IN VITRO EVALUATION OF SOME ESSENTIAL OILS AND MIXTURES FOR THE CONTROL OF Paenibacillus larvae subsp. larvae, THE CAUSAL AGENT OF AFB*
Adriana M. Alippi 1, Jorge A. Ringuelet 2, Cynthia P. Henning 2 and Arnaldo Bandoni 3
* Poster presented at the XXXVI Apimondia Congress, Vancouver, Canada, September 12-17,1999.
1CIC and Laboratorio de Fitopatología, Facultad de Ciencias Agrarias y Forestales, calles 60 y 118, c.c. 31, Universidad Nacional de La Plata, 1900 La Plata, Argentina - 2Curso de Fitoquímica - 3 Fac. Farmacia y Bioquímica, U.B.A.
Essential oils from basil, coriander, laurel, false camphor, and marigold were tested for antimicrobial activity against Paenibacillus larvae subsp. larvae strains from different geographical origins. The principal components of the essential oils were analyzed by gas chromatography. Regarding in vitro activities, in trials with 10 P. l. larvae strains from different geographical origins, basil was the most effective with minimal inhibitory concentrations between 350 and 450 ppm, according to each strain tested.
Five mixtures of essential oils were also evaluated for their activity against 10 strains of the Foulbrood pathogen from Argentina and other countries, isolated from AFB infected colonies. Three mixtures showed the most significant growth inhibition: a) lemon grass 20 % + thyme 80 %; b) lemon grass 5 % + thyme 11 % + savory 21 % + oregano 26 % + basil 37 % and c) lemon grass 10 % + thyme 20 % + basil 70 %.
The results obtained suggest that the use of mixtures of essential oils instead of pure essences or its principal components may enhance their biological activity against P. l. larvae.