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Tomato  Disease  Identification  Key By Affected Plant Part: Stem and Whole Plant Symptoms
Tomato drawing

Generalized tomato plant adapted from Plant Pathology 4th edition by G. N. Agrios copyright 1997 as Figure 1-1 published by Academic Press, San Diego, CA, with permission from Elsevier.
Stem and Whole Plant Symptoms (Crown rot, damping off, roots, stunting, wilt, and vascular discoloration ) by Pathogen Groups and Other Causes.
Bacterial
Fungal
Oomycetes

Viruses

Viroids

 

Phytoplasma

Nematodes

  • Northern root-knot
  • Southern root-knot

Parasitic plants

Damage From Herbicides

Damage From Insecticides

Damage From Insects

Physiological/Weather

Nutritional Disorders

 

 

Tomato  Disease  Identification  Key

Bacterial

 Plant Part Affected   Other parts affected
    Stem Whole Plant Roots Characteristic Symptoms  
bacterial canker
Canker
X
X
 X browning of vascular tissue and browning and mealy appearance of pith at crown and above; external discoloration, enlargement of nodes and stem cracking sometimes occurs; yellow and necrosis of plant associated with plant wilt; foliage characteristically remains attached to plant leaves, fruit
bacterial speck
Speck
X
X
   tiny, dark brown to black spots with surrounding yellow halo; may result in leaf and plant stunting leaves, fruit
bacterial spot
Spot
X
X
   dark brown, oval to elongated spots; coalesce to streaks; considerable loss of lower leaf foliage can occur leaves, fruit
bacterial pith necrosis
Pith necrosis
X
X
 X yellowing and wilting of leaves, blacking and enlarging of petioles and nodes, and progressing to top of plant; yellowing and wilt of entire plant leaves
bacterial stem rot
Stem rot
X
X
   outward blacking of stem and leaf tissue; blackened pith tissue leaves
bacterial crown gall
Crown gall
X
X
X
 plant stunting and wilting; gall formations obvious on roots leaves
bacterial wilt
Bacterial wilt
X
X
 X yellowing followed by leaf necrosis and wilting of entire plant; longitudinal cutting of stem reveals brown vascular discoloration and eventual hollowness leaves

Fungal          
    Stem Whole Plant Roots Characteristic Symptoms Other parts affected
 

Alternaria stem canker
X
X
   dark brown stem cankers with concentric rings; cankers may girdle plant leaves
early blight Early blight
X
X
   on stems appears as lesion with dark border and gray center; can encompass and girdle stem causing death of lower canopy leaves leaves, fruit
rhizoctonia damping off Damping off (Rhizoctonia)
X
X
   responsible for damping off in the small seedling stage; causes restrictions near the plant crown resulting in wilting and death leaves
fusarium crown rot Fusarium crown and root rot
X
X
 X brown vascular tissue in stem from crown to slightly above; stem surface can be brown; roots are brown and rotting  
fusarium wilt Fusarium wilt
X
X
 X brown vascular tissue in stem from crown to far above  
Gray leaf spot Gray leaf spot  
X
   symptoms are restricted to leaves and whole plant affects leaves
gray mold Gray mold
X
X
   large, light brown elliptical spots; gray fungal growth; lesions can girdle the stem resulting in plant death  leaves, fruit
  Leaf mold
X
X
   can result in considerable leaf defoliation but unlikely resulting in plant death  
  Powdery mildew (Leveillula)
X
X
   affected plants can show considerable defoliation, but not resulting in plant death leaves
powdery mildew Powdery mildew (Oidium)
X
X
   affected plants show considerable defoliation, but not resulting in plant death leaves, flower parts
Septoria leaf spot Septoria leaf spot
X
X
   dark elongated spots develop on petioles and stems leading to loss of lower canopy, and unthrifty plants; concern with overwintering inoculum for the next season leaves, flower parts
Southern blight Southern blight
X
X
   fungus can cause damping off or in older plants a crown rot leading to wilt and plant death; look for tan sclerotia in mass of whitish fungal growth above the soil line  
White mold White mold
X
X
   brown soft rot of stem at crown or above; becomes light gray; white cottony fungal growth when moist; hard, black, pea-like objects (sclerotia) eventually form; causing wilt and eventual plant death  
White mold minor White mold minor
X
X
   similar to above but with smaller sclerotia  
target spot defoliation Target spot
X
X
   stem lesions may eventually girdle the stem and result in plant death fruit, leaves
Verticillium wilt Verticillium wilt
X
X
 X brown vascular tissue in stem at crown of plant; plants will wilt in the heat of the day leaves

Oomycetes       Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
damping off Damping off (Pythium)
X
X
 X common cause of seedling loss with water-soaked and mushy stems; results in stem girdling and plant wilt and death  
  Buckeye rot
X
X
   can cause seedling damping off; on older plants can cause vascular discoloration affecting roots and stem fruit
late blight Late Blight
(several genotypes)
X
X
   newer genotypes of late blight are more aggressive, especially to stems; plant death is common under wet and cool and moderately warm temperatures; see leaf and fruit section for more images fruit, leaves

Viruses       Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
Alfalfa mosaic Alfalfa mosaic
X
X
  X yellowing and bronzing with necrosis of leaves; leaves stop growing and curl downward; longitudinal cut of stem reveals brown streaking of phloem and pith; also noted in roots; frequently occurs when tomatoes are planted next to alfalfa (illustrated) or red clover infected fields fruit, leaves
Cucumber mosaic Cucumber mosaic
X
X
   plant stunting and malformation of foliage is common especially if plants are infected at an early age fruit, leaves
Curly top Curly top
X
X
   plants have an erect growth habit, are stunted and leaves are curled upward fruit, leaves
Potato leafroll Potato leafroll
X
X
   plants are stunted and have yellowing leafroll symptoms especially if infected at an early age fruit, leaves
Potato virus Y Potato virus Y
X
X
   plants are stunted and have downward curling leaves with mottle, veinbanding and possible necrosis depending on the strain involved fruit, leaves
Pseudo curly top Pseudo curly top
X
X
   plants are stunted with greatly reduce foliage with upward curling leaves; found in south Florida and spread by treehoppers fruit, leaves
Tobacco etch Tobacco etch
X
X
   plants are stunted and foliage shows extensive rugosity when plants are infected at an early age fruit, leaves
Tobacco (tomato) mosaic Tobacco (tomato) mosaic
X
X
   depending on the strain and age of plants when infected, plants are stunted with mosaic or fernleaf like symptoms fruit, leaves
Tobacco mosaic & potato virus X
Tobacco mosaic & potato virus X
X
X
   plants are stunted and show a great amount of black streaks on leaves, stems and discoloration on fruit fruit, leaves
tomato yellow leaf curl Tomato yellow leaf curl X X   a devastating viral diseases of cultivated tomato in tropical and subtropical regions worldwide, and now present in southern US; denoted by plant stunting and pronounced chlorotic leaves that curl upward leaves
Tomato spotted wilt Tomato spotted wilt
X
X
   Plants show a variety of symptoms depending on when plants are infected; young plants show necrotic streaks or spots along with leaf distortion; older plants show yellowing and bronzing on the foliage, stunt and wilting from the apical tissue to the lower plant parts fruit, leaves

Viroids          
    Stem Whole Plant Roots Characteristic Symptoms Other parts affected
tomato bunch top Tomato bunchy top
X
X
   stunting, apical proliferation, leaf narrowing, chlorosis, necrosis, crinkling and brittleness of leaf tissue  
Tomato apical stunt Tomato apical stunt
X
X
   see above  
tomato planta macho Tomato planta macho
X
X
   see above  

Phytoplasma       Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
big bud Big bud
X
X
 X stiff erect growth, brittleness, leaf yellowing or purpling; aerial roots fruit, leaves

Nematodes       Characteristic Symptoms Other parts affected
  Stem Whole Plant Roots    
Northern root-knot  
X
X
    
Southern root-knot  
X
X
    

Parasitic Plants       Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
dodder Dodder
(Cuscuta spp.)
X
X
      

Damage From:
Herbicides

       Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
2,4-D damage 2,4-D
X
X
fernleaf-like symptoms of foliage with leaf curl and plant stunting fruit, leaves
Banvel
X
X
X
 plant stem deforming with aerial foot initials leaves
Treflan
X
X
X
 stem and crown damage with swelling and loss of roots; whole plant stunting leaves
Roundup
X
X
plant stunting and leaf rolling with leaf center chlorosis; degree of damage depends on dosage and plant stage at exposure fruit, leaves

Damage From:
Insecticides 		      Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
malation Malathion
X
X
   plant unthriftiness and marginal chlorosis and necrosis; seen with older formulations leaves
Thiodan injury Thiodan
X
X
   leaf and petiole burn but general no plant stunting; localized leaves

Damage From:
Insects 		      Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
broad mite damage Broad mite       plants are stunted and leaves are irregularly shaped and twisted enough so as to show an overall pattern of affected plants in the field  
hornworm damage Hornworm
X
X
   extensive removal of leaves, stems and petioles fruit, leaves

Damage From:
Physiological/Weather		          
    Stem Whole Plant Roots Characteristic Symptoms Other parts affected
physiological leafroll Physiological leafroll
X
X
   leafrolling seen on entire plant leading to an unthrifty appearing plant leaves
Walnut wilt Walnut wilt
X
X
   poor plant growth and plant wilt when plants are grown in the root zone of walnut and butternut trees leaves
hail damage Hail damage
X
X
   spotty plant damage consisting of necrotic depressions and wholes to leaves, petioles and stems fruit, leaves
Lightning damage Lightning
damage
X
X
   damage occurs in circular pattern with most severely affected plants in center; branches, stems and petioles show shrinkage due to collapse of pith; ladder-like internal stem damage leaves

Damage From:
Nutritional Disorders 		      Characteristic Symptoms Other parts affected
    Stem Whole Plant Roots    
  Nitrogen
X
X
   plant stunting may occur and oldest leaves turn chlorotic and younger leaves turn yellowish-green leaves
phosphorous Phosphorous
X
X
   leaves on young seedlings turn purplish and the leaves on older plants are unthrifty and turn reddish-purple on the undersides leaves
Magnesium Magnesium
X
X
   interveinal chlorosis begin on oldest leaves and continue to younger leaves; midribs remain green and leaves may become necrotic leaves
  Manganese
X
     a checkerboard appearance of interveinal yellowing beginning on apical leaves and near the main veins leaves
  Iron
X
X
   interveinal yellowing or whitening beginning on apical leaves with veins remaining green leaves