Weeds & Control
(a) Weeds compete with crop plants, while pests and diseases damage them all, reducing productivity. Properties of annual weeds include rapid growth, short life cycle, high seed output, long-term seed viability. Properties of perennial weeds with competitive adaptations — storage organs and vegetative reproduction.
Most of the pests of crop plants are invertebrate animals such as insects, nematode worms and molluscs. Plant diseases can be caused by fungi, bacteria or viruses, which are often carried by invertebrates.
(b) Control of weeds, pests and diseases by cultural means.
The advantages of plant protection chemicals which are selective or systemic. Protective applications of fungicide based on disease forecasts are often more effective than treating a diseased crop.
