Key Area 3 Flashcards
Why do plants often die when in the same soil as weeds?
They are competing for light, space, water and nutrients
What reduces a plants productivity
Weeds that compete against the plant and diseases which damage the crops
What is an annual weed
Complete their entire life cycle in a year
Grow very quickly, have a short life cycle, produce lots of seeds that are viable for a long period of time
What is a perennial weed
Weeds that live for several years becoming dormant in the winter and growing in spring
they are full established in the habitat, are able to reproduce asexually, have storage organs for when food supply runs low
What pests affect crop plants
Invertebrates
Insects
Molluscs
Nematodes
What can cause plant diseases
Pathogens carried by fungi, bacteria and viruses
How can weeds be controlled
Biological or chemical methods
Cultural methods such as ploughing, weeding and crop rotation
What are the different types of pesticides
Herbicides, insecticides, molluscicides, nematocides and fungicides
What are the different types of herbicides
Selective and systemic
What does a selective herbicide do
Mimics the action of plant growth hormones, speeds up the metabolism of broad leafed plants and they use up their food reserves and die
What does a systemic herbicide do
They are absorbed by the plant and are transported to all areas of the plant and kills the root
What are the two types of fungicides
Contact - sprayed onto crops and it is absorbed by the fungal spores stopping germination
Systemic - absorbed by the plant and only kills the fungi affecting the plant
What are some problems with pesticides
- Toxicity to non target species
- persistence in the environment
- bioaccumulation
- Biomagnification
- Resistance in pest populations
What is bioaccumulation
The build up of a chemical in an organism
What is biomagnification
An increase in the concentration of a chemical moving between trophic levels
What is a biological control
The reduction of a pest population through the introduction of a natural predator of the pest
What is integrated pest management
Using a combination of chemical, biological and cultural methods to improve plant resistance to improve yield
