Tomato brown rot: what can you do about the disease?

Brown spots on tomato plants? The fruits are rotting on the stalk? The leaves turn brown? Maybe it is tomato brown rot. Although plants infected with this disease die relatively quickly, you can still save some of your tomatoes thanks to these tips.

Recognize brown rot in tomatoes

when to spray tomatoes against brown rot

Late blight is a disease caused by the fungus Phytophthora infestans that can affect both tomatoes and potatoes. Late blight can occur at any time during the growing season, especially when the weather is cool and humid. Long periods of hot drought can slow but not stop the spread. Both green and ripe tomatoes can be infected.

why do tomatoes get brown rot

The pathogen not only destroys the fruits of the plants it infects, but can also spread very quickly and widely and cause devastating damage in your garden if it is not combated in good time and correctly. Worst of all, late blight can hibernate, which means it can reappear next year even after a cold frost if the plants and soil that contain the pathogen are not removed.

It is difficult to identify brown rot in tomato plants in the early stages of the disease. Many farmers do not immediately realize that their crops are infected. If brown spots appear on the leaves, this can be mistaken for leaf spot disease (Alternaria tomatophila).


This is how you can recognize tomato rot:

  • The leaves have large, dark brown spots with a green-gray margin that are not limited by the main veins of the leaf.
  • These spots enlarge until the entire leaf or stem turns brown and dies. Dead leaves usually stick to the stems.
  • Dark brown, irregular spots cover large parts of the fruit. The stains can become mushy when secondary bacteria enter.
  • When the air humidity is high, a thin, white coating of mold forms on infected leaves, fruits and stems.

It’s not uncommon for tomatoes to be damaged inside as well. In this case, the disease develops without any visible signs. The buds ripen quickly and fall off. A lesion on the pulp is only discovered when the vegetable is cut open.

Brown rot – Can you eat the tomatoes??

How can you recognize brown rot in tomatoes?

After the discovery of late blight in tomatoes, gardeners wonder whether ripening tomatoes are still edible. Opinions are divided.

“The unaffected parts are likely to be safe to eat. Tomato pieces without symptoms of disease are unlikely to pose a health risk to the consumer, ”says Dr. Margaret McGrath, a plant pathologist at Cornell University who specializes in the disease.

Barbara Ingham, food safety specialist at the University of Wisconsin Extension, however, advises consumers to resist the temptation to eat sick tomatoes or potatoes.

“Since the consumption of fruit that has been infected by late blight has been shown not to be harmful, it may be tempting to simply cut off the infected part. But the fruits then taste bitter and may harbor other organisms that can cause food infections.

which tomatoes are resistant to brown rot

Ingham also advises that diseased fruit, even if the infected part has been removed, should not be preserved or frozen. “Don’t be tempted to pickle or preserve infected tomatoes,” says Ingham. “The virus can change the acidity of tomato fruits, which is crucial for the safe preservation of tomatoes. However, healthy tomatoes can be safely preserved or even frozen, ”she says.

What if you have undamaged tomatoes growing on plants whose leaves, stems, or neighboring fruits show signs of infection? These can be safely eaten and even preserved, says Ingham.

Why do tomatoes get brown rot?

Prevent late blight and brown rot in tomatoes

Tomato brown rot is most commonly caused by the following reasons:

  • Often the disease is actively manifested with an intense change in weather. If one month is cool and rainy and the next hot and dry, the onset of the disease is inevitable.
  • Bad soil. Sometimes gardeners don’t even know the pH of the soil on their property. If the pH is too high or too low, the tomatoes will rot.
  • Calcium deficiency is a problem for most gardeners. The experienced gardener knows that tomatoes must be fertilized with calcium nitrate during their growing season to prevent brown rot.
  • Large quantities of nitrogen fertilizers lead to late blight.

To protect your vegetable garden from disease, you need to know how to deal with these problems and how to prevent tomato rot.

What to do with tomatoes brown rot?


So what should you do if you discover latex in your garden? Unfortunately, you cannot “cure” this disease, but you should uproot and remove the plants with late blight symptoms immediately. This will protect your neighbors’ gardens and local farmers.

Here’s what you should do:

1. Remove the infected plants: Remove infested plants, pack the leaves and unripe tomatoes in black garbage bags and dispose of them with household waste. Do not try to compost infected potato or tomato plants. Most compost heaps aren’t hot enough to kill the spores and you risk re-infecting your plants the next season. You can read more about this here.

tomato diseases brown rot

2. Prevent the spores from overwintering: The late blight can only survive on living tissue. The winters in the north kill any spores that can be found above the ground on trellises and tomato cages. However, late blight can overwinter in plant remains, seeds and potato tubers below the frost line. To be on the safe side, at the end of the season you should remove all plant debris, buy fresh seeds for the next year, and remove any potato and tomato plants that sprout from the ground.

3. Make a fresh start next year: At this point we can only limit our losses and hope for a better growing season next year.

Combat brown rot on tomatoes

what to do when tomatoes have brown rot

In the fight against this disease, you can use several proven methods to prevent it from spreading.

Soda against brown rot

At the first signs of damage to the plants, it is recommended to spray the leaves with a 1-2% sodium bicarbonate solution. To do this, 10 to 20 grams of baking soda are dissolved in 10 liters of warm water.

Use of wood ash

Use of wood ash in tomatoes

Remove all infected fruits and leaves and treat the remaining plants with wood ash. The ash contains phosphorus, calcium, magnesium and boron and also acts as a fertilizer. How to prepare wood ash brew:

  • Put 100 grams of ash in 10 liters of boiling water.
  • Then let the mixture cool down and then strain it off.
  • Pour the solution into a plant syringe and treat the fruits, leaves and roots.

what to do with tomatoes brown rot

Calcium chloride and calcium nitrate

External use of calcium chloride and calcium nitrate can correct a calcium deficiency and stop the development of putrefactive lesions. To prepare the solution you will need:

version 1.

Calcium nitrate – 5 to 10 grams

1 liter of water

Variant 2.

Calcium chloride – 30 to 40 grams

10 liters of water

First you should moisten the soil and then spray the tomato plants with the calcium solution.

Superphosphate fertilizer strengthens the plants

Superphosphate fertilizer strengthens the plants

Phosphate additives help stop brown rot from developing and prevent it from spreading to healthy shrubs. Superphosphate has been shown to be effective. To prepare the base you will need:

3 liters of water

15 to 20 tablespoons of superphosphate

Since the fertilizer dissolves more easily at high temperatures, bring the water to a boil and pour the granules into it. Occasionally stir the solution throughout the day until the granules are completely dissolved. This way you get a mix with a light texture.

To get the remedy for the treatment of tomatoes against brown rot, put 150 ml of the basic solution in 10 liters of water and add 20 g of nitrogen fertilizer as a necessary additive.

Prevent tomatoes from brown rot

Tomato varieties resistant to brown rot

The best way to combat late blight on tomatoes consists primarily of preventive measures. These are essentially:

  • select resistant tomato varieties
  • disinfect the seeds before sowing
  • prepare the soil before planting the plants
  • to pay attention to regular watering

If the tomato varieties are resistant to brown rot, this is usually indicated by the manufacturer on the packaging. The most resistant types of tomatoes are:

  • Philovita
  • De Berao
  • Resin fire
  • Phantasia
  • Mountain Magic (F1)
  • Plum shelf (F1)
  • Philovita cocktail tomato (F1)
  • Mountain Merit (F1)
  • Tomato Fantasio (F1)
  • Sky-striker
  • Legend
  • Wapsipinicon Peach
  • Lemon drop
  • Pruden’s Purple

Seeds in potassium permanganate

The fight against the pot column of tomatoes begins with the Disinfection of the seeds before sowing. If the seeds are bought from specialist retailers, this treatment is usually not necessary. If you are using your self-harvested seeds, you can disinfect them with potassium permanganate. The planting material is soaked in a 3% potassium permanganate solution for about half an hour, then washed off under warm running water and dried.

Proper preparation of the soil before planting the tomato plants also helps protect the fruits from brown rot. Experts recommend adding 2 to 3 tablespoons of fine lime or ordinary chalk to the earth.

Wood ash used as fertilizer when planting tomato plants in the ground

The usage of Wood ash as fertilizer when planting the tomato plants in the ground also helps to prevent late blight on the fruit. To prevent the disease, put a coffee cup of ash in each planting hole.

When growing tomatoes it is important for one timely watering to care. Drought reduces the plant’s calcium supply, which can lead to brown rot. Since calcium is better absorbed at night, it is advisable to water in the evening. A layer of mulch helps to keep the moisture in the soil longer.

Tomato brown rot fungicides

Tomato brown rot fungicides

Fungicides can help protect healthy, uninfected plants if they are sprayed regularly on all parts of the plant. A copper finingicide is less effective, but probably the best choice for organic gardeners. In all cases, you need to apply the fungicide before infection for it to be effective. Always follow the directions on the label when using fungicides.

  • Organic fungicides. Treat the plants with a copper fungicide that you can buy online, at a hardware store, or at a home improvement store. Follow the directions on the label. You can apply it once a week and after each rain until the leaves drain. Serenade® ASO also belongs to the group of biofungicides.
  • Chemical fungicides. Some gardeners prefer chemical fungicides, such as Ranman and Signum, which are effective in inhibiting fungal growth. You can also opt for crop protection products with the active ingredient mancozeb, although they have a longer waiting time before you can safely harvest the tomatoes.

Once the late blight is there and progressing, it becomes more and more resistant to biofungicides and fungicides. Treat the plants as soon as possible and on a specific schedule.