Plant and Animal Health (Pests, Diseases and Parasites)
Principles of plant health
Know the difference between a pest (insect, mite, rodent, bird, mollusc), a disease (caused by fungus, bacterium, virus or nematode) and a weed (unwanted plant). Diseases are recognised by symptoms (what the plant shows) and signs (the pathogen itself, such as mould or spores). Understand the disease triangle: susceptible host, virulent pathogen and favourable environment.
Control methods
Group controls as cultural (rotation, resistant varieties, sanitation, spacing, timely planting), physical/mechanical (hand-picking, traps, barriers), biological (natural enemies), chemical (pesticides, fungicides, herbicides, used per label) and integrated pest management (IPM), which combines methods and uses chemicals as a last resort. Traps: calling a fungus an insect, and forgetting that resistance, sanitation and rotation reduce chemical use.
Animal health and parasites
Know external parasites (ticks, fleas, lice, mites, flies) versus internal parasites (roundworms, tapeworms, flukes) and their control: dipping/spraying, deworming, rotational grazing and clean water. Know vaccination (prevention) versus treatment (cure). Important diseases to name with their cause type: foot-and-mouth disease (viral), anthrax (bacterial, zoonotic), lumpy skin disease (viral, spread by insects), rabies (viral, zoonotic) and mastitis (bacterial, udder).
Notifiable disease and reporting
Suspected notifiable diseases must be reported to veterinary authorities at once, with movement control and isolation. Trap: advising treatment instead of reporting.
Worked example
Maize leaves show small brown spots with powdery grey centres spreading in humid weather. Reasoning: fungal leaf disease favoured by humidity. Response: remove infected debris, rotate with a non-cereal, plant resistant varieties, avoid overhead irrigation, and apply a recommended fungicide only if the outbreak is severe.