PEST PROBLEM - in natural systems organisms have parasites

Transcription

PEST PROBLEM - in natural systems organisms have parasites
TOPIC 6: PESTS AND PEST CONTROL
WHAT IS A PEST?
- any organism that causes plants to die or
produce less. Pests also affect our ability to
produce food and fibre.
EXAMPLES OF PESTS
- insects, weeds, fungus, animals and birds
could be considered pests
PEST PROBLEM
- in natural systems organisms have parasites,
predators or competing plants to keep their numbers
down.
- Insects and diseases consume over 50% of Canada’s
annual harvest.
- Commons pests
♣ Weeds – steal moisture, nutrients, space or light
♣ Insects – eat part of the plant
♣
Fungi and Bacteria – cause infections or
destroy parts or all of the plant.
INTRODUCED SPECIES
- pests introduced from other countries have few or no
natural controls
SOME EXAMPLES OF INTRODUCTED SPECIES
- dandelions
purple loosestrife
European Bark-boring Beetle
CONTROLLING PESTS
How did we control pests in the past?
1. - large pests were chased away or smaller ones picked
off the plant
2. - practice crop rotation, grow different crops in fields
each year
3. - zero tillage cultivators cut weeds off near the soil
surface to disturb soil as little as possible
4. - biological controls using a pest natural enemies to
control it.
What is used to control pests now?
- chemicals are used to control pests
What is wrong with chemical control of
pests?
- chemicals can accumulate in the food chain and move
from one level to the next
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What is BIOACCUMALATION?
- chemicals move from one level to the next level and get
stored in organisms in the same way food energy get
stored
What is soil residue?
- chemicals wash off plants and collect in
soil, water and ice
How can soil residue be a problem?
- found thousands of kilometers away from the source.
If pesticides are toxic to more than one pest
that is a problem. Why is this a concern?
- can kill good insects like bees
What happens as pesticide use
increases? Why is this a problem?
- as a pesticide is used more often, the insects
begin to withstand the effects
- this is called resistance
ORGANIC FOOD PRODUCTION
What is an organic food?
- food grown without the use of chemicals
Five things farmers can do to reduce the use of pesticides
1.
2.
3.
4.
sowing good quality seeds
removing weeds before they mature
cutting weeds along property edges
cleaning equipment so it does not transfer weeds from
one field to another
5. increase diversity or variety of crops grown
Explain how farmers can use biological
control to control pests?
- using the pest's natural enemies to control it
ladybug
predatory wasp

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