Pest, Disease, and Weed Management
What the domain covers
This domain tests integrated pest, disease, and weed management: recognition, prevention, threshold decisions, and safe pesticide use. The exam favours IPM reasoning over routine spraying.
Core rules and concepts
- IPM combines cultural, mechanical, biological, and chemical methods, with chemicals as a last resort.
- Pests include insects, mites, nematodes, and molluscs; diseases are caused by fungi, bacteria, viruses, and abiotic disorders.
- The disease triangle requires a susceptible host, a pathogen, and favourable environment; remove one leg to reduce disease.
- Weeds compete for water, light, and nutrients; manage them before seed set.
- Use economic threshold levels (ETL) to decide intervention, and rotate modes of action to slow resistance.
- Follow the label: dose, target, protective equipment, pre-harvest interval (PHI), and safe disposal.
Worked example
A few aphids appear on mustard seedlings. The reasoned action is to check the ETL, inspect natural enemies such as ladybird beetles, and use a strong water jet or insecticidal soap for a light infestation. A broad-spectrum spray would kill predators and invite resurgence. Chemical control is justified only if the threshold is crossed.
Traps
- Treating every spot as fungal: viral and nutrient symptoms may not respond to fungicide.
- Spraying by calendar rather than need.
- Ignoring PHI, which leaves residues above safe limits.