Plant Protection and IPM: Thresholds Before Sprays
What this domain tests
Recognition of insect pests, diseases and weeds of the main West Bengal crops, and selection of control measures within an integrated pest management (IPM) framework.
Pest and disease specifics
- Rice: yellow stem borer (dead hearts, white ears), brown plant hopper, gall midge, leaf folder; blast, bacterial blight, sheath blight.
- Jute: stem weevil, hairy caterpillar, yellow mite.
- Potato: aphids and tuber moth; late blight (Phytophthora infestans) and early blight in cool humid weather.
- Brinjal: shoot and fruit borer. Pulses: pod borer.
IPM rules
- IPM combines cultural (resistant varieties, timely sowing, crop rotation, clean cultivation), mechanical (light traps, hand picking), biological (Trichogramma, neem-based products, Bt) and chemical methods, with pesticides as the last resort.
- Spray only when the pest crosses the economic threshold level (ETL) - for example, 5% dead hearts in rice or one egg mass per m². Zero infestation is not the target.
- Follow label dose, use PPE, respect the waiting period before harvest, and rotate insecticide groups to slow resistance.
Worked example
A field shows 2% dead hearts, below the 5% ETL. Reasoning: do not spray; remove affected tillers, check light-trap catches, and re-inspect after three days. Spraying below ETL costs money and kills natural enemies.
Traps that cost marks
Calling blast or sheath blight a pest; spraying at first sighting; mixing two insecticides without need; ignoring the waiting period.