Master Gardener General Plant Pathology Talk

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2008Specialized Master Gardener
TrainingDiseases of Vegetables
Brian D. Hudelson Department of Plant
Pathology University of Wisconsin-Madison/Extensio
n
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Diseases of VegetablesDamping-Off/Seedling
Blights

• Pathogens
• Pythium spp.
• Rhizoctonia solani
• Fusarium spp.
• Hosts Seedlings of virtually any vegetable
• Environmental trigger Cool, wet soil conditions

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Diseases of VegetablesDamping-Off/Seedling
Blights

• Control
• Use a pasteurized soil mixture
• Use decontaminated pots, working surfaces and
  tools
• Moderate soil moisture
• Use a soil with adequate drainage
• Dont overwater

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Diseases of VegetablesDamping-Off/Seedling
Blights

• Control
• Germinate seeds at higher temperatures
• Use fungicides to protect seedlings
• Etridiazole, metalaxyl, mefenoxam, captan
• Applied as a seed treatment or drench

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Diseases of VegetablesTomato Leaf Blights/Spots

• Causes
• Alternaria solani (early blight)
• Septoria lycopersici (Septoria leaf spot)
• Host Tomato, potato (early blight)
• Environmental trigger Long periods of leaf
  wetness

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Diseases of VegetablesTomato Leaf Blights/Spots

• Control
• Remove and destroy infected debris
• Move tomatoes to new location (?)
• Plant resistant varieties (?)
• Space plants far apart
• DO NOT overhead water
• DO NOT overmulch
• Remove infected leaf tissue (?)

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Diseases of VegetablesTomato Leaf Blights/Spots

• Control
• Use fungicides for to prevent infections
• Chlorothalonil
• Applications every 7-14 days

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Diseases of VegetablesBlossom End Rot

• Cause Calcium deficiency
• Hosts
• Tomato
• Pepper
• Eggplant
• Cucurbits
• Environmental trigger Drought conditions

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Diseases of VegetablesBlossom End Rot

• Management
• Test soil to determine level of calcium present
• Add calcium as needed
• Bone meal
• Egg shells
• Water plants adequately

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Diseases of VegetablesRoot Knot

• Cause Meloidogyne spp.
• Host Tomato
• Environmental trigger None

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Diseases of VegetablesRoot Knot

• Control
• Plant non-hosts in infested areas
• Use resistant tomato varieties (N)
• Start with clean materials
• Use soil-less growing media or pasteurized soil
• Discard infected plants

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Diseases of VegetablesHerbicide Injury

• Causes
• Growth regulator herbicides
• 2,4-D
• Dicamba
• Other herbicides
• Affected plants
• All vegetables, particularly tomatoes

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Diseases of VegetablesHerbicide Injury

• Control
• Apply herbicides only when needed
• Follow application directions exactly
• Apply herbicides only when wind speed is low (lt 5
  mph)
• DO NOT apply herbicides too close to nontarget
  plants
• Apply herbicides at low pressure
• Use amine rather than ester forms of herbicides

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Diseases of VegetablesVascular Wilts

• Hosts
• Tomato
• Potato
• Pepper
• Eggplant
• Cucurbits

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Diseases of VegetablesVascular Wilts

• Causes
• Verticillium spp. (Verticillium wilt)
• Fusarium oxysporum (Fusarium wilt)
• Environmental trigger Wet soil conditions,
  followed by
  drought

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Diseases of VegetablesVascular Wilts

• Control
• Move tomatoes to a new location
• Plant resistant varieties (VFF)
• DO NOT overwater
• DO NOT overmulch

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Diseases of VegetablesScab

• Cause Streptomyces scabies
• Host Potato
• Environmental trigger High soil pH

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Diseases of VegetablesScab

• Control
• Move potatoes to another location
• Plant scab-free potato stock
• Plant scab resistant varieties
• Lower soil pH

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Diseases of VegetablesBacterial Soft Rot

• Cause Pectobacterium carotovorum
• Host Potato
• Environmental trigger Wet soils

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Diseases of VegetablesBacterial Soft Rot

• Control
• Moderate soil moisture
• Have good soil fertility (particularly calcium)
• Harvest tubers promptly
• DO NOT bruise/injure tubers
• Keep harvested tubers dry
• Remove any rotted tubers immediately

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Diseases of VegetablesPowdery Mildew

• Causes
• Sphaerotheca fuliginea
• Erysiphe cichoracearum
• Oidium spp.
• Hosts Cucurbits

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Diseases of VegetablesPowdery Mildew

• Control
• Plant resistant varieties
• DO NOT crowd cucurbit plants
• Apply fungicides for control
• S
• 1.5 Tsp. baking soda 3 Tsp. horticultural oil
  in 1 gal water
• Applications every 7-14 days

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Diseases of VegetablesBacterial Wilt

• Cause Erwinia tracheiphila
• Hosts Cucurbits
• Environmental trigger High cucumber beetle
  populations

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Diseases of VegetablesBacterial Wilt

• Control
• Keep cucumber beetles under control
• Water plants adequately if infections occur

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Diseases of VegetablesCucumber Mosaic

• Cause Cucumber mosaic virus
• Hosts
• Cucurbits
• Pepper
• Tomato
• Environmental trigger High aphid populations

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Diseases of VegetablesCucumber Mosaic

• Control
• Plant resistant/tolerant varieties
• Plant based resistance
• Plant based tolerance
• Genetically modified plants
• Attempt to control aphid vectors (?)
• Attempt to eliminate alternate hosts (?)

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Diseases of VegetablesCommon Rust

• Cause Puccinia sorghi
• Host Corn
• Environmental triggers
• Moderate temperatures
• Long periods of leaf wetness

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Diseases of VegetablesCommon Rust

• Control
• Plant resistant varieties

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Diseases of VegetablesCommon Smut

• Cause Ustilago maydis
• Host Corn
• Environmental trigger Hail

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Diseases of VegetablesCommon Smut

• Control
• Plant resistant varieties
• Reduce physical damage to corn plants
• Give up on your corn and eat the smut

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Diseases of VegetablesBean Leaf Diseases

• Causes
• Pseudomonas syrinage pv. syringae (bacterial
  brown spot)
• Pseudomonas syringae pv. phaseolicola(halo
  blight)
• Xanthomonas campestris pv. phaseoli (common
  blight)
• Hosts Snap bean, kidney bean, lima bean
• Environmental trigger Driving rain

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Diseases of VegetablesBean Leaf Diseases

• Control
• Purchase high quality seed
• Use resistant varieties where available
• DO NOT overhead water
• Apply bactericides for control (copper) (?)

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Diseases of VegetablesRoot Rots

• Causes
• Pythium spp. (Pythium root rot)
• Rhizoctonia solani (Rhizoctonia root rot)
• Hosts
• Snap beans
• Other vegetables
• Environmental trigger Wet, cool soil conditions

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Diseases of VegetablesRoot Rots

• Control
• Rotate beans (and other crops) to new locations
  whenever possible
• DO NOT overwater
• DO NOT overmulch

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Diseases of VegetablesWhite Mold

• Cause Sclerotinia sclerotiorum
• Host Snap beans (and other vegetables)
• Environmental trigger Cool, humid conditions

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Diseases of VegetablesWhite Mold

• Control
• Buy high quality seed
• Rotate beans to new locations whenever possible
  (5-7 yrs)
• Plant beans with wider row spacings
• DO NOT overwater
• DO NOT overmulch
• Control broadleaf weeds

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Diseases of VegetablesAster Yellows

• Cause Aster yellows phytoplasma
• Hosts Carrot, potato
• Environmental trigger None

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Diseases of VegetablesAster Yellows

• Control
• Control leafhopper vector (?)
• Remove infected plants

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Diseases of VegetablesWhere to Go for Help
Plant Disease Diagnostics Clinic Department of
Plant Pathology University of Wisconsin-Madison 16
30 Linden Drive Madison, WI 53706-1598 (608)
262-2863 bdh_at_plantpath.wisc.edu http//pddc.wisc.e
du (http//wihort.uwex.edu)