Abstract:
The study was aimed to determine the chemical composition, toxicity effect and field
varroacidal efficacy of essential oil from leaf of Eucalyptus robusta (Er), Eucalyptus
sideroxylon (Es) and Eucalyptus globulus (Eg) grown in Algeria. The brine shrimp lethality
(BSL) assay and bee hives infected by Varroa destructor were used to assess the toxicity and
acaricidal effect, respectively. Steam distillation of (Er), (Es) and (Eg) leaves yielded 0.83%,
1.09 % and 0.93% (v/w) of essential oil (EO) respectively. GC/MS Analysis revealed 13
compounds for (Er), 36 for (Es) and 39 for (Eg). The main constituents for Er EO were 1,8-
cineole (65,97%), p-cymene (7,83%) and o-cymene (4,75%), for Es EO 1,8-cineole (20,57%),
octane (4.83%) and p-cymene (1,35%), and for Eg EO, 1,8-cineole (78.45 %), o-cymene
(2.18 %), and isopinocarveole (1.74 %). The BSL assay of Er EO, Es EO and Eg EO revealed
a highly toxic value of LC50 (µg/ml): 9.42, 34.80 and 67.55 respectively. Furthermore, field
efficacy testing on bee hives infected with Varroa destructor has confirmed the effectiveness
of Eucalyptus robusta essential oil (Er EO), (Es EO) and (Eg EO) and thymol (p < 0, 05) as
varroacidal agents. Moreover (EEO + thymol) association was more effective than EEO or
thymol alone. Finally the use of (EEO + thymol) may constitute a viable alternative to the
thymol based commercial treatment.
