According to Viégas, 1962, septoria or septoria spot was reported for the first time occurring in tomato plants in Boca del Riachuelo, Argentina, in 1882, by Spegazzin, and its pathogenicity was confirmed only in 1916, by Levin, in the USA, after the conclusion of Koch's postulates. Currently, it is a very common and important fungal disease for the crop, occurring everywhere in the world where it is cultivated. In general, it is more severe under climatic conditions of high relative humidity and moderate temperatures that allow leaves to remain wet for longer periods after rain or irrigation. The main damages caused by the disease are the loss of vigor, the widespread defoliation of plants and the burning of fruits - due to their direct exposure to the sun.
The disease can occur at any stage of plant development. Symptoms initially appear on the underside of older leaves, through small and numerous water-soaked lesions, circular to elliptical in shape, measuring 1mm to 3mm in diameter. As the disease progresses, the lesions become grayish brown in the center, with dark brown edges, and may or may not be surrounded by a yellowish halo and reaching more than 5mm in diameter. In conditions of high humidity, fungal pycnidia (black dots) can be seen in the center of the lesions, where conidia (spores) are formed. Over time, the disease progresses upwards in plants, reaching the youngest parts. In severe attacks, coalescence of the lesions occurs, causing yellowing, followed by dryness and leaf fall. Defoliation visibly reduces the vigor and productive potential of plants, in addition to exposing the fruits to sunburn. Symptoms similar to those observed on leaves can also be seen on the stem, petioles and sepals, however, the lesions are smaller and tend to be darker and more numerous. Fruits are rarely affected. In general, plants tend to be more susceptible to septoria after the beginning of fruiting, when the demand for nutrients is greater for fruit formation and growth.
the fungus Septoria lycopersici Speg. 1881 produces hyaline conidia, long, thin, with three to nine septa, measuring 60-120x2-4µm in short conidiophores, which form inside structures called pycnidia, globose, ostiolated and dark. The conidial mass of this fungus is pink, salmon or dark brown in color. The mycelium is hyaline, branched and septate.
Temperatures considered conducive to infection and disease progression range from 16°C to 28°C (ideal 25°C). The conidia are released from the pycnidia in conditions of high humidity, forming cirri, agglutinated together by a mucilaginous substance that is dissolved when in contact with water, thus dispersing the conidia that begin to be disseminated by the impact of rainwater drops or water. irrigation.
For the conidia to germinate and the fungus to infect the plants, high relative humidity (100%) is necessary for a minimum period of 48 hours to 72 hours. Under these conditions, the first symptoms of the disease can be observed between six days and 7 days after contact between the conidia and the host. Spread in the field can also occur during cultural treatments - through the movement of workers and agricultural implements, as well as insects and birds.
Even though it is not considered a soil fungus, the main survival route of S. lycopersici from one crop to another are the cultural remains. It can also infect other solanaceae of economic importance, such as petunia (Petunia sp.), eggplant (Solanum melongena), the jiló (Solanum aethiopicum), pepper (Capsicu mannuum) and some invaders such as Maria Pretinha (Solanum americanum L.), the fig tree of hell (Daturas tramonium L.) and physalis (Physalis sp).
Despite several attempts to discover sources of resistance to the pathogen, there are still no tomato cultivars or hybrids resistant to septoria on the market. Therefore, other control methods must be adopted so that the development of serious epidemics is avoided.
When choosing the planting location, give preference to sunny areas, without accumulation of humidity, well ventilated and away from plantings at the end of the cycle.
The main sources of initial inoculum of the fungus are seeds, seedlings, ratoons, crop residues and other solanaceous species. Therefore, it is recommended to use healthy seeds and seedlings; avoid successive planting of nightshades (crop rotation at intervals of three to four years is recommended); and the elimination of cultural remains, possible host species and also weeds in general, which can compete for space, light, water and nutrients and make it difficult to dissipate moisture in the foliage.
The adoption of wider spacing and vertical conduction can reduce the occurrence of the disease, thanks to greater air circulation and less humidity between plants.
Due to the great importance of humidity in the development of the disease, it is recommended to minimize the time and reduce the frequency of irrigation in affected fields, also avoiding carrying them out in the late afternoon. The adoption of localized irrigation can be an important ally in the management of septoria, as it significantly reduces the spread of the pathogen.
Chemical control is the main method used in the management of septoria. It is carried out through the preventive application of protective and systemic fungicides to the aerial part of the plant. Protective or contact fungicides, such as copper-based products, capitan, chlorothalonil and mancozeb, are characterized by forming a protective film on the surface of the plant, which prevents the pathogen from penetrating. Systemic fungicides, such as those belonging to the groups of triazoles, benzimidazoles, phenylpyridinylamine, carboxamide and strobilurins, are those that can move through the plant through conductive vessels, reaching locations distant from those deposited. To avoid the development of cases of resistance, it is recommended to use products from different groups in the same production cycle, avoiding the repetitive use of fungicides with the same mechanism of action and curative applications in situations of high disease pressure. For organic cultivation systems, Bordeaux and lime sulfur mixtures stand out as the options with the best results in controlling septoria in this type of production. Bordeaux mixture can be phytotoxic to tomato plants, therefore spraying should start with lower concentrations than recommended (for example: 0,5%) and gradually reach 1%. Lime sulfur syrup also has the capacity to cause phytotoxicity when applied on hot days.
Fungicide application technology directly contributes to the successful control of septoria. Poor quality in the application of products can seriously compromise and limit their effectiveness, especially in relation to protective fungicides. Factors such as type of nozzles, application volume, pressure, bar height and tractor speed must always be considered, with the aim of providing the best possible coverage of the crop. The use of fungicides must follow all manufacturer recommendations regarding dose, volume, intervals, number of applications, use of Personal Protective Equipment (PPE), withdrawal period, product storage and packaging disposal. Information on fungicides registered with the Ministry of Agriculture, Livestock and Supply (Mapa) for septoria in tomato crops can be obtained at the website http://agrofit.agricultura.gov.br/agrofit_cons/principal_agrofit_cons.
The tomato (Solanumly copersicum) is a vegetable crop originating in Central and South America that became known after its introduction to Europe by the Spanish in the 16th century. It represents one of the most important crops on the global agricultural scene. Wide adaptability, high production potential and culinary versatility make this nightshade suitable for consumption fresh or industrialized in the most diverse forms. The fact that it has low calories, considerable amounts of vitamins A, C and B complex, mineral salts and lycopene makes tomatoes a food also recognized for its antioxidant and anti-cancer properties.
Brazilian tomato farming is widespread throughout the national territory, however, the main production centers are in the Southeast and Center-West. Today, the tomato production chain has great economic and social importance and assumes well-defined business characteristics, with constant technological advances, land change and advanced management of the production process.
Ricardo José Domingues, Jesus G. Töfoli and Josiane Takassaki Ferrari, Apta - Instituto Biológico
With each new edition, Cultivar Hortaliças e Frutas publishes a series of technical content produced by renowned researchers from all over Brazil, which address the main difficulties and challenges encountered in the field by rural producers. Through research focused on controlling the main pests and diseases in vegetable and fruit cultivation, the Magazine helps farmers in the search for management solutions that increase their profitability.
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