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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
Agriculture- form of primary industry that involves the cultivation of crops and pastures, rearing of animals to provide meat, milk, fibres and other products for humans
Australia is isolated from the rest of the world
agriculture is relatively free of infectious diseases that affect animals and plants
makes products highly sought after around the world
strict biosecurity measures are in place
reduce likelihood of disease transmission from pathogens
Infectious diseases in Australian agriculture
Endemic diseases
Examples include bovine Johne's disease in cattle, sheep and goats, anthrax in sheep and cattle and footrot in sheep
Exotic (introduced) diseases
Examples include foot and mouth disease, avian influenza, bovine tuberculosis, equine influenza
Factors that contribute to the development of infectious diseases
Host factors
Susceptibility to disease, access to pathogen, poor nutrition (weakened immune response), drought and heatwaves
Pathogen factors
availability, ability to transfer between hosts, adhesion and invasion of host tissues- successful establishment inside tissues
Environmental factors
Overcrowding and lack of hygiene- build up of wastes which provides a suitable environment for pathogen reservoirs
Factors that contribute to the risk of infectious disease
Increased mobility of human populations
Rise of intensive and industrial-type agriculture
Changing patterns of land use
Climate change
Antimicrobial resistance
Pesticide resistance
Loss of genetic diversity
Increase in use of aquaculture
Case study: Footrot in sheep
Infectious disease of the hooves of sheep, goats and cattle
Caused by the pathogenic bacterium Dichelobacter nodosus
Causes painful abscesses between toes, lameness and weight loss
Pathogen factors
Dichelobacter nodosus must be present for footrot to occur
Environmental factors
Bacterium 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
Temp is important: warm weather favours growth of bacteria
Host factors
Dry feet with intact tissues are not infected
Reservoirs of bacteria may form in individual animals' feet for years
Some dermatitis between toes must already be present for bacteria to invade and establish
Overgrown hooves provide a suitable environment
Plant diseases of agricultural significance
Plants grown in Australia
grains
fruits and vegetables
fodder
fibre
horticultural plants
forestry plants
Australia is relatively free of most damaging plant pest species
Causes of infectious diseases in plants
Fungi
most common cause of plant disease
rust, smut, blight and mildew are used to describe fungal diseases
reservoirs of fungal spores exist in contaminated seeds, farm machinery, soil and nearby weeds
transmitted by wind, water and contact with the reservoirs
enter plans through stomata or any other opening caused by mechanical damage
destroy conducting tissues and absorb nutrients
Insects and mites
can act as vectors for other pathogens
Examples aphids, fruit fly, citrus, leaf miner and mealybugs
Bacteria
reservoirs may occur in soil, weeds and seeds
humans can harbour bacteria on their hands and equipment from work with contaminated crop of plants
can only multiply and spread when certain conditions are met
humid, warm weather, overcrowding of plants, inappropriate soil conditions (pH, salinity) and poor air circulation
Examples, black rot of brassicas, bacterial blight of peas
Nematodes
thousands live in soil but only a few act as plant pathogens
Example is the root knot nematode- effects tomato growers
attacks plant roots, creating galls and lumps causing the plant to wilt, turn yellow and die
Viruses
obligate, intracellular parasites
examples, tobacco mosaic virus, tomato mosaic virus
stable in the environment and can persist in plant material left over after cropping
can form a reservoir on contaminated equipment
frequent handling of plants by humans- transmission
Phytoplasmas
related to bacteria but do not have a cell wall
transmitted from plant to plant by insect vectors and inhabit phloem tissue
reported in plants such as tomatoes, strawberries, grapes and pumpkins
Effects of infectious diseases in plants
biological effects on the individual plant
social and economic effects on the farmer
social and economic effects on Australia's economy
Abiotic factors that cause disease
temp variation
light availability
chemical agents
water quantity and quality
nutrient availability in soils
Case study: Panama disease of bananas
most banana plantations are in North Qld
in 2015, pathogen that causes panama disease of bananas was detected in North Qld
Panama Tropical Race 4 disease is causes by the highly contagious fungus Fusarium oxysporum
causes yellowing and wilting of leaves and splitting of stems
conducting tissues are damaged- the plant is starved of water and food
disease is spread through root-to-root contact and contaminated soil from machinery and shoes
fungus contaminates soil permanently
biosecurity risk