Caracterização e manejo de infecção microbiana em Spodoptera frugiperda.

Abstract

Spodoptera frugiperda, popularly known as the corn cartridge caterpillar, is a present pest insect that has the ability to reduce corn plant productivity by up to 70%. Knowing the biological parameters of an insect is essential for the development of strategies and methodologies for its efficient management. The creation of insects under laboratory conditions and in artificial means makes it possible to carry out entomological studies that generate significant advances in techniques and strategies to be implemented in pest management in agricultural systems. A frequent problem in these creations is the occurrence of pathogens or microbial contaminants, among the most observed microorganisms are fungi and bacteria. Thus, the present work aims to determine the microorganisms that cause the infection observed in a commercial population of Spodoptera frugiperda and to evaluate the efficiency of some drugs in the control of this infection. For this, it was necessary to identify the infected individuals, isolate and identify the microorganisms present in the insect's body and then induce the infection following Koch's postulates. Antimicrobial drugs were used in order to reduce or control the infection caused by the microorganisms found. Four different microorganisms were isolated, being two yeasts (Candida sp. and Brettanomyces sp.), one bacterium (Streptococcus sp.) and one microsporidium. It was possible to reproduce the symptoms that were observed in industrial breeding, as well as to identify the microorganism responsible for 55.71% of caterpillar mortality from the fifth day in contact with the pathogen, reaching 8x103 spores/mm3. The antimicrobial used showed no significant difference in infection control. It was possible to conclude, by identifying and studying the microorganisms that cause mortality in the commercial breeding of S. frugiperda, that yeasts and bacteria were not responsible for the disease present in the original breeding. Confirmation based on Koch's Postulates demonstrated that microsporidia was the microorganism with the greatest patogenic potential and that it should be better studied in future works.