Propolis as a natural alternative for the treatment of hives infected with spores of Paenibacillus larvae, causative agent of American foulbrood

Abstract

Paenibacillus larvae is the causative agent of American Foulbrood (AFB), a severe disease affecting larvae of honeybee. The aim of the present work was to evaluate the effect of a propolis ethanolic extract (EEP) against P. larvae and as a  herapeutic tool for the control of AFB. In vitro activity of PEE against P. larvae isolates was evaluated by the disk diffusion method and the minimum inhibitory concentration (MIC) was determined. Then the toxicity for honeybees was evaluated by oral administration. Lastly, the in vivo activity against P. larvae naturally infected colonies was determined. All isolates resulted sensitive to EEP and the MIC median resulted in 52 ppm and it was not toxic for bees at least at 50.000 ppm. Field assays showed that 21 and 42 days after the application of the PEE treatments by aspersion or by supplementation of the food, the number of P. larvae spores/g of honey resulted significantly lower in colonies treated with PEE compared to the control colonies. This work constitutes the first report about the use of propolis for the treatment of beehives affected with P. larvae spores, appearing as a novel, natural and innocuous alternative for the treatment of AFB-affected hives.