IN VITRO ACTIVITY OF CYMBOPOGON CITRATUS PLUS FIVE DILUENTS AGAINST ASCOSPHAERA APIS ISOLATES

ALBO, G.1; VIVOT, W.; REYNALDI, F.J.; SZUSZ, W. ; CÓRDOBA, S.

Ciudad Autònoma de Buenos Aires

Congreso; 42 Congreso Internacional de Apicultura APIMONDIA; 2011

Sociedad Argentina de Apicultores SADA

  Chalkbrood is a disease of the honeybee (Apis mellifera L) caused by the fungus Ascosphaera apis that transforms larvae into mummies. Different essential oils have been used in the control of chalkbrood; among them, Cymbopogon citratus. However, the treatment is not always successful, probably due the intra species variability. The objective was to determine and compare the in vitro activity of Cymbopogon citratus against A. apis; using 5 different diluents. Thirty A. apis isolates obtained from larvae suffering chalkbrood were studied. Cymbopogon citratus at final concentration of 250 and 750 ppm was tested. Tween 80, dimethylsulfoxide (DMSO), propylene glycol 2,5%, water and alcohol 70, were used as diluents. The growth in water was used as control. The agar diffusion method was employed. The inoculum was performed from cultures of A. apis during 7-10 days at 35 ºC in MY20 medium. Holes of 7 mm diameter were realized in the agar surface of plates containing MY20 medium, essential oil plus the diluents. Then, the inoculum was placed inside the hole. The plates were incubated at 35°C in darkness and read after 24 to reach 144 h. Zone diameter end points were read visually and measured with a ruler. Data were analyzed using the ANOVA test and LSD. No statistical differences were observed among susceptibility profiles of the isolates studied; Cymbopogon citratus inhibited the growth at 72 h. For DMSO and Tween 80, significant differences were observed at both concentrations of the essentials oil tested when compared with the control (water). For propylene glycol 2,5% and alcohol 70 significant differences were observed only at 750 ppm. These findings provide useful information not only at the moment to decide the essentials oil to be tested, but also the diluents due the potential inhibitory activity of some diluents could exhibit.