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Causes and Effects of Disease in Agricultural Production - Coggle Diagram
Causes and Effects of Disease in Agricultural Production
Importance of Agriculture in Australia
highly sought from other countries
as agriculture is relatively free from infectious diseases
due to Australia's isolation
Australia's Top 10 Agricultural Exports
Causes
of Infectious Diseases in Australian Agriculture
Two types of plant and animal diseases are of concern in Australia
endemic diseases
diseases consistently present within a country or region
exotic diseases
introduced disease
factors contributing to the development of infectious diseases
host factors
susceptibility to disease
access to pathogen
concurrent disease or poor nutrition leading to weakened immune response
drought and heatwave stress on the host
pathogen factors
the pathogen’s availability
its ability to transfer between hosts
virulence factors - adhesion and invasion of host tissues
and successful establishment inside host tissues
environmental factors
overcrowding and lack of hygiene
leads to a build-up of waste
provides a sustainable environment for pathogen reservoir
causes disease
factors contributing to the risk of infectious diseases
increased mobility of human population
travellers/imported livestock and carry infectious diseases into Australia
cellular and non-cellular pathogens can form a reservoir in food, soil and seeds
through shoes and
in infected animals and animal products that are moved from one area to another via humans.
Rise of intensive and industrial-type agriculture
caused a change to intensive feedlots
Feedlots carry a higher risk of disease outbreak
due to the higher stocking densities of animals
the closer animals are, the more
rapidly a pathogen can spread from animal to animal or plant to plant.
due to increase in world population
Changing patterns of land use
Deforestation and irrigation practices may change the distribution of insects
Loss of habitat can bring animal into closer proximity to humans and other animals
may spread infectious diseases
Climate Change
Distribution and abundance of insect vectors may change
Changes in rainfall patterns may favour the formation of reservoirs of pathogens
Changes in ecosystems can change availability of nutrients to plants and animals
can reduce animals
immune responses to pathogens.
Antimicrobial resistance
Antimicrobials are used to treat infections in livestock
'off-label' use or overuse hastens the development
of antimicrobial resistance
due to rapid natural selection of resistant bacteria
'off-label' use = used in a way
that has not been officially approved
Antibiotic-resistant bacteria may be transferred between animal bacteria and human pathogens
through direct contact with animals
consumption of their meat or transfer of genes
Pesticide resistance
overuse has led to the emergence of resistant forms of
parasites and weeds
makes it harder to manage infectious diseases on farms.
Loss of genetic diversity
necessary for a population to evolve in response to a disease threat
practices such as inbreeding and monoculture decrease genetic diversity
due to the desire to reproduce organisms with favourable traits
Plant Diseases
Causes
Fungi
Reservoirs of fungal spores exist in contaminated seeds, farm machinery, soil, and weeds
are generally transmitted by wind, water and contact with the reservoirs through normal farming operations
enter plants through their stomata or any other opening
openings caused by mechanical damage to the plant, such as pruning and insect bites
damage the plant by destroying conducting tissues and
absorbing its nutrients
Insects and mites
caused direct damage to plants
are vectors for other pathogens
can inhibit growth, especially in young plants
Bacteria
Reservoirs of pathogenic bacteria may occur in soil, weeds, seeds, hands and equipment
only
multiplies and spreads when certain conditions are met
Conditions
humid
poor air circulation
overcrowding of plants, inappropriate soil conditions
warm weather
Nematodes
Thousands of nematode species live in soil but only a few act as plant
pathogens
Virus
Plant viruses are obligate intracellular parasites
are stable in the environment
and can persist in plant material left over after cropping
can also
form a reservoir on contaminated equipment
Phytoplasmas
are related to bacteria but do not have a cell wall
They are
transmitted from plant to plant by insect vectors
inhabit phloem tissue
Case Study: Panama disease of bananas
About
When a fungus blocks the plant's vascular system preventing movement of water and nutrients
Cause
fungus
Fusarium oxysporum
Panama
Tropical Race 4
spread through root-to-root contact and contaminated soil from machinery and shoes
disease is
Abiotic factors
temperature variation
light availability
chemical agents (natural and synthetic)
water quantity and quality
nutrient availability in soils.
Effect
causes yellowing and wilting of leaves and
splitting of stems
conducting tissues are damaged
so the plant is starved of water and food
Farming operations are ceased and the affected property was sold
to the Australian Banana Growers Council
as the fungus
contaminates the soil permanentlyand remains a biosecurity risk
No other plants can be grown
commercially on this property for this reason
Strict quarantine rules enforced to prevent the spread
stabilising ground cover was established to prevent soil runoff into neighbouring
properties and waterways
Animal Example
Case Study: Footrot in Sheep
About
infectious diseases of the hooves of sheep, goats and cattle
Causes
pathogenic bacterium
Dichelobacter nodosus
will only survive in soil outside the host for a maximum of
4 days
Pastures that are long, dense and wet aid in pathogen survival and transfer
Temperature is
important: warm weather favours growth of the bacteria
. Overgrown hooves
dermatitis between the toes must already be present for bacteria to
invade and establish an infection
Effects
painful abscesses between the toes
lameness
weightloss
