Ch 3. Crop Protection Flashcards
What is a monoculture?
The expansion of land devoted to single crops and year to year production of the same crop species on the same land.
What 3 factors reduce the sustainability of monocultures in agriculture?
- Weed Competitors
- Pest Populations
- Diseases
What is a weed?
An unwanted plant in a human-controlled setting i.e. farm fields and gardens.
What is an Annual weed?
A weed which grows from seed and disperses its seeds in one year.
What 4 properties make Annual weeds successful?
- Rapid Growth
- Short life cycle
- High seed output
- Long-term seed viability
Give two examples of Annual weeds.
- Chickweed.
2. Speedwell.
What is a Perennial weed?
A weed that lives for more than 2 years, will generally die back over winter and grow in spring.
What 3 properties make Perennial weeds successful?
- Storage
- Vegetative Reproduction
- Rhizomes
Give two examples of Perennial weeds.
- Dandelion
2. Bramble
Why are Annual weeds particularly problematic in cultivated areas of farmland?
Because the constant tilling of the soil unearths seeds that germinate and grow quickly.
Why are Storage Organs useful to Perennial weeds?
Because they provide food for the weeds when rates of photosynthesis are low.
What is Vegetative production?
A feature which some Perennial weeds possess, which means they have reproductive structures such as bulbs and tubers which new plants can grow from.
What makes Perennial weeds most compatible with crop plants?
They are already well established in the area the crop is being planted.
Name 3 different types of Invertebrate Pests to crops.
- Insects
- Nematode worms
- Molluscs
How do insects cause damage to plants?
By feeding on them.
How do Nematode worms cause harm to plants?
They are found in the soil and attack plants root systems.
How do molluscs cause harm to plants?
By eating them.
Give two examples of molluscs.
Snails
Slugs.
How do these pest invertebrates reduce crop yield?
Damage caused to leaves can reduce the rate of photosynthesis and therefore reduce crop yield.
What 3 things can plant diseases be caused by?
- Fungi
- Bacteria
- Viruses
How do Invertebrate pests cause disease?
They often act as vectors, facilitating the spread of disease caused by microorganisms.
How does disease reduce crop yeild?
Because a proportion of the diseased crop plant may be unmarketable due to its appearance.
Name a disease to tomatoes which reduces crop yield.
Bacterial speck disease.
What is Bacterial speck disease caused by?
A bacterium called Pseudomonas syringae.
What affect does Bacterial speck disease have on the tomatoes? (2)
- Reduced growth - due to a lower rate of photosynthesis (this is what causes a reduced crop yield).
- Black lesions on the fruit, leaves and stems.
How can a high crop yield be obtained?
- Through Cultural means (traditional) of controlling weeds, pests and diseases and to prevent their spread.
- Through the use of crop Protection chemicals
Why are Crop Protection chemicals useful in agriculture?
They provide farmers with a cost-effective way of improving the yield and quality of their crops.
They also make harvesting more straightforward and maintain consistent yields from year to year.
Name 5 different types of Pesticides.
- Insecticides
- Herbicides
- Fungicides
- Molluscicides
- Nematicides
What do herbicides do?
They kill weeds
What do Insecticides do?
They kill insects
What do Fungicides do?
They kill fungi which can cause disease in plants. (control of fungal disease).
What do Molluscicides do?
They kill mollusc pests.
What do Nematicides do?
They kill nematode pests.
What do crop plants and weeds compete for?
- Sunlight
- Nutrients/Minerals
- Water
Identify three different types of herbicide.
- Selective herbicide
- Contact herbicide
- Systematic herbicide
What is a selective herbicide?
A herbicide which is applied to crops which are well established in a field.
Because they are selective they only kill weeds.
What do many selective herbicides contain?
Synthetic plant hormones which encourage the accelerated growth of plants which absorb them.
How are selective herbicides selective in only killing weeds?
Weeds often have broad leaves and take up large quantities of the chemical. Cereal plants have narrow leaves and absorb very little of the chemical, and so are hardly affected.
What are Contact herbicides?
These act non-selectively and destroy all green plants they come into contact with.
How do Perennial weeds survive when sprayed with Contact herbicides?
Contact herbicides do not affect underground organs. Therefore well established perennial weeds with tap roots/storage organs soon reappear and compete with crop plants.
What are Systemic herbicides?
These kill all plant matter they come into contact with.
What are Systemic herbicides often used for?
To prepare a field before planting (to clear it of all weeds).
How do Systemic herbicides kill plants?
They are absorbed into the phloem and xylem and transported throughout the plant. All parts of the plant are killed including any reproductive structures under the soil.
Why are Systemic herbicides less harmful to the environment?
They are biodegradable so do not persist in the environment.
Name two types of pesticides.
- Contact pesticide
2. Systemic pesticide
What is a Contact pesticide?
Kills the invertebrate when it comes into contact with the pest. e.g. spraying greenfly
What is a Systemic pesticide?
How does it kill the pest?
A type of chemical which is sprayed onto crops and absorbed by the tissues of the crop plant.
When a pest feeds on the plant they ingest the chemical and either be deterred from further feeding or die.
How is a Systemic pesticide accumulated by a plant?
It is absorbed through the roots and translocated to leaves, stems, and flowers.
Name two types of Fungicide.
- Contact fungicides
2. Systemic fungicides
What are Contact Fungicides?
How do they work?
These are sprayed onto crop plants prior to fungal attack. When the fungal spores Land and begin to germinate, they absorb the poison and die.
What is a Systemic Fungicide?
These are absorbed by crops and transported to all parts of the plant giving them protection from disease-causing fungi.
How can farmers give their crops protective applications of fungicide to prevent the growth of fungus?
Different fungal diseases require different environmental conditions e.g. potatoe blight is caused by a fungus which needs specific humidity levels and temperatures to grow.
Farmers can give their crops protective applications of fungicide by monitoring these conditions.
Why do farmers give their crops protective applications of fungicide to prevent the growth of fungus?
Because protective applications of fungicide based on disease forecasts are often more effective than treating a diseased crop.
What are the disadvantages of using plant protection chemicals?
- They may be toxic to animal species.
- Some plant protection chemicals may be persistent in the environment.
- They can also bioaccumulate (accumulate in the body of an organism.
How can bioaccumulation occur from plant protection chemicals?
Even if levels of chemical in the environment are relatively low accumulation can occur if the organism absorbs the chemical at a faster rate than it is excreted (lost). This accumulation can mean that the chemicals build-up to a toxic level in an organism, causing poisoning.
What is Bio magnification?
Where plant protection chemicals are magnified along food chains - meaning that the concentration of the chemical increases as it moves from one trophic level to the next.
Name a plant protection chemical or insecticide which which bio accumulates and bio magnifies
DDT
Is DDT biodegradable?
No.
Give an example of a pest which has become resistant to several pesticides used for its control.
The Colorado potato beetle.
This beetle is legendary.
The high beetle fecundity (birth) rate (600 eggs/female average) increases the probability of mutation of an offspring for resistance to the pesticide. This also means that the pesticide resistance can spread rapidly through the population.
What is Biological control?
This involves the introduction of a biological agent which could be a predator or parasite of the pest.
What is Integrated Pest Management?
This combines both chemical and biological controls and aims to reduce the use of chemicals and effectively control pest levels.
What is the greatest risk with Biological Control?
That the control organism used may become an invasive species, parasite, or pray on other species.
