Tomato leaf mold: how and what to treat

Diseases and pests

The scientific name for leaf mold is Cladosporiosis. This disease is also commonly known as brown spot. It typically affects tomatoes grown indoors. It poses no threat to plants grown outdoors, as temperatures are too low for it to spread. In the early stages, brown mold can be eliminated using folk remedies. In cases of severe plant infestation, fungicides are used.

Causes of the disease

Cladosporiosis is caused by the fungus Cladosporium fulvum Cooke. In a dormant state, the spores remain viable for 12 months. The colony can withstand low temperatures and prolonged periods without moisture. The fungus can overwinter in the soil without access to plant debris. With the arrival of spring, the pathogen reoccurs to the tomato crop.

Important!

The fungal conidia penetrate the soil to a depth of 10 cm. Therefore, when this disease appears, it is best to remove this layer of soil and replace it with fresh soil.

Soil contamination in greenhouses occurs through water, air, tools, and workers' protective clothing. Favorable conditions encourage the fungus to actively develop. The disease affects all crops and weeds in the greenhouse.

Leaf mold is sensitive to humidity. For the disease to thrive, humidity levels must exceed 80%. Ideal conditions occur when humidity in the greenhouse reaches 90-95%. High temperatures promote rapid reproduction and spread of the fungal colony. Weakened plants, stressed by sudden temperature changes due to improper ventilation or cold watering, are usually the first to suffer.

Signs of leaf mold

Cladosporiosis affects only tomato foliage. The pathogens do not infect other parts of the plant. This disease develops gradually:

The infection initially manifests itself during flowering. Irregular, yellowish-green patches appear on the lower leaves. On the underside of the leaf, a velvety, light-gray, mold-like growth develops in the affected area.
At the next stage, if left untreated, the disease spreads to the upper leaf layer. This disrupts photosynthesis, causing a deficiency of nutrients and affecting the condition of the fruits and stems.
In the final phase of the disease, the spots change color to yellow-brown and spread to the entire leaf blade. The gray coating turns brown. The leaves curl and die. The fungus then moves on to a new plant.

Sometimes the spots spread to the petioles or stems. This indicates a critical level of infestation. Such tomatoes are beyond saving.

Treatment

To successfully rid plants of Cladosporiosis, treatment must begin promptly. It's best if the spots are just beginning to turn yellow when they're discovered. Then, treatment is more likely to be successful, and the harvest can be preserved without loss.

If suspicious spots are discovered on leaves at any stage, they should be removed immediately. This should be done carefully to avoid disturbing the spores and increasing their spread. The leaves should be placed immediately in plastic bags and removed from the greenhouse. Infected plant parts should be destroyed by burning.

Treatment with folk remedies

These methods are effective only in the initial stages of infection. But even then, the measures taken may be insufficient. Then, within a few days, signs of infection on tomatoes will reappear. Folk remedies can be successfully used as a preventative measure to prevent the disease from reappearing in a greenhouse where it was eradicated last year.

To spray infected bushes and soil use iodine solutionTo prepare it, mix 40 drops of iodine in 10 liters of water. To effectively kill the fungus, the solution should soak the soil to a depth of 10 cm.

Important!

Tomatoes don't tolerate chlorine well. Therefore, chlorine-based solutions are not used to kill leaf mold during the ripening stage. However, this solution is recommended for treating the soil in the fall after harvest, if the tomatoes are to be uncovered for the winter. To prepare this solution, mix 10 liters of water, 40 drops of iodine, and 30 g of calcium chloride.

Treatment with dairy products also provides good results against brown spot. This recipe can use regular fresh milk or fermented milk. A solution prepared with whey is most effective. To prepare the solution, mix 10 parts water with 1 part of the chosen product. Adding 30 drops of iodine enhances the effect of the solution.

Cladosporiosis spores are killed by spraying the affected bushes with potassium permanganate. The solution is made from warm water and a few crystals of potassium permanganate until it turns pink.

A wood ash infusion is suitable for spraying plants and watering the soil. To prepare it, mix 3 liters of water and 0.3 kg of wood ash and boil for 20 minutes. Then add water to fill a 10-liter bucket and let it steep for 3 days. For better adhesion, add a small amount of liquid soap or shampoo. This solution is used to water the soil and spray infected bushes. It is most effective to alternate treatments with the ash solution and potassium permanganate solution once a week.

Treatment with chemicals

When the disease is detected at an advanced stage, folk remedies won't help. In this case, treating the plants with fungicides is the most reliable option. It's important to apply the treatment three weeks before harvest. Otherwise, traces of the chemicals will remain in the harvested tomatoes.

For treatment, preparations effective against are suitable late blightBravo, HOM, Abiga-Peak, Poliram, and Zineb have proven highly effective. They are diluted and applied according to the included instructions. The recommended time between treatments is strictly observed. The first spray is applied immediately after the first spots are detected on the leaves. A second spray is applied after two weeks. The final treatment is 21 days before harvesting ripe fruit.

Agrotechnical methods

These methods can be used if the disease strikes tomatoes at the ripening stage, when chemical treatments are no longer possible. In this case, the active spread of the fungus can be suppressed by creating unfavorable conditions.

Important!

The use of agricultural techniques is recommended at any stage of Cladosporiosis development. They do not harm plants, but significantly increase the chances of eradicating the disease.

Methods of influence:

Humidity levels are reduced to 65%. At this level, the fungal colony stops developing. Tomatoes are not harmed in this situation.
The temperature under the greenhouse cover is increased to 25-30 degrees Celsius. Tomatoes thrive in these conditions, but the fungal colony cannot survive. Temperatures above 30 degrees Celsius should not be exceeded. This degrades fruit quality and reduces the number of ovaries.
All weeds are pulled out. Fungus develops on them and then infects crops.

Prevention

To prevent infection, create conditions in the greenhouse that prevent the fungus from surviving and actively spreading. Until the plants bloom, maintain the following temperature:

from +18 to +19 degrees during the day, if the weather is cloudy;
from +20 to +22 degrees during the day on a sunny day;
from +16 to +18 degrees at night.

Once flowers appear on the bushes, the temperature is adjusted. Daytime temperatures are maintained at 26 to 30 degrees Celsius, and at night, they are reduced to 14 degrees Celsius. Soil humidity is maintained at 80%, while the air humidity is 65%. The greenhouse is regularly ventilated, but cold drafts are avoided.

Tips to help prevent the spread of brown spot:

To ensure proper ventilation, sufficient light and nutrients, tomatoes are planted at the distance recommended in the variety description.
All plant residues, including roots and weeds, are collected and burned.
At the end of the season, after harvesting and destroying plant debris, the greenhouse is disinfected with sulfur checkers or formalin.
Plants are watered with a moderate amount of water in the morning or evening.
The beds are mulched to reduce the spread of weeds.
Unnecessary shoots and leaves are cut off.
Weeds are pulled out in time.
After watering, the greenhouse is ventilated.

To generate additional profits in heated greenhouses, a new crop is often planted immediately after the previous harvest. This creates favorable conditions for the spread of infection. If the plants are infected with leaf mold, it will take at least 10 months for the spores to die.