Plant Protection (Entomology and Plant Pathology)
Entomology basics
The exam tests insect orders, mouthparts (chewing, piercing-sucking, siphoning), metamorphosis and damage symptoms. Major pests include rice yellow stem borer (dead heart and white ear), brown planthopper (hopper burn), rice leaf folder, cotton bollworms, sugarcane early shoot borer, coconut rhinoceros beetle and red palm weevil, and banana pseudostem weevil.
Plant pathology
The disease triangle involves a susceptible host, a virulent pathogen and a favourable environment. Important diseases are rice blast (Magnaporthe oryzae), bacterial leaf blight (Xanthomonas oryzae pv. oryzae), sheath blight (Rhizoctonia solani), banana Panama wilt (Fusarium oxysporum f. sp. cubense), banana bunchy top virus and citrus canker.
Management
Use resistant varieties, cultural practices, mechanical removal, biological agents such as Trichoderma, Bacillus thuringiensis and NPV, and chemicals only as a last resort. Follow label dose, waiting period and personal protective equipment.
Worked example
Prepare 400 L of 0.05% spray from a 50% wettable powder. Active ingredient needed = 0.05 ÷ 100 × 400 = 0.2 kg. Product needed = 0.2 ÷ 0.50 = 0.4 kg. The reasoning is that spray percentages refer to active ingredient, so divide by the formulation strength. Add the product to water, stir well and use the suspension immediately.
Traps that cost marks
Calling hopper burn a disease; confusing dead heart with white ear, which are stages of the same stem borer attack; mixing pesticides without a compatibility check; ignoring the waiting period; and treating the product dose as the active-ingredient dose.