higher biology - unit 3.3: crop protection

weed

any kind of plant that grows where it is not wanted

what do weeds compete with crops for?

light, water, carbon dioxide, soil nutrients

properties of annual weeds

rapid growth, short life cycle, high seed output, seeds viable for long periods of time

properties of perennial weeds

vegetative reproduction, storage organs to provide food in poor conditions

weeds compete with crop plants while pests and diseases...

damage crop plants

pest

damage all the plants reducing productivity

examples of pests

insects, nematodes, molluscs

when pests destroy the leaves this reduces...

the plants ability to carry out photosynthesis and therefore ability to produce sugar. Reduction in vigour and yield

plant diseases can be caused by...

fungi, bacteria or viruses which are often carried by invertebrates

control of weeds, pests and diseases by cultural methods

ploughing, weeding and crop rotation

control of weeds, pests and diseases by chemical methods

pesticides, fungicides, insecticides, molluscicides, nematicides

herbicides

kills weeds

fungicides

control fungal diseases

insecticides

kill insect pests

molluscides

kill mollusc pests

nematicides

kill nematode pests

selective herbicides

have a greater effect on certain plant species (broad leaves weeds)

systemic herbicides

spreads through vascular system of plant and prevents regrowth

problems with pesticides

toxicity to non-target species, bioaccumulation, biomagnification

bioaccumulation

an increased concentration of a chemical within an organism over time

biomagnification

accumulation of pollutants at successive levels of the food chain

biological control

control agent is a natural predator, parasite or pathogen of the pest

integrated pest management

the use of both biological and chemical methods to control pests safely and economically

risks with biological control

the control organism may become an invasive species, parasitise, prey on or be a pathogen of other species