Unit 3 - Key Area 2 - Crop protection. Flashcards
How to maximise food production?
Crop plants must be protected from weeds, from pests, and from pathogens which may cause disease.
What is a weed?
A weed is any kind of plant that grows where it is not wanted. They compete with crop plants for resources such as light, water and nutrients. This reduces the productivity of the crop plants and lowers the economic yield.
Properties of an annual weed?
They have a short life cycle, completing their life cycle within one year.
They have a high seed output.
They grow rapidly.
Their seeds are viable for long periods of time.
Properties of perennial weeds?
They live for several years, becoming dormant in winter and growing again in spring.
They reproduce through vegetative reproduction - this is a form of asexual reproduction where new plants can grow from underground stems.
They have underground storage organs which ensure the plant has food even under poor conditions.
^ All of these are competitive adaptations which make the weed very difficult to remove.
What is a pest?
These are animals that feed on plants, damaging crops and reducing yield. They fall into 3 groups:
1. Insects.
2. Molluscs.
3. Nematode worms.
What are diseases caused by?
They are caused by pathogens, these damage crops, reducing productivity. They are often harmful microorganisms (bacteria, virus or fungi) which cause disease.
How do we control weeds, pests and diseases?
- Cultural methods.
- Chemical pesticides.
- Biological control.
What are cultural methods of control?
These are non chemical methods which include ploughing, weeding and crop rotation.
What is ploughing?
This turns over the top layer of earth before crop plants are sown. Existing weeds are damaged or buried during ploughing, the prevents the weeds from growing and competing with future crops for resources.
What is weeding?
Weeds are removed after the crop has been planted so they do not compete with the plant for resources.
What is crop rotation?
The type of crop plant grown in a field is changed. This prevents crop specific pest species or pathogens from building up.
What is a chemical pesticide?
A pesticide is a chemical substance used for destroying organisms harmful cultivated plants.
Different types of pesticides include:
1. Herbicides to kill weeds.
2. Fungicides to kill fungal diseases.
3. Insecticides to kill insect pests.
4. Molluscicides to kill mollusc pests.
5. Nematicides to kill nematode pests.
What is a selective pesticide?
They have a greater effect on a certain plant or invertebrate species.
eg. Selective herbicides only kill broad leaved weeds, leaving crop plants unharmed.
What is a systemic pesticide?
These spread through the vascular system of a plant to prevent regrowth. These are good for destroying perennial weeds as they reach and kill all parts of the plant, including the underground storage organ and roots.
What is a systemic insecticide/molluscicides/nematicide?
These spread through the vascular system of the plant and kill the pest feeding on them, without the plant being harmed itself.
