the soil and soil moisture content has a major role to play in influencing plant susceptibility to diseases.
SELECTED DISEASE OF CROPS
Name | Casual organism | Method of transmission | Symptoms and economic importance | Prevention and control measure |
Maize Smut | Fungus (Ustilago maydis) | Fungus spores deposited on fruits |
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Rice Blight | Fungus (Piricularia oryzae) | Airborne spores on leaves |
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Maize Rust | Fungus (Puccinis polysora) | Airborne spores deposited on leaves |
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Cercopora a Leaf spot of Cowpea | Fungus | Through Wind |
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Rosette disease of Groundnut | Virus | By piercing and sucking insect (Aphid) |
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Cassava Mosaic | Virus |
(Bemisia nigerensis)
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Leaf blight of Cassava | Bacterium Xanthomonas manihotis |
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Cocoa black pod disease | Fungus Phytophthora palmivora |
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Coffee Leaf rust | Fungus |
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Black arm (bacterial Blight of cotton) | Bacterium |
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Root Knot of Tomatoes/ Okra | Nematodes | Nematodes in soil |
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Damping off Disease of Okra | Fungus | Infected soil |
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Onion Twister Disease | Fungus |
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Stored produce mould fungicides | Fungus |
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Presentation :
The topic is presented step by step
Step 1: The class teacher revises the old topic
Step 2: The class teacher introduces the new topic
Step 3: The class teacher allows the pupils to give their own contributions and gives room for pupils” participation
Class Teacher and Pupils Activities. Interaction or Participation
This involves class teacher and pupils’ interaction, conversation, imitation or modeling through discussion, play method or just by recitation or asking and answering questions that are related to the topic that has just been taught.
EVALUATION
- What is plant disease?
- List four common disease causing organisms.
Conclusion :
The class teacher concludes the lesson by giving the pupils some notes on the topic that has just been taught. He goes round to mark and he does the necessary corrections.