Tomato leaf problems

If you’ve taken the time to read through our section of green and ripe tomato problems you’re probably wondering by now why in the world would anyone bother growing tomatoes.

Over simplified it’s—- Taste, texture, nutrition and flavor.

This section on tomato problems is broken into three segments. Disease, virus and physiological problems.

LEAF diseases:

Leaf alternaria canker

Symptoms:
Symptoms of Alternaria canker appear on stems, leaves and fruit. Large areas of the leaf lamina between veins is killed, leading to leaf curling and eventual death of the entire leaf.

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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Leaf 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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Leaf bacterial speck

Symptoms:
Bacterial speck is widely distributed. Symptoms may appear on any plant part. Leaves of infected plants are covered by small, dark brown, irregular patches of necrotic 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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Leaf 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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Leaf early blight2

 

Leaf early blight1

Leaf blight1

Symptoms:
Leaf symptoms of early blight are large irregular patches of black, necrotic tissue surrounded by larger yellow areas. The leaf spots have a characteristic concentric banding appearance (oyster-shell or bull’s eye).

 

Control:

Minimize wetting of the leaves by using drip or furrow irrigation. Infection occurs rapidly during periods of warm, wet weather. Fungicide sprays control the disease effectively.

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Leaf gray spot

Symptoms:
Small brownish-black specks first appear on undersides of leaves. These later develop into larger necrotic areas, and the tissue often falls out, leaving a shot hole type appearance. Spots may be surrounded by a yellow halo. Yellowing, leaf drop, and defoliation may occur in severe cases.

Control:
The fungus can survive from year to year on Solanaceous weeds, so weed control is important. Leaf moisture from rains or dew increases disease severity. Fungicides may be used as recommended. Many commercial varieties are resistant.

 

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Leaf 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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Leaf mold

Leaf mold

Symptoms:
Symptoms appear as light green patches on upper surfaces of older leaves. Underneath the leaves in these areas, a purplish or olive-green patch of mold growth is visible. Infected leaves turn yellow and drop off the plant.

Control:
Fungus is spread is by wind currents. High humidity and warm temperatures encourage mold growth. The problem is especially severe in greenhouses, where adequate ventilation and air movement reduce disease severity by lowering moisture at the leaf surface. Fungicides are effective controls.

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Leaf mildew

Symptoms:
Powdery mildew is first noticed on older leaves as a yellow spotted appearance, that upon closer inspection has a whitish-gray powder on the surface. The leaves will eventually die, but usually remain attached to the stem. The disease is worse under warm, dry conditions.

Control:
Sulfur dusts or wettable sulfur sprays are effective preventative controls. The established disease will require one of the labelled mildew fungicides.

 

 

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Leaf septoria

Symptoms:
Circular water-soaked lesions occur first on older leaves. These spots eventually turn brown with gray centers and die, and if infection is severe enough, the entire leaf will die.

Control:
The fungus can survive in the debris from previous crops and/or weeds. Clean cultivation is important. The disease can be controlled by labelled fungicides.

 

 

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Leaf verticillium wilt

Symptoms:
Older leaves on verticillium wilt-infected plants begin wilting at leaf margins and turn yellow, then brown. Plants are stunted and wilting is not alleviated by watering. A light tan discoloration of the stem can be seen in cross section.

Control:
The disease develops more rapidly in cool weather. The most effective control is planting one of the widely available resistant varieties.

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VIRUSES

Cucumber mosaic virus wilt

Symptoms:
Virus-infected plants are stunted, often with poorly expanded leaves. Plants are bushy in appearance. Leaves may be mottled, and often have a “shoestring” appearance. Fruit are small and misshaped.

Control:
Aphids often are virus vectors, so an attempt to control the aphids is the first step. Eliminate weeds and remove infected plants from the field as soon as they are seen.

 

 

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Leaf 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. Leaves show yellow speckling, with dark streaks along the petiole. Growing tips of the leaves may die. 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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PHYSIOLOGICAL problems

Salt damage

Symptoms:
Excess salt accumulates in the tomato plant in the older leaves. Leaves turn yellow, and will eventually fall off. The plant is stunted and not vigorous, but other symptoms may be lacking. Tomatoes are relatively salt tolerant.

Control:
Salt damage is rarely encountered in field situations except under very poor water quality situations. Salt damage may become a problem in pot culture or in hydroponics. Select salt tolerant varieties.

 

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Phosphorous deficiency

Symptoms:
Phosphorus deficiency is most often manifested as purpling of the leaves, particularly the leaf veins. In severe cases the whole plant may take on a purple hue. Tomato roots growing in cold soil, either in the greenhouse or the field, take up phosphorus poorly. Deficient plants lose vigor and yield poorly.

Control:
While phosphorus deficiency due to improper fertility may be a problem in hydroponic, pot culture, and some sandy soil conditions, it is most likely a result of cool root zone temperatures. Plastic mulch will alleviate the problem in early field plantings, and a balanced liquid feed fertilizer will alleviate the problem in greenhouse and pot culture.

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Go to Tomato diseases

 

Go to Tomato insect invadersĀ 

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