Toxicity of botanical insecticides on the stingless bee Tetragonisca angustula

This study aimed to investigate the toxicity of botanical insecticides on the stingless bee Tetragonisca angustula (Apidae: Meliponini). Bioassays evaluated the effects of essential oils (EO) of Allium sativum (Amaryllidaceae), Eucalyptus citriodora (Myrtaceae), and commercial oil (CO) of Azadirachta indica (Meliaceae), in addition to ethanolic extracts (EE) of Piper nigrum (Piperaceae), and Eugenia caryophyllata (Myrtaceae). It was also assessed the effect of Surfactant addition to essential oils. The probit analysis was used to determine LC50 and LC90. Results showed essential oil of E. citriodora at 1% v/v was toxic to T. angustula, with mean mortalities of 42.00 and 46.00% at 96 hours and survival times of 107.52 and 105.60 hours for contact and ingestion, respectively. Ethanolic extracts of P. nigrum and E. caryophyllata caused 100% mortality within 24 hours through ingestion but were less toxic through contact. Surfactants increased mortality caused by the essential oil of E. citriodora from 47.67 to 93.33% and the commercial oil of A. indica from 38.00 to 100%. Essential oil of E. citriodora had the lowest LC50 and LC90 (0.075 and 1.45% v/v), indicating high toxicity to T. angustula. Ethanolic extracts of P. nigrum and E. caryophyllata had higher LC50 and LC90 values, showing lower toxicity. In conclusion, the oils of A. indica and E. citriodora and ethanolic extracts of P. nigrum and E. caryophyllata are toxic to stingless bee T. angustula.