Cultural Practices for Disease Management

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Cultural Practices for Disease Management

• Chris Smart
• Cornell University, NY State Ag Expt Station,
  Geneva NY
• cds14_at_cornell.edu

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Resource Guide

• Free on web
• Order on-line
• IPM guidelines also free on-line

http//www.nysaes.cornell.edu/pp/resourceguide/ind
ex.php
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Plant Diseases

• Causes (Pathogens)
• Bacteria
• Fungi and water molds
• Viruses
• Nematodes

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Bacterial colonies on agar
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Bacterial Blight of Geranium
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Fungi Kill Plants!

• The vast majority of plant pathogens are fungi

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Powdery Mildew of Lilac
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Tomatoes are Susceptible to Many Fungal Diseases
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Viruses are Common in Ornamentals
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Cultural Practices for Disease Control

• Buy resistant varieties!
• Good air circulation
• Keep leaves as dry as possible, diseases LOVE
  moisture
• Sanitation, Sanitation, Sanitation
• The cleaner the better remove sick plants
• Keep leaves and fruit from touching soil
• Use mulches
• Plant on well-drained soil
• Use raised beds
• Crop rotation where possible

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Plant resistant varieties
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Resistant Varieties Sometimes Available

• Read catalog or information on transplants
  closely
• For example many (but not all) tomatoes will say
  VFN resistant. This means the plants are
  resistant to two root infecting fungi
  (Verticillium and Fusarium) as well as nematodes

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Cultural Practices for Disease Control

• Buy resistant varieties!
• Good air circulation
• Keep leaves as dry as possible, diseases LOVE
  moisture

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Spacing and Pruning

• Give plants enough room such that leaves can dry
  rapidly
• If foliage gets too dense, prune some out
• Its also important to prune out disease!

Apple tree with Fire Blight
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Trellising

• Improves air circulation, dries leaves
• Keeps fruit off the ground
• Be certain to clean stakes

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Row Covers??

• Row covers are great
• They can extend the period of leaf wetness
• If you have any disease plants prior to row cover
  application REMOVE

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Cultural Practices for Disease Control

• Buy resistant varieties!
• Good air circulation
• Keep leaves as dry as possible, diseases LOVE
  moisture
• Sanitation, Sanitation, Sanitation
• The cleaner the better remove sick plants
• Keep leaves and fruit from touching soil
• Use mulches

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Sanitation
All activities aimed at eliminating or reducing
the amount of a pathogen present in a plant, a
garden, a field or a storage facility
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Sanitation

• Plowing under or removing diseased plants
• Removing infected leaves
• Prune or rake away overwintering form of pathogen
  (Maple leaves with Tar spot, apple leaves with
  scab)
• Clean pruning shears
• Washing soil from equipment
• Clean stakes and other items between seasons
• Washing hands cigarettes transmit virus!

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Pruning to Remove Disease

• For perennials, the best time is in the fall
• For annuals, prune out disease ASAP

Black Knot on Plum
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Remove Infected Leaves
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Clean Trellising Stakes

• Wash soil and debris from stakes
• Disinfect with household bleach (1 part bleach 9
  parts water)

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Cull Piles Kill
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Sanitation A Case Study

• A disease called Phytophthora blight is moving
  through the state of NY
• The disease is in the soil, and spreads on
  diseased vegetables and by moving soil

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Phytophthora BlightPhytophthora capsici
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Phytophthora BlightPhytophthora capsici
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Life Cycle
Phytophthora capsici
One spore will produce 20-40 zoospores swimmers
Pathogen spreads in water Splashing rain,
irrigation
Infected plants and fruit produce millions of
spores
These asexual spores are called sporangia
Oospores can survive for years in soil, and will
infect roots or fruit when conditions are
favorable
A2
A1
Infected plant dies Pathogen remains in debris
If both mating types present, oospores produced
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Phytophthora Blight on Commercially Available
Pumpkins
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Early Lesions are Difficult to Notice
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Cull Piles Kill
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Removing Diseased Plants
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Control Strategies

• Use tolerant varieties, plant susceptible hosts
  in well-drained fields, and rotate
• Plant on raised beds with plastic mulch (except
  susceptible vine crops)
• Irrigate conservatively
• Remove diseased plants/fruit from field
• Never dump culls into production fields
• Harvest fruit asap from problem fields

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Cultural Practices for Disease Control

• Buy resistant varieties!
• Good air circulation
• Keep leaves as dry as possible, diseases LOVE
  moisture
• Sanitation, Sanitation, Sanitation
• The cleaner the better remove sick plants
• Plant on well-drained soil
• Use raised beds

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Raised Beds
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Avoid Fruit/Veggie Contact With Soil

• Plant on raised beds
• Improves drainage
• Mulches
• Prevent fruit from touching ground
• Prevent splashing
• Trellising
• Improved air circulation, dries leaves

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Cultural Practices for Disease Control

• Buy resistant varieties!
• Good air circulation
• Keep leaves as dry as possible, diseases LOVE
  moisture
• Sanitation, Sanitation, Sanitation
• The cleaner the better remove sick plants
• Keep leaves and fruit from touching soil
• Use mulches
• Plant on well-drained soil
• Use raised beds
• Crop rotation where possible

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Crop Rotation
The amount of a soilborne pathogen can be reduced
by planting crops belonging to species or
families not attacked by the particular pathogen
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Crop Rotation

• Soilborne pathogens
• Effectiveness depends on host range and longevity
  of pathogen
• Phytophthora blight pathogen can stay in soil
  for 10 years, but the amount is greatly reduced
  after 3 years

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Verticillium Wilt

• Over 200 species are host

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Verticillium Wilt
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Microsclerotia

• Overwintering structure

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Will Rotation Work?
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Will Rotation Work?

• Host range is very wide
• Microsclerotia persist for long time
• As a preventative, not a curative

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Early blight on tomato

• Overwinters in debris in soil
• Small host range (tomato, potato)
• Crop rotation works really well

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Seed treatment can also reduce disease

• Some vegetable seeds are hot-water treated to
  kill pathogen
• Kills pathogen on/in the seed
• The temperature and duration of heating varies
  with the type of seed

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Bacteria-infested Seeds Hot Water-Treated
Untreated
Data from Sally Miller, The Ohio State University
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The Bottom Line

• Things will help reduce disease on your plants
• Plant resistant varieties when possible
• Keep the leaves dry
• Sanitation is very important
• Remove sick plants (or leaves or branches) ASAP
• Provide good drainage (raised beds)
• Rotate if possible