The best control of tomato diseases is to follow the fundamental rules in tomato management such as choice of disease resistant varieties, good cultural practices, and the use of appropriate chemicals at the proper time. Early detection and correct identification of the disease are essential in order to select the proper control practice and reduce extensive damage. The diseases are generally classified as infectious or non-infectious.
Non-infectious (physiological) diseases are caused by adverse environmental, chemical, or soil factors that result in abnormal plant growth and development. These diseases are not contagious and therefore do not spread from plant to plant and increase over time. Plants may sometimes recover when the adverse conditions are corrected.
Infectious diseases, on the other hand, can spread rapidly and devastate a crop. It is very important to differentiate between the type of microorganism causing an infectious disease (fungal, bacterial, viral, or nematodal) before applying a chemical. For example a fungicide used to treat a bacterial disease will do no good, delay correct treatment, and is a waste of money.
The following key has been prepared to assist you in the identification of the major diseases attacking tomatoes in Oklahoma. It provides a brief description of the symptoms of the various diseases. Determine the entry that best describes your situation then click on the Fact Sheet number at the end of your symptoms. This will link you to the appropriate Fact Sheet at Oklahoma State University which will discuss the disease in more detail.
| SELECT A SYMPTOM | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |
| IMAGE LINKS | Wilting Problem description | ||
| -- Gradual wilt and death. Lower leaves turn yellow and die. Inside of stems reddish brown discoloration when cut. (FUSARIUM WILT) Fungal. See F-7625 | |||
| -- Rapid wilting entire plant. Water soaked lesion on stem near soil line expands and turns brown and girdles stem. A White mold (mycelium) covers stem lesion and surrounding moist soil. Sclerotia form on mycelium. (Southern Blight) Fungal. See F-7625 | |||
| -- Rapid wilting and death. No yellowing or spotting of leaves. Brown discoloration and decay on inside of stems. (Bacterial Wilt) Bacterial. See F-7626 | |||
| -- Plant wilts easily even with adequate water. Growth stunted. Plants appear yellow, or pale green. (Root-knot) Nematodes. See F-7626 | |||
| SELECT ANOTHER SYMPTOM? | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |
| IMAGE LINKS | Growth Problem description | ||
| -- Growth stunted. Plant wilts easily even with adequate water. Plants appear yellow, or pale green. (Root-knot) Nematodes. See F-7626 | |||
| -- New growth stunted. May have one-sided growth. Bronzing of young leaves. May have dark purple to brown ringspots on leaves. Brown streaking on terminal stems. Fruit may have ringspots, light green on green fruit, yellow on ripe fruit. (Tomato Spotted Wilt) Viral. See F-7626 | |||
| -- Top growth weak and spindly. Internodes lengthened. Young plants stunted, set few fruits. Older leaves thickened, upward rolling of their bases. Younger leaves narrower than normal, dwarfed, curl slightly upward at tips with petioles twisted, yellowish green. Stems become purplish. Fruit, yellowish-red. (Psyllid Yellows) Physiological. See F-7627 | |||
| SELECT ANOTHER SYMPTOM? | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |
| IMAGE LINKS | Leaf Problem description | ||
| -- Leaf spots on older leaves first. The circular lesions, up to 1/2 inch, are brown with concentric rings like a target. Surrounding area usually turns yellow. Leaves turn brown and drop from bottom to top. Fruit may have sunken, dry lesions near stem end with a target-like appearance. (Early Blight) Fungal. See F-7625 | |||
| -- Leaf spots start as yellow areas on lower leaves, after fruit set. Leaf spots become circular with gray centers and dark borders, < 1/8 inch, with yellow halo. They develop tiny black specks in center. Defoliation progresses upward. (Septoria Leaf Spot) Fungal. See F-7625 | |||
| -- Leaf spots on oldest leaves first. Appear as small brownish-black flecks with a narrow yellow halo. Centers turn gray, crack, and fall out giving a shot hole appearance. There is NO small, black fruiting bodies in center. Leaves turn yellow and fall to ground. (Gray Leaf Spot) Fungal. See F-7625 | |||
| -- Rapidly expanding, greasy, gray, spots on upper surface of leaves. White mold at margin of affected areas. Stem and petioles may become infected, wilt and die. Fruit infections begin as brown, greasy spots that rapidly expand to cover entire fruit. (Late Blight) Fungal. See F-7625 | |||
| -- Leaf spots are dark brown and appear greasy when wet and are usually < 1/3 inch. A general yellowing of leaf followed by leaf scorch. Spots are not uniformly distributed over leaf surface, have no tiny fruiting bodies (specks), and no concentric rings as in other similar appearing diseases. Green fruit may have raised and scabby, dark brown spots, < 1/3 inch. Ripe fruit spots are similar except they are sunken. (Bacterial Spot) Bacterial. See F-7626 or Diagnostic Lab | |||
| -- Leaf spots are dark brown to black, may have yellow border. Green fruit may have dark-superficial specks, < 1/16 inch, surrounded by intense green color, may be raised. Ripe fruit has small dark superficial speck, surrounded by a zone of delayed ripening and is sunken. (Bacterial Speck) Bacterial. See F-7626 | |||
| -- Leaves are light and dark green mottled, small, curled, and malformed (fernleaf). Fruit may show uneven ripening or unusual mottling symptoms.(Tobacco Mosaic) Viral. See F-7626 | |||
| -- Leaves dwarfed, crinkled, rolled inward, and cupped upward. Underside veins have purple discoloration. Roots stunted. (Beet Curly Top Virus) Viral | |||
| -- Malformed leaves. Young leaves have a downward curvature to leaflets, prominent light-yellow veins, rolled edges, distorted leaf surfaces, and sharp points on leaflets. (2,4-D Damage) Physiological. See F-7627 | |||
| -- Leaflets of older leaves may have upward rolling of margins, be cup-shaped and may overlap. Rolled leaves firm, leathery. (Leaf Roll) Physiological. See F-7627 | |||
| SELECT ANOTHER SYMPTOM? | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |
| IMAGE LINKS | Fruit-rotting Problem description | ||
| -- Water soaked spot on fruit near blossom end, enlarges, darkens, sunken,and leathery. (Blossom-End Rot) Physiological. See F-7627 | |||
| -- Ripe fruit have small, sunken, circular spot up to 1/2 inch in diameter. The center turns blackish. (Anthracnose) Fungal. See F-7625 | |||
| -- Ripe fruit, sometimes green fruit. Grayish-green or brownish, water soaked spots where fruit touches soil or water spashes. May cover half of fruit diameter, appears brown with concentric rings resembling markings of buckeye chestnut. (Buckeye Rot) Fungal. See F-7625 | |||
| -- Ripe fruit develops sunken, yellowish lesion becoming star shaped, water soaked where fruit touches soil or water spashes. White mold on lower side of rotted fruit. (Southern Blight) Fungal. See F-7625 | |||
| -- Small water-soaked spot, where fruit touches soil. Rapid rotting. Skin ruptures, watery contents spill out, white, cottony growth within lesions under humid conditions. ( Pythium Rot) Fungal. See F-7625 | |||
| -- A brown rot with alternating light and dark colored zonate bands, sharply defined margins where fruit touches soil. Fruit becomes mushy. (Rhizoctonia Soil Rot) Fungal. See F-7625 | |||
| SELECT ANOTHER SYMPTOM? | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |
| IMAGE LINKS | Fruit (non-rotting) Problem description | ||
| -- Uneven ripening, or unusual mottling symptoms. Leaves are light and dark green mottled, small, curled, and malformed (fernleaf). (Tobacco Mosaic) Viral. See F-7626 | |||
| -- Bands of scar tissue between protuberances on fruit. Cavities or indentations deep into fruit. Ripens unevenly. (Catface) Physiological. See F-7627 | |||
| -- Fruit, yellowish-red. Older leaves thickened, upward rolling of their bases. Younger leaves narrower than normal, dwarfed, curl slightly upward at tips, petioles twisted and yellowish green. Stems become purplish. Internodes lengthened. Top weak and spindly. Young plants stunted with few fruits. (Psyllid Yellows) Physiological. See F-7627 | |||
| -- Yellow or white soft patch on side towards sun. (Sunscald) Physiological. See F-7627 | |||
| -- Green fruit develop spots that are raised and scabby, dark brown, < 1/3 inch. Leaf spots are dark brown, appear greasy when wet, <1/3 inch. General yellowing of leaf followed by scorch. Spots are less uniformly distributed over leaf surface, no tiny fruiting bodies (specks), no concentric rings, as in similar appearing diseases. Ripe fruit develop spots that are sunken, scabby, dark brown, < 1/3 inch. (Bacterial Spot) Bacterial. See F-7626 | |||
| -- Green fruit has dark-superficial specks, < 1/16 inch, surrounded by intense green color, may be raised. Leaf spots are dark brown to black, may have yellow border. Ripe fruit has small dark sunken, superficial specks, surrounded by a zone of delayed ripening. (Bacterial Speck) Bacterial. See F-7626 | |||
| -- Ripe fruit develop spots that are sunken, scabby, dark brown, < 1/3 inch. Leaf spots are dark brown, appear greasy when wet, <1/3 inch, General yellowing of leaf followed by scorch. Spots are less uniformly distributed over leaf surface, no tiny fruiting bodies (specks), no concentric rings, as in similar appearing diseases. (Bacterial Spot) Bacterial. See F-7626 | |||
| -- Ripe fruit develop small, dark, sunken superficial specks surrounded by a zone of delayed ripening. Leaf spots, dark brown to black, may have yellow border. Green fruit has dark-superficial specks, < 1/16 inch, surrounded by intense green color, may be raised. (Bacterial Speck) Bacterial F-7626 | |||
| SELECT ANOTHER SYMPTOM? | ||||
|---|---|---|---|---|
| WILTING | GROWTH | LEAF | FRUIT ROTTING | FRUIT (NON-ROTTING) |