Plant Protection: Entomology and Plant Pathology
Plant Protection: Entomology and Plant Pathology
This domain tests pest and disease recognition, damage symptoms, integrated pest management (IPM) and safe pesticide use. Questions often link insect mouthparts or pathogen type to the correct control method.
Core rules
- Chewing insects remove plant tissue; sucking insects remove sap and may transmit viruses. Contact insecticides work poorly against hidden or sucking pests; systemic insecticides move within plant tissue.
- IPM uses monitoring, economic threshold level (ETL), cultural methods, resistant varieties, biological control and judicious chemicals. ETL is the pest density at which control is justified, not zero tolerance.
- The disease triangle requires a susceptible host, virulent pathogen and favourable environment. Symptoms are plant responses; signs are pathogen structures such as mycelium, spores or bacterial ooze.
- Fungicides control fungi; bactericides and antibiotics may be used for bacterial diseases; viruses are managed mainly through vectors, resistant varieties and clean seed.
Worked example
A knapsack sprayer holds 15 L. The recommendation is 2 mL product per litre and spray volume 500 L/ha. Product per hectare = 2 x 500 = 1,000 mL. Number of tanks = 500/15 = 33.3, so 34 tank loads. Product per tank = 15 x 2 = 30 mL. The reasoning is to calculate total product from spray volume, then divide by tank capacity; rounding tanks upward avoids running short.
Traps
Do not spray at the first insect sighting if the ETL is not reached. A fungal symptom is not automatically cured by a bactericide. Confusing symptoms with signs loses marks. Mixing products without compatibility testing can cause phytotoxicity. Always follow label dose and pre-harvest interval.