crop protection

Cards (20)

  • crop productivity is reduced by
    competition from weeds
    damage from pests and weeds
  • annual weeds
    grow from seed and complete their life cycle in on year
    • rapid growth
    • short life cycle
    • high seed output
    • long term seed viability
  • perennial weed
    persist from year to year
    • competitive advantage through being established prior to crop growth
    • have storage organs
    • vegetative reproduction: using runners and bulbs from which plants can grwo
  • pests
    insects, nematode worms and molluscs
    damage caused to leaves can reduce the rate of photosynthesis and reduce crop yeild
  • diseases
    can be caused by fungus, viruses or bacteria
    invertebrates act as vectors
  • cultural control of weeds, pests and diseases
    does not require chemicals
  • crop rotation
    involves changing the crops which are grown in a field each year, preventing the build up of pests, weeds and diseases
  • ploughing
    turns over the 20cm soil. perennial weeds are cut and buried to a depth at which they die and decompose
  • weeding
    physical removal of weeds from the crop
  • pesticides
    cost effective, maintain consistent yeilds
  • herbicides
    weeds
    • selective - applied to the whole crop. greater effect on certian plant species
    • systemic - spread through the vascular system of the plant. this kills roots underground and prevents regrowth
  • insecticides
    insects - systemic: absorbed by the plant and transported to all of its parts of the plant through the vascular system, pests killed when feed on tissue
  • fungicides
    fugal parasites - systemic: absorbed by the plant and transported to all of its parts through the vascular system, pests killed when feed on tissue
  • molluscides
    mollusc pests - systemic: absorbed and transported to all of its parts through the vascular system. pests are killed when they feed on the tissue
  • nematicides
    nematodes
  • problems with using plant protection chemicals
    toxicity - pesticides are often poisonous to a broader range of non target species
    persistence - some plant protection chemicals are not biodegradable and remain in the environments for long periods of time
    bioaccumulation - the chemicals are taken into an organism and build up
  • problems with using plant protection chemicals
    biomagnification - the concentration of the chemical increases as it moves from one trophic level to another
    resistant populations - a population thats no longer affected by the chemical. due to repeated exposure and resistant individuals survive and pass on resistance to next generations
  • biological control
    a natural predator parasite or pathogen of the species is applied to a crop in order to reduce the population size of the pest
  • problems with biological control
    • harm of non target insects or crop damage
    • organism may become an invasive species, prey for another organism, be a pathogen for another species
  • integrated pest managment
    combines chemical, biological and cultural control