Tomato, diseases

I don’t recall where I originally ran on these pictures/information—probably one of the agricultural sites I visited, but I’d like to thank those responsible for this invaluable information.

Tomatoes may be one of the easiest of fruits to grow but they come with a unique set of potential problems.

Every wonder what those spots are or that ugly looking growth on your favorite tomato is?  The following may help.

This section is devoted to green tomatoes in their various stages of growth.

The lower section is devoted to ripe tomatoes.

One thing that is OUTSTANDING in the remedies is the strong emphasis on drip or furrow irrigation—avoiding wetting of the leaves. Sprinkler or overhead irrigation is a major contributing factors to tomato disease.

GREEN tomato diseases

Bacterial speck

Symptoms:
Symptoms may appear on any plant part. Leaves of infected plants are covered by small, dark brown, irregular patches of rotting tissue that are surrounded by yellow halos. Disease severity is increased by leaf wetness from sprinkler irrigation, rain, or heavy dews.

Control:
Minimize wetting of the leaves by using drip or furrow irrigation. Copper sprays provide effective control.

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Bacterial canker

Symptoms:
Bacterial canker is characterized by wilting and eventual death of the lower leaves, with the leaves drying up while still attached to the stem. Vascular tissue is discolored, brown, or brownish-yellow, and a characteristic yellow slime can be squeezed from affected stems. The bacterium that causes this disorder may be seed or soil born.

Control:
Crop rotations and careful seed source selection are primary considerations. Seed beds in infected areas should be sterilized. Mechanical damage to the transplants (such as topping) spreads the disease.

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Late blight

Symptoms:
Lesions on leaves appear as large watersoaked areas, that eventually turn brown and papery. Fruit lesions are large irregular greenish-brown patches having a greasy rough appearance. Green to black irregular lesions are also present on the stems.

Control:
The fungus develops during periods of cool wet weather. Fungicide sprays as a preventative measure during these periods may be needed if the crop is being grown near large areas of tomato relatives (Solanaceous weeds, potatoes).

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Canker

Symptoms:
Symptoms of Alternaria canker appear on stems, leaves and fruit. Brown or black necrotic lesions are usually visible on plants from which infected fruit are picked. Fruit are infected when green, but symptoms persist into the ripening period. Sunken grayish lesions are present on fruit.

Control:
Fungus overwinters in crop residue and is easily spead by wind. Wounding of young plants (by mechanical damage or pruning) provides an entry site for infection. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.

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Buckeye rot

Symptoms:
Buckeye rot is one of a number of fruit rotting diseases that attacks both green and ripe fruit, especially where the fruit touches the soil. The lesion is rounded with alternating bands of light and dark brown in concentric circles. The lesion appears water-soaked at first, but later may become leathery on the surface.

Control:
Staking or plastic mulch to prevent fruit from contacting the soil is an effective control. The disease is worse in hot, wet weather. Fungicides offer little control to soil-contact type diseases.

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Spotted wilt

Symptoms:

Fruit are malformed, with raised yellow, red, and green mottled bull’s eye rings. Plants from which fruit are harvested are stunted, with older leaves turning yellow. The virus is carried by flower and onion thrips that have carried the virus from infected weeds and ornamentals.

Control:
Elimination of plants that serve as hosts to thrips is the most important control measure. Clean cultivation, with special attention to border strips is important. Locate production away from large grain fields.

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Bacterial spot

Symptoms:
Dark brown water soaked spots appear on the leaves; later these spots become blackish, and eventually the affected tissue drops out leaving a hole in the leaf. Black, raised specks that later become scab-like spots appear at the same time on fruit.

Control:
Crop rotations and careful transplant selection are important. Copper sprays provide some control. Good sanitation practices including prompt plow-down of stubble and weed control help prevent the disease.

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Radial cracking

Symptoms:
Fruit develop large cracks radiating out from the stem scar. Cracking may occur on green fruit. Cracks appear weathered and corky if they occur in green fruit. Fruit may develop any of a number of fungal fruit rots at the point of cracking.

Control:
Select varieties that have less cracking under your growing conditions. Prevent wide swings in moisture by even irrigation or mulching.

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Sun scald

Sun scalding

Symptoms:
Fruit have yellowish or whitish patches on side exposed to sunlight. These patches turn leathery and dry out. They may become infected with various types of mold as secondary infections in the wounded tissue. Fruit protected by shade from leaf cover or shading material are unaffected..

Control:
Select varieties noted to retain leaf cover throughout season. Use good fungicide/insecticide program to prevent leaf loss due to insects and disease. On small scale, can cover fruit with straw or shade plants with row cover.

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Mosaic

Symptoms:
Tomato mosaic virus (TMV) infected plants have a green/yellow mottled appearance and are usually stunted. Infected fruit may have necrotic brown patches on them.

Control:
The virus is most commonly transmitted by handling or mechanical damage. Gardeners who smoke may infect plants with virus particles left on their hands after handling cigarettes. A variety of insects can also transmit the disease from infected weeds in the Solanaceae. Avoid planting in a field where infected tomato or tobacco plants were grown, and in greenhouse situations, all pruning equipment should be steam sterilized regularly. Use resistant varieties.

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Blossom rot

Symptoms:
Blossom end rot can affect fruit at all stages of development. The characteristic symptom is a progressive deterioration of the blossom end of the fruit, from a water-soaked appearance to a sunken, black, leathery lesion. While secondary fungal infections may occur, blossom end rot is a physiological disorder caused by calcium deficiency induced by water stress.

Control:
Careful water management practices are a key. Irrigation and/or mulching are important. Application of lime or calcium prior to planting may help. Liquid fertilization using calcium nitrate can be used for small plots.

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RIPE tomato diseases.

Anthracnose in ripe tomato

Symptoms:
Anthracnose is a common fruit disorder affecting primarily ripe fruits. Lesions appear first as sunken, circular spots that deepen and become dark in the middle. The lesion often takes on a “bull’s eye” appearance due to the concentric ring effect of the enlarging lesion. Water splashed on the fruit during rains or irrigation carry the fungal spores to the fruit.

Control:
Crop rotations, fungicide sprays.

 

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Black mold in ripe tomato

Symptoms:
Numerous fungi cause fruit rots on tomato. Lesions may be superficial, or black or brown sunken areas that extend into the internal fruit tissue. Lesions often occur near the stem end scar.

Control:
Fruit should be kept off the soil and surface wetting should be minimized. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.

 

 

 

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Sour rot, ripe tomato

Symptoms:
Numerous fungi cause fruit rots on tomato. Lesions are water-soaked, and may have a white scummy growth in the cracks. Lesions often occur near the stem end scar.

Control:
Fruit should be kept off the soil  and surface wetting should be minimized. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.

 

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Alterneria canker, ripe tomato

Symptoms:
Symptoms of Alternaria canker appear on stems, leaves and fruit. Brown or black necrotic lesions are usually visible on plants from which infected fruit are picked. Fruit are infected when green, but symptoms persist into the ripening period. Sunken grayish lesions are present on fruit.

Control:
Fungus overwinters in crop residue and is easily spead by wind. Wounding of young plants (by mechanical damage or pruning) provides an entry site for infection. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.

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Cottony leak, ripe tomato

Symptoms:
Numerous fungi cause fruit rots on tomato. Large areas of the fruit appear water-soaked, with off color darker or lighter patches. Fruit may appear intact until touched. Handling usually punctures skin and internal watery tissue escapes.

Control:
Fruit should be kept off the soil and surface wetting should be minimized. Furrow or drip irrigation is preferred over sprinkler irrigation. Preventative fungicide sprays may be required if a “zero tolerance” for defects production system is needed.

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Cloudy spot, ripe tomato

Symptoms:
Fruit are covered with white or yellow flecks and patches that occur in the tissue just beneath the skin. Peeling fruit in the affected areas reveals white corky (not red) tissue.

Control:
Stink bugs often attack tomatoes from surrounding weeds. Feeding on young fruit is barely noticeable, but improper ripening and blemishes develop as fruit matures. Use a recommended insecticidal program to control stink bugs.

 

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Spotted wilt, ripe tomato

Symptoms:
Fruit are malformed, with raised yellow, red, and green mottled bull’s eye rings. Plants from which fruit are harvested are stunted, with older leaves turning yellow. The virus is carried by flower and onion thrips that have carried the virus from infected weeds and ornamentals.

Control:
Elimination of plants that serve as hosts to thrips is the most important control measure. Clean cultivation, with special attention to border strips is important. Locate production away from large grain fields.

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Blossom rot, ripe tomato

End rot, ripe tomato

Symptoms:
Blossom end rot can affect fruit at all stages of development. The characteristic symptom is a progressive deterioration of the blossom end of the fruit, from a water-soaked appearance to a sunken, black, leathery lesion. While secondary fungal infections may occur, blossom end rot is a physiological disorder caused by calcium deficiency induced by water stress.

Control:
Careful water management practices are a key. Irrigation and/or mulching are important. Application of lime or calcium prior to planting may help. Liquid fertilization using calcium nitrate can be used for small plots.

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Early blight, ripe tomato

Symptoms:
Fruit damage caused by early blight is the appearance of sunken, leathery, dark lesions near the stem scar. Fruit become infected when green. This disorder is more commonly known as a foliar or stem disorder. Leaf infection is notable first on older leaves with the appearance of irregular brown necrotic lesions surrounded by an area of yellowing tissue. Early season damp rainy weather encourages infection, and the symptoms become noticeable rapidly with increasing temperatures in mid-season. Heavy dews and overhead irrigation can contribute to disease spread.

Control:
Crop rotations, fungicide sprays.

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See also: Peroxide treatment for plant diseases

Continue to tomato leaf problems

Go to Tomato insect invaders 

 

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