Crop Protection

Question 1

What is an annual weed?

Answer 1

Annual weed plants grow, flower, set seed and die all within the space of one year

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 perennial weed plants?

Answer 3

Perennial weed plants live for more than two years.

Question 4

Why are perennial weeds able to compete with crops?

Answer 4

they are already well established in the area the crop is being planted

Question 5

What are properties of perennial weeds?

Answer 5

Perennial weeds have storage organs which provide food when rates of photosynthesis are low. Some perennial weeds are also capable of vegetative reproduction; this means they have reproductive structures such as bulbs and tubers which new plants can grow from.

Question 6

Example of pest of crop plants

Answer 6

invertebrate animals such as insects, nematode worms, and molluscs

Question 7

How can insects damage crops?

Answer 7

Insects cause damage to plant crops by feeding on them. Damage caused to leaves can reduce the rate of photosynthesis and therefore reduce crop yield.

Question 8

What causes plant diseases?

Answer 8

Plant diseases can be caused by fungi, bacteria or viruses.

Question 9

What can act as a vector to spread disease?

Answer 9

Invertebrates

Question 10

Define cultural means

Answer 10

This form of control does not require chemicals but involves farmers adopting practices which make the environment unfavourable for the pest

Question 11

Explain crop rotation

Answer 11

growing a different crop in the same area each successive year, this denies pests repeated access to their food source.

Question 12

Explain ploughing

Answer 12

this buries crop residues that frequently harbour pests and diseases

Question 13

How does systemic pesticides work?

Answer 13

spread through the vascular system of plants. When a pest feeds on the plant they ingest the chemical and die. Systemic pesticides can be incorporated into the soil of crop plants. The chemical is absorbed by roots and translocated to leaves, stems, and flowers. An insect that feeds on a treated plant may acquire a lethal dose of insecticide or at least be deterred from further feeding.

Question 14

How does herbicide work?

Answer 14

Herbicides are chemicals used to kill weeds. Herbicides can be applied to control the growth of weeds which would otherwise grow amongst a crop, competing with it for water, nutrients and sunlight and reducing its yield.

Question 15

How does selective herbicide works?

Answer 15

Many selective herbicides contain synthetic plant hormones which encourage the growth of plants which absorb them. This causes their growth to speed up; they use up their food stores and die

Question 16

Why do selective herbicides only kill weeds and not crop plants

Answer 16

Weeds often have broad leaves and take up large quantities of the chemical. Crop plants such as cereals have narrow leaves therefore they do not take up as much of the chemical and are largely unaffected

Question 17

Why do selective herbicides not damage the environment?

Answer 17

Selective herbicides mimic natural plant hormones and therefore do not cause harm to the environment.

Question 18

When is it best to use a systemic herbicide and why?

Answer 18

Systemic herbicides kill all plant matter they come into contact with. They can be used to prepare a field before planting to clear it of all weeds

Question 19

How does systemic herbicide work?

Answer 19

When systemic herbicides are sprayed on plants, they are absorbed and transported throughout the plant. This kills all parts of the plant including any reproductive structures under the soil. Systemic herbicides are biodegradable therefore they do not persist in the environment.

Question 20

What are fungicides and why are they used?

Answer 20

Fungicides are used to kill fungi which can cause disease in plants.

Question 21

How do systemic fungicides work?

Answer 21

Systemic fungicides are absorbed by crops and transported to all parts of the plant giving them protection from disease-causing fungi.

Question 22

How does watching environmental conditions and disease forecast protect crops from fungicides.

Answer 22

Different fungal diseases require different environmental conditions. By monitoring these conditions, farmers can give their crops protective applications of fungicide to prevent growth of the fungus. Protective applications of fungicide based on disease forecasts are often more effective than treating a diseased crop.

Question 23

What does it mean if a pesticide is persistent in the enviroment

Answer 23

it is not biodegradable and remain in the environment for long periods of time after their application

Question 24

What is bioaccumilation?

Answer 24

build up of a chemical in an organism

Question 25

What is biomagnification?

Answer 25

increase in concentration of a chemical moving between trophic levels

Question 26

Explain biological control

Answer 26

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

Question 27

What are advantages of biological control

Answer 27

Advantages of biological control include its specificity, the predator/parasite only kills the pest. The predators will breed in the environment, so they do not need to be constantly reapplied and they do not cause harm to other organisms or accumulate in food chains. The predator/parasite is unlikely to harm humans and pests cannot become resistant.

Question 28

What are disadvantages of biological control

Answer 28

The predator/parasite does not kill all the pests; they work by controlling pest numbers, and keeping them at manageable levels. Also, the predator itself may become a problem in the environment

Question 29

Advantages of chemical controls?

Answer 29

Advantages of chemical control are that the chemicals can kill all the pests and they are easy to use

Question 30

Disadvantages of chemical control?

Answer 30

Disadvantages include the fact that the chemicals are expensive and non-specific so they may kill other organisms as well as pests. Many pesticides are persistent and remain in the environment or the bodies of organisms for a long time. Pests may become resistant to them as a result of mutation, so they are no longer effective.