The use of an organism to reduce the population of another organism, aiming to reestablish the balance that already existed in nature, is a practice adopted in agriculture for decades. This concept is part of the integrated management of pests and diseases, and its main objectives are the maintenance of diversity in the agro-ecosystem, the preservation of chemical molecules, as well as the promotion of a sustainable and regenerative production system.
In recent years, we have seen significant growth in this sector, with total sales increasing by around 67% from the 2020/21 harvest to the 2021/22 harvest. This occurs mainly due to the loss of efficiency of chemical molecules and the selection of pests and diseases resistant to these molecules. Other factors that corroborated this were the global call for agriculture that increasingly adopts sustainable technologies in its production and the emergence of challenges that we did not have 40 years ago, such as leafhoppers in corn.
Investment in formulations aimed at maximizing biological technologies
In this sense, the estimated evolution of the biodefensive market in Brazil jumps from 2.9 billion, invoiced in 2022, to around 16 billion by 2030. Among the pillars responsible for this evolution is the very strong investment in research, innovation and formulation, by companies providing biological technologies.
The formulation must always aim to maximize the performance of the technology, to guarantee longer shelf life, storage in a non-refrigerated environment, as well as presenting a broad spectrum of action through the synergism of more than one microorganism and/or in mixture with plant extracts. . Furthermore, it must enable application in a mixture with chemical molecules and favor better dilution and rapid absorption by the plant and/or pathogen, these among other factors will guarantee its success in the field.
Biological insecticides
Regarding the use of biological insecticides, we observed greater obstacles to the adoption of macrobiological insecticides, that is, the group that includes predators and parasitoids, such as mites, insects and nematodes, due to the difficulty of using them on a large scale and/or together. to chemical technologies. While microbiological insecticides - viruses, bacteria, protozoa and fungi, have demonstrated greater acceptance, due to improvements in formulations and efficiency.
Nematode management
Regarding the management of nematodes through microbiological insecticides, we can mention the action of some bacteria of the genus Bacillus, such as B. pumilus, B. amyloliquefaciens and B. subtilis, which have numerous direct and indirect mechanisms of action.
One of the actions will be the production of biofilm around the roots, which will act as a physical barrier preventing the penetration of this pathogen.
Another action will be antibiosis, through the production of metabolites (zwittermycin-A and plantazolicin) harmful to nematodes.
Furthermore, these bacteria produce some enzymes (chitinases, proteases and collagenases) that act in the degradation of the egg membrane and even in the degradation of the membranes of the nematode itself (juvenile phase), and also produce volatile compounds (benzyl benzoate, benzaldehyde and 2 -heptanone) which will degrade nematodes and prevent their reproduction.
Caterpillar management
To manage caterpillars through microbiological insecticides, we have technology using formulations based on Bacillus thuringiensis and Brevibacillus laterosporus, which have the production of CRY proteins and VIP toxins as virulence factors. Depending on the subspecies of B. thuringiensis, different types of CRY proteins will be produced.
The mode of action occurs from the moment the caterpillar ingests the contaminated leaf, then the toxins will bind to the receptors present in its intestine and cause it to perforate. Between 18 hours and 72 hours later, we can observe that the insect will stop feeding, presenting loss of mobility, paralysis and, then, death due to generalized infection. Afterwards, it will be possible to verify the germination of the spores of these bacteria in the insect's body.
It is important to highlight that the dissolution of the crystals responsible for the mode of action of these bacteria will only occur in an environment with an alkaline pH, that is, in caterpillars up to the 3rd instar (8 mm to 10 mm), which is why we must apply this technology at the beginning of the infestation. or associated with the chemical.
Leafhopper management
Finally, I highlight a technology used in the management of leafhoppers in corn, which is the sum of the action of two Pseudomonas, P. fluorescens and P. chlororaphis.
Its mechanisms of action will be multiple (FIT toxins, hydrogen cyanide, proteases, chitinases, siderophores) and its contamination may occur through contact, ingestion and tarsal absorption.
After contamination of the insect, the enzymes proteases and chitinases will act causing the degradation of its digestive tract and the degradation of its exoskeleton, respectively. Furthermore, the FIT toxins, hydrogen cyanide and siderophores will come into contact with the leafhopper's hemolymph, and will be responsible for sequestering nutrients and causing complete intoxication of the insect, thus resulting in a total shutdown of the planthopper's basic functions. , and causing the death of the insect. A diagram of this mode of action can be viewed below.
Scheme of the mode of action of Pseudomonas fluorescens and P. chlororaphis in the control of leafhoppers (Dalbulus maidis). Source: Jakeline Pinheiro.
Indirect effect: root growth stimulation
The bacteria mentioned here for agricultural pest control also promote the production of phytohormones - such as auxin, which will be responsible for stimulating greater root growth in plants.
As a result, this root will have greater access to water and nutrients, and will become stronger, even in the presence of nematodes and other stressors, in addition to promoting greater development of the aerial part. Enabling the plant to reach its maximum production ceiling more easily.
