3.3 - crops, weeds, pesticides

• What are the 2 types of weeds?

  • annual
  • perennial
• what are annual weeds?

  Weeds that complete their life cycle in one year.
• what are perennial weeds?

  weeds with competitive adaptations like storage organs and vegetative reproduction
• what are plant diseases caused by?

  fungi, bacteria, viruses
• what are 3 cultural controls of weeds, pests and diseases?

  • ploughing
  • weeding
  • crop rotation
• how does ploughing control weeds?

  damages or buries perennial weeds
• what is a disadvantage of weeding?

  time consuming if done by hand
• How does crop rotation control weeds?

  specific pests die out between plantings of same crop
• what is a pesticide ?

  a chemical used to kill various pests, such as herbicides
• what are the 2 types of pesticide?

  • selective
  • systemic
• what are selective pesticides?

  have a greater effect on certain plant species like broad leaved weeds
• what are systemic pesticides?

  spreads through vascular system of plant to prevent regrowth
• why can pesticides be problematic?

  • toxicity to non-target species
  • persistence in the environment
  • bioaccumulation or biomagnification in food chains
  • producing resistant populations of pests
• what is bioaccumulation?

  a build up of a chemical in an organism
• what is biomagnification?

  increase in the concentration of a chemical moving between trophic levels
• what is biological control?

  the use of a control agent to control the population of a pest, like a natural predator, parasite or pathogen of the pest
• what are issues with biological control?

  the control organism may become an invasive species, parasitise, prey on or be a pathogen of other species
• what is integrated pest management?

  a combination of chemical, biological and cultural control
• Why are weeds regarded as pests when they grow amongst crop plants?

  weeds will compete with crop plants, reducing productivity of crop plant