Lesson Notes By Weeks and Term v4 - SHS 2
HEALTH ISSUES IN CROP PRODUCTION
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HEALTH ISSUES IN CROP PRODUCTION
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Subject: Agriculture
Class: SHS 2
Term: 2nd Term
Week: 8
Grade code: 2.4.1.LI.3
Strand code: 4
Sub-strand code: 1
Content standard code: 2.4.1.CS.1
Indicator code: 2.4.1.LI.3
Theme: AGRICULTURE AND HEALTH
Subtheme: HEALTH ISSUES IN CROP PRODUCTION
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This lesson focuses on the critical measures farmers must take to protect their crops from diseases and pests. In Ghana, where agriculture is the backbone of our economy and provides food for our families, losing crops to diseases can mean losing income and food. We will explore how to prevent these problems before they start and how to control them when they appear. Crucially, we will connect these actions to food safety, ensuring that the food we grow and eat is not only plentiful but also safe and healthy for consumption. Understanding these measures is vital for anyone considering a future in farming, food processing, or agricultural science.
A. Foundational Definitions Crop Disease: An impairment of the normal state of a plant that interrupts or modifies its vital functions. It is caused by pathogens (like fungi, bacteria, viruses) or environmental factors. *Ghanaian Example:* Black Pod Disease in cocoa, caused by the fungus *Phytophthora palmivora*, which turns cocoa pods black and destroys the beans. Pest: Any organism that is harmful to cultivated plants or their products. This includes insects, mites, nematodes, and even weeds. *Ghanaian Example:* Fall Armyworm (*Spodoptera frugiperda*), which eats the leaves and tassels of maize plants, severely reducing yield. Preventive Measures: Actions taken *before* a disease or pest infestation occurs to stop it from happening in the first place. It is proactive. Think of it like washing your hands to prevent getting sick. Control Measures: Actions taken *after* a disease or pest has been identified on the farm to reduce its population or spread and minimise damage. It is reactive. Think of it like taking medicine when you are already sick. Food Safety: The practice of handling, preparing, and storing food in a way that prevents contamination and foodborne illnesses. In crop production, it means ensuring that harvested produce is free from harmful levels of pathogens and chemical residues. B. Preventive Measures in Crop Production
These are often the most cost-effective and environmentally friendly ways to manage crop health. Use of Resistant Varieties: Explanation: This involves planting crop varieties that have been scientifically bred to resist specific diseases or pests. Ghanaian Example: Farmers are encouraged by MoFA (Ministry of Food and Agriculture) to plant maize varieties like "Obaatampa" or "Abontem" which have tolerance to the Maize Streak Virus and drought. For cassava, farmers plant varieties resistant to the Cassava Mosaic Virus. Good Cultural Practices: These are the day-to-day farming activities done correctly. Crop Rotation: Not planting the same type of crop on the same piece of land season after season. This breaks the life cycle of pests and diseases that are specific to one crop family. *Example:* A farmer plants maize (a grass) in the major season, followed by cowpea (a legume) in the minor season. This prevents the build-up of maize-specific pests like the stem borer in the soil. Proper Spacing: Planting crops at the recommended distance. Overcrowding reduces air circulation, creating a damp environment that encourages fungal diseases like leaf spots. Field Sanitation (Cleanliness): Removing and destroying weeds, old crop residues, and diseased plants from the field. These can harbour pests and pathogens. *Example:* After harvesting tomatoes, a good farmer will clear all the old vines instead of leaving them to rot, as they can carry fungal spores that will infect the next crop. Proper Tillage: Ploughing and harrowing the land well before planting exposes soil-borne pests (like larvae and pupae) to the sun and predators. Seed Treatment: Explanation: Coating seeds with a fungicide or insecticide before planting. This protects the young seedling from soil-borne diseases and pests during the vulnerable germination stage. *Example:* Many commercial maize seeds sold in Ghana come pre-treated with a pink or green chemical coating to protect against damping-off disease. Plant Quarantine / Legislative Measures: Explanation: These are laws and regulations enforced by the government to prevent the introduction and spread of foreign pests and diseases. In Ghana, the Plant Protection and Regulatory Services Directorate (PPRSD) is responsible for this. They inspect imported plant materials at borders and ports. C. Control Measures in Crop Production
When prevention fails, these methods are used to manage an existing problem. Cultural Control: Explanation: Using farming practices to reduce the pest or disease population. Rouging: The act of identifying, removing, and destroying diseased plants from a field to prevent the disease from spreading to healthy ones. Pruning: Cutting off diseased or infested parts of a plant (like a branch with canker or leaves with mildew) to stop the infection from spreading further on the plant. Physical/Mechanical Control: Explanation: Using physical barriers or mechanical actions to kill or remove pests. Hand-picking: Manually removing large insects (like caterpillars or grasshoppers) from plants. This is effective on small farms or in gardens. Trapping: Using traps with lures (like pheromones or sticky substances) to attract and capture insects. *Example:* Using yellow sticky traps in a vegetable farm to catch whiteflies. Biological Control (Biocontrol): Explanation: Using living organisms (natural enemies) to control pests and diseases. This is an environmentally friendly method. Predators: Introducing insects that eat pests. Example: Ladybugs (ladybird beetles) are voracious predators of aphids. Parasitoids: Introducing insects that lay their eggs inside pests, and the larvae eat the pest from the inside out. Example: A specific type of wasp can be used to control the cassava mealybug. Pathogens: Using microbes (bacteria, fungi) that cause diseases in pests. Example: *Bacillus thuringiensis* (Bt) is a bacterium used to create organic pesticides that kill caterpillars. Chemical Control: Explanation: Using synthetic chemicals (pesticides) to kill pests or pathogens. This method is fast and effective but has significant risks if not used properly. Types of Pesticides: Insecticides: Kill insects (e.g., Lambda-cyhalothrin). Fungicides: Kill fungi (e.g., Mancozeb for controlling vegetable blights). Herbicides: Kill weeds (e.g., Glyphosate). Nematicides: Kill nematodes (microscopic worms). The Crucial Link to Food Safety: Personal Protective Equipment (PPE): The farmer must wear protection (boots, overalls, gloves, goggles, nose mask) to avoid direct contact with the chemical, which can be poisonous. Correct Dosage: Using too much chemical is wasteful, can damage the crop ("phytotoxicity"), and leaves excessive harmful residues on the food. Using too little may be ineffective. Always follow the manufacturer's instructions. Pre-Harvest Interval (PHI): This is the most important food safety rule. It is the number of days that must pass between the last chemical application and when the crop is harvested. If a farmer harvests a cabbage a day after spraying, the cabbage will have high levels of chemical residue, making it unsafe to eat. Each chemical has a specific PHI.
Guided Practice (With Solutions)