The main trigger for late blight is often rainy weather, in which the tomatoes are left permanently unprotected. Measures against the fungal disease must be taken before the first signs of the disease.
How can you prevent and combat brown rot on tomatoes?
To avoid brown rot on tomatoes, you should ensure a regulated water balance, a large planting distance and fertilization. You can also thin out the foliage and plant resistant varieties. Infected plants and fruits should be completely removed and disposed of with residual waste.
How is brown rot recognized and combated?
Late blight is noticeable through dark brown-gray spots on leaves. In the later stages the fruits develop brown spots. Brown rot cannot be controlled. The disease can be prevented through a regulated water balance, large planting distances, fertilization and thinning out foliage that is too dense. Remove and dispose of infected plants completely so that surrounding ones do not become infected.
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Infestation first appears on thelower leaves, which develop brown spotsand wilt over time. The same thing happens to thefruits- they getbrown spots, regardless of whether they are ripe or not yet ripe. The fungus also damages thestem, on which brown-black areas formWet weather significantly promotes infection and spread.
Eye blight extends to both the leaves and fruits of the tomato plant
Fruits
Yellow, green or red tomatoes have the same damage. They usually get light brown or yellowish spots on the upper half. While they are still hard in the early stages, the discolored areas gradually soften until they are mushy and rotten.
leaves
The leaves turn brown-black starting from the tip. Spots form that are blurred and appear moist. Over time, the entire leaf wilts until it eventually falls off. The underside of the leaves reveals a whitish coating, similar to that of powdery mildew. From this point on, the entire plant is usually affected.
How can early blight and brown blight be recognized?
The initial stage of late blight can usually be observedon the lower foliage:
- blurred gray-brown spots
- white down on the underside of the leaf
- Stem turns black in places
- rotting tomato fruits
The fungal infection is most likely caused by infected potato tubers. For this reason, tomatoes and potatoes should not be planted in crop rotation and should not be direct neighbors. In spring, the fungal spores spread through the ground and air, infecting the tomato plants. In the advanced growth stage of the plant, the first characteristics usually appear on the leaves.
What helps against late blight on tomatoes?
All parts of the tomato plant should bechecked regularly for brown spots. Early detection of acute late blight enables countermeasures. And if you had to deal with late blight in the previous year, preventative methods such as spraying with home remedies and protection from the weather are recommended.
Home remedies
Before you get the chemical club out of the cellar, we recommend using sustainable home remedies. The tomato itself, the bed and, last but not least, people also benefit from ecological treatment. That's why chemical sprays should always be used behind equally effective home remedies.
Acute treatment with home remedies
Decoction from field horsetails: As a preventive measure, the decoction should be sprayed onto the leaves at regular intervals from spring to summer. If a slight infestation is noticeable, all parts of the plant should be sprayed three days in a row. Alternatively, a ready-made field horsetail broth can also be used. The concentrate from the Brandling brand is available in a 3 L canister for around 25 euros.
Sage tea with baking soda: If the infestation is already advanced, sage tea with baking soda can stop the fungus. To do this, sage is boiled like tea with hot water and left to steep for about 10 minutes. After cooling, two teaspoons of baking soda are added to the infusion. Stir everything well, pour into a spray bottle and spray the plant until it is dripping wet.
Preventive measures with home remedies
Spraying with skimmed milk: Mix 100 ml of skimmed milk with a liter of water. Once mixed well, the solution can be sprayed generously onto the plant. The microorganisms in milk create an inhospitable surface for all kinds of fungi without harming the tomato itself.
Spraying with baking soda: Probably the most cost-effective method to sustainably protect tomato plants from fungal attack. For the correct mixing ratio, 8 g of baking soda are dissolved in 1 L of water. The liquid can then be sprayed onto the leaves using a spray bottle.
Sprays
If the worst-case scenario occurs - late blight attacks the entire bed or greenhouse - chemical sprays are usually the last resort. The worst can be prevented with the COMPO fungus-free (€17.00 at Amazon). For around 15 euros you get 20 ml of the highly effective fungicide, which, when diluted, produces 33 liters of spray water.
Are the fruits affected by late blight still edible?
Even if the tomato of a plant suffering from late blight still looks edible, it may already be infected with the pathogen Phytophthora infestans. This releases toxins that can be carcinogenic. We strongly advise against consumption. Since the pathogen is heat-resistant, cooking or frying does not help. Dispose of the fruits and affected plant parts in the residual waste (source: Federal Environment Agency).
How can late blight and brown blight be prevented?
Apart from sustainable household products that are sprayed on the foliage and fruits, the location, the variety and, last but not least, the care are crucial to avoid infection with late blight. A happy plant is a he althy plant!
Selection of location
Potatoes should be planted as far away from other nightshade plants (this includes tomatoes) as possible. The egg fungus Phytophthora infestans “hibernates” in the roots of potatoes. This dissolves in the soil and is transported to nearby plants via splash water and wind. The further away the tomato and potato are from each other, the lower the chance of infection.
Planting spacing
In addition, tomato plants should be planted about 70-80 cm apart from each other. On the one hand, this gives the tomatoes more space to grow so that infected leaves do not touch each other. On the other hand, the distance between the bushes improves the evaporation of water.
Sunny place
Everyone knows that tomatoes love the sun. But a sunny spot not only ensures sweet, ripe fruit, but also promotes the evaporation of water. The fruits need at least six hours of sun for he althy growth and dry leaves. The sensitive plants don't like rain or watering from above.
Resistant tomato varieties
Although breeders around the world are doing their best, there is no tomato variety that is resistant to late blight. However, there are naturally particularly resilient varieties of wild tomatoes. There are also one or two varieties of the refined varieties that, on average, can deal better with fungal diseases.
Wild Tomatoes
The fruits of the Humboldt tomato (Solanum humboldtii) do not go anywhere in the world, but they almost certainly end up in salads. They are about the size of cherry tomatoes and have a unique berry flavor. If you like it even more “original”, you should consider the currant tomato. It is much smaller and has a mildly sweet taste. What both varieties have in common is their high resistance to late blight.
Refined Tomatoes
The selection of cultivated tomatoes is significantly larger (and more colorful). The Primabella variety provides a good mix of popularity and resistance. The robust cocktail tomato tastes tangy and sour and is therefore often grown for a pure snacking experience. Lots of pulp and colorful sub-varieties make De Berao tomatoes a favorite of sauce specialists. The cut-resistant Phantasia F1 is ideal for salads and Italian cuisine.
Care
Preventative care essentially includes three aspects: rain protection, correct watering and rooting out. So that you don't have to constantly stand with an umbrella by your tomatoes, we recommend either a location under the roof or the construction of a rain roof. However, when it comes to watering and pinching out, you can't avoid paying attention every day.
Rain protection
Mushrooms need moisture to spread and grow. Therefore, the benefit of rain protection is self-explanatory: keep the tomato foliage as dry and fungus-free as possible. To do this, either look for a covered (but still sunny!) place for the tomato to plant or build a small roof in the bed.
Proper watering
Watering from below literally doesn't mean everything is in order. A hard jet of water on the soft soil can quickly create splashes that land on the lower parts of the plant. There are many pests in the soil, which – when well moistened – find their way to the tomato.
Pot with a hole in the bottom: A clay pot with a hole in the bottom is inserted in the immediate vicinity of the root of the tomato plant and buried up to the edge. The irrigation water is therefore only added to the pot, which releases the moisture evenly into the soil.
Casting ring: The plastic rings, which cost around 10-20 euros, work on the same principle as the simple pot with a hole. However, when placed in the ground, the stem is also surrounded by its personal moat, which keeps pests such as snails away.
Olla: An olla is similar to a clay pot with a hole in the bottom, but is a closed vessel. The water is continuously released into the soil as the soil becomes dry. The advantage of the Olla is its capacity. With up to 6 L you can keep 1 m² of bed area sustainably moist even during dry periods and supply several plants.
Picture and defoliation
There are two types of shoots in tomatoes: the fruit-bearing ones and the stingy ones. The latter form exclusively in the armpits between the trunk and the first-mentioned growth shoots. They are stingy because they do not produce fruits, only leaves. Therefore, the stingy shoots should be removed, which promotes ventilation.
Same location the following year despite brown rot?
The old location has several disadvantages. The risk of infection there is generally high because a plant has already been infected. There may be a potato plant in the neighboring garden that infected its own tomato through the wind (and through the fence). In addition, the soil at the old location is contaminated by the infection.
Brown rot in the greenhouse: replace soil or not?
The soil in the greenhouse does not need to be replaced despite an infestation. However, it is important to mulch well and incorporate fresh substrate into the soil. Poles and cords that served as climbing aids must be cleaned with hot water or destroyed.
Brown rot in the bed: Same location the following year?
As a preventative measure, it is good to choose a different location. However, due to the usually limited space in the garden, new substrate can be incorporated - as in the greenhouse - and the soil can be treated by mulching and fertilizing. This adds new nutrients to the soil.
Stem rot, fruits brown – Similar diseases
Not all brown spots on the fruits and leaves have to be caused by late blight. There are other tomato diseases that have similar symptoms. These include stem rot and blossom end rot.
Stem Rot
Stem rot can be recognized by the brown spots on the trunk of the tomato plant. The fungus Didymella lycopersici is the trigger. Unlike late blight, the trunk first becomes mottled and discolored. Black, bulging marks form in the bark. But the leaves and fruits also become rotten. Find out about black spots on tomatoes.
Causes: The fungus enters the plant via splash water through injuries or breathing openings. There the pathogen first spreads via the channels, which then show the corresponding symptoms of the disease.
Symptoms: Black, bulging spots on the stem are the first to become visible. The fungus then spreads to the leaves, which have circular brown spots that become progressively paler. Dark dots appear inside the circles. The fruits become rotten from the base of the stem.
Prevention: Resistant varieties that come from he althy seeds are less likely to suffer from stem rot. In addition, great importance should be placed on hygiene on the bed. When removing the bark, be careful not to cause major damage to the bark, as this acts as an entry point for pests.
Blossom end rot
Blossom end rot is not a classic disease, but rather a sign of a nutrient imbalance. The tomato fruits become rotten around the flower base. There is a lack of calcium, which is responsible for stable cell walls. As a result, the skin of the fruit becomes softer and softer until it eventually collapses. The underlying tissue becomes putrid and soft and then hardens.
Blossom end rot can be recognized by sunken and dark areas on the fruit
Causes: If blossom end rot occurs, there is a lack of the important plant nutrient calcium. It may be that there is too little in the soil. The use of too much nitrogen fertilizer is often the cause. This causes the tomato plant to grow so quickly that it can no longer supply other minerals.
Symptoms: Small black dots can suddenly be seen on the former flower base of the tomato fruit. After a short time the skin turns brown, soft and sinks. Then the tissue becomes hard and feels leathery.
Prevention: If the plant has excessive growth, nitrogen fertilization should be suspended for a week or two. If this is not the case or the symptoms do not improve, the tomato can be given primary rock flour. A special calcium fertilizer is also suitable, which can also be sprayed onto affected parts of the plant. We recommend the liquid calcium fertilizer from Wuxal.
FAQ
Can tomato plants with brown rot be put in the compost?
No, tomato plants with late blight are not allowed in the compost as the spores survive for a long time.
Does copper wire help with late blight?
No, scientifically, the use of copper wire could neither prevent nor acutely help with late blight.
What helps against late blight and brown blight?
Good prevention helps the most. In addition to treatment with home remedies, this primarily includes appropriate care.
How does late blight occur?
Late blight is caused by a fungus called Phytophthora infestans. The pathogen gets to the tomato plant through touch, wind or splash water.
