Main Concepts Today

• Importance of disease management

• Disease management vs. disease control

• Disease management concepts

  • exclusion

  • avoidance

  • eradication

  • protection

S. N. Jeffers, 2010

Disease Development:

Plant Disease Triangle

Susceptible Virulent

Host Pathogen

Disease

(over time)

Conducive

Environment

Management vs. Control

• Disease control – the “old school” approach…

  • implies total elimination of the problem

  • usually not possible or necessary

  • often not practical – too costly or other consequences

• Disease management – a more progressive approach

  • implies an on ongoing process to keep disease levels manageable and below economic thresholds

  • economic threshold = the level of disease at which treatment will provide an economic return • meaning: it’s cost effective to manage the disease

• Therefore, management is the better approach

Know Your Problem!

• First step to effective disease management is accurate diagnosis of the problem!

•Why??

• symptoms of some diseases are not diagnostic

• i.e., different diseases have similar symptoms

  • management strategies for different diseases can vary dramatically

• root rots are a good example!

Integrated Disease Management

• An integrated approach is the most effective strategy for long-term, sustained disease management

• Integrated disease management (IDM)

• or IDM = “intelligent” disease management

• taking advantage of all possible management options

• requires a basic understanding of pathogen biology and disease epidemiology

  • pathogen survival & reproduction – monocyclic vs. polycyclic

  • environmental effects on disease

  • host susceptibility and resistance, planting date, etc.

Management Concepts vs. Options

• Management concepts = the big picture

• exclusion – targets the pathogen

• avoidance – targets the environment

• eradication – targets the pathogen

• protection – targets the host

• Management options = specific control practices used to achieve effective disease management

• legal and regulatory actions

• cultural practices

• pesticides

• biological controls

• host resistance

Exclusion

• Targets the pathogen component of D

• Goal: Exclude the pathogen

  • prevent introduction of a pathogen to a field, farm, nursery, state, country, continent

• Regulatory and legal restriction on movement of plants and soil

  • quarantines, inspections, certifications

• Use of pathogen-free seeds, propagation material, and plants

  • introduced pathogens have resulted in some of the most devastating diseases on a worldwide basis— throughout history!

Quarantines and Inspections:

Federal Agencies

• APHIS: Animal and Plant Health

Inspection Service

• specific charge: “Protecting American

Agriculture”

• responsible for federal quarantines • PPQ: Plant Protection and

Quarantine – branch of APHIS

• mission: “APHIS-PPQ safeguards agriculture and natural resources from the risks associated with the entry, establishment, or spread of animal and plant pests and noxious weeds.”

  • conducts inspections & certifications

Quarantines and Inspections:

State Agencies

• SC Department of Plant Industry

  • “…to protect South Carolina's agricultural resources and natural ecosystems from the introduction and spread of plant and honeybee pests and invasive species…”

  • conducts local inspections

• Cooperative Agricultural Pest

Survey (CAPS)

• another branch of APHIS that surveys for exotic pests

• functions at the state level

• Plum pox virus, Phytophthora ramorum, citrus greening

Insect-proof screens on greenhouse openings to exclude arthropod vectors of viruses

Avoidance

• Targets the environment component

• Goal: Avoid exposure to inoculum and favorable environmental conditions

• Avoiding inoculum

  • don’t plant where a known pathogen is present!!

• can be on a local, national, international level • gardens, fields, regions, etc.

  • grow ornamental plants in soilless media in pots to avoid soilborne pathogens

• like species of Fusarium, Pythium, Phytophthora, Rhizoctonia

Avoidance

• Targets the environment component

• Goal: Avoid exposure to inoculum and favorable environmental conditions

• Avoiding a conducive environment

▪ choice of or preparing a planting site

• plant in well-drained soil to avoid damping-off & root pathogens

• grow seed crops in arid climates to avoid seed-borne pathogens

• time of planting

• plant when conditions are less conducive for infection and more favorable for plant growth

• avoid cool, damp soil – which can slow plant growth & favor the pathogen

• know the time of the last frost in your area ▪ to avoid predisposing abiotic injuries & stresses

Phytophthora root rot on plants that stayed too wet at the low end of a sloped bed where water accumulates

Eradication

• Targets the pathogen component of D

• Goal: Eradicate or eliminate pathogen inoculum

  • this targets survival structures and primary inoculum

• Cultural practices

  • crop rotation/fallow/flooding: reduce pathogen survival

  • eliminate alternate or alternative hosts

  • sanitation of tools and equipment

  • heating: composting, solarization, burning, steam

• Chemicals: pesticides, fumigants, disinfestants

• Biologicals: introduce or promote beneficial microbes

  • green manures, organic amendments

Protection

• Targets the host component of D

• Goal: Protect the host from infection

  • so identify periods when plants are most susceptible

• Cultural practices: to favor plant/inhibit pathogen

  • mulches: organic, plastic – prevents splashing

  • manipulate plant nutrition and soil pH

  • water management: soil drainage, leaf wetness

• through irrigation, plant spacing, row orientation

• Chemicals: fungicides, antibiotics, nematicides, insecticides

• Biologicals: antagonists and competition

• Host manipulation: can be a very effective first-line of defense – like resistance, tolerance, cross protection

Logical Order to Implementing

Disease Management Concepts

1. Exclusion

• keep pathogens out if at all possible

2. Avoidance

• if you cannot keep pathogens out, then avoid exposure to inoculum or environmental conditions conducive to disease development

3. Eradication

• if pathogens are present, try to eradicate survival propagules and sources of primary inoculum

4. Protection

• if all else fails, protect the plant from infection…

Wrapping Things Up…

• More oral presentations today in lab…

  • presentations on Tuesday went well

• PDP Papers: Due today – by 11:59 pm

  • submit through Canvas & Turnitin

• Review session: Friday 08 Dec @ 9:00 AM

  • here in this room and via Zoom

• Online Course Evaluation – please do this…

▪ ***bonus points as incentive

• Final exam: Friday 15 Dec @ 8:00 – 10:30 AM

  • 175 points = 100 points on new information

+ 75 points on cumulative information

• similar format to other exams

• Contact me or Linus if you have questions