The complex of pathogens related to leaf spots can freely survive in the soil, lodge in straw or in volunteer plants that remain between harvests. For disease to occur, in addition to pathogens, the presence of a host plant and a favorable environment is necessary for the development of the pathogen and infection in the plant.
The use of fungicides, chemical or biological, act on the development of the pre-infection and/or post-infection pathogen. When we think of protective and translaminar fungicides, they act as a barrier to disease colonization, whereas systemic fungicides act on plant metabolism.
Products based on bacteria and fungi have gained prominence as aids in disease control in large crops, mainly soybeans, corn and wheat. These microorganisms stood out for increasing the efficiency of chemical products (especially in the control of leaf spots and end-of-cycle diseases), for acting alone in the control (in environments with lower inoculum pressure) and for promoting growth in plants, at the same time time they act in pathogenic control.
The main biofungicides available on the market are produced based on bacteria and among the most important are the microorganisms of the genus Bacillus. These bacteria stood out in studies of microorganisms with biological control action because they colonize different cultures, have more than one form of action in positively influencing plant development and, mainly, because they produce resistance structures called endospores. This ensures greater versatility of use in agricultural management and tolerance to some mixtures with chemical products, a practice that is not possible for several other beneficial microorganisms available for agriculture.
These bacteria that make up biofungicides can act in different ways when applied to plants:
> Competition for infection space: pathogens that cause leaf spot infect the plant through natural openings (mainly stomata and leaf wounds), and these are the same openings through which Bacillus colonizes the plants. This results in competition for space, reducing the entry points for the pathogen.
> Production of antibiotic compounds: microorganisms produce secondary compounds that act in biological control (enzymes, volatile compounds, antimicrobials). These compounds can inhibit the growth of the pathogen, decreasing the severity and evolution of the disease in the plant. In addition, they can damage the structure of the pathogenic microorganism, destroying the structures of fungi and bacteria, and alter the composition of metabolites in the areas of infection, (imbalance the biochemical signals that attract microorganisms).
> Induction of resistance: the colonization of Bacillus in the plant triggers an immunization effect. From this, it activates defense genes that act in metabolic processes of plant protection, such as, for example, synthesis of antimicrobials, enzymes that degrade the structure of the pathogen and deposition of lignin in plant cell walls, leaving the plant prepared to defend itself from possible pathogenic microorganisms.
Studies have indicated that management with biofungicides must be carried out in advance, ensuring that the beneficial microorganism has the necessary time to colonize the plant of interest and produce antimicrobial compounds, so that when infection occurs, the protection process is already in progress. full functioning.
A successful case was observed at the 3tento Research Center, with the use of biofungicides associated with chemical management in soybean cultivation. The result was an increase of up to 7% in productivity, when used in the first entry (2021/22 season), and up to 10% when applied in the first and second entry, associated with the chemical fungicide (2021/22 season).
The addition of biological inputs in management has been gaining ground, driven mainly by the delivery of results and economic viability. New technologies, such as biofungicides, have been adopted to complement traditional practices.
