Pest Identification, Biology and Integrated Pest Management
IPM is a decision process, not a product choice. The sequence to memorise is: identify → monitor/scout and quantify → compare counts with a threshold → choose the least-risk tactic that will work → apply → evaluate and record. Thresholds come in two flavours: the economic threshold (density at which the value of crop loss exceeds the cost of control) and the action threshold (slightly lower, triggering treatment before damage reaches the economic threshold). Knowing the pest's life cycle identifies the vulnerable stage - contact insecticides are largely useless against eggs, while granules and soil drenches target soil-dwelling stages.
Identification skills: weeds (monocot vs dicot, leaf arrangement, ligule/auricle, seedhead); insects by order and mouthpart (chewing vs piercing-sucking, which decides whether a stomach poison can work at all); mites (eight legs - not insects); and diseases via the disease triangle - susceptible host plus virulent pathogen plus favourable environment. Distinguish signs (the organism itself: mycelium, frass, egg masses) from symptoms (plant response: chlorosis, gall, wilt).
Natural and cultural controls matter: predators, parasitoids, resistant varieties, sanitation, rotation, physical barriers and timing. Broad-spectrum calendar sprays are the classic IPM failure because they flare secondary pests and select for resistance.
Traps: "IPM means no pesticides" - it does not; pesticides are one option, justified by monitoring. And confusing damage with the pest: shot-holes in leaves can be disease or herbicide injury, not chewing insects.
Worked example: sticky traps catch 3 whiteflies per trap and the threshold is 5 per trap on two consecutive counts - no spray yet; re-check in five days and record the result.