Crop Protection: Entomology and Plant Pathology
Crop protection combines entomology and plant pathology. The exam tests pest identification, damage symptoms, disease diagnosis, IPM, and safe pesticide use.
Pests and damage
Chewing insects remove plant tissue; piercing–sucking insects remove sap and may transmit viruses. Brown planthopper (Nilaparvata lugens) causes hopper burn in rice. Yellow stem borer (Scirpophaga incertulas) causes dead heart in vegetative stage and white ear in reproductive stage. Leaf folder rolls leaves and scrapes chlorophyll. Cotton pink bollworm damages bolls; sugarcane early shoot borer causes dead heart; coconut rhinoceros beetle damages the crown.
Disease and IPM
The disease triangle requires a susceptible host, virulent pathogen, and favourable environment. Rice blast is caused by Magnaporthe oryzae; bacterial leaf blight by Xanthomonas oryzae pv. oryzae; tungro is a virus transmitted by green leafhopper. Banana Panama wilt is caused by Fusarium oxysporum f. sp. cubense. IPM uses resistant varieties, cultural methods, mechanical removal, biological control, and need-based chemicals. ETL is the pest density at which control is justified.
Worked example
A 50 EC formulation is recommended at 2 mL/L. For 500 L/ha spray volume, formulation needed = 2 × 500 = 1,000 mL = 1 L per hectare. If the label gives dose as active ingredient, convert using formulation concentration.
Traps that cost marks
Fungicides do not cure viral diseases. BPH is not controlled like a chewing caterpillar. ETL is not zero pests. Observe the pre-harvest interval. Do not mix incompatible products without checking.