Toxicidade do extrato etanólico de Sophora flavescens sobre a abelha Apis mellifera (Hymenoptera: Apidae).

Abstract

The existence of the honey bee Apis mellifera is fundamental for many cultures, being one of the economically significant pollinators for agriculture all over the planet, as it ensures cross-pollination and increases fruit productivity. Botanical insecticides are considered low toxicity products for men, animals, however, little is known about its effects on pollinating agents. In view of this, the objective was to evaluate the toxicity of the ethanolic extract of Sophora flavescens on A. mellifera, through the ingestion of contaminated food and direct spraying with the referred bioinsecticide on the bees. The work was carried out at the Entomology Laboratory belonging to the CCTA/UFCG, Campus Pombal/PB. The study consisted of two bioassays: exposure to contaminated diet and direct spraying, carried out in a completely randomized design, where each one was composed of five treatments [Absolute control – distilled water; Positive control – Thiamethoxam: 600g/ha (0.30 g i.a./L-1) and three doses of the bioinsecticide ethanolic extract of S. flavescens: 0.6 L/ha (0.228 g i.a./L-1), 1 L/ha (0.381 g i.a./L-1) and 1.2 L/ha (0.457 g i.a./L-1)] and 10 repetitions, each experimental unit consisting of 10 adult bees. After the application of treatments, mortality and behavior (prostration, paralysis, tremors and reduced feeding) of the bees were evaluated at 1, 2, 3, 4, 5, 6, 12 and 24 hours after the beginning of exposure to the product. Regarding the contaminated diet, the ethanolic extract of S. flavescens caused the death of 52%, 51% and 66% of the bees, at doses 0.228 g i.a./L, 0.381 g i.a./L and 0.457 g i.a./L, respectively and, providing Median Lethal Time (TL50) of 35.0 hours for doses 0.228 g i.a./L and 0.381 g i.a./L and, TL50 of 25.6 hours for dose 0.457 g i.a./L. As for direct spraying, the ethanolic extract of S. flavescens caused a mortality of 100% of the bees in all evaluated doses, respectively, being as lethal as the positive control, the insecticide thiamethoxam, which also caused 100% of mortality. the ethanolic extract of S. flavescens provided a Median Lethal Time (TL50) of 1.1 hours for all evaluated doses. With regard to behavior, bees exposed to the ethanolic extract of S. flavescens showed tremors, mobility deficit followed by paralysis and prostration before death. Regardless of the dose, the ethanolic extract of S. flavescens was moderately harmful via ingestion of contaminated diet and highly harmful via direct spraying on A. mellifera adults.