Pest, Disease, and Weed Management
Domain 4 tests integrated pest management and the legal frame around pesticide use. Questions ask you to identify the pest, decide whether action is justified, and choose the least-risk effective tactic in the correct order.
The IPM sequence
Identify first - insect, mite, pathogen, nematode or weed - including host and life stage; misidentification wastes everything that follows. Monitor and set a threshold: the density at which damage exceeds the cost of treatment. Some defoliation is tolerable. Prevent with resistant cultivars, correct planting depth and spacing, sanitation, mulch, balanced nutrition and avoidance of wounding. Then biological and mechanical controls: predators and parasitoids, hand removal, traps, barriers, flame or mechanical weeding. Chemical control comes last, targeted and rotated by mode of action (FRAC for fungicides, IRAC for insecticides, HRAC for herbicides) to slow resistance. Weeds: distinguish monocots (grasses, parallel veins) from dicots (broadleaf, netted veins) - selective herbicide choice depends on it. Pre-emergent herbicides form a soil barrier and must be applied before germination and left undisturbed; post-emergents need active growth and good coverage. Mulch at 50–80 mm suppresses most annual weeds.
The label is the law
Follow FIFRA labelling: rate, timing, PPE, restricted-entry interval, preharvest interval, buffer zones and disposal. Apply only to labelled sites and pests. Calibrate sprayers before use and keep application records.
Worked example
Aphids on new rose growth, ladybird larvae present, no leaf distortion. Reasoning: predators are active, the threshold is not met and new growth tolerates feeding - take no action but monitor twice weekly. If colonies expand and leaves curl, use insecticidal soap or a selective aphicide at label rate, avoiding open bloom and spraying in the evening to protect pollinators.
Traps that cost marks
Calendar spraying. Applying a herbicide where a fungicide is needed. Pre-emergent onto emerged seedlings. Exceeding label rate 'to be sure'.