Oral and contact toxicity of the extract obtained with hexane from Achyrocline satureioides on larvae and adult honey bees

DIANA C. PIMENTEL-BETANCURT; NATALIA V. TONELLO; FRANCISCO PADILLA-ALVAREZ; MARÍA F. PALETTI-ROVEY; MARÍA M. OLIVA; JUAN M. MARIOLI

SPANISH JOURNAL OF AGRICULTURAL RESEARCH

SPANISH NATL INST AGRICULTURAL & FOOD RESEARCH & TECHNOLO

Lugar: Madrid; Año: 2021

1695-971X

Aim of study: To evaluate the antimicrobial activity of the hexanic extract (HE) of Achyrocline satureioides on Paenibacillus larvae - agram-positive spore-forming bacillus that affects the larval stage and causes American Foulbrood (AFB) - and its oral and contact toxicityon larvae and adult honey bees.Area of study: A. satureioides plants were collected in Santa Monica (32° 05? 29? S, 64° 36? 54? W, Córdoba. Argentina). The larvae andadults of Apis mellifera were obtained from the experimental apiary of the University of Córdoba, Spain.Material and methods: P. larvae 9 was previously isolated and identified in the Laboratory of General Microbiology (Dept. of Microbiology,National University of Río Cuarto, Argentina). The HE was obtained by liquid-liquid extraction. The minimum inhibitory concentration(MIC) of HE was determined by a microdilution method. This concentration and 2 ½ MIC were used for in vitro toxicity tests. Oraltoxicity was tested on larvae, feeding them with both concentrations of the HE, while on adult bees the HE was spread to determine contacttoxicity.Main results: The HE showed antimicrobial activity, the MIC obtained was 0.4 μg/mL. The HE presented very low toxicity at theMIC and 2 ½ MIC, with survival percentages to be around 95% for adult bees and larvae.Research highlights: The results show that this extract could be used for the development of an alternative product for a safe and effectivetreatment of AFB.