Lesson Notes By Weeks and Term v5 - Grade 11

Lesson Video

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Performance objectives

• Explain the principles and importance of IPDWM.
• Identify and describe three cultural control methods.
• Evaluate the pros and cons of biological control.
• Outline the proper and safe use of pesticides in an IPDWM strategy.
• Develop a basic IPDWM plan for a South African crop.

Lesson summary

This week, we delve deeper into Integrated Pest, Disease, and Weed Management (IPDWM). South African agriculture faces constant challenges from pests, diseases, and weeds that significantly reduce crop yields and impact farmers' livelihoods. Understanding and implementing IPDWM strategies is crucial for sustainable agricultural practices that minimize environmental damage while maximizing productivity. Imagine a maize farmer in the North West Province whose entire crop is decimated by stalk borer. This farmer's livelihood is threatened, food security is compromised, and the local economy suffers. IPDWM provides a toolkit to prevent such disasters.

Lesson notes

Integrated Pest, Disease, and Weed Management (IPDWM) is a sustainable approach to managing pests, diseases, and weeds in agricultural systems. It emphasizes prevention, monitoring, and the use of multiple control tactics, integrating them to minimize environmental and economic risks. IPDWM is NOT simply about eliminating pests at all costs; it's about keeping their populations below economically damaging levels while preserving beneficial organisms and the environment.

Key Principles of IPDWM: Prevention: Implementing practices to prevent pests, diseases, and weeds from becoming established in the first place. This includes using disease-free seeds, resistant varieties, crop rotation, and sanitation.

Monitoring: Regularly scouting fields to identify and assess pest, disease, and weed populations. Accurate identification is crucial for selecting the appropriate control measures. Thresholds, i.e., action thresholds, are set to determine when intervention is necessary.

Identification: Correctly identifying the pest, disease or weed is paramount. Misidentification can lead to ineffective and even harmful control measures. Use field guides, consult with agricultural advisors, or utilize diagnostic labs when needed.

Decision Making: Selecting the most appropriate control tactics based on the identified pest, disease, or weed, its population level, economic thresholds, and potential environmental impacts.

Implementation: Carefully implementing the selected control tactics, following label instructions and safety precautions.

Evaluation: Evaluating the effectiveness of the implemented control tactics and making adjustments as needed. This involves monitoring pest, disease, and weed populations after treatment to determine if further action is required.

Control Methods in IPDWM: Cultural Control: These are practices that modify the growing environment to make it less favorable for pests, diseases, and weeds.

Crop Rotation: Alternating crops can disrupt pest life cycles and reduce disease buildup in the soil.

Example:* Rotating maize with soybeans can reduce stalk borer populations. If a farmer in the Free State has a maize crop infected with nematodes, rotating to wheat or sunflower, which are non-hosts for the nematode, can help break the nematode life cycle in the soil.

Sanitation: Removing crop residues and weeds can eliminate overwintering sites for pests and diseases.

Example:* Burning maize stalks after harvest can reduce stalk borer populations. Removing volunteer plants (e.g., weeds or previous crop plants growing unintentionally) prevents them from acting as reservoirs of pests and diseases.

Resistant Varieties: Planting varieties that are resistant to specific pests or diseases can significantly reduce the need for other control measures.

Example:* Using nematode-resistant tomato varieties in KwaZulu-Natal. Many maize varieties are now resistant to certain races of stalk borer.

Tillage: Certain tillage practices can disrupt weed seed germination or bury weed seeds deep in the soil, reducing weed pressure.

Example:* Ploughing can bury weed seeds, preventing them from germinating.

Water Management: Proper irrigation can reduce the incidence of certain diseases.

Example:* Avoiding overhead irrigation in tomatoes can reduce the spread of fungal diseases.

Optimizing Planting Dates: Adjusting planting dates can avoid periods of peak pest or disease activity.

Example:* Planting sunflowers early in the season can avoid infestation by sunflower head borers.

Biological Control: Using natural enemies to control pests and diseases.

Predators: Organisms that kill and eat other organisms.

Example:* Ladybugs feeding on aphids. Certain spiders prey on various insects and can be encouraged by providing suitable habitat (e.g., conservation tillage, reduced pesticide use).

Parasitoids: Organisms that live in or on another organism (the host) and eventually kill it.

Example:* Parasitic wasps laying their eggs inside stalk borers.

Pathogens: Disease-causing organisms that can infect and kill pests.

Example: Using Bacillus thuringiensis (Bt) to control caterpillars. The use of fungal pathogens for controlling locust outbreaks is another example.

Conservation Biological Control: Modifying farming practices to create a favorable environment for natural enemies.

Example:* Planting flowering plants near crops to provide nectar and pollen for beneficial insects.

Augmentative Biological Control: Releasing commercially produced natural enemies into the field.

Example:* Releasing Trichogramma wasps to control moth eggs.

Advantages of Biological Control: Environmentally friendly, sustainable, reduces reliance on chemical pesticides.

Disadvantages of Biological Control: Can be slow-acting, may not be effective against all pests, and can be expensive. Success depends on carefully choosing the right natural enemy and providing a suitable environment for it to thrive.

Mechanical Control: Using physical methods to control pests and weeds.