3. crop production Flashcards
Explain why weeds are of economic concern and reduce food security
weeds compete with crop plants, while other pests and diseases damage crop plants, all of which reduce productivity
what are the properties of annual weeds
rapid growth, short life cycle, high seed output and long-term seed viability.
what are the properties of perennial weeds with competitive adaptations
storage organs and vegetative reproduction (produce identical offspring without sexual reproduction)
what are the properties of an effective annual weed
a plant that grows from seed, sets seed then dies within the year
what are the properties of an effective perennial weed
a plant that survives for more than one year
describe pests found on plants
most of the pests of crop plants are invertebrate animals such as insects, nematode worms and molluscs
Damage caused to leaves can reduce the rate of photosynthesis and therefore reduce crop productivity.
describe plant diseases
can be caused by fungi, bacteria or viruses, which are often carried by invertebrates
describe cultural control and name the 4 cultural control methods
includes practices which try to prevent any weeds, pests or diseases from getting established in the crop. (eg. ploughing, weeding, crop rotation and removal of crop residue)
describe crop rotation reason for effectiveness
Prevents pests’ repeated access to their food source, especially if the pest is soil-based
describe ploughing reason for effectiveness
Buries crop residues that frequently harbour pests and diseases
describe weeding reason for effectiveness
Removes a competitor of the crop plant
describe removal of crop residue reason for effectiveness
Removes material that might harbour pest insects from outside the crop area
name 5 pesticides
-herbicides to kill weeds
-fungicides to control fungal diseases
-insecticides to kill insect pests,
-molluscicides to kill mollusc pests
-nematicides to kill nematode pests.
what is a selective herbicide
designed to kill specific plants
have a greater effect on certain plant species (broad leaved weeds).
describe systemic herbicides
Systemic herbicide spreads through the vascular system of the plant and prevents regrowth
describe systemic insecticides
Systemic insecticides, molluscicides and nematicides spread through the vascular system of plants and kill pests feeding on plants
Why do you think that protective applications of fungicide, based on disease forecasts, often more effective than treating a diseased crop?
A disease forecast using up-to-date local weather information can forecast the probability of increased risk of fungal growth. This means you can spray fungicides in advance of the fungicide growing and damaging your crop. (this maintains crop protection and food security)
what are some problems with using pesticides
toxicity to non-target species,
persistence in the environment (non-biodegradable—do not break down or be excreted)
bioaccumulation (a build-up of a chemical in an organism)
biomagnification ( an increase in the concentration of a chemical moving between trophic levels) in food chains
producing resistant populations of pests.
describe biological control
the control agent is a natural predator, parasite or pathogen of the pest
describe integrated pest control management
a combination of chemical, biological and cultural control.
what are some risks with biological control
the control organism may become an invasive species, parasitise, prey on or be a pathogen of other species.
