Disease Cycles Flashcards
Disease triangle sides
Environment, virulence and abundance, susceptibility of host, human practices
Environment
Moisture- favours innoculum, what effect on host?
Nutrients- poor are more susceptible, high n is more susceptible
Temperature- may inhibit host not pathogen, vice versa, temp reduces horizontal resistance and abolishes vertical resistance
Susceptibility of host
Nutrition, age of plant, abundance of innoculum near host, mode of propagation
Virulence and abundance
Virulence- how well pathogen effects host
Affected by time of planting and dispersal
Monoculture puts selective pressure on parasite
Genetically identical are more susceptible
Human practices
Agricultural practices, propagation tools, introduction of new pathogens, disease control
Monocyclic
Vascular wilt, root rot
Polycyclic
Potato blight, aphid viruses
Polycyclic bimodal
Trees, in blossoms and again in ripening fruit
Rm
Monocyclic, only 1 round of innoculum on crop, usually smaller than r
R
Many rounds of innoculum on same crop
Measure plant disease
Severity, incidence, yield loss, economic threshold
Economic threshold
The cost of control is less than the the cost of crop returns
Yield loss
The proportion of harvestable crop lost
Disease control
Biological, chemical, physical, regulations, agricultural practices
