Prospecção de novas ferramentas inseticidas para o controle bioracional de euschistus heros

Abstract

Selection of resistant individuals and toxicity to non-target organisms have been suggested as the main undesirable effects of chemical insecticides commonly used in the control of insect pests. In addition, the occurrence of adverse effects on both human health (e.g., handling and ingestion) and the environment has been reported as an inconvenience for the use of these control tools. These risks associated with the use of contemporary chemical molecules have led to the search for alternative tools that reduce these risks while maintaining effectiveness in pest control. Therefore, this dissertation was carried out with the objective of evaluating the insecticidal potential of new insecticidal tools for the biorational management of the soybean brown stink bug, Euschistus heros (Heteroptera: Pentatomidae). In the first chapter, the insecticidal potential of Negramina, Siparuna guianensis Aub., essential oil was evaluated for the control of E. heros. The lethal concentrations were estimated in concentration-mortality bioassays from the interaction of insects with dry oil residues. The results obtained showed significant values of toxicity, allowing the use of this oil as an alternative tool for the management of E. heros. In the second chapter, the toxicity of new synthetic molecules to E. heros was evaluated, as well as the selectivity of these tools for two species of pollinating bees - i.e., the stingless bee Partamona helleri (Apidae: Meliponini) and the Africanized bee Apis mellifera (Apidae: Apini). In relation to the novel molecules toxicity, concentration-mortality bioassays were conducted on 3rd instar nymphs, that were exposed to dried residues of these molecules, which allowed lethal concentrations (LC). Regarding the selectivity to pollinator bees, the toxicity was assessed by exposing foraging bees to feed upon diets containing the molecules at the concentrations estimated to control E. heros (LC80). The results demonstrate significant values of toxicity to E. heros for all new synthetic molecules. The selectivity data indicate that P. heleri is more tolerant than A. melífera, and that both do not present statistical mortality when compared to the control. However, analysis of the consumption of contaminated diets indicates that A. mellifera reduced food consumption during exposure when compared to the consumption of diets without the molecules. For P. heleri, the consumption of contaminated diet does not differ from the consumption of diets without the presence of molecules. Interestingly, P. heleri foragers that fed on DE12 presented a higher consumption of uncontaminated food, once the contaminated diet was replaced by the clean diet. Collectively, our findings demonstrate the potential use of both Negramina essential oil and new synthetic molecules (e.g., DE12) as insecticidal tools for the biorational control of E. heros.