In vitro activity of Laurus nobilis, Calamintha officinalis and Lippia alba against Ascosphaera apis. Evaluation of the potencial toxic effects on adults and larvae of Apis mellifera

RODRIGUEZ S; REYNALDI F. J.; RINGUELET, J.; CÓRDOBA, S.; ALBO G. N.

Ciudad Autónoma de Buenos Aires

Congreso; 45th Annual Meeting of the Society for Invertebrate Pathology; 2012

Society for Invertebrate Pathology

Chalkbrood is a disease of the honeybee (Apis mellifera L) caused by the fungus Ascosphaera apis. The activity of the essences of Laurus nobilis, Calamintha officinalis and Lippia alba was evaluated in vitro-in vivo. The potential toxic effects of the essences on adults and larvae of A. mellifera L were also studied. The in vitro activity of different concentrations of essences (50, 100, 200, 400, 800, 1600 ppm) was tested against seven isolates of A. apis. The Lethal dose 50 (LD50) of essences on adult bees was calculated. The doses employed were: 0.25; 0.50; 1; 2; 4; 8 µg a.i/bee. Dimethoate and sucrose in water solution were used as a toxic and the non-toxic control. Mortality was assessed after 24, 48, and 72 h. The LD50 was calculated by PROBIT. To evaluate the toxicity on larvae, an area of 180 brood cells (instars 1?5) was marked, at day 0, in each colony and larval mortality was assessed at 7 and 21 days after the application of treatments by counting number of eggs, open brood, sealed brood, and empty cells. ANOVA and LSD tests were used. The susceptibility profile of isolates studied not showed significant differences. Thus, after 72h the fungal growth was inhibited by L. nobilis, C. officinalis and L. alba at 1600, 800 and 800 ppm respectively. The LD50 of the essences on adult bees showed ?virtually no-toxicity?. The in vivo essay of larval toxicity showed that C. officinalis was the only essence no toxic to larvae.