Bacillus spp. aplicado em milho e seu efeito sistêmico na planta sobre Spodoptera frugiperda

Abstract

The finding of an increase in populations of Spodoptera frugiperda resistant to chemical insecticides after control applications has made the management of this pest very difficult. An alternative technique to overcome this problem can be done through the use of corn cultivars that have varietal resistance, which has been shown to be very efficient for controlling this pest. Aiming to improve this pest control method, the objective of this work was to identify the best way to apply bacterial isolates of neem (Azadirachta indica), to induce systemic resistance in creole maize plants and to study its effect on the development of S. frugiperda. In the first chapter of this study, the bacteria B. pumilus, Bacillus sp. and B. subtilis isolated from neem were inoculated in the newly germinated seeds and in the collar of the creole maize plants, in addition to being sprayed on them, in order to identify the best way to apply these microorganisms for the induction of resistance in maize and the control of S. frugiperda. As a result of this experiment, it was found that the bacterial suspension applied to the newly germinated corn seeds and to the stem of the plants were the forms of application of the microorganisms that made it possible to observe the most drastic adverse effects on the S. frugiperda caterpillars. In the second chapter of this study, 11 bacterial isolates of neem were evaluated and applied to the seeds and stem of maize plants, with the objective of selecting those with the greatest potential to induce resistance to S. frugiperda. As a result of this experiment, considering the biological variables evaluated in the larval and pupal stages of S. frugiperda, it was found that the bacterial isolates acted as elicitors and induced systemic resistance in maize plants, especially the isolate Bacillus sp. (Epi 13 ). In the third chapter of this study, the reproduction and longevity of adults of S. frugiperda, from caterpillars that ingested corn leaves with resistance induced by bacteria isolated from A. indica, was evaluated. As a result of this work, all isolates evaluated induced resistance in maize plants and caused some adverse effect on females of S. frugiperda, however, it was found that the caterpillars when ingesting maize plants treated with Bacillus isolate (Epi 13) negatively affected four of the six biological variables evaluated.