Alternaria in tomato plants: all you need to know to control the disease

Alternaria affecting tomato plants is one of the most common diseases with the greatest impact on this crop worldwide. We are talking about one of the main crop pathogens in general. This disease is caused by the fungal pathogen of the same name, which has a wide variety of species. 

As a polyphagous fungus it feeds on the different plants it attacks and can cause significant economic losses and reduced crop yields. Prevention and control of the disease is fundamental, based on strategies that use fungicides, among which those of biological origin such as the fungicides developed by Seipasa.

Alternaria or early blight (black spot) in tomato plants appears when the spores germinate inside the plant. The infection can be direct or via the presence of small fissures on the plant's epidermis, caused by small lesions or bites by parasitic insects.

The germination of the spores and the subsequent propagation of hyphae occurs in conditions of high humidity and warm temperatures. The risk of suffering an attack of Alternaria in tomato plants is greater in the rainy season. Humid conditions favour the germination of spores, which are quickly disseminated by the action of the wind, rainwater splashes or due to the action of the spray systems used in irrigation. The plant is also more vulnerable to the attack of Alternaria when it undergoes a period of stress, such as when fruiting occurs or due the presence to abiotic factors. 

Alternaria in tomato plants forms resistant structures that can survive in the soil and in plant waste. The fungal conidia and mycelium hibernate in this medium and can also persist in crop remains. Thus, it is of utmost importance to get rid of all remaining infected plant material after pruning the plant back, as well as disinfecting all the pruning tools used. 

Alternaria or early blight in tomatoes particularly affects the aerial part of the plant. It is most clearly visible when the plant is most leafy. Lesions on leaves appear as dark, coffee-coloured or black spots (blight), with a series of concentric rings surrounded by a yellowish halo. The fungus can attack the plant stem as well as the fruit, where the lesions cause spots and sometimes dark or greenish splits that can appear on both mature and immature fruits. 

In practice, Alternaria in tomato plants causes wilting and leaf fall, and in the most severe infections, the plant's death. 

Fungicides to control Alternaria

Preventive measures must be adopted to control Alternaria in tomato plants.  Early detection of blight is extremely important to prevent propagation of the disease.  At this stage it is essential to monitor plants constantly to determine their evolution before taking other control measures.  

Controlling the disease involves finding solutions that are effective against the pathogen, that respect the environment and that are authorised and registered for their use and application.

Fungisei is a fungicide and bactericide of microbiological origin, developed and registered by Seipasa for the control of fungal diseases in different countries in the world, such as Mexico, USA, Turkey, Morocco, and Peru.  It is also in the process of obtaining registration in other countries.  Fungisei is recommended for the control of Botrytis, Oidium and Alternaria (early blight) in a wide range of crops, including tomatoes. 

Fungisei is developed from Seipasa's exclusive Bacillus subtilis strain, a highly effective fungicidal microorganism for the control of different diseases. The key to this product's action lies in its exclusive formulation that protects its active ingredient and endows it with maximum stability and preservation capacity.

The active ingredient in Fungisei biological fungicide, the Bacillus subtilis, is present in the form of spores, and it maintains the same concentration and viability in each final bottle of the product, guaranteeing the purity and efficacy of the solution in all conditions of use and application.

The spores are present in a latent state, retaining the full potential of the active ingredient. When the product is applied, the spores begin a cycle of exponential multiplication and implant themselves on leaves, fruits, and roots. 

As a fungicide for the control of Alternaria in tomatoes, one of the ways in which Fungisei acts is via its antagonistic action. The action of the Bacillus subtilis creates a physical barrier that protects the whole of the plant surface to which it is applied, blocking possible infections by competing with the pathogen for space and access to nutrients. 

Induced systemic resistance (ISR)

Thanks to its exclusive formulation and the activity of the exclusive Bacillus subtilis strain, after it is applied to the plant (leaves, fruits, and roots) molecules are produced that induce a systemic response in the plant. In the case of Alternaria in tomato plants, Fungisei activates genes in the plant that increase its protection against invasive pathogenic agents and boost the plant's natural resistance to the attack of fungi.

By applying Fungisei, a wide range of antibiotics are also produced naturally, which are capable of inhibiting the growth of fungi and bacteria. The product also generates lytic enzymes that are responsible for the breakdown of the main polysaccharides forming the cell wall of fungi.

For the control of early blight in tomato plants and other fungal diseases, Fungisei is a solution that is totally eco-friendly and has practically zero effect on auxiliary fauna and beneficial insects used in biological control methods. In fact, its active ingredient is classed as Low Risk by the European Union.