Application of Chemical Agents: Pesticides are applied via spraying or as solid granules. Effective application requires correct timing relative to the pest's life cycle and consideration of weather conditions to prevent the chemical from washing away or drifting into non-target areas.
Introduction of Biological Agents: This involves releasing a specific organism into the crop environment. For example, parasitic wasps are released in greenhouses to control whiteflies, and ladybirds are used to manage aphid infestations on outdoor vegetable crops.
Environmental Monitoring: Successful control requires regular auditing of pest levels. If biological control is used, the farmer must ensure the predator population remains healthy and localized to the crop area to provide continuous protection.
| Feature | Chemical Control (Pesticides) | Biological Control |
|---|---|---|
| Action Speed | Immediate and rapid effect | Slow; relies on predator growth |
| Specificity | Often broad; may kill beneficial insects | Highly specific to target pest |
| Sustainability | Requires repeated applications | Often self-sustaining and long-lasting |
| Eradication | Can eliminate entire populations | Never kills 100% of pests (predator needs food) |
| Resistance | Pests can develop genetic resistance | No resistance development possible |
The Bioaccumulation Mechanism: When explaining bioaccumulation, always emphasize that the concentration increases as you move up the food chain. Mention that top predators are the most severely affected because they consume many contaminated lower-level organisms.
Resistance vs. Immunity: In exams, never use the word 'immunity' when discussing pests. Pests develop resistance through natural selection (a population change), not an immune response (an individual change).
Non-Specific Effects: If asked about the disadvantages of insecticides, specifically mention the risk to pollinators like bees. This demonstrates a broader ecological understanding of the negative impacts of non-specific chemical control.
The Eradication Myth: A common misconception is that biological control should 'remove' all pests. Because predators depend on the pest for food, a successful biological system maintains a stable, low-level pest population rather than total elimination.
Misidentifying Pesticide Types: Ensure you use the specific term required by the scenario: insecticide for animals, herbicide for weeds, and fungicide for diseases. Using the generic term 'pesticide' when a specific one is appropriate can lose marks.
Lag Time in Bio-Control: Students often forget that biological control takes time to become effective. The predator population must first reproduce and increase in number before it can significantly reduce the pest population.
