Content uploaded by Natalia Damiani
Author content
All content in this area was uploaded by Natalia Damiani
Content may be subject to copyright.
Bulletin of Insectology 62 (1): 93-97, 2009
ISSN 1721-8861
Advances in the apiary control of the
honeybee American Foulbrood with Cinnamon
(Cinnamomum zeylanicum) essential oil
Liesel Brenda GENDE
1,2,3
, Matías Daniel MAGGI
1,3
, Natalia DAMIANI
1,3
, Rosalia FRITZ
2
, Martin Javier
EGUARAS
1,3
, Ignazio FLORIS
4
1
Departamento de Biología, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina
2
Departamento de Química, Facultad de Ciencias Exactas y Naturales, Universidad Nacional de Mar del Plata, Argentina
3
CONICET, Universidad Nacional de Mar del Plata, Argentina
4
Dipartimento Protezione delle Piante, Sezione Entomologia agraria, Università degli Studi di Sassari, Italy
Abstract
The activity of Cinnamomum zeylanicum Nees essential oil (cinnamon oil) against Paenibacillus larvae (Withe) was evaluated in
the laboratory and in a field experiment in order to improve the biological control of the Apis mellifera L. disease American foul-
brood (AFB). The MICs (Minimal Inhibitory Concentration) against P. larvae were determined by the tube dilution method. Bee
lethality was estimated using cages with approximately 374 bees, fed with the essential oil at different concentrations diluted in
ethanolic syrup. The security index was calculated as LD50 of A. mellifera/MIC of P. larvae strain at 24, 48 and 72 h in both
tests. The apiary trial, using three groups of five hives each, was carried out in April-May 2006 in an experimental apiary of J. J.
Nágera coastal station (Mar del Plata, Argentine). The first group was treated with cinnamon oil (two doses of 1000 µg/ml per
hive), the second with oxytracycline-HCl (three doses of 0.4 g per hive) and the third was left untreated as a control. All of the
treatments were performed at 7-day intervals. The evaluation of treatment efficacy was made by counting the number of infected
brood cells in both sides of a central comb, using a brood surface of 360 cm
2
(18 x 20 cm). For the Mar del Plata AFB strain the
C. zeylanicum essential oil and antibiotic MICs were 50 µg/ml and 3.125 µg/ml, respectively. Regarding the systemic administra-
tion method, bees LD50 at 24 h was 456.07 µg of essential oil of cinnamon/bee. LD50 estimated at 48 h showed a slight decrease
with respect to that recorded at 24 h. Security index was 9.1214 (ml/bee) for 24 h. In relation with field trials, after 24 and 31 days
from the beginning of treatments the cinnamon oil-treated hives showed a lesser incidence of infected larvae (7.89% and 52.42%)
than the control group highlighting a clear efficient control. No significant differences between the two treated groups were re-
corded. These results represent a further proof of the potential of cinnamon oil to control American Foulbrood with only minor
toxicological risks to bees. Furthermore, the use of cinnamon oil avoids problems with antibiotic residues in honey. This is impor-
tant in marketing honey in the EU where antibiotics in honey are generally forbidden by law.
Key words: Cinnamon oil, oxytetracycline, antimicrobial activity, American Foulbrood control, apiary trial.
Introduction
The American Foulbrood (AFB) is considered the most
serious bacterial disease of honeybees (Shimanuki and
Knox, 1997). It is caused by the spore-forming bacte-
rium Paenibacillus larvae (Withe) (Genersch et al.,
2006) that affects the larval stage of honeybees (Apis
mellifera L.), with a rapid widespread and destructive
effects on the colony. The spores are extremely infec-
tious and resistant to physical and chemical agents
(Haseman, 1961). A dead larva may contain billions of
spores (Hansen and Brødsgaard, 1999). The use of anti-
biotics in hives is illegal in some EU countries because
up to now there are no formulations that have obtained
the necessary Ministerial registration for manufacture,
transport, and sale. Moreover, there are no MRLs
(Maximum Residue Limits) of tetracyclines and sul-
phonamides established for honey according the Euro-
pean Community regulations (Mutinelli, 2003). Only in
exceptional cases, the veterinary authority can authorize
in the prophylaxis of this disease the employment of an-
tibiotic formulations registered for other veterinary use
alone or in association with manipulative treatments,
such as the “shaking” method, consisting in transferring
bees from diseased colonies onto new combs into empty
box. However, affected honeybees colonies often have
to be destroyed and the equipment adequately decon-
taminated (Bailey and Ball, 1991). In other countries as
in the USA, Canada and Argentina, preventive treat-
ments with antibiotics are allowed, being considered a
routine procedure to prevent outbreaks of AFB (Lind-
strom, 2006). Consequently, various strains of P. larvae
showing resistance to antibiotics, such as oxytetracy-
cline-HCl (OTC), have been discovered in Argentina
(Alippi, 2000) as well as in many United States areas
(Miyagi et al., 2000). Moreover, the extensive use of
antibiotics leads to an accumulation of residues in bee-
hive products (especially in honey), decreasing their
quality and making their marketing more difficult (Fu-
selli et al., 2005).
Because of legal and biological issues associated with
antibiotic use in hives, we have been examining natural
antimicrobial products for AFB management. Based on
previous experiences (Gende et al., 2008b), we chose to
study the antimicrobial activity of cinnamon oil against
a specific Argentinean strain of P. larvae and the oils
toxicity to A. mellifera using both laboratory and field
tests.
94
Materials and methods
Essential oil
Cinnamon essential oil, was furnished by Cruciani
Company (Rome, Italy) and derived from the bark of
Cinnamomum zeylanicum Nees, the essential oil/product
was the same previously employed and analysed by Flo-
ris et al. (1996).
Antimicrobial assay
A bacterial strain of P. larvae was isolated from hon-
eybee brood combs of colonies with clinical symptoms
of AFB; these were collected in hives located in Mar del
Plata (38°0'S-57°33'W), Buenos Aires province. The
Argentinean strain of P. larvae was previously identi-
fied in laboratory by biochemical assays (Alippi, 1992)
and tests based on PCR and restriction fragment analy-
sis of the 16S rRNA genes (rDNA), using the primers
PL 5 (5’-CGAGCGGACCTTGTGTTTCC-3’) and PL 4
(5’-TCAGTTATAGGCCAGAAAGC-3), which am-
plify a fragment of the P. larvae 16S rRNA gene (Pic-
cini et al., 2002; D’Alessandro et al., 2006). The pure
strain was maintained on MYPGP agar with 15% v/v
glycerol until used. Vegetative cells of P. larvae were
grown on MYPGP agar for 48 h at 35 ± 0.5 °C, and then
suspended in double distilled autoclaved water. To
measure antimicrobial activity with serial dilution
method, microbial biomass concentration was adjusted
to 0.5 of MacFarland scale (Scott, 2006). The minimal
inhibitory concentration (MIC) of cinnamon essential
oils and antibiotic (oxytetracycline-HCl) separately, was
directly assessed by turbidity observation. Stock solu-
tions of each antimicrobial agent in sterile water were
made; essential oil of cinnamon was emulsified with 8%
v/v propylene glycol (1-2 propanediol). One milliliter of
each stock solution was added to MYT broth (Gende et
al., 2008a) and serially diluted (final range 12.5-2000
µg/ml from essential oil and 0.000315-100 µg/ml for
antibiotic). Microbial biomass suspension was then
added to each serial dilution tube with agitation, at room
temperature, using a Vortex dispersing tool (Fbr
®
by
Decalab Srl). All sample tubes (as well as positive and
negative controls) were incubated at 35 ± 0.5 °C for 48
h in order to determine MIC values under microaerobic
conditions (5-10% of CO
2
). All MIC tests were per-
formed by triplicate for microbial agent and strain.
Bees lethality test
To evaluate the oil effect on A. mellifera, an average
of 374 ± 45 adult worker bees taken from the nest were
placed in each cage (16 x 12 x 6 cm) with nylon mesh
on the walls for air circulation. After being starved for 4
hours, to allow bees to feed during the experiment, a
cylindrical feeder (8 x 3.5 cm) were placed inside each
cage (Maggi et al., 2009) with 10 ml of sugar-water
syrup (2:1) in 70% ethanolic solution containing 2000,
4000, 8000, 16000 µg/ml of cinnamon oil concentra-
tions, respectively. Bees in cages fed with sugar syrup
in 70% ethanolic solution without oil and other treated
with dimethoate were also included as controls. Each
treatment was replicated five times. After 24 h, the
cages received only 2:1 syrup, depending on demand of
bees. All cages were maintained at room temperature
(22 °C and 65% RH) and a synthetic queen pheromone
was also introduced in them. Bee mortality was re-
corded at 24, 48 and 72 h. Once the experiment fin-
ished, the bees were killed by immersing the cages in a
70% alcoholic solution container. The final number of
bees was recorded to calculate the proportion of dead
bees attributable to each time (24, 48 and 72 h), and sta-
tistical analysis was made by linear regression method.
The Security Index was determined as LD50 of A.
mellifera/ MIC of P. larvae, modifying the expression
given by Lindberg et al. (2000).
Apiary trial
The field trial was carried out from April to May 2006
in the Arthropods Laboratory at the Universidad Na-
cional de Mar del Plata (Argentine) and in an experi-
mental apiary of J. J. Nágera coastal station placed on
route 11 Km 32 (38°10'06"S, 57°38'10"W).
Twenty days before treatments, 15 nuclei of homoge-
neously strong-bees were prepared; each colony consists
of 5-6 combs of bees. Capped and open broods as well as
food reserves were included in same proportion. The
colonies from which these combs were extracted had not
been treated with antibiotics during the 24 months prior
the experiment. The young queens were marked to be
easily recognized. Hives were divided into three groups
of five. All the hives were artificially infected with the
same number of scales of pre-pupae or pupae affected by
AFB. Inoculation was made with brood comb sections (5
x 5 cm) collected from colonies showing AFB clinical
symptoms. Each infected comb section had 45 ± 5 scales
and they were introduced into nuclei in central position
of a nest central comb. After 3 days, the piece of incor-
porated brood comb was modified in its entirety by the
bees and converted with new wax, giving up the comb of
experimentation with normal and similar characteristics
to the remaining breeding ones. The Argentinean strain
of P. larvae used in the artificial inoculation was the
same that had been analyzed previously.
The first group of hives (O) was treated with oxytetra-
cycline-HCl and received three weekly doses, each of
0.4 g antibiotic mixed with an equal quantity of pow-
dered sugar. The second group (Ci) received two
weekly treatments of 250 ml syrup (solution 2:1 of
sugar/water) added with cinnamon oil at a concentration
of 1000 µg/ml. In this case, it was also necessary to use
an emulsifier of 70% ethanol in the syrup. The third
group (Co) was left as a control and received only etha-
nolic syrup (solution 2:1 of sugar/water with ethanol).
The evaluation of AFB disease incidence following
the treatments was made by counting the number of in-
fected brood cells in both sides of a central comb por-
tion of 360 cm
2
(18 x 20 cm). For each hive, the number
of cells with infected larvae and/or scales and the num-
ber of cells with healthy larvae were weekly counted
until the 31
st
day after the experimental infection.
Statistical analysis
Experimental data were analyzed by analysis of vari-
ance (ANOVA) after arcsine ¥ y/100) transformation, in
the case of percentages, to reduce the heterogeneity of
95
Table 1. Medium lethal dose (LD50) (µg of cinnamon essential oil/bee) at different exposure-time intervals.
Hours Regression equation R
2
LD50 (µg essential oil/bee)
24 y = 0.0031 x í2.82144 0.5419 456.07
48 y = 0.00316 x í1.01723 0.5327 432.13
72 y = 0.00316 x í0.44988 0.5319 427.32
Table 2. Security index values (SI), ratio between medium lethal concentration (µg of cinnamon essential oil/bee)
and minimal inhibitory concentration (MIC, µg/ ml) of essential oil against P. larvae.
Hours LD50 (µg essential oil/bee) MIC (µg/ml) SI (ml/bee)
24 456.07 50 9.1214
48 432.13 50 8.6426
72 427.32 50 8.5464
Table 3. Mean values (percentage ± s.d.) of infected larvae at different days from experimental infection.
Days Control Essential oil Antibiotic F-value
17 0.59 ±0.30 a 0.14 ± 0.13 b 0.23 ± 0.31 b 4.54 (P = 0.0341)
24 13.08 ± 5.23 a 5.19 ± 2.95 b 4.75 ± 3.41 b 6.82 (P = 0.0105)
31 83.91 ± 13.39 a 31.49 ± 5.84 b 19.06 ± 6.3 b 29.39 (P = 0.0000)
Means in each line followed by different letters are significantly different (LSD test, P < 0.05).
the variance. When the F-tests were significant, means
were separated applying the least significant difference
(LSD) test (P < 0.05) (Statgraphics Plus 2001). Tables
show non-transformed values.
Results
Antimicrobial assay
Against P. larvae strain used in these experiments,
MIC values were 50 µg/ml and 3.125 µg/ml respectively
for the essential oil of C. zeylanicum and for oxytetracy-
cline-HCl.
Bees lethality test
Estimated A. mellifera LD50s were 456.07 µg/bee,
432.13 µg/bee and 427.32 µg/bee at 24 h, 48 h and 72 h,
respectively (table 1). Referring to the ICBB (1985), the
theoretical LD50 values for the bees of specific active
ingredient, like dimethoate, range between 0.1-0.3
µg/bee; this level corresponds to a highly toxic com-
pound (Gough et al., 1994). Therefore, the highest
LD50 value for the C. zeylanicum essential oil, would
correspond to a "virtually non-toxic" product, according
to the ICBB (1985).
As an adaptation of the methodology used by
Lindberg et al. (2000) the security index was employed
to estimate a safe factor of the colony (table 2). This pa-
rameter diminished after 24 h, because LD50 values de-
creased over time, while MIC values remained stable.
This trend shows that when oil exposure-time of bees
increases, toxicity is expected to grow.
Apiary trial
After the artificial infection of bee colonies, the ex-
perimental model allowed to follow the development of
the disease in all beehives. From the 3
rd
to the 5
th
day
after the scales inoculation, the bees cleaned the in-
fected cells and the queen laid eggs inside. After the 10
th
day, infected larvae were not detected during inspec-
tions. From the beginning of the treatments to the 17
th
day, colonies treated with essential oil showed an aver-
age of 0.14% infected larvae, which is similar to levels
recorded in colonies treated with antibiotics, but lower
than untreated ones. After the 24
th
day, colonies treated
with essential oil showed a higher number of infected
larvae than those treated with antibiotics, but even lar-
ger numbers of infected larvae were recorded in the
control hives. Significant differences (P < 0.05) among
treated and control groups were verified (table 3). From
the beginning of the treatments to the 24
th
and 31
st
day,
the essential oil-treated hives group showed a reduction
in infected larvae percentages of 7.89% and 52.42%,
respectively, in comparison with the untreated ones. By
contrast, these values increased of 0.44% and 12.43%,
respectively, when compared to the antibiotic treated
group. However, no statistical differences were recorded
between the two treated groups (table 3).
Discussion and conclusions
MIC values of cinnamon essential oil obtained from
Mar del Plata AFB strain were similar to those obtained
against others P. larvae strains isolated from infected
honeybee brood combs of Buenos Aires province
(Gende et al., 2008b). In relation with minimal inhibi-
tory concentration of the antibiotic, the Mar del Plata
strain was susceptible by introducing a value of MIC
less than 5 µg/ml (Alippi, 1996).
When the essential oil was administered in sugar syrup
by systemic way, regression equations presented in table
96
1 shows that the mortality in bees fed with 1000 µg/ml
syrup did not exceed 10.0% on any day. Although the
oral toxicity of essential oils has been already studied on
the bees (Ebert et al., 2007), following the preliminary
test carried out by Carta and Floris (1989), to our knowl-
edge this is the first report regarding the use of cinnamon
essential oil by oral administration in vitro assays.
In the experimental apiary control beehives showed
higher levels of infected cells than treated ones. There-
fore, both tested products, the antibiotic and the cinna-
mon oil, were effective in the control of AFB. However,
as already known, the use of antibiotics compared to the
essential oil can generate toxicological and biological
risks due to an accumulation of residues in beehive
products which decreases their quality and can also in-
duce resistance to P. larvae strains or other bee patho-
gens (Miyagi et al. 2000; Evans, 2003; Thompson et al.,
2005; Martel et al., 2006). Although we can exclude
that the Argentinean strain of P. larvae tested is par-
tially resistant to antibiotics (Alippi, 1996), the analo-
gous disease development in the treated groups (O and
Co), proved that cinnamon oil may represent an impor-
tant alternative natural product for AFB control in api-
ary. Its efficacy was statistically comparable to the
tested antibiotic. The results of our experiments support
other research findings (Carta and Floris, 1989; Carpana
et al. 1996; Floris et al., 1996; Floris, 2001). Moreover,
several recent studies proved the use of cinnamon as a
stimulus for honey bee learning (Abramson et al., 2006,
2008) or its use against other important mites and dis-
ease vectors (Abramson et al., 2007). In addition, the
apparently lower ability of other natural essence-based
products to keep down bacterial infestation levels (Albo
et al., 2003), encourages the employment of cinnamon
oil in the hives. Nevertheless, in our case the experi-
mental infection was based on an initial inoculum corre-
sponding to a very high dosage of bacterial spores in
comparison with a natural infection. In fact, a dry scale
formed from a diseased larva affected by AFB usually
contains approximately 2 x 10
9
spores/bee (Shimanuki
and Knox, 1997); in our tests an average number of 45 ±
5 scales corresponding to about 9 x 10
10
spores/bee,
were introduced in the previously healthy beehives. On
the other hand, it is generally agreed that the use of
naturally infected beehives better mimic the reality and
consequently provide more reliable treatment efficacy
evaluations. Beyond, in order to avoid the possible loss
of honeybee orientation observed by Higes et al. (1997),
we included only two doses of cinnamon essential oil in
two weekly treatments. So that, enhanced efficacy of
cinnamon oil in comparison with antibiotic treatments,
might have been obtained by either using three different
doses or with an experimental infection based on a
lower number of scales. Finally further improvements
might be obtained employing different and more appro-
priate treatment application techniques. For instance,
manipulative treatments, such as the cited “shaking”
method (Bailey and Ball, 1991) aimed at salvaging adult
bees from combs containing diseased brood, before the
administration of cinnamon oil, is supposed to provide
optimal efficacy in preventing AFB. Enhancement of
treatment efficacy might be possible also if this oil is
used in combination with other active ingredients such
as thymol (Fuselli et al., 2006); plant extracts, other es-
sential oils and their principal components (Gende et al.,
2008b; 2008c; 2009) involved in integrated pest man-
agement strategies of the hive.
Everything considered, this study represents a further
progress of a larger research, involving the chemical
composition and the concentration of the main cinna-
mon essential oil compounds, with special regard to the
components inhibiting bacterial growth (Gende et al.,
2008b). All these findings have helped to define rec-
ommended concentrations for apiary application in or-
der to minimize the toxicological risks for bees and to
avoid the honey taste threshold (Bogdanov et al., 1999)
or other undesirable effects, such as the appearance of
resistance strains as a consequence of the indiscriminate
use of antibiotics.
Acknowledgements
The authors would like to thank Claudia Faverin for the
assistance in providing the statistical analysis also Ser-
gio Ruffinengo and Gabriel Sarlo for their help in the
fields experiments and to Giovanni Formato for critical
review and Michael Robeson for English revision. This
work was supported by UNMDP, ANPCyT and CONI-
CET.
References
ABRAMSON C. I., SINGLETON J. B., WILSON M. K., WANDERLEY
P. A., RAMALHO F. S., MICHALUK L. M., 2006.- The effect of
an organic pesticide on mortality and learning in Africanized
honey bees (Apis mellifera L.) in Brasil.- American Journal
of Environmental Science, 2: 37-44.
ABRAMSON C. I., ALDANA E., SULBARAN E., 2007.- Exposure
to citral, cinnamon, and ruda disrupts the life cycle of a vec-
tor of Chagas disease.- American Journal of Environmental
Science, 3: 7-8.
ABRAMSON C. I., MIXSON T. A., CAKMAK I., PLACE A. J.,
W
ELLS H., 2008.- Pablovian conditioning of the proboscis
extension reflex in harnessed foragers using paired vs. un-
paired and discrimination learning paradigms: Test for dif-
ferences among honeybee subspecies in Turkey.- Apidology,
39: 428-435.
A
LBO G. N., HENNING C., RINGUELET J., REYNALDI F. J., DE
GIUSTI M. R., ALIPPI A. M., 2003.- Evaluation of some es-
sential oils for the control and prevention of American
Foulbrood disease in honey bees.- Apidologie, 34 (5): 417-
427.
ALIPPI A. M., 1992.- Characterization of Bacillus larvae
White, the causal agent of AFB of honey bees. First record
of its occurrence in Argentina.- Revista Argentina de Micro-
biología, 24: 67-72.
A
LIPPI A. M., 1996.- Caracterización de aislamientos de Pae-
nibacillus larvae mediante tipo bioquímico y resistencia a
oxitetraciclina.- Revista Argentina de Microbiología, 28:
197-205.
ALIPPI A. M., 2000.- Is Terramycin losing its effectiveness
against AFB? The Argentinian experience.- Bee Biz, 11: 27-
29.
B
AILEY L., BALL B.V., 1991.- Honey bee pathology. 2
nd
Ed.-
Academic Press, London, UK.
97
BOGDANOV S., LÜLLMAN C., MARTIN P., VON DER OHE W.,
R
USSMANN H., VORWOHL G., PERSANO-ODDO L., SABATINI
A. G., MARCAZZAN G. L., PIRO R., FLAMINI C., MORLOT M.,
H
ERITIER J., BORNECK R., MARIOLEAS P., TSIGOURI A.,
K
ERKVLIET J., ORTIZ A., IVANOV T., D’ARCY B., MOSSEL B.,
V
IT P., 1999.- Honey quality and international regulatory
standards: review by the international honey commission.-
Bee World, 80 (2): 61-69.
C
ARPANA E., CREMASCO S., BAGGIO A., CAPOLONGO F., MUTI-
NELLI
F., 1996.- Profilassi e controllo della peste americana
in alcune regioni italiane.- Apicoltore Moderno, 87: 11-16.
CARTA C., FLORIS I., 1989.- Prospettive di controllo della
peste americana delle api con oli essenziali. Prove prelimi-
nari.- Atti Società Italiana di Ecologia, 8: 183-187.
D’A
LESSANDRO B., ANTÚNEZ K., PICCINI C., ZUNINO P., 2006.-
DNA extraction and PCR detection of Paenibacillus larvae
spores from naturally contaminated honey and bees using
spore-decoating and freeze-thawing techniques.- World
Journal of Microbiology & Biotechnology, 23: 593-597.
E
BERT T. A., KEVAN P. G., BISHOP B. L., KEVAN S. D.,
D
OWNER R., 2007.- Oral toxicity of essential oils and or-
ganic acids fed to honey bees (Apis mellifera).- Journal of
Apicultural Research and Bee world, 46 (4): 220-224.
E
VANS E., 2003.- Diverse origins of tetracycline resistance in
the honey bee bacterial pathogen Paenibacillus larvae.-
Journal Invertebrate Pathology, 83: 56-50.
F
LORIS I., 2001.- Controllo delle malattie delle api con
l’impiego di oli essenziali.- Regione Autonoma della Sarde-
gna. Assessorato Agricoltura e Riforma Agro-pastorale,
3esse, Serramanna, Italy.
FLORIS I., CARTA C., MORETTI M. D. C., 1996.- Activites in
vitro de plusieurs huiles essentielles sur Bacillus larvae
White et essai au rucher.- Apidologie, 27 (2): 111-119.
F
USELLI S. R., GENDE L. B., GARCÍA DE LA ROSA S. B.,
E
GUARAS M. J., FRITZ R., 2005.- Inhibition of Paenibacillus
larvae subsp larvae by the essential oils of two wild plants
and their emulsifying agents.- Spanish Journal of Agricul-
tural Research, 3 (2): 220-224.
FUSELLI S., GARCÍA DE LA ROSA S., GENDE L., EGUARAS M.,
F
RITZ R., 2006.- Inhibición de Paenibacillus larvae subsp.
larvae empleando mezcla de aceites esenciales y agregado
de timol.- Revista Argentina de Microbiología, 38: 89-92.
G
ENDE L. B., EGUARAS M. J, FRITZ R., 2008a.- Evaluation of
culture media for Paenibacillus larvae applied to studies of
antimicrobial activity.- Revista Argentina de Microbiología,
40: 147-150.
GENDE L. B., FLORIS I., FRITZ R., EGUARAS M. J., 2008b.- An-
timicrobial activity of cinnamon (Cinnamomum zeylanicum)
essential oil and its main components against Paenibacillus
larvae from Argentine.- Bulletin of Insectology, 61 (1): 1-4.
GENDE L. B., PRINCIPAL J., MAGGI M. D., PALACIOS S. M.,
F
RITZ R., EGUARAS M. J., 2008c.- Extracto de paraíso (M.
azedarach) y aceites esenciales de (C. zeylanicum), (M.
piperita), (L. officinalis) como control de Paenibacillus lar-
vae.- Zootecnia tropical, 26 (2): 151-156.
GENDE L. B., BAILAC P., MAGGI M. D., PONZI M., FRITZ R.,
E
GUARAS M. J., 2009.- Antimicrobial activity of Pimpinella
anisum and Foeniculum vulgare essential oils against Paeni-
bacillus larvae.- Journal Essential Oil Research, 21: 91-93.
G
ENERSCH E., FORSGREN E., PENTIKAINEN J., ASHIRALIEVA A.,
R
AUCH S., KILWINSKI J., FRIES I., 2006.- Reclassification of
Paenibacillus larvae subsp. pulvifaciens and Paenibacillus
larvae subsp. larvae as Paenibacillus larvae without sub-
species differentiation.- International Journal of Systematic
and Evolutionary Microbiology, 56: 501-511.
G
OUGH H. J., MC INDOE E. C., LEWIS G. B., 1994.- The use of
dimethoate as a reference compound in laboratory acute tox-
icity tests on honey bees (Apis mellifera L.) 1981-1982.-
Journal of Apicultural Research, 33 (2): 119-125.
HANSEN H., BRODSGAARD C., 1999.- American Foulbrood: a
review of its biology, diagnosis and bee control.- Bee World,
80 (1): 5-23.
H
ASEMAN L., 1961.- How long can spores of American foul-
brood live?- American Bee Journal, 101: 298-299.
HIGES M., SUAREZ M., LLORENTE J., 1997.- Comparative field
trials of varroa mite control with different components of es-
sential oils (thymol, menthol and camphor).- Research and
Reviews in Parasitology, 57 (1): 21-24.
ICBB, 1985.- 3
rd
Symposium on the harmonisation of methods
for testing the toxicity of pesticides to bees, 18-21 March
1985. International Commission for Bee Botany, Rotham-
sted Experimental Station, Harpenden, UK.
LINDBERG C. M., MELATHOPOULUS A. P., WINSTON L. M.,
2000.- Laboratory evaluation of miticides to control Varroa
jacbsoni (Acari: Varroidae), a honey bee (Hymenoptera:
apidae) parasite.- Journal of Economic Entomology, 93:
189-198.
L
INDSTROM A., 2006.- Distribution and transmission of
American Foulbrood in honey bees. Doctoral thesis, Swed-
ish University of Agricultural Sciences, Uppsala, Sweden.
M
AGGI M. D., RUFFINENGO S. R, GENDE L. B., BAILAC P. N.,
P
ONZI M. I., SARLO E. G., EGUARAS M. J., 2009.- Laboratory
evaluations of Syzygium aromaticum (L.) Merr. et Perry es-
sential oil against Varroa destructor.- Journal Essential Oil
Research. (In press).
MARTEL A. C., ZEGGANE S., DRAJNUDEL P., FAUCON J. P., AU-
BERT
M., 2006.- Tetracycline residues in honey after hive
treatment.- Food Additives and Contaminants, 23: 265-273.
MIYAGI T., PENG C. Y. S., CHUANG R. Y., MUSSEN E. C.,
S
PIVAK M. S., DOI R. H., 2000.- Verification of oxytetracy-
cline-resistant American Foulbrood pathogen Paenibacillus
larvae in the United States.- Journal of Invertebrate Pathol-
ogy, 75: 95-96.
MUTINELLI F., 2003.- European legislation governing the au-
thorisation of veterinary medicinal products with particular
reference to the use of drugs for the control of honey bee
diseases.- Apiacta, 38: 156-168.
PICCINI C., D’ALESSANDRO B., ANTÚNEZ K., ZUNINO P., 2002.-
Detection of Paenibacillus larvae subspecies larvae spores
in naturally infected larvae and artificially contaminated
honey by PCR.- World Journal of Microbiology & Biotech-
nology, 18: 761-765.
T
HOMPSON H. M., WAITE R. J., WILKINS S., BROWN M. A., BIG-
WOOD
T., SHAW M., RIDGWAY C., SHARMAN M., 2005.- Ef-
fects of European foulbrood treatment regime on oxytetra-
cycline levels in honey extracted from treated honeybee
(Apis mellifera) colonies and toxicity to brood.- Food Addi-
tives and Contaminants, 22: 573-578.
S
COTT S., 2006.- Measurement of cell concentration in sus-
pension by optical density.- Pharmaceutical Microbiology
Forum Newsletter, 12 (8): 3-13.
S
HIMANUKI H., KNOX D. A., 1997.- Bee health and interna-
tional trade.- Revue science et technique, 16: 172-176.
Authors’ addresses: Ignazio F
LORIS (corresponding au-
thor: ifloris@uniss.it), Dipartimento Protezione Piante, Sezio-
ne Entomologia, Università degli Studi di Sassari, via E. De
Nicola, 07100 Sassari, Italy; Liesel Brenda G
ENDE
(lgende@mdp.edu.ar), Matías Daniel M
AGGI (biomaggi@
gmail.com), Natalia D
AMIANI (ndamiani@mdp.edu.ar), Rosa-
lia F
RITZ (rfritz@mdp.edu.ar), Martin Javier EGUARAS
(meguaras@mdp.edu.ar), Universidad Nacional de Mar del
Plata, Funes 3350 (7600), Mar del Plata, Buenos Aires, Argen-
tina.
Received September 4, 2008. Accepted March 15, 2009.
