CROP PROTECTION U3 Flashcards
State the impact of weeds, pests and diseases on crop production
Weeds compete with crop plants, while other pests and diseases damage crop plants. All of which reduce productivity.
Describe annual and perennial weeds
Annual weeds
eg Annual Nettle
These have rapid growth, a short life cycle; high seed output and long-term seed viability.
Perennial weeds
eg Dandelion
Contain underground storage organs and use vegetative reproduction. These underground storage organs will grow into another weed even if the (surface) plant itself has been removed.
State examples of pests of crop plants and causes of plant diseases
Most of the pests of crop plants are invertebrate animals such as insects, nematode worms and molluscs (slugs).
Plant diseases can be caused by fungi, bacteria or viruses, which are often carried by invertebrates.
Describe cultural methods in the control of weeds, pests and diseases
Ploughing, weeding and crop rotation are cultural methods in controlling weeds, pests and diseases.
Ploughing
Turning the topsoil by about 20cm will uproot any underground storage organs.
Weeding
Simple pulling out of any weeds.
Crop rotation
Not planting the same crop in the same field every year. Eg if you have a disease or pest that infects potatoes in one
field, by rotating the potatoes you can reduce the build-up.
State 5 examples of pesticides and the organism that each affects
Herbicide- kills weed
Fungicide-controls fungal diseases
Insecticide-kills insect pests
Molluscicides- kills mollusc pests
Nematicides-kells nematode pests
Describe a selective herbicide
Selective herbicides have a greater effect on certain plant species (broad leaved plants).
They only kill a particular type of weed, not all plants they come into contact with.
Describe systemic herbicides, insecticides, molluscicides and nematicides
Systemic simply means that it travels into the vascular system of the plant.
Systemic herbicides - spreads through the vascular system of the plant including the underground storage organs and prevents regrowth.
Systemic insecticides, molluscicide and nematicide – spreads through the vascular system of plants and kill pests feeding on plants.
State 3 problems associated with pesticides
The three problems associated with pesticides are:
toxicity to no-target species.
persistence in the environment.
bioaccumulation or biomagnification in food chains producing resistance pests.
Describe bioaccumulation and biomagnification
Bioaccumulation is a build-up of a chemical in an organism.
Biomagnification is an increase in the concentration of a chemical moving between trophic levels.
Describe biological control of pests and diseases and the role of integrated pest management
In biological control, the control agent is a natural predator, parasite or pathogen of the pest.
Integrated pest management uses a combination of biological control, cultural and chemical methods to control pests and diseases.
State the risks associated with biological control methods
The control organism my become an invasive species, parasite, prey on or be a pathogen of other species other than the pest.
