Crop Protection Flashcards
What is an annual weed?
Annual weed plants grow, flower, set seed and die all within the space of one year
What are the properties of annual weeds?
rapid growth, short life cycle, high seed output and long-term seed viability
What are perennial weed plants?
Perennial weed plants live for more than two years.
Why are perennial weeds able to compete with crops?
they are already well established in the area the crop is being planted
What are properties of perennial weeds?
Perennial weeds have storage organs which provide food when rates of photosynthesis are low. Some perennial weeds are also capable of vegetative reproduction; this means they have reproductive structures such as bulbs and tubers which new plants can grow from.
Example of pest of crop plants
invertebrate animals such as insects, nematode worms, and molluscs
How can insects damage crops?
Insects cause damage to plant crops by feeding on them. Damage caused to leaves can reduce the rate of photosynthesis and therefore reduce crop yield.
What causes plant diseases?
Plant diseases can be caused by fungi, bacteria or viruses.
What can act as a vector to spread disease?
Invertebrates
Define cultural means
This form of control does not require chemicals but involves farmers adopting practices which make the environment unfavourable for the pest
Explain crop rotation
growing a different crop in the same area each successive year, this denies pests repeated access to their food source.
Explain ploughing
this buries crop residues that frequently harbour pests and diseases
How does systemic pesticides work?
spread through the vascular system of plants. When a pest feeds on the plant they ingest the chemical and die. Systemic pesticides can be incorporated into the soil of crop plants. The chemical is absorbed by roots and translocated to leaves, stems, and flowers. An insect that feeds on a treated plant may acquire a lethal dose of insecticide or at least be deterred from further feeding.
How does herbicide work?
Herbicides are chemicals used to kill weeds. Herbicides can be applied to control the growth of weeds which would otherwise grow amongst a crop, competing with it for water, nutrients and sunlight and reducing its yield.
How does selective herbicide works?
Many selective herbicides contain synthetic plant hormones which encourage the growth of plants which absorb them. This causes their growth to speed up; they use up their food stores and die
Why do selective herbicides only kill weeds and not crop plants
Weeds often have broad leaves and take up large quantities of the chemical. Crop plants such as cereals have narrow leaves therefore they do not take up as much of the chemical and are largely unaffected
Why do selective herbicides not damage the environment?
Selective herbicides mimic natural plant hormones and therefore do not cause harm to the environment.
When is it best to use a systemic herbicide and why?
Systemic herbicides kill all plant matter they come into contact with. They can be used to prepare a field before planting to clear it of all weeds
How does systemic herbicide work?
When systemic herbicides are sprayed on plants, they are absorbed and transported throughout the plant. This kills all parts of the plant including any reproductive structures under the soil. Systemic herbicides are biodegradable therefore they do not persist in the environment.
What are fungicides and why are they used?
Fungicides are used to kill fungi which can cause disease in plants.
How do systemic fungicides work?
Systemic fungicides are absorbed by crops and transported to all parts of the plant giving them protection from disease-causing fungi.
How does watching environmental conditions and disease forecast protect crops from fungicides.
Different fungal diseases require different environmental conditions. By monitoring these conditions, farmers can give their crops protective applications of fungicide to prevent growth of the fungus. Protective applications of fungicide based on disease forecasts are often more effective than treating a diseased crop.
What does it mean if a pesticide is persistent in the enviroment
it is not biodegradable and remain in the environment for long periods of time after their application
What is bioaccumilation?
build up of a chemical in an organism
