Pest, Disease and Weed Management in Nurseries
This domain tests integrated pest management in a nursery, where dense plants, frequent watering and young tissue favour rapid spread of pests and diseases. The exam expects sanitation, monitoring and correct dilution calculations.
IPM rules
- Sanitation: remove diseased and dead plants, control weed hosts, sterilize media and clean tools and benches.
- Monitoring: scout regularly and use yellow sticky traps for whitefly and aphids, blue traps for thrips, and hand lenses for mites.
- Cultural control: resistant cultivars, correct spacing, air movement, balanced nutrition, avoiding overhead irrigation and rotating beds.
- Biological control: Trichoderma and Bacillus for soil-borne disease, neem-based products, and predators where available.
- Chemical control: use only labelled products, rotate modes of action, observe the pre-harvest interval and never spray during hot afternoon hours.
Common problems
Damping-off (Pythium/Rhizoctonia), root rot, wilt, powdery mildew and leaf spot are common diseases. Aphids, whitefly, thrips, mites, caterpillars and root-knot nematodes are common pests. Weeds are managed by mulching, hand weeding and a stale seedbed before sowing.
Worked example
A sprayer tank holds 15 L. The label recommends 2 mL/L. Product per tank = 15 × 2 = 30 mL. For a 500 L spray, total product = 500 × 2 = 1,000 mL = 1 L, and the number of tanks = 500 ÷ 15 = 33.3, so prepare 34 tank loads but measure product for 500 L. The reasoning is that the dose is per litre of water, not per plant or per tank.
Traps that cost marks
Guessing the dose; spraying in strong heat; repeating one chemical until resistance develops; using banned pesticides; ignoring the pre-harvest interval; failing to remove diseased plants.
Key points
- Sanitation and monitoring come before spraying.
- Yellow traps for whitefly/aphids; blue traps for thrips.
- Dose is per litre of water; calculate tank loads carefully.
- Rotate modes of action and follow the label.