Organic Approaches to Disease Control

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Organic Approaches to Disease Control

• George Driever
• Area Pest Management Specialist
• Cooperative Extension Service
• Oklahoma State University

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Plant pathogens

• Fungi
• Bacteria
• Viruses
• Phytoplasms
• Nematodes

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DISEASE TRIANGLE
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Identifying Diseases by Symptoms

• Fungi spots, lesions, blights, yellowing of
  leaves, wilts, cankers, rots, fruiting bodies
• Bacteria water-soaking, spots, wilts, rots,
  blights, cankers, exudates, galls, yellowing
• Viruses mottling, leaf and stem distortions,
  stunting
• Phytoplasms similar to virus symptoms
• Nematodes stunting, dying plants

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Difficulties in Identification

• Plant pathogens are very small
• Similar symptoms between bacteria and fungi and
  between fungal groups
• Field diagnosis is difficult
• Multiple pathogens may be present at the same
  time.
• Multiple symptoms may be present

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Methods of Disease Control

• Cultural
• Chemical
• Biological

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Cultural Disease Control

• Develop soil rich in organic matter
• Plant on raised beds
• Plant tolerant or resistant varieties
• Crop rotation
• Plants adapted to area
• Plant at proper depth (below crown or graft)
• Use only thoroughly composted material

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Cultural Disease Control contd

• Soil pH adjustment
• Improve air circulation by staking, trellis or
  pruning
• Remove weeds carry disease, circulation
• Water in the morning
• Avoid high angle sprinklers
• Do not over fertilize
• Remove diseased plants and destroy

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Exclusion of Disease

• Certified disease free plants
• Prevent introduction of diseased plants or soil
• Disease free water source
• Control insects that can carry disease
• Soil solarization

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Chemical Controls

• Hydrated Lime
• Lime sulfur
• Coppers
• Horticultural Oils
• Essential Oils
• Bicarbonates
• Antibiotics

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Hydrated Lime

• pH adjustment
• Component of Bordeaux mixture

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Lime Sulphur

• Use as a protectant dust or spray to control some
  fungal or bacterial diseases
• Helps control peach leaf curl, rust, powdery
  mildew (PM), brown rot
• Lilly Miller Poly Sul Lime Sulfur Calcium
  Polysulfide 28.7
• Generic and other brands available

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Coppers

• Controls some fungi and Fireblight
• Free Cu - Copper sulfate Bordeaux mixture
• Fixed Cu - copper hydroxide, copper oxide, copper
  oxychloride, copper octanoate
• Kocides restricted use, requires license
• Safer Garden fungicide Cu 12 or 0.4 rust,
  scab, brown spot, black spot, others

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Copper

• Bonide Liquid Cu Cu octanoate 0.08 PM, rust,
  black spot, late blight, others
• Bonide Copper Garden Dust copper sulfate and
  rotenone for fruits, garden, and flowers
• Lilly Miller Cueva Cu soap Cu octanoate 0.08
  PM, DM, gray mold, blight, spots
• Many other brands

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Horticultural oils

• Mostly controls foliar insects, but also peach
  leaf curl, and some other fungi
• Dormant, suffocating, summer oils
• Fungus Pharm soybean oil plus Rosemary oil 0.1

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Essential Oils

• Neem oil up to 70 many brands that control
  insects, mites and some fungi such as PM, rust,
  scab, leaf spots, anthracnose and black spot
• Green Light Organic fungicide Rosemary Oil
  0.2 anthracnose, blights, gray mold, PM, DM,
  leaf spots, scab, rusts, others

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Bicarbonates

• Potassium Bicarbonate disrupts cell membrane K
  balance
• Bi Carb - K bicarbonate PM, others
• Safer 3 in 1 K salts PM Black spot, leaf
  spots, rusts for seed, transplants or established
  plants
• Sodium Bicarbonate ?

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Antibiotics

• Streptomycin sulfate many brands for
  agricultural use to control bacteria, fireblight
• Fertilome Fireblight spray also for bacterial
  wilt, stem rot, leaf spots and crown gall
• Tetracycline - fireblight

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Antagonists/ Competitors

• Trichoderma harzium is the most researched
• Many others are being looked at

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Biological Controls

• Bacillus subtillus
• Seranade Garden Disease Control control and
  suppression
• Streptomyces griseoviridis Pythium, Botrytis,
  Fusarium, Alternaria, Phomopsis, slightly on
  Phytopthora, Rhizoctonia
• Pythium oligandrum DV 74 hyperparasite in
  testing on many pathogenic fungi

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Nematode Control

• Exclusion
• Resistant varieties
• Crop rotation
• Cover crops
• Grain Rye (Elbon rye) for root knot
• Solarization

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Take Home Message

• Plan
• Keep records
• Scout
• Learn disease symptoms
• Be proactive in control