Weed Management and Crop Protection (Insects, Diseases, Nematodes)
Weed Management and Crop Protection (Insects, Diseases, Nematodes) - This domain tests weed identification, herbicide use, integrated pest management, disease diagnosis and nematode control.
Core rules
- Weeds are classified by morphology (grass, sedge, broadleaf), life cycle (annual, perennial) and habitat.
- The critical period of crop–weed competition is usually the early vegetative stage; keep the crop weed-free then.
- Herbicides: pre-emergence (pendimethalin), post-emergence (2,4-D in cereals), selective versus non-selective (glyphosate).
- IPM: monitoring, economic threshold level (ETL), resistant varieties, biocontrol (Trichogramma, NPV), pheromone traps and need-based pesticide.
- Nematodes: root-knot (Meloidogyne) causes galls; manage with crop rotation, neem cake, resistant varieties and nematicides.
Worked example
A herbicide is recommended at 1.0 kg a.i./ha as a 50% WP formulation. Product needed = 1.0 ÷ 0.50 = 2.0 kg/ha. For a 0.2 ha plot, 2.0 × 0.2 = 0.4 kg = 400 g. Reasoning: a.i. means active ingredient; divide by the formulation concentration to get product, then scale to plot size.
Traps
- Do not confuse a.i. with commercial product.
- A pre-emergence herbicide must be applied before weed emergence, not after.
- 2,4-D controls broadleaf weeds and can injure broadleaf crops such as cotton.
- ETL is not the same as zero pest population.
- A sedge such as Cyperus rotundus is neither a grass nor a broadleaf weed.