What is wrong with my tomato plants?

In this brief article, we will provide you with the answer to the question: “What is wrong with my tomato plants?”, and discuss how to treat the most common diseases of tomato plants. 

What is wrong with my tomato plants?

Tomato plants, like other plants, are exposed to maladies that are damaging to their growth and development. They have the potential to harm tissues or jeopardize the plant’s development at any stage, reducing both production and the quality of the harvested tomato.

Three tomato diseases demand special attention: late blight, septoria leaf spot, and leaf mold. These illnesses, produced by various fungi, are huge difficulties for tomato farmers who must respond swiftly.  We will discuss some of these common diseases of tomato plants:

Late blight 

Late blight can destroy a crop in a matter of days if it is exposed to excessive humidity and temperatures around 20 degrees Celsius. The fruit develops indentation dots as the leaves become light brown and papery.

The signs of this illness can be found throughout the entire plant. It first appears in the top half and has the potential to kill the terminal bud. Large black wet patches will form on the leaves, which will necrotize over time, creating the impression of “burning.”

Lesions on the stem are dark, nearly black, and brittle. The fruits, for their part, exhibit deformations and brown blotches while remaining solid inconsistency

Septoria leaf spot 

The appearance of tiny, round, white patches with black dots in the middle of the lesion on the leaves characterizes the illness. Severe infections also harm the stems, peduncles, and calyx. The fruits, on the other hand, are still nutritious.


Leaf mold

Leaf mold, also known as sclerotinia rot, is caused by a fungus (Sclerotinia sclerotiorum or Sclerotinia minor) that can induce seedling damping-off. However, the most severe damage is seen in mature plants during the blooming and crop closure periods.

How to treat the most common diseases of tomato plants?

Late blight control

For the chemical treatment of late blight to be more effective, weather conditions must be monitored to choose which product to administer at the appropriate time, preventing the disease from emerging in the crop and inflicting losses.

The appropriate timing to apply the fungicide is critical to disease control. Contact fungicide applications should begin when climatic circumstances are not yet favorable for the disease, before its manifestation, and should be continued throughout the crop cycle.

They have a quick absorption time of around 30 minutes and a protective span of about 10 to 14 days. This fungicide protects the entire crop, owing to its systemic and contact action, excellent control power, and minimal resistance risk.

Control of Septoria

As with late blight, foliar treatment of contact and systemic fungicides is routinely used to control septoria in tomato plants. Contact fungicides are designed to prevent the illness before it infects and manifests itself. The systemic ones are mostly utilized at the onset of the initial symptoms.

Fungicides based on triazoles, strobilurins, isophthalonitrile, dithiocarbamates, and cupric are often employed in this control and should be repeated at 7 to 14-day intervals if necessary.

Leaf mold control

Leaf mold is a difficult disease to eradicate, owing to the lack of resistant cultivars and the survival of S. sclerotiorum in resistant structures, which can survive in the soil for several years.

For these reasons, chemical control has been the most often employed method of control in tomato agriculture. However, chemical management must be used in concert with other measures for the fight against the mold to be more effective. 

Fungicide usage, for example, can be linked to the production of straw, which helps to minimize sclerotia in the soil.

Finally, it is critical to use a fungicide that is capable of controlling both septoria and white mold.

Finally, to increase the management of both septoria and white mold, a fungicide capable of treating both diseases in tomatoes must be used.

This is a contact and systemic fungicide that provides for increased application safety, especially under difficult climatic circumstances. It also serves as an unparalleled tool in resistance management, enabling improved productivity retention.

Check here tips for growing tomatoes at home.

Other FAQs about Tomatoes that you may be interested in.

Can dogs eat tomatillos?

Does roasting tomatoes reduce acidity?

Can you eat overripe tomatoes?

How long do tomato plants live?


In this brief article, we provided you with the answer to the question: “What is wrong with my tomato plants?”, and discussed how to treat the most common diseases of tomato plants. 


Gardening Know How. “Tomato Growing Problems: Problems With Tomato Plants And Fruit.” Accessed February 18, 2022. https://www.gardeningknowhow.com/edible/vegetables/tomato/tomato-plant-problems.htm.

Ihara. “Doenças do tomateiro: conheça as mais comuns e saiba como controlar,” January 29, 2021. https://www.canalrural.com.br/ihara/doencas-tomateiro-como-controlar/.

Vamos Comer Melhor. “5 dicas para quem quer plantar tomates em casa,” September 15, 2017. https://vamoscomermelhor.com.br/5-dicas-para-quem-quer-plantar-tomates-em-casa/.