1. Higher Biology
Crop Protection
Mr G R Davidson

2. Crop Protection
There is a huge diversity of plants and animals living in natural ecosystems.
They live on each other, compete with each other and generally co-exist with each other.
Population numbers rise and fall and very much depend on other populations.
Thursday, 08 November 2018
G R Davidson

3. Crop Protection
In agricultural ecosystems, however, only one plant makes up the community.
This leaves the crop open to competition from weeds, disease and pests.
This can have a reduction in the yield of the crop.
Thursday, 08 November 2018
G R Davidson

4. Crop Weeds
Weeds compete with the crop plant for basic resources like water, light, space and nutrients.
They can also release chemicals which can inhibit the growth of the crop.
Weeds fall into 2 groups:
Annual weeds
Perennial weeds
Thursday, 08 November 2018
G R Davidson

5. Annual Weeds
An annual weed is a plant which completes its whole life cycle in one year.
They have a number of helpful adaptations:
Short life cycle
Seeds are viable for a number of years
Grow very quickly
Produce many many seeds.
Thursday, 08 November 2018
G R Davidson

6. Perennial Weeds
A perennial weed is one which persists from year to year.
They have a number of helpful adaptations:
Storage organs
Can reproduce asexually, e.g. with runners, as well as sexually
Already established before the crop was put there so has the ‘edge’ competitively.
Thursday, 08 November 2018
G R Davidson

7. Pests Invertebrates are the biggest threat to a monoculture of crops.
They mainly fall into 3 groups:
Insects, e.g. caterpillars, aphids
Molluscs, e.g. snails, slugs
Nematodes, e.g. potato cyst nematode, eel worms.
Thursday, 08 November 2018
G R Davidson

8. Insect Pests Herbivorous insects eat leaves, stems, roots, etc.
They cause millions of pounds worth of damage every year.
Some of these insects have several different stages in their life cycle, and each stage can result in different types of damage.
Thursday, 08 November 2018
G R Davidson

9. Mollusc Pests
Slugs and snails can cause a lot of damage to a crop plant.
They have rasping mouthparts which can do a lot of damage to leaves.
They are usually more active at night.
Thursday, 08 November 2018
G R Davidson

10. Nematode Pests Nematode worms tend to be found in the soil.
They bore into plant tissue where they find a good food supply.
This makes them parasites.
Thursday, 08 November 2018
G R Davidson

11. Plant Diseases
Crop disease is caused by pathogens such as viruses, bacteria and fungi.
They may be spread by insects, airborne or found in the soil.
Thursday, 08 November 2018
G R Davidson

12. Plant Diseases Micro organism Disease Host Plant Fungus Blight Potato
Bacteria
Wilt
Tomato
Virus
Bushy stunt
Thursday, 08 November 2018
G R Davidson

13. Plant Diseases
Cultural methods of weeds, pests and disease prevention have been used in agriculture for many years.
They tend to prevent rather than cure and include the following:
Ploughing which involves damaging or burying perennial weeds.
Weeding which involves the removal of young annual weeds.
Crop rotation which involves using different fields for crops every year and prevents disease from setting in. This is usually done on a 4 year cycle.
Thursday, 08 November 2018
G R Davidson

14. Plant Diseases
Chemical methods of plant disease control are used alongside the cultural methods.
Herbicides are chemicals used to kill weeds.
Selective weedkillers are chemicals which resemble plant growth substances.
Thursday, 08 November 2018
G R Davidson

15. Plant Diseases
They work by being absorbed through the leaves and they resemble plant growth substances which causes rapid growth to the point where the plant’s food reserves are exhausted and it dies.
The crop plants have narrow leaves and therefore don’t absorb enough of the chemical.
Selective weedkillers are usually biodegradable.
Thursday, 08 November 2018
G R Davidson

16. Plant Diseases
Systemic herbicides work differently in that they are absorbed into the plant’s transport system and delivered to all parts of the plant.
This then kills every part of the plant preventing it from regenerating.
Contact herbicides are used to kill all plants they come in contact with.
Their effect is very short-lived and they are also biodegradable.
Thursday, 08 November 2018
G R Davidson

17. Plant Diseases
They only kill the surface tissues which means perennial weeds with underground storage organs soon regrow.
Fungicides are used to kill off fungal parasites.
Pesticides are used to kill off pests.
Thursday, 08 November 2018
G R Davidson

18. Plant Diseases
Non-selective pesticides are general pesticides which kill a variety of pests.
Selective pesticides are used to kill off specific pests such as aphids, but do not affect ladybirds which are their natural predators.
Thursday, 08 November 2018
G R Davidson

19. Problems with Plant Protection Chemicals
Explanation
Toxic
Some pesticides are poisonous.
Bioaccumulation
Some pesticides can be passed up a food chain and at each level their concentration gets greater.
Persistence
Persistent pesticides are non-biodegradable and therefore last longer in the soil.
Resistance
A few of the population may be resistant to the pesticide and so will survive to reproduce further organisms which are also resistant.
Thursday, 08 November 2018
G R Davidson

20. Problems with Plant Protection Chemicals
Pesticides should be safe, short-lived and specific to the pest.
Otherwise a number of problems can arise.
Thursday, 08 November 2018
G R Davidson

21. Biological Control
Biological Control involves the introduction of a natural enemy to reduce the population of a pest.
Natural Enemy
Example
Pathogen
B. thuringiensis is a bacterium that infects butterfly larvae.
Predator
Ladybirds feed on greenfly.
Parasite
Encarsia wasp larvae feed on whitefly.
Thursday, 08 November 2018
G R Davidson

22. Biological Control
The main advantage of biological control is that no chemicals are used which will persist in the environment.
The main disadvantage of biological control is that the organisms introduced may increase in population to the extent that they become a threat to other species.
Thursday, 08 November 2018
G R Davidson

23. Integrated Pest Management
IPM involves a combination of methods to control a pest population.
It involves chemical, cultural and biological control.
This reduces the use of pesticides.
Thursday, 08 November 2018
G R Davidson

24. Integrated Pest Management
The techniques involved in IPM include:
Identifying the pest
Monitoring the pest and any damage it is doing
Controlling factors which make conditions for the pest unsuitable
Combining control methods which should be more effective than one single control method.
Thursday, 08 November 2018
G R Davidson