Pathology L5 Management Flashcards
Epidemiology
The study of epidemics and the factors that affect them (summarized by disease triangle)
Epidemiology disease triangle
Includes conducive environmental conditions, susceptible host, and pathogen source of inoculum
Epidemic
The increase of disease in a plant population or the dynamics of change in plant disease in space and time
Southern leaf corn blight epidemic
June 15-sept 1, 1970
Caused by cochliobolus heterostrophus and spread very quickly
What was added to the disease triangle after the southern leaf corn blight epidemic
Time
Inoculum
Any part of a pathogen that can initiate disease
Examples of an inoculum
Spores, sclerotia, mycelium
Primary inoculum
Inoculum that initiates the disease
Example of primary inoculum
Ascospores
Secondary inoculum
Inoculum produced by infections that take place during same growing season
Examples of secondary inoculum
Conidia
Pycnidiospores
3 types of disease cycles
Monocyclic disease
Polycyclic disease
Polyetic disease
Monocyclic disease
One disease cycle per growing season
Polycyclic disease
Multiple disease cycles in a growing season
Polyetic disease
Epidemic over a period of many growing seasons
When does the sexual stage occur and the inoculum released in monocyclic diseases
Sexual stage occurs in fall or spring
Inoculum is released in spring
Primary inoculum in monocyclic disease
Sexual spores
When does the asexual/secondary inoculum stage occur in Polycyclic disease
During the growing season
What is needed for a disease to occur in a field
Disease must enter field
Field must contain susceptible hosts
Inoculum must be released, transported, or deposited
How can inoculum be dispersed
Rain/irrigation splash
Air currents
Infected seeds/pollen/plant matter
Vectors
What is integrated pest management
The selection, integration, and use of pest management techniques based on economic, aesthetic,sociological, and ecological consequences
IPM components
Scouting
Obtaining information
Exclusion
Cultivar choice
Cultural controls
Chemical controls
Biological controls
Decision support systems
Field scouting
Going through the field to determine what diseases are present and is required to identify the pest and the severity of the infection/infestation
Scouting in the spring
Examine crop residue and look for signa of pathogens
Scouting in the summer
Identify disease and support foliar fungicide application decisions
Scouting pre and post harvest
Investigate cause of diseased plants, and determine effectiveness of disease management program to plan for next season
How many locations should be scouted in a field of 80-100 acres
5+ locations
How many locations should be scouted per quarter section (160 acres)
10+ locations
You _________ scout field margins
Should not
Reasons for randomly distributed symptoms
Biotic and spreading to nearby plants
Abiotic or genetic
Reasons for symptoms most abundant near field edge
Herbicide drift
Diseases moving in from the headlands
Reasons for linear or repetitive symptoms
Agronomic
Abiotic stress
Herbicide damage
What comes after scouting
Identification
Steps in identification
Field history
Past and current agronomic practices
Identifiy
Risk of disease increases with….
Poor seed quality
Rotation is short
Field is adjacent to infected field
Variety is susceptible
Fertility and moisture levels are high
What does a field history include
Environmental stress
Nutrient deficieny/toxicity
Herbicide injury
Insect damage
Genetic off-types
Exclusion
Preventing disease from entering the field through careful sanitation and moving of soil or vegetation
What is the Canadian food inspection agency responsible for
Protecting Canada’s plant life and ag by preventing the import/export/establishment of pests and controlling and eradicating pest present in canada
Cultivar choice
Selecting varieties resistant to diseases in your area
Cultural control
Methods that prevent conditions for disease and other pests from becoming established
Crop rotation
Rotating crops planted in the field to reduce availability of susceptible hosts to pathogens in the field
First reliable chemical control of plant pathogens
Bordeaux mixture (copper sulfate, lime, and water)
How many classes of fungicide
13 modes of action classes
Considerations of foliar fungicides
Causes of disease, time to/between scouting, when and what to apply, varietal differences, fertility impact on disease, yield potential
How are disease surveys interpreted
Prevalence- # of fields with disease
Incidence- # of infected plants
Severity- strength of disease
Distribution - locations of symptomatic plants
