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Tomato Disease Identification Key by Affected Plant Part: Leaf Symptoms
Tomato plant 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.

Guía sinóptica para hoja de tomate en espanol.

Leaf Symptoms by pathogen groups or other causes

Bacterial

Fungal

Oomycetes

Viruses

Viroids

Phytoplasma

Physiological/Weather

Damage from

Nutritional disorders

 

Leaf Symptoms

Black or dark brown spots usually circular and varying in size (see individual characteristic symptoms to fine tune diagnosis

Symptoms  

Disease

Characteristic symptoms

Other parts affected

bacterial speck Bacterial speck   tiny, dark brown to black spots with surrounding yellow halo fruit, stem
bacterial spot Bacterial spot    small dark brown to black circular spots, initially water-soaked, coalescing and becoming angular, may have yellow halo fruit, stem
Syringae leaf spot brown spots with and without a halo, appearing similar to bacterial speck fruit, stem
early blight Early blight  initially appears a irregular lesions on oldest mature leaves near the ground; lesions expand, becoming dark brown and necrotic with concentric black rings giving a target-like appearance; may have a chlorotic area surrounding lesion fruit, stem, whole plant
septoria leaf spot Septoria leaf spot  initially small circular water-soaked spots beginning on older leaves; spots enlarge in diameter with a black or brown border and with gray centers that are speckled with small black fruiting bodies stem, whole plant
gray leaf spot Gray leaf spot small brownish lesions becoming irregular and often surrounded by chlorotic areas; lesion will dry up and develop cracks; southern states whole plant
target spot lesions Target spot initially as tiny lesions, expanding with yellow halos; lesions coalesce leading to collapse of tissue; southern states fruit, stem
tomato spotted wilt Tomato spotted wilt virus tiny irregular brown spots, streaks, and ring spots usually on the youngest leaves; southern states

fruit, stem,
whole plant


Marginal browning of leaf tissue, with necrotic spots and irregular interveinal lesions later in disease development

Symptoms  

Disease

Characteristic symptoms

Other parts affected

bacterial canker Bacterial canker brown margin with yellow border to inside; characteristically the leaves remain attached to the plant fruit, stem, whole plant

Chlorotic lesion on upper surface, sporulation on lower surface

Symptoms  

Disease

Characteristic symptoms

Other parts affected

leaf mold Leaf mold light yellowish areas on upper surface corresponds with olive-brown fungal masses on lower surface; primarily a greenhouse disease and taken to the field on transplants fruit, stem
  Powdery mildew (Leveillula) yellow lesions on the upper surface with a light powdery fungal sporulation on the lower surface; typically found in dryer western states stem

Broad irregular water-soaked lesion turning dark brown or beige with white sporulating growth during wet weather

Symptoms  

Disease

Characteristic symptoms

Other parts affected

late blight Late blight large water-soaked lesions which become black with white sporulation on the margin of lesion, usually on lower surface but occasionally on upper leaf surface; appear beige in color once lesions dry out in hot weather fruit, stem, whole plant

Broad irregular lesion with gray fungal sporulation

Symptoms  

Disease

Characteristic symptoms

Other parts affected

gray mold (botrytis) Gray mold  light brown spots, often start at wound or dead tissue; fuzzy gray fungal growth when moist; common in greenhouse production when poorly ventilated fruit, stem, whole plant

Zonate shaped lesions during wet weather

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Zonate spot Zonate spot
(Cristulariella)
light tan lesions with distinct concentric rings; occurs during wet weather and could be confused with late blight; associated with nearby infected box elder and black walnut trees fruit, stem

Whitish fungal growth mainly circular or upper surface

Symptoms  

Disease

Characteristic symptoms

Other parts affected

powdery mildew (Oidium) Powdery mildew (Oidium) white, powdery fungal growth appears on upper and lower leaf surface; typically a greenhouse problem, but can be taken to the field on transplants stem

Yellowing, necrosis and wilting of leaves

Symptoms  

Disease

Characteristic symptoms

Other parts affected

bacterial canker Bacterial canker brown marginal lesions and later developing interveinally as irregular lesions; yellowing leaves on wilting plants, remain attached to stems fruit, stem, whole plant
bacterial pith necrosis Bacterial pith necrosis yellowing and wilting of leaves, blacking and enlarging of petioles and nodes, and progressing to top of plant stem, whole plant
  Fusarium foot rot (F. solani) interveinal chlorosis and necrosis of leaves later turning brown stem, roots, whole plant
  Fusarium crown and root rot (F. oxysporum f. sp. radicis-lycopersici) yellowing of older leaves and progressing to top of plants after mature green fruit stages stem, roots, whole plant
  Fusarium wilt (F. oxysporum f. sp. lycopersici, 3 races) begins as yellowing of oldest leaves, and progressing upward, often with yellowing on one side of leaf or branch; brown vascular tissue in stem at crown and above stem, roots, whole plant
verticillium wilt

Verticillium wilt

 

yellowing with a V-shaped pattern turning brown with brown vascular tissue inside stem at crown of plant stem, roots, whole plant

Yellowing and bronzing, or calico with stunting

Symptoms  

Disease

Characteristic symptoms

Other parts affected

tomato spotted wilt Tomato spotted wilt virus as the full manifestation of disease develops (see above), leaves will also show yellowing and bronzing fruit, stem, whole plant
Alfalfa mosaic Alfalfa mosaic virus yellowing and purpling develops on mature plant leaves, while calico symptoms appear on young leaves fruit, stem, whole plant

Fernleaf appearance or symptoms as green mottling

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Cucumber mosaic Cucumber mosaic leaves are susceptible at all stages, but symptoms can consist of mottling and severe fernleaf or “shoestring” appearance; occurrence of satellite viruses can greatly modify symptoms fruit, stem, whole plant

Leaf distortion and mottling

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Tobacco etch Tobacco etch leaves are susceptible at all stages; symptoms consist of mottling and leaf distortion fruit, stem, whole plant
Potato virus YPotato virus Y Potato virus Y faint mottling and slight distortion along with veinbanding mosaic; field symptoms include dark brown dead areas; other necrotic strains reported fruit, stem, whole plant

Chlorotic mottling or fernleaf under cool growing conditions

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Tobacco (tomato) mosaic Tobacco (tomato) mosaic common strains cause mottled areas of light and dark green on the leaves; aucuba strains cause yellowing; leaves also may exhibit leafrolling and fernleaf-like symptoms fruit, stem, whole plant

Dark brown streaks on foliage, stems, fruit

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Tobacco mosaic & Potato virus X-double streak Tobacco mosaic & Potato virus X-double streak mixture of two viruses prompts dark brown to black streaks with downward leaf curl fruit, stem, whole plant

Leafroll, marginal yellowing and rugosity

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Potato leafroll Potato leafroll leaf rolling and marginal leaf chlorosis fruit, stem, whole plant

Leafroll, but without yellowing or rugosity

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Physiological leafroll Physiological leafroll pronounced leafroll of foliage over most of plant whole plant

Plant stunting, rugosity and leaf distortion

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Tomato planta macho Tomato planta macho stunting, apical proliferation, leaf narrowing, chlorosis, necrosis, crinkling and brittleness of leaf tissue fruit, stem, whole plant
Tomato bunchy top Tomato bunchy top see above fruit, stem, whole plant
Tomato apical stunt Tomato apical stunt see above fruit, stem, whole plant

Big bud of flower parts

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Tomato big bud Tomato big bud leaves are small, distorted and yellowish green fruit, stem, whole plant

Green callus-like growth on upper and lower surface

Symptoms  

Disease

Characteristic symptoms

Other parts affected

edema on tomato leaves Edema green callus-like growth on both the upper and lower leaf surface; tissue may tear as leaf matures as shown in illustrations  

Insect related injury; virus-like or herbicide-like damage (plant growth regulator or toxin)

Symptoms  

Pest

Characteristic symptoms

Other parts affected

irregular ripening Silverleaf whitefly both adult and nymphal stages have piercing-sucking mouthparts that cause spotting and later chlorosis fruit
Broad mite damage Broad mite symptoms on tomato and potato appear similar with leaf necrosis, particularly along the veins on the underneath surface with rugosity and stunting of terminal leaf growth.
 

Virus-like symptoms caused by herbicides

Symptoms  

Disease

Characteristic symptoms

Other parts affected

2,4-D (Phenoxy) 2,4-D (Phenoxy) extent of damage depends upon dosage received; growth distortion and fernleaf-like symptoms fruit, stem, whole plant
Glyphosate (Roundup, Phosphono amino acids) Glyphosate (Roundup, Phosphono amino acids) extent of damage is illustrated and depends upon dosage received; terminal epinasty with fernleaf distortion, yellowing and necrosis and stunting, or bright yellowing fruit, stem, whole plant

Insecticide injury

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Malathion (insecticide) Malathion (insecticide) classical pesticide burn on upper and lower leaf surface, free of any fungal growth, unless secondaries have invaded tissue fruit, stem, whole plant

Nutrient deficiencies

Symptoms  

Disease

Characteristic symptoms

Other parts affected

Magnesium damage Magnesium chlorosis and chlorotic blotches later becoming necrotic whole plant
iron damage Iron yellowing between veins and rare on mature leaves whole plant