Monday, February 13, 2012

5.4a Pesticides

Understand the reasons for pest control and the advantages and disadvantages of using pesticides and biological control with crop plants

1. Pests = organisms that reduce the yield of crop plants by causing economic damage to the farmer.

2. Pests = any type of organism - plants, animals, bacteria, viruses, fungi, protoctists.

3. Pests can be controlled by chemicals called pesticides 

a) Pesticides can be used to kill them or their numbers can be reduced by biological control. 
  • Chemicals = easy to obtain 
  • Easy to apply/spray on field
  • Very effective 
  •  Toxic to other plants/animals/humans 
  • Bio accumulation - pesticide builds up through the food chain causing problems to animals in the higher trohpic levels eg:DDT
  • Mutation in pest --> resistance --> Pesticides is applied in higher concentrations = more toxic

4. Monoculture:

 Involves giving over large areas of land to a single crop eg: Maize.

harvesting these vast areas of crops  in a short period time means using huge machinery and this also means that pests can spread very easily. 

If the crop becomes infested there are millions of crop plants in which the pest can spread. 

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