key area 3.4 - crop protection

Question 1

weeds

Answer 1

• unwanted plant in a monoculture which competes with the crop plant for resources
• reduce productivity and yield by competing for resources such as light water and minerals

Question 2

monoculture

Answer 2

• single crop species cultivated over a large area to improve efficiency of farming

Question 3

properties of annual weeds

Answer 3

• they colonise in fields prior to growth of crop
• rapid growth rate
• short life cycle
• produce a large number of seeds which are viable for long periods of time

Question 4

properties of perennial weeds

Answer 4

• they live for more than two years and have adaptations which allow them to outcompete the crop plant
• they possess storage organs which allow growth even when conditions are not ideal
• ability to use vegetative (asexual) reproduction

Question 5

pests

Answer 5

• organism which damages the crop plant and reduces plant productivity
• eg insects, molluscs and nematode worms

Question 6

diseases

Answer 6

• caused by fungi, bacteria or viruses which damage the crop plant and reduce plant productivity
• can spread rapidly by invertebrates carrying the disease but can also be spread through soil and air

Question 7

control by cultural methods

Answer 7

• non chemical methods of preventing problematic organisms from establishing and damaging the crop plants
• eg ploughing, removal of weeds, crop rotation or removal of alternative hosts

Question 8

ploughing

Answer 8

• top layer of soil is turned over p to bury perennial weeds which then die and decompose

Question 9

removal of weeds

Answer 9

• removal of weeds early in the life of the crop, to reduce competition and give the crop plant a head start

Question 10

crop rotation

Answer 10

• growing very different crops in a field in successive years
• this prevents the build up of pathogens which could cause issues if the same crop was grown the year after in the same field

Question 11

removal of alternative hosts

Answer 11

• weeds are removed at the edge of fields as they may provide a habitat for pests or vectors of disease

Question 12

control by chemical means

Answer 12

• when chemicals are used to control pests such as herbicides, fungicides or insecticides (pesticides)

Question 13

selective herbicide

Answer 13

• overstimulates growth until the broad leaved plants exhausts its food reserves and dies

Question 14

systematic herbicide

Answer 14

• absorbed through the weeds vascular system where it is then transported all around the plant to prevent regrown

Question 15

disease forecasts

Answer 15

• predicting when outbreaks of pathogens may occur and applying fungicides during these conditions to prevent an outbreak from occurring
• cost efficient, more effective and better for the environment

Question 16

problems with chemical methods of control

Answer 16

• toxicity to non target species
• persistence in the environment
• bioaccumulation
• biomagnification
• production of resistant pest species

Question 17

toxicity to non target species

Answer 17

• pesticides can be poisonous to not just the pest but a wider range of animals including humans

Question 18

persistence in the environment

Answer 18

• some chemicals do not biodegrade and remain in the environment for long periods of time

Question 19

bioaccumulation

Answer 19

• if an organism absorbs a chemical from the environment at a faster rate than it is lost bioaccumulation occurs
• the build up of a chemical in an organism

Question 20

biomagnification

Answer 20

• increase in concentration o a chemical moving between tropic levels eg primary consumer to secondary consumer and so on

Question 21

production of resistant pest populations

Answer 21

• continued pesticide use exerts a selection pressure on the pest population
• few individuals are already resistant due to a random mutation/variation so have a selective advantage
• resistant individuals are then selected for and survive to breed the next generation
• over generations the resistant individuals increase in number to produce a pest resistant population

Question 22

biological control

Answer 22

• reduction in a pest population by the deliberate introduction of one of its natural predators, parasite or pathogen

Question 23

biological control advantages and disadvantages

Answer 23

advantages :
- avoids use of persistent chemicals so environmentally friendly
- doesn’t exert a selection pressure that produces resistant pests

disadvantages :
- may become a pest itself
- be invasive and reduce biodiversity
- could introduce parasites or pathogens
- may be a parasite to another organism
- may disrupt food chains and webs

Question 24

integrated pest management

Answer 24

• combines cultural methods, chemical methods and biological controls in a combinational approach to manage pest populations whilst reducing the impacts of management strategies on the environment