Efeitos de novaluron, glifosato e Metarhizium rileyi sobre o sistema imune, parâmetros biológicos e metabolismo redox de Anticarsia gemmatalis

Abstract

Success in implementing effective integrated pest management programs requires understanding the action mechanisms of control agents and agrochemicals on insects and their compatibility. Anticarsia gemmatalis (Hübner, 1818) (Lepidoptera: Erebidae) is one of the most important pests of the world's soybean crop, causing major losses to agricultural production. The objective of the present study was to evaluate the changes that occur in the immune system, biological parameters and redox metabolism in A. gemmatalis when infected by entomopathogenic fungus Metarhizium rileyi and under treatments with novaluron and glyphosate. For this purpose, were performed bioassays for total (THC) and differential (DHC) hemocytes count, evaluation of biological parameters and secondary effects, analysis of redox metabolism by superoxide dismutase and catalase enzyme activities and nitric oxide levels in A. gemmatalis, as well as the sensitivity of entomopathogenic fungus to agrochemicals novaluron and glyphosate. The major changes in the insect’s immunity were observed with novaluron, and the hemocytes were not effective, generating a collapse in the immune system. The insecticide affected the sporulation and mycelial growth of M. rileyi. Regarding the evaluations with M. rileyi, there was an increase in the number of defense cells at lower concentration (1.107 conidia/mL) suggesting that immune system was able to attenuate the entomopathogenic action. Action of the glyphosate on insect’s immunity was slighter, and soon after the infection the system is activated, acting in elimination of the molecule. Moreover, it was observed that the glyphosate also caused changes on caterpillar’s antioxidant system by means of redox metabolism analyzes, along with malformations in pupae and adults. The herbicide also affected mycelial growth and sporulation of the entomopathogenic fungus, which may compromise its effectiveness. In this way, more studies related to the interval of the exposure between the two agents are suggested so that they can be used without interferences in their respective mechanisms of action. [resumo fornecido pelo autor]