Topic 11: Biotic Factors And Their Control

Question 1

Biotic factors that need to be controlled

Answer 1

Pests
Pollinators
Soil biota

Question 2

How do pests reduce agricultural productivity or product quality?

Answer 2

Predators to livestock/crops
Compete for resources-e.g water and nutrients
Pathogens that cause disease
Carry pathogens
Reduce marketability e.g. spoil appearance of fruit

Question 3

Pest groups

Answer 3

Weeds
Insects
Fungi
Bacteria
Molluscs
Nematode worms
Vertebrates

Question 4

What affects can weeds have?

Answer 4

Compete for nutrients/light etc
Harvested with the crop reduces quality
Provides food for other pests

Question 5

An example of a weed that can reduce agricultural productivity

Answer 5

Striga
Seeds germinate when a particular chemical signal is given out by another plant
Striga tendrils reach chemical signal and oxidise the plant root
They attack the plant by tendrils going up the xylem and taking nutrients

Question 6

Endemic pests

Answer 6

Always present once established
Don’t have to be indigenous
Usually in small or moderate numbers

Question 7

epidemic pests

Answer 7

Pests aren’t normally present
But where outbreaks could rapidly become a major problem
E.g. locusts

Question 8

Indigenous pests

Answer 8

Native to the area where they are found

Question 9

introduced pests

Answer 9

From other areas
Can be more dangerous because of the lack of natural protection against them

Question 10

What is cultural pest control?

Answer 10

Non-pesticide methods
Crops and livestock are cultivated in a way that reduces pest damage, using natural ecosystem services

Question 11

Methods of cultural pest control

Answer 11

Crop rotation,companion crops, predators habitats,biological control,sterile male techniques,pheromone traps,genetic resistance to disease,GM crops and pest control

Question 12

Explain predator habitats as a method of cultural pest control

Answer 12

Providing suitable habitats increases populations of natural pest predators e.g. beetle banks or hedgerows

Question 13

Explain pheromone traps se s method of cultural pest control

Answer 13

In many insect species, mates are attracted by scent
Traps release an artificial scent to concentrate them in one place to get rid of them

Question 14

What are the properties to consider when controlling pests with chemical pesticides?

Answer 14

Toxicity, specificity,persistence,solubility in water/lipids,mode of action,antibiotics,hormone pesticides

Question 15

2 modes of action for use of chemical pesticides

Answer 15

Contact action
Systemic action

Question 16

Contact action

Answer 16

Kill plants by damaging the tissues they are sprayed onto
May be washed off by the rain

Question 17

Systemic action

Answer 17

Absorbed by the plant and translocated throughout which protects the plant
They cant be washed off bit they can retain in harvested crop and be eaten

Question 18

What is integrated control?

Answer 18

Has an order in which techniques are used based on cost,ease of use,effectiveness and environmental impacts
It is a combination of techniques that can maximise effectiveness and minimise environmental impacts

Question 19

Principles of integrated control

Answer 19

Use of cultural techniques to make growth environment less suitable for pests
Use of cultural techniques to prevent build up of pest populations
Cultivating species and fire ties less likely to suffer pesticide attack
Use of pesticides if essential
Use of other appropriate non pesticide techniques

Question 20

How can the services provided by pollinators be aided?

Answer 20

Providing food supplies- growing plants that provide nectar
Restricting the use of pesticides that harm pollinators
Introducing bee hives

Question 21

Why is it important to maintain soil biota?

Answer 21

They are important for soil fertility/crop productivity
They increase nutrient availability
Produce organic acids that increase rock weathering
Earthworms increase aeration