SANTOS, João Vitor Linhares dos.
Résumé:
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.