Crop Protection: Insect Pests, Diseases and Their Management
What the exam asks
Crop Protection tests recognition of insect pests and diseases, economic thresholds, integrated pest management (IPM) and safe pesticide use. Items often describe symptoms or a field count and ask for the logical action.
Core rules
- IPM combines monitoring, cultural methods, resistant varieties, biological control, mechanical methods and judicious pesticides.
- Economic threshold level (ETL) is the pest density at which control prevents economic loss. It is not zero pest incidence.
- Examples: wheat rusts produce orange or black pustules on leaves; rice blast causes spindle-shaped lesions; brown planthopper sucks sap and causes hopperburn; chickpea pod borer damages pods; mustard aphid colonises shoots and pods.
- Disease management relies on clean seed, resistant varieties, rotation, sanitation and correct fungicide timing; pest management relies on scouting and stage-specific action.
- Pesticide label directions, protective clothing and pre-harvest intervals are mandatory for safety and residue control.
Worked example
A control operation costs ₹1,200 ha−1. Scouting shows that without control, 0.2 t ha−1 yield would be lost, and the crop price is ₹20,000 t−1. Value of loss avoided = 0.2 × 20,000 = ₹4,000 ha−1. Benefit-cost ratio = 4,000 ÷ 1,200 = 3.3. Reasoning: action is economically justified here, but if the expected loss were only ₹800, the ratio would be below 1 and spraying would waste money.
Traps
Do not spray at first sight of a pest; ETL and natural enemies matter. Do not confuse disease symptoms with insect damage. Do not use a pesticide because a neighbour used it; match the pest and label. Overdosing increases cost, resistance and residue risk.