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Tomato Disease Identification Key by Affected Plant Part: Leaf Symptoms

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

Canker
Speck
Spot
Pith necrosis
Syringae leaf spot

Fungal

Early blight
Fusarium crown and root rot
Fusarium foot rot
Fusarium wilt
Gray leaf spot
Gray mold
Leaf mold
Powdery mildew (Leveillula)
Powdery mildew (Oidium)
Septoria leaf spot
Target spot
Verticillium wilt
Zonate spot

Oomycetes

Late blight

Viruses

Alfalfa mosaic
Cucumber mosaic
Potato leafroll
Potato virus Y
Tobacco etch
Tobacco (tomato) mosaic
Tobacco mosaic & Potato virus X-double streak
Tomato spotted wilt

Viroids

Tomato planta macho
Tomato bunchy top
Tomato apical stunt

Phytoplasma

Tomato big bud

Physiological/Weather

Air pollution
Edema
Physiological leafroll

Damage from

Silverleaf whitefly
Broad mite
Malathion (insecticide)

2,4-D (Phenoxy)
Glyphosate (Roundup, Phosphono amino acids)

Nutritional disorders

Magnesium
Iron

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	tiny, dark brown to black spots with surrounding yellow halo	fruit, stem
	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	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	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	small brownish lesions becoming irregular and often surrounded by chlorotic areas; lesion will dry up and develop cracks; southern states	whole plant
	Target spot	initially as tiny lesions, expanding with yellow halos; lesions coalesce leading to collapse of tissue; southern states	fruit, stem
	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	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	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	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	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 (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)	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	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	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	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 virus	as the full manifestation of disease develops (see above), leaves will also show yellowing and bronzing	fruit, stem, whole plant
	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	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	leaves are susceptible at all stages; symptoms consist of mottling and leaf distortion	fruit, stem, whole plant
	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	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	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	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	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	stunting, apical proliferation, leaf narrowing, chlorosis, necrosis, crinkling and brittleness of leaf tissue	fruit, stem, whole plant
	Tomato bunchy top	see above	fruit, stem, whole plant
	Tomato apical stunt	see above	fruit, stem, whole plant

Big bud of flower parts
Symptoms	Disease	Characteristic symptoms	Other parts affected
	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	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
	Silverleaf whitefly	both adult and nymphal stages have piercing-sucking mouthparts that cause spotting and later chlorosis	fruit
	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)	extent of damage depends upon dosage received; growth distortion and fernleaf-like symptoms	fruit, stem, whole plant
	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)	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	chlorosis and chlorotic blotches later becoming necrotic	whole plant
	Iron	yellowing between veins and rare on mature leaves	whole plant