Lesson Notes By Weeks and Term v5 - Grade 11
Integrated pest, disease and weed management – Week 9 focus
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Integrated pest, disease and weed management – Week 9 focus
Download the Lessonotes Mobile South Africa app for faster lesson access on Android and iPhone.
Subject: Agricultural Management Practices
Class: Grade 11
Term: 3rd Term
Week: 9
Theme: General lesson support
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South Africa's agricultural sector is vital for food security, employment, and economic growth.
However, pests, diseases, and weeds significantly threaten crop yields and quality, impacting farmers' livelihoods and consumers. The overuse of synthetic pesticides can lead to environmental damage, pesticide resistance, and health risks. Integrated Pest, Disease, and Weed Management (IPM) is a sustainable approach that minimizes these negative impacts by combining various control methods. This week, we will focus on the practical application of IPM strategies relevant to South African farming contexts, emphasizing preventative measures and environmentally friendly approaches.
2.1 What is Integrated Pest, Disease, and Weed Management (IPM)? IPM is a sustainable approach to managing pests, diseases, and weeds by combining various strategies that minimize economic, health, and environmental risks. It's not about eradicating pests completely but about keeping their populations below the Economic Threshold Level (ETL). IPM emphasizes prevention, monitoring, and using multiple control methods in a coordinated and ecologically sound manner. 2.2 Key Principles of IPM: Prevention: Proactive measures to prevent pest, disease, and weed problems from occurring in the first place.
Monitoring: Regularly inspecting crops and the surrounding environment to detect and identify potential problems early.
Identification: Accurately identifying the pest, disease, or weed to select the most effective control methods.
Economic Threshold Level (ETL): The pest density at which control measures are needed to prevent economic losses. Intervention is only justified when the pest population reaches or exceeds the ET
L. Multiple Control Tactics: Using a combination of control methods rather than relying solely on chemical pesticides.
Evaluation: Assessing the effectiveness of control measures and adjusting the IPM plan as needed. 2.3 IPM Strategies: Preventative Control: Crop Rotation:* Alternating different crops can disrupt pest and disease life cycles. For example, rotating maize with legumes can break the life cycle of maize stalk borer and improve soil health.
Resistant Varieties:* Planting crop varieties that are resistant to specific pests and diseases. Many maize varieties are now resistant to certain strains of stalk borer.
Sanitation:* Removing crop residues and weeds that can harbor pests and diseases. Burning or composting crop residues after harvest can reduce pest and disease carryover.
Proper Irrigation and Fertilization:* Maintaining healthy plants are more resilient to pest and disease attacks. Avoid over-watering, which can create favorable conditions for fungal diseases.
Use of Certified Disease Free Seeds:* Using certified disease free seeds ensures that disease are not spread during planting Cultural Control: Tillage:* Ploughing or cultivating the soil can bury weed seeds and disrupt pest life cycles.
Timing of Planting and Harvesting:* Adjusting planting and harvesting dates to avoid peak pest or disease periods. Planting maize early in the season can help it avoid severe stalk borer infestations.
Intercropping:* Growing two or more crops together can reduce pest and disease incidence. Planting marigolds alongside vegetables can deter nematodes.
Trap Crops:* Planting a crop that is more attractive to pests than the main crop, diverting the pests away. Planting mustard as a trap crop for diamondback moth in cabbage fields.
Biological Control: Natural Enemies:* Utilizing beneficial insects, predators, and parasites to control pests. Introducing ladybugs to control aphids or using parasitic wasps to control caterpillars.
Microbial Control:* Using microorganisms, such as bacteria, fungi, and viruses, to control pests and diseases. Bacillus thuringiensis (Bt) is a bacterium that produces toxins that are effective against certain caterpillars. Trichoderma is a fungus that can suppress soilborne diseases.
Chemical Control: Selective Pesticides:* Using pesticides that are specific to the target pest or disease and have minimal impact on non-target organisms. Choose pesticides that are registered for use on the specific crop and pest in South Africa and always follow the manufacturer's instructions.
Proper Application Techniques:* Applying pesticides at the correct dosage and using appropriate application methods to minimize environmental contamination. Avoid spraying on windy days or during periods of heavy rain.
Rotation of Pesticides:* Rotating different classes of pesticides to prevent the development of pest resistance. 2.4 Economic Threshold Level (ETL) The ETL is a critical concept in IPM. It represents the pest density at which control measures are economically justified. Applying pesticides before the ETL is reached can be wasteful, expensive, and harmful to the environment. Determining the ETL requires monitoring pest populations, estimating potential crop losses, and calculating the cost of control measures.
Example: A farmer growing tomatoes notices an infestation of tomato leaf miners. To determine whether to spray, they need to estimate the potential yield loss if no action is taken. They monitor the number of leaf miners per leaf and find an average of 5 leaf miners per leaf. Research indicates that each leaf miner causes an average of 1% yield loss.
Therefore, the estimated yield loss is 5% (5 leaf miners x 1% loss per leaf miner). The farmer estimates that a 5% yield loss would result in a loss of R5,000 in revenue. The cost of spraying, including the pesticide and labor, is R2,000.