3.3 Crop Protection

Question 1

What is the productivity of crops affected by?

Answer 1

competition with weeds

Question 2

What is a weed?

Answer 2

A weed is defined as simply a plant growing in the wrong place
A field planted with rows of potatoes may be contaminated with weeds growing both between the rows of potato plants, and between the individual plants themselves

Question 3

TOPTIP

Answer 3

Plant productivity is the rate of new material (biomass) per unit area per unit of time factors limiting the rate of photosynthesis and therefore plant productivity include light intensity, carbon dioxide concentration and temperature.

Question 4

TOPTIP

Answer 4

When two or more members of a community need the same resources which are in short supply competition occurs. Plants compete for light, water, minerals and root space.

Question 5

Crop weeds that grow among crop plants reduce what?

Answer 5

reduce yields by competing for resources needed by crops

Question 6

What two types of plants can weeds be?

Answer 6

annual or perennial plants

Question 7

Adaptations of annual weeds?

Answer 7

sexual reproduction
short life cycle (one year)
rapid growth
high number of seeds produced
dormant seeds remain viable for long periods of time

Question 8

Examples of annual weeds?

Answer 8

goosegrass, knotweed, sheperd’s purse

Question 9

Adaptations of perennial weeds?

Answer 9

asexual production
long lifecycle (two years +)
broken pieces of plant can root and grow into individual plants
storage organs provide food for plant in autumn/winter

Question 10

Examples of perennial weeds?

Answer 10

couch grass, nettles, buttercup

Question 11

Examples of pests?

Answer 11

Insects cause leaf damage such as greenfly, blackfly and leatherjackets
Nematodes are roundworms in soil that attack roots and storage organs
Molluscs like slugs and snails damage leaves

Question 12

Examples of Diseases?

Answer 12

Fungi - yellow rust on leaves of cereal plants; brown rot on stone fruits, peaches and plums
Bacteria affect stems, roots and leaves and cause leaf spot, blight and galls
Virus - yellow mosaic of lettuce leaves caused by lettuce mosaic virus reduces photosynthesis

Question 13

TOP TIP

Answer 13

A vector is any agent such as an animal which carries and transmits a pathogen into another living organism
Some invertebrates are also vectors of fungi bacteria or viruses and so are responsible for transmitting plant diseases

Question 14

TOPTIP

Answer 14

A weed is a plant growing in the wrong place

Question 15

TOPTIP

Answer 15

Weeds within a growing crop can
compete with crop plants for nutrients
contaminate crop at harvest time
release chemicals into the soil which inhibit the growth of the crop plant provide habitats for pest species

Question 16

What are methods that can control crop pests?

Answer 16

prevention
cultural control
chemical control

Question 17

Explain the method prevention?

Answer 17

preventing the introduction of weeds to the soil can be easier than removing established weeds
Good practice includes the removal of weed seeds and vegetative structures from tools and machinery used to prepare the soil, ensuring seeds are certified to be free of weeds and controlling weeds in the surrounding areas

Question 18

Explain cultivation control?

Answer 18

cultivation and good management of soil help to prevent the build up of weeds, pests and diseases.

Question 19

There are 4 methods of cultivation these are?

Answer 19

Ploughing
autumn sowing
weeding
crop rotation

Question 20

Describe Ploughing?

Answer 20

This destroys perennial root systems in the soil and clears the field of any previous crop residue which may harbour some pests and plant diseases

Question 21

Describe autumn sowing?

Answer 21

seeds planted in the autumn allow a crop to become established before a surge of pests and diseases in the spring, improving crop tolerance

Question 22

Describe weeding?

Answer 22

Growing weeds are removed by cultivation between rows of crop plants

Question 23

Describe crop rotation?

Answer 23

Planting different crops in each field each year helps to break the lifecycle of pest species

Question 24

What are herbicides, pesticides and fungicides?

Answer 24

chemicals that are sprayed onto a growing crop

Question 25

What are herbicides?

Answer 25

chemicals that kill weeds and are grouped according to how they attack a weed

contact - non selective kills all green plants on contact e.g. resolva

selective - selective attacks only broad leaved plants, narrow leaved plants such as grass are unaffected e.g. preen

systematic - non selective herbicide absorbed into the transport system of the plant (xylem and phloem) Kills all parts of the plant e.g. roundup

Question 26

What are pesticides and fungicides?

Answer 26

chemicals that kill pests and fungal species on plants

Question 27

Describe pesticides by contact and systematic?

Answer 27

contact - kills pests on contact with spray

systematic - spray absorbed by plant to prevent invasion and growth of fungus

Question 28

Describe fungicides by contact and systematic?

Answer 28

contact - sprayed onto crop to prevent growth of fungus, following consultation with the disease forecast or the region

systematic - spray absorbed by plant to prevent invasion and growth of fungus

Question 29

Disadvantages of chemical crop protection?

Answer 29

Toxic to wild animals
Chemical remains in the soil and surrounding environment following harvest of crop
Chemical enters the food chain and bioaccumulates in the body tissues of animals. The concentration of the chemical increases through the trophic levels of the food chain, with the final predator containing the highest concentration of the chemical in body tissues such as fat -this is called biomagnification

Question 30

TOPTIP

Answer 30

An adaptation is an inherited characteristic that makes an organism well suited to survival in its environment or niche
Organisms which are better adapted to their environment are more likely to survive reproduce and pass on their favourable genes to their offspring
this is survival of the fittest and is the basis of natural selection

Question 31

What are disease forecasts?

Answer 31

plant disease forecasting is used to predict the likliehood of the occurence of a plant disease
Fungal diseases in particular are influenced by climate and weather patterns so collaboration between plant pathologists and meteorologists allows predictions about the risk of disease.
This enables farmers to make decisions about applying a particular fungicide to protect crops applying a particular fungicide to protect crops before they become they become diseased which is more effective than treating a diseased crop

Question 32

What is biological control?

Answer 32

no chemicals are used
pest population is reduced by the deliberate introduction of a natural predator
A greenfly infestation in a glass house can be biologically controlled by introducing ladybirds which eat greenfly
Introduction of a natural parasite or disease may also reduce pest numbers

Question 33

Example 1 Glasshouse Whitefly?

Answer 33

glasshouse whitefly is a common pest in greenhouses and has a large range of host plants including tomatoes, cucumber, peppers, grapes and beans
The flies suck sap from the phloem, which results in reduced plant vigour, stunted growth and leaf fall
They also secrete a sticky fluid called honeydew on the host plants allowing mould to grow on the leaves
Insect populations reproduce rapidly and many pesticide resistant strains have evolved, making biological control more effective
The tiny parasitic wasp encarsia attacks whitefly nymphs

Question 34

Example 2 Red Spider Mites?

Answer 34

Red spider mites pierce leaf cells and suck plat juices, resulting in discolouration of the leaves, stunted growth and death of the plant.
A natural predator of the red spider mite is the predatory mite
Pesticide control would also kill the natural predator of the red spider mite and make the problem worse long term

Question 35

Example 3 Butterfly Caterpillars?

Answer 35

The bacterium bacillus thuringiensis occurs naturally in the soil and on plants producing a protein that is toxic to specific groups of insects including butterfly caterpillars

Question 36

TOPTIP

Answer 36

biological control is a method of reducing numbers of pests using their natural enemies such as predators, parasites or pathogens
A parasite is an organism which lives in or on the body of another organism its host. the parasite benefits and the host is harmed.

Question 37

What are the risks with biological control?

Answer 37

possible risks associated with biological control include harm of non target insects or crop damage by control species - the control agent may itself become a pest.

Question 38

Example Cane toad?

Answer 38

The cane toad was introduced into Australia to control the population growth of cane beetles on which it feeds
However the cane toad itself became a pest as it kills many other small invertebrates
The cane toad has poisonous skin which kills any predator which tries to eat it.

Question 39

What is integrated pest management?

Answer 39

Integrated pest management (IPM) is a process for controlling pests while minimising any risks to other organisms including humans and the environment.
It involves a range of techniques, using pesticides as a last resort.

Question 40

What are the techniques and processes used in IPM?

Answer 40

identification of the pests
monitoring the number of pests and the damage caused
long term pest prevention by controlling environmental factors to create unfavourable conditions for the pest
using a combination of control methods which may be more effective than a single method of control

Question 41

TOPTIP

Answer 41

Many IPM programmes combine cultural chemical and biological control

Question 42

TOPTIP

Answer 42

Integrated pest management IPM uses a combination of chemical and biological techniques to control the population size of a pest
Instead of killing the whole population