3.3 Criteria Flashcards
Weeds compete with crop plants for what?
light, soil nutrients, aerial and root space which reduces productivity
Pests and diseases damage crop plants which reduces what?
Productivity
Describe annual weeds as showing: (5)
- Rapid growth
- Short life cycle (1 growing season)
- Sexual reproduction
- High seed output
- Long term seed viability
Describe perennial weeds as: (3)
- Growing for several years
- Sexual and asexual (vegetative) reproduction
- Having competitive advantage early in the growing season due to vegetative (storage) structures (they don’t have to germinate first)
Most pests of crop plants are invertebrates give 3 examples:
Insects (aphids e.g. whitefly), nematode worms (e.g. potato cyst nematode), molluscs (e.g. snails and slugs)
Plant diseases can be caused by what?
Fungi, bacteria or viruses which are often carried by invertebrates
Sowing dense populations of crop plants controls weed species by what?
Competition
Manual weed removal (weeding), hoeing, digging and mulching all reduce weed species numbers by what?
Taking the weed plants away
Crop rotation controls pests and disease by what?
Preventing the build up of their numbers
What are the 5 types of pesticide?
Herbicides, fungicides, insecticides, molluscicides, nematocides
Selective herbicides have a greater affect on certain (targeted) plant species such as?
Broad leaved weeds such as dandelions
Systematic herbicides spread through the vascular system of a plants preventing what?
Plant regrowth
Systematic insecticides, molluscicides and nemotocides spread though the vascular system too and kill pests when they…
feed on the plant
What are some potential problems with pesticide use? (5)
- Toxicity to non-target species
- persistence in the environment
- pest populations may become resistant
- Bioaccumulation where the chemical builds up in an individual organism.
- Biomagnification where the chemical concentration increases from one trophic level to the next e.g. DDT
Disease forecasts through observing weather conditions allow for what?
Preventative application of fungicides
Define biological control:
The use of a natural predator, parasite or pathogen of the pest e.g. Encarsia against whitefly
What are 4 potential risks with biological control?
- becoming an invasive species
- parasitizing non-target species
- preying on non-target species
- being a pathogen of non-target species
Define integrated pest management (IPM)
A combination of chemical, biological and cultural control
