Dark brown to black spots on tomato fruit and leaves indicate a wide variety of diseases. Depending on the disease status, your plants will be treated differently.

Table of Contents

Show all
  1. the essentials in brief
  2. Black spots on tomatoes and leaves - Three possible diseases
  3. Eat tomatoes with black spots or not?
  4. Prevent tomato diseases with nettle manure
  5. FAQ

    6. the essentials in brief

    • Blossom end rot, late blight and late blight, but also a phosphorus deficiency can be the cause
    • Close inspection of the entire plant is required to take correct and effective action
    • Fruits are often still edible despite the discoloration
    • Preventively avoidable through species-appropriate care and comprehensive fertilization

    Black spots on tomatoes and leaves - Three possible diseases

    There are many causes of black spots on the fruit and leaves of the tomato plant. Therefore, for a correct determination of the disease and subsequent treatment, an extensive examination of the entire bush is required.

    blossom end rot

    Blossom end rot is one of the most common diseases of fast-growing vegetables, including tomatoes, peppers and zucchini.

    Blossom end rot can be recognized by sunken and dark areas on the fruit

    Damage and identification features

    Leaves. The leaves are usually less affected by the rotting processes. Nevertheless, in addition to the formations on the fruits, there are slight deformations on the leaves on the same shoot.

    Fruit. Blossom end rot particularly affects ripening tomatoes, which have a brown to black spot around the base of the blossom. Over time, the spot continues to grow in size and droop inwards.

    Calcium deficiency as a trigger

    The mineral calcium is essential for building the cell membranes and thus the structure of the fruit and leaves. Due to the plant-internal line systems, the supply of the leaves is preferred to that of the fruits. As a result, the symptoms of deficiency are primarily found in the tomatoes themselves. In addition to a pure calcium deficiency, other causes can also lead to reduced absorption by the tomato plant:

    • excessive potassium or magnesium concentration
    • Soil pH highly acidic
    • imbalanced fluid balance of the plant

    Fertilize with calcium and other home remedies

    In order to compensate for an existing calcium deficiency as quickly as possible, the following remedies have proven themselves in practice:

    medium definition application
    algae lime Lime fertilizer made from coral and algae is sprinkled around the plant in powdered form, after which vigorous watering is required
    Calcium Effervescent Tablets chemically manufactured tablets crushing the tablets into powder and subsequent incorporation into the soil
    calcium carbonate known as garden lime (€9.70), concentrated calcium compound sprinkle in powdered form around the plant, then vigorous watering
    eggshells empty egg shells, which should be free of protein residue Soak the crushed shells of two to three eggs in a liter of water for several days, water the plant with the broth
    rock flour made of basalt or granite sprinkle in powdered form around the plant, after which vigorous watering

    Immediate action

    Undersupplied fruits that already have discolored areas should be removed from the plant. In addition, you should supply the plant with one of the aforementioned sources of calcium for a short time and ensure appropriate irrigation. This allows the plant to take care of the fruit that is still ripening and avoid infection with further diseases.

    prevention

    The basis for defending against blossom end rot is a healthy tomato plant with an intact immune system. In addition to the correct care in relation to the choice of location and irrigation, fertilization plays a particularly important role. The addition of a special fertilizer with a high calcium content is a proven preventive measure in addition to a complete fertilizer.

    Late blight and late blight

    Late blight is a fungal disease that occurs particularly in tomato plants grown outdoors.

    Late blight extends to both the leaves and fruit of the tomato plant

    Damage and identification features

    Leaves. The first signs of the fungal disease can be seen on the leaves, which develop misshapen brown-black spots. In addition, a white fluff can often be seen on the underside of the leaf, which is also commonly known as fungal turf. As the disease progresses, the leaves wither, and then dry up completely.

    Fruit. The fruits are only attacked in an advanced stage of late blight. The disease is symptomatic of rotten and mushy areas around the tomato that are brownish to greyish in colour.

    trigger

    Late blight is caused by the spread of Phytophthora infestans fungal spores by wind and rain. Basically, the pathogens can be found in almost any substrate, but they are inactive in the soil most of the time. When the spores are stirred up by strong gusts of wind or heavy rainfall, they get onto the leaves and fruits of the tomato plant and infect them.

    Immediate action

    The affected parts of the plant should be disposed of in the residual waste. You should refrain from adding it to the compost to avoid reinfection. In addition, the plant should be defoliated altogether. The tools used for pruning should be thoroughly cleaned before the next use to prevent infections on other plants. Fighting with a fungicide is often no longer promising when the symptoms are already recognizable.

    prevention

    In order to keep the spread of the spores as low as possible during the growth cycle of the tomato, a location that is protected from wind and rain should be chosen. You should therefore pay attention to the following tips when planting and caring for them:

    • Grow in a sheltered spot like a greenhouse
    • Minimum distance of 50 cm between the individual plants
    • Only water with a soft water jet and directly onto the root ball to avoid splashing water
    • Application of a fertilizer containing potassium to strengthen the plant tissue

    phosphorus deficiency

    The mineral phosphorus is essential for almost all metabolic processes in the tomato plant. In addition to its function as an energy carrier, which is important for the development of flowers and fruits, phosphorus also serves as a building block of DNA.

    A phosphorus deficiency can be recognized by the purple-black discoloration of the leaves, which runs from the outside inwards

    Damage and identification features

    Leaves. A phosphorus deficiency can be recognized without a doubt by the violet discoloration of the leaves, which runs from the edge of the leaf inwards. This is often accompanied by an overall stunted growth of the leaves in combination with deformations.

    Fruit. If there is a persistent phosphorus deficiency, in most cases neither flowers nor fruits form on the shrub. If you do find a few tomatoes, they are usually small and gaunt in shape.

    trigger

    The most common cause of a phosphorus deficiency is an insufficient supply of the mineral. In particular, heavy consumers, to whom the tomato plant is botanically assigned, need a consistently high amount of the vital nutrients for steady growth and a lush harvest. If you supply your tomatoes with sufficient phosphorus fertilizer, deficiency symptoms can also be caused by insufficient nutrient absorption. This can be caused by an outside temperature that is too low, but also by soil that is too acidic.

    Immediate action

    If an undersupply of phosphorus cannot be completely ruled out, the plant should be supplied with a slightly increased dose as a first step. Applying a liquid fertilizer directly to the leaves should prevent further leaves from discoloring. The already discolored leaves do not necessarily have to be removed from the plant, as they do not affect the growth of new healthy leaves. We also recommend separate cold protection, which protects outdoor plants in particular from the cool temperatures at night.

    prevention

    In order to avoid reduced nutrient uptake due to the cold, the tomatoes should not be planted out before mid-May or after the ice saints. In cool temperatures at night, a cover made of jute or fleece can also help. In addition, a possible phosphorus deficiency should be counteracted at an early stage by ensuring an adequate supply of nutrients when planting. Various natural fertilizers are suitable for both initial fertilization and ongoing fertilization. In addition to phosphorus, the fertilizers listed below also contain many other essential minerals.

    • ash
    • guano
    • horn shavings
    • horse manure

    You can find more recommended phosphorus fertilizers here.

    Eat tomatoes with black spots or not?

    blossom end rot. Despite the unappetizing dark spots, tomatoes infected with blossom end rot are still edible without problems. However, you should cut out the relevant areas generously before consumption.

    Late blight and late blight. Once late blight spreads to the fruits of the tomato plant, they are no longer edible. Among other things, the putrefaction processes are accompanied by a loss of taste, which makes them inedible. However, as long as only the leaves and stems are affected, the fruits are still edible.

    phosphorus deficiency. In principle, the tomatoes of plants that are burdened with a phosphorus deficiency are edible. However, in the case of acute deficiency symptoms, the shrub often produces no or only very small fruits.

    Prevent tomato diseases with nettle manure

    Nettle manure is known for its high level of effectiveness in repelling pest infestations. This is mainly due to the concentration of the minerals nitrogen and potassium as well as silicic acid, which also strengthen the plant's immune system.

    The production of nettle manure takes about two weeks, but is worth it due to the quantity produced

    The production and use of nettle liquid manure can be done in just a few simple steps:

    1. Pour 1 kilogram of fresh nettles with 10 liters of rainwater in a bucket and stir vigorously
    2. Cover the bucket with a wooden board or similar to protect the brew from environmental influences
    3. Stir the mixture daily for one to two weeks until no more bubbles appear
    4. Remove remaining plant parts using a sieve

    The manure should never be administered undiluted to avoid over-fertilizing the plant. Dilution in a ratio of 1:10 with rainwater and a maximum bi-weekly application are perfectly sufficient.

    FAQ

    What helps with blossom end rot?

    An already advanced disease with blossom end rot can no longer be treated in the already affected parts of the plant. It is therefore advisable to remove the externally changed fruits from the plant as quickly as possible and to supply the shrub with a fertilizer containing calcium.

    Are tomatoes with black spots edible?

    The extent to which black-spotted tomatoes are still edible depends on the disease in question. While blossom end rot and phosphorus deficiency have no effect on edibility, fruits affected by late blight should no longer be eaten.

    Why do tomatoes get black spots?

    The causes of discoloration of tomatoes are varied, but in most cases it is related to improper care of the plant and the resulting disease.

    What can I do about black spots on tomatoes?

    Tomatoes that have already discolored cannot be restored to their original state. However, by taking preventive measures such as applying fertilizers containing calcium and phosphorus, choosing the right location and general care adapted to the tomato variety, any diseases can be avoided.

Category:

Vegetable garden