3. crop production

Question 1

Explain why weeds are of economic concern and reduce food security

Answer 1

weeds compete with crop plants, while other pests and diseases damage crop plants, all of which reduce productivity

Question 2

what are the properties of annual weeds

Answer 2

rapid growth, short life cycle, high seed output and long-term seed viability.

Question 3

what are the properties of perennial weeds with competitive adaptations

Answer 3

storage organs and vegetative reproduction (produce identical offspring without sexual reproduction)

Question 4

what are the properties of an effective annual weed

Answer 4

a plant that grows from seed, sets seed then dies within the year

Question 5

what are the properties of an effective perennial weed

Answer 5

a plant that survives for more than one year

Question 6

describe pests found on plants

Answer 6

most of the pests of crop plants are invertebrate animals such as insects, nematode worms and molluscs

Damage caused to leaves can reduce the rate of photosynthesis and therefore reduce crop productivity.

Question 7

describe plant diseases

Answer 7

can be caused by fungi, bacteria or viruses, which are often carried by invertebrates

Question 8

describe cultural control and name the 4 cultural control methods

Answer 8

includes practices which try to prevent any weeds, pests or diseases from getting established in the crop. (eg. ploughing, weeding, crop rotation and removal of crop residue)

Question 9

describe crop rotation reason for effectiveness

Answer 9

Prevents pests’ repeated access to their food source, especially if the pest is soil-based

Question 10

describe ploughing reason for effectiveness

Answer 10

Buries crop residues that frequently harbour pests and diseases

Question 11

describe weeding reason for effectiveness

Answer 11

Removes a competitor of the crop plant

Question 12

describe removal of crop residue reason for effectiveness

Answer 12

Removes material that might harbour pest insects from outside the crop area

Question 13

name 5 pesticides

Answer 13

-herbicides to kill weeds
-fungicides to control fungal diseases
-insecticides to kill insect pests,
-molluscicides to kill mollusc pests
-nematicides to kill nematode pests.

Question 14

what is a selective herbicide

Answer 14

designed to kill specific plants

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

Question 15

describe systemic herbicides

Answer 15

Systemic herbicide spreads through the vascular system of the plant and prevents regrowth

Question 16

describe systemic insecticides

Answer 16

Systemic insecticides, molluscicides and nematicides spread through the vascular system of plants and kill pests feeding on plants

Question 17

Why do you think that protective applications of fungicide, based on disease forecasts, often more effective than treating a diseased crop?

Answer 17

A disease forecast using up-to-date local weather information can forecast the probability of increased risk of fungal growth. This means you can spray fungicides in advance of the fungicide growing and damaging your crop. (this maintains crop protection and food security)

Question 18

what are some problems with using pesticides

Answer 18

toxicity to non-target species,

persistence in the environment (non-biodegradable—do not break down or be excreted)

bioaccumulation (a build-up of a chemical in an organism)

biomagnification ( an increase in the concentration of a chemical moving between trophic levels) in food chains

producing resistant populations of pests.

Question 19

describe biological control

Answer 19

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

Question 20

describe integrated pest control management

Answer 20

a combination of chemical, biological and cultural control.

Question 21

what are some risks with biological control

Answer 21

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