Large fields of crops of the same type are called Monoculture.
Monocultures tend to be really susceptible to pests which uses the crops as their own food source.
This reduces the productivity of the farm which reduces the amount of crop yield making a financial impact on the farmer as less is produced.
To overcome this, one of the solutions is to use pesticides - chemicals used to kill the pests
- Chemicals are easy to obtain
- Easy to apply
- Very effective
Disadvantage
- Many of the chemicals are toxic which can damage other plants and animals, other than the pests and may be harmful to humans as well.
- Bio accumulation - where the pesticides build up through the food chain causing problems for animals in the higher trophic levels.
- Mutation in the pest often lead to resistance - the pesticide will need to be applied at a higher level, ->the pests have complete resistance to the pesticide and so the farmers have to find an alternative pesticide.
Biological Control:
- A great example of this is Australia where the prickly pear cactus ( of North America) was first introduced into gardens and escaped into the countryside and flourished under the Australian climate system.
- The cactus started to cover a good deal of agricultural land and was necessary to get rid of it
- But there was no natural herbivore of the cactus so an alien specie (non-native specie) was introduced from another country which was a moth (Cactoblastis) which feeds on the cactus.
- This moth was introduced and had no competitors so they started to remove the prickly pear cactus.
- This control of pests by herbivore is called Biological control.
Advantages
- No toxic is involved
- Less image on the human /wildlife
Disadvantages
- Not 100% completely effective
- Often difficult to control - often a danger that the alien specie would start preying on native species causing native specie population to diminish
- Difficult to match a predator to the prey which can effectively remove the pest
- Takes time
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