Plant Protection (Entomology and Plant Pathology)
Plant Protection (Entomology and Plant Pathology)
This domain tests pest and disease diagnosis, the disease triangle, integrated pest management (IPM), pesticide calculation and safe use in field crops and vegetables.
Core rules and concepts
- Insect damage depends on mouthpart type: chewing insects remove tissue; sucking insects extract sap and may transmit viruses.
- Complete metamorphosis has egg, larva, pupa and adult stages; incomplete metamorphosis lacks a pupal stage.
- The disease triangle requires a susceptible host, virulent pathogen and favourable environment. Fungi, bacteria, viruses and nematodes produce different symptoms.
- IPM combines resistant varieties, cultural methods, mechanical control, biological control and judicious chemical use based on economic threshold level.
- Pesticide labels state formulation, active ingredient, dose, waiting period and precautions. Resistance develops with repeated use of one mode of action.
Worked example
A recommendation is a 0.05% spray of a 50% wettable powder in 200 litres of water. Product required = 0.05% of 200,000 g = 100 g. Reason: percentage concentration is usually expressed on the formulated product basis unless the label states active ingredient. If the label instead specifies active ingredient, the product quantity must be divided by the formulation concentration.
Traps that cost marks
Confusing active ingredient with commercial formulation; spraying on a calendar instead of scouting; ignoring the pre-harvest waiting period; diagnosing every leaf spot as fungal; forgetting that virus diseases are often vectored by sucking insects.