Disease cycle (week 1-2)

• Botany
• Mycology
• Bacteriology
• Virology
• Nematology
• Genetics
• Entomology
• Molecular biology
• Biochemistry
• Plant physiology

• Etiology
• -causes
• -biology
• -taxonomy
• Epidemiology
• -disease spread
• -disease cycle
• -forecasting
• Control
• -principles
• -methods

Alteration of the normal physiological and biological development of a plant that results in abnormal morphological and physiological changes

-alteration results in reduced biomass and or reproductive output yield

• Foliar pathogens- reduce amount of photosynthetic tissue
• Root pathogens- interfere with water and mineral uptake
• Vascular pathogens-limit water and mineral movement within a plant
• Structural pathogens-wood decay fungi

• Disease- a process that develops over time
• -non random event
• -infectious
• Injury- event that occurs suddenly
• - random event like weather
• -non infectious

Disease is at the center of the the triangle with environment host and pathogen on each corner

• Temperature
• - soil pH
• -moisture
• -humidity

• Resistance and susceptibility
• - escape ( a single or a few plants in a population does not get infected due to distance between plants)

• Virulence
• Pathogenic specialization

Use Kochs postulates

• 1. Suspected pathogen is consistently associated with diseased plants
• 2. Isolate the suspected pathogen in pure culture. Make notes of its characteristics and identify it.
• 3. Inoculate a healthy host with pure culture of pathogen.
• 4. Look for signs of disease and isolate suspected pathogen see if it is the same as step 2

• Biotic- infectious and transmissible
• Abiotic- non infectious and non transmissible

• Fungi
• Viruses and viroids
• Nematodes
• Bacteria
• Parasitic plants- mistletoe
• Protoctistans- single celled eukaryotes

• Unfavorable weather conditions ( heat or cold damage)
• Water relations ( waterlogging or uneven water supply)
• Unfavorable soil pH
• Nutrient deficiencies
• Air pollutants
• Herbicides

The study of causation or organization

• Pathogen
• Pathogenicity
• Virulent pathogen
• Susceptible host

An organism that derives nutrition from dead organic matter

• Obligate (obligated or has no choice)
• Facultative (has the ability to be if needed)

Derives nutrition from living plant cells. Cannot survive on dead host (powdery mildew).

Derives nutrition from dead or dying cells of a plant.

• Narrow host ranges
• Cannot grow as a saprophytes ( in culture)
• Attack healthy plant at any stage
• Kill host cells slowly
• Penetrate directly or via natural openings

• Generally have wider host ranges
• Can grow in absence of host (saprophytic)
• Attack young weak or senescent tissues
• Kill host cells rapidly -toxins
• Penetrate through wounds or natural openings

A sequence of events involved in disease including appearance development perpetuation and survival of the pathogen.

Events that occur in the disease cycle from infection to final reaction

• Inoculum production
• -primary inoculum
• -secondary inoculum

• Dissemination
• -the spread of inoculum via humans water wind vectors.

• Inoculation
• -appropriate infection court
• - must land on plant area it can infect

• Penetration
• - directly indirect or wounds

• Infection
• -local vs systemic
• -Infection court
• -Incubation period
• -latent period

The tine between infection and the appearance of symptoms

The time between infection and reproduction of the pathogen

• Colonization/growth and reproduction
• - intercellular vs intracelluar
• -biotrophic vs nectrophic

• Formation of survival structures
• -chlamydospores sclerotia

• Survival
• - overwintering or over summering
• -survival in the absence of a host
• -possible alternative hosts

• Primary inoculum only
• -single cycle only or monocyclic diseases
• - simple interest disease

• Primary and secondary inoculum
• -multiple cycle or polycyclic diseases
• -compound interest disease

• It is a eukaryotic heterotrophic organism devoid of chlorophyll that obtains all of its nutrients by absorption and reproduces by spores.
• -primary carbohydrate storage is glycogen
• -most have a thallus composed of hyphae that elongate by polar growth from its tip