3.3 crop protection Flashcards
pesticides
used to kill unwanted pests on crops
biological control
uses natural predators to kill pests
monoculture
growing one single crop over a wide area
why are weeds an issue
causes a significant reduction in productivity of the crop due to competition
they release chemical inhibitors into the soil which further reduces crop growth
act as hosts for crop pests and disease
annual weeds (once a year)
grow very quickly
short life cycle
produce lots of seeds
seeds remain dormant but viable for a long period of time
perennial weeds (year after year)
already established in the habitat
have storage organs from previous years that provide food in unfavourable conditions
reproduce vegetively
examples of plant pests
nematode worm
molluscs
insects
disease
how can insects affect plants
act as vectors of disease
how s yield decreased by pests
damages leaves which reduces photosynthesis which in turn reduces the energy available to the plant for growth
cultural means of crop potection
crop rotation
ploughing
weeding
time of sowing
removal of alternative hosts (weeds)
specific pests die out between plantings of same crop
crop rotation
perennial weeds damaged or buried
ploughing
early hoeing removes annual weeds before they can affect growth of young weeds
weeding
systemic herbicides
absorbed into vascular system to kill weed
slower to act than contact but more effective
it reaches underground storage organs and root stopping regrowth
stimulates rates of growth in broad leaf plants and exhaust supply until it dies
systemic herbicides
destroys all green plant issue in which they come into contact with
short lived
no effects on root so the weed regrows
contact herbicides
contact pesticide
kills the insect when it comes into contact with it and leaves the plant with a protective poisonous layer and kills any pests that come into contact with it
systemic pesticide
absorbed by the plant and transported to all its parts
sap sucking insects ingest it and die
sprayed before fungal attack
can be washed away by rain
newly emerging leaves are unprotected
the fungal spores absorb the poison and die when they land
contact fungicide
absorbed by the plant and transported throughout
gives better protection against fungal attack
systemic fungicide
how is weather data used as crop protection
can forecast infection and warn farmers so can use fungicides in advance
saves money by only using when necessary
problems with chemical pesticides
some pesticides have toxic effects on humans and other animals
persist in the environment
accumulate and magnify in food chains
what is bioaccumulation
an increase in the concentration of a chemical in a biological organism over time,
disadvantage of biological control
can become an invasive species
prey on or become a pathogen of another species
use of more than one method of control
integrated pest management.
