the efficacy of certain essential oils and their mixtures on the parasitic mite varroa destructor
TRANSCRIPT
THE EFFICACY OF CERTAIN ESSENTIAL OILS AND THEIR MIXTURES ON THE PARASITIC MITE VARROA DESTRUCTOR (Anderson and Trueman)
Salah M. Hussein, Dahi M. Moustafa and A. R. Hassan
Plant Protection Dept., Faculty of Agriculture , Minia Univ.
Abstract
The ectoparasitic mite Varroa destructor (Anderson and Trueman) is considered one of the most serious
pests of beehives, causing tremendous damage to honey bees (Apis mellifera L) and great economic loses to the
beekeeping industry. Efficacy of six essential oils (Marjoram oil , Thymol,
Cinnamon, Clove, Eucalyptus, Citronella, and 15 of their mixtures were
evaluated against varroa mite infested the honeybee colonies for two
successive seasons. The tested oils were applied on the infested bee
colonies at 28 days intervals.
Results indicated that Cinnamon + clove and Marjoram oil gave the
reduction % against mites on adult (95.30% and 89.15% ) followed by
Thymol oil (87.5%), cinnamon oil (87.22%). From the mixtures Marjoram
+ clove oil gave the highest effect against Varroa on adult (84.47%).
Cinnamon oil and the mixture of Cinnamon and clove with concentration
of 1.5 ml / hive gave the highest reduction on mites parasite on adult bees
and brood mite infestation and highly knockdown thus they can be used as
a good elements in integrated mite control.
Introduction
Honey bee colonies are subject to infestation by insects, mites and diseases.
The ectoparasitic mite Varroa destructor (Anderson and Trueman) is considered one of the most serious
pests of beehives. Parasitism can result in a loss of up to 25% of adult weight, severe deformations of the wing and
reduced longevity of worker and drone honey bees. Colonies infested with Varroa destructor have significantly reduced
worker bee populations and eventually die if left without controlling.( Adams2001(
The widespread use of synthetic lipophilic acaricides has lead to the
accumulation of residues in beeswax, propolis and to a much lesser degree,
in honey (Hussein, 2009). The development of acaricide resistance in V.
destructor populations and the spectre of the contamination of hive products
provide considerable incentive to develop new treatment strategies that
minimize the potential for the rapid development of resistance and the
accumulation of residues.
Plant essential oils have potential as products for varroa mite control because
some of them are selective and have little or no harmful effects on non target
organisms. They may be applied to hiding places or host ( bees) in the same
way as other conventional acaricides. Many essential oils are known to
posses various bioefficacies such as ovicidal, various arthropod pests
repellent. Anti- feeding and biocidal activities against various arthropod pests
without any adverse effects on non target species. And they are found to be
highly effective against insecticide resistant pests .
Thus the present studies were carried out to Evaluate the efficacy of certain
essential oils and their mixtures on the parasitic mite Varroa
destructor( adult and brood infestation) to find out one of the natural
products or mixture which maximizing Varroa control and minimizing the
site effect on the honeybee colonies and environmental, with minimal costs.
MATERIALS AND METHOD
1-Experimental honeybee colonies:
Sixty six honeybee colonies of the first hybrid carnelian bees ( Apis
mellifera Carnica) were selected among the colonies of a private a piary
at Dahrout village. The selected colonies dequeened at August and three
days later, each received virgin sister queen. The successful natural mated
queens were marked on their thoraxes and were left in their colonies till
the end of the flow season. At the end of September, the colonies having
an equal strength and healthy marked queens were chosen for conducting
the experiments.
The experimental colonies were divided into groups, each having three
colonies as replicates. Average strength of the tested colonies was 8 combs
covered with bees housed in langstroth hive.
Types of the tested essential oils
Efficacy of six essential oils and 15 of their mixtures were evaluated
against varroa mite infested the honeybee colonies. Evaluation of the
tested oils were continued over two successive seasons the tested oils
(Table 1) were obtained from El- Gomhoria chemicals company, Cairo.
Preparation of the essential oils:
Emulsions of three concentrations (1.5, 0.75, and 0.38 ml/hive) of each
tested oil were prepared through mixing the specified concentration with
0.5 ml of an emulsifier ( Triton – X) and sufficient amount of water to
obtain 30 ml emulsion. Volume of the prepared emulsion was sufficient to
treat one infested bee colony (one hive). Preparation of the emulsions of
the tested oils have been done just before application.
Table (1): English and scientific name of the source of the essential oil:
English name Scientific name of plant source
1-Marjoram oil Majorana harensis
2-Citronella oil Cymbopogon nardul L
3- Cinnamon oil Cinnamomum zeylanicum Blume
4-Clove oil Eugenia caryophyllus L
5-Eucalyptus oil Eucalyptus globulis, labill
6-Thymol oil Thymus vulgaris L.
Application of the tested oils:
Hand sprayer was used for delivery of a particular concentration on the
combs covered with bees of the infested colony. Spraying had been done
on the end of the day hours to insure presence of most individuals of the
bee colony. Each concentration was replicated three times on three
infested colonies. Three colonies were used as control treatment, and
treated with emulsion of water and emulsifier. Treatments of the tested
oils were applied periodically at 28 days intervals
Evaluation the efficacy of the tested materials.
The efficacy of the tested materials were evaluated through estimation the
infestation percentage of Varroa mite on colony individuals and its brood.
Level of infestation on live bees was determined through randomly
collection of about 50 bees / colony in a gar partially filled with water and
few drops of detergent (Liquid soap). The collected bees were shaken for
30 seconds, then bee were filtered through muslin ( 8 to 12 mesh/ inch) to
remove the bees, and the passed adults of mite were then counted
(Komeill, 1988). This procedure was done before the application and after
24h, 48, 7; 14 and 28 post days application and the treatment was applied
new.
Also, infestation of brood was determined at the same time of examination
of the adult bees. One hundred of sealed brood worker per colony were
randomly chosen. The cell capping were removed by forceps and the
pupae were picked up to examine for mites presence ( Marcangeli et al.,
1992).
Besides above measurements, the hive debris were examined periodically
for determination the number of the natural mite fall per hive a day.
Amount of dead mites was used as indicator of mite population counting
the number of dead mites was done through providing the bottom brood of
each brood chamber with sticky white paper smeared with thin layer of
Vaseline.
For evaluation the efficacy of the tested essential oils in controlling Varroa
mite, two ways were considered, the first, estimation average effectiveness
period. While the second one was calculation reduction percentage of mite
infestation by applying Henderson and Telton 1955 equation.
The reduction rate of infestation =
( Ta X Cb)
= 100 x 1-
( Tb X Ca)
where:
Tb is % infestation of mite before treatment
Ta is % infestation of mite after treatment
Cb is % infestation of mite before treatment for the control.
Ca is % infestation of mite after treatment for the control.
Statistical analysis:
The collected data were subjected to one way analysis of variance
according to method of Mead et al. (1993). The statistical analyses were
conducted using the SPSS II and F- test. Differences among means were
determined by Duncan's multiple range test (P < 0.05 or < 0.01 ).
Results and Discussion
Efficacy of the tested essential oils with 1.5 ml./hive against Varroa
mite
The statistical analysis of the obtained data indicated that there were
significant differences among different treatments and concentrations.
Data shwed that the the concentration of 1.5 ml/hive gave the highest
effect as showen in Fig 1, 2 and 3 .
Data presented in Fig. 1 showed that the highest average reduction % of
mite infestation on adult bees (95.30%) was recorded with applying the oil
mixture of Cinnamon and Clove, followed by Marjoram oil ( 89.15%), and
Thymol oil (87.56%)
As regard to brood infestation the results showed much variation in
reduction infestation percentage, the highest reduction percentage ( 75%)
was obtained when the colonies treated with clove oil or the oil mixture of
Cinnamon and Eucalyptus.
On the other hand, recording the average of fallen mites for two seasons
showed that the highest number of dead varroa mite ( 17.25 mites/ colony)
was recorded with spraying Cinnamon oil, followed by Thymol oil ( 14.35
mites/ colony) and oil mixture of Cinnamon and Eucalyptus.
Fig.(1): Effect of spraying essential oils and their mixture on their
infestation level of the parasitic mite (Varroa destructor) with the highest
concentration (1.5 ml /hive
Fig.(2): Effect of spraying essential oils and their mixture on their
infestation level of the parasitic mite (Varroa destructor) with the
highest concentration (0.75 ml /hive)
Fig.(3): Effect of spraying essential oils and their mixture on their
infestation level of the parasitic mite (Varroa destructor) with the
highest concentration (0.36 ml /hive).
Table(2): Effect of spraying essential oils and their mixture on their infestation level of the parasitic mite (Varroa destructor) during two seasons with the highest concentration (1.5 ml /treatment).
Average effect on
TreatmentsReduction
% in varroa on adult
bees
Reduction % On brood
No. of Dead fallen Varroa mites
78.1125.006.88Marjoram oil
62.5837.507.63Citronella oil
73.7716.678.53Cinnamon oil
73.3850.0016.25Clove oil
76.8025.007.25Eucalyptus oil
75.5435.008.75Thymol oil
60.3225.003.75Marjoram oil + Citronella oil
69.7325.009.13Marjoram oil + Cinnamon oil
61.5035.008.75Marjoram oil + Clove oil
61.2050.004.35Marjoram oil + Eucalyptus oil
71.3437.507.50Marjoram oil + Thymol oil
64.0637.509.88Citronella oil+ Cinnamon oil
69.7332.504.25Citronella oil + Clove oil
67.9150.004.13Citronellal oil + Eucalyptus oil
67.4916.674.40Citronella oil + Thymol oil
79.0437.504.75Cinnamon oil + Clove oil
55.8242.509.13Cinnamon oil +Eucalyptus oil
69.3329.177.65Cinnamon oil + Thymol oil
68.5212.507.65Clove oil + Eucalyptus oil
66.8850.004.75Clove oil + Thymol oil
66.3737.505.15Eucalyptus oil + Thymol oil
0.000.001.50Control
From the data presented in fig1, 2 and 3 the maximized effect was
observed with spraying the high concentration 1.5 ml . The other
concentrations 0.75 and 0. 375 ml/ hive showed a little effect Fig 2 and 3
Thus we advise to use a high concentration which gave mortality more
than 90% reduction and gave highly mortality on mites. The low
concentration cannot used because it may develop the resistance of mite.
From our results, it is clear that Marjoram, Cinnamon, and Thymol
essential oils have biological activity against varroa mite and environment
friendly (non- polluting and lesser or no toxicological concerns ) (Isman,
2006).
The obtained results may permitted us to conclude the following points:
1-The tested essential oils in general were more effective in reduction of
Varroa mite population parasited on adult bees than those parasited on the
brood of the same colonies. These findings may be due to the direct
toxicity of these substances on the Varroa mite parasited on adult bees,
while this effect not reached rapidly, and directly to the brood and their
associated mite which lived together in the capped cells.
2-Application of the tested essential oils at 28 days with the concentration
1.5 ml/ hive, they showed various efficacy against Varroa mite which can
managed in the following descending order the oil mixture of cinnamon
and clove > Marjoram oil > Thymol oil > Cinnamon oil which
gave(95.30, 89.15, 87.56 and 87.22 reduction % on adult respectively.
These findings are in agreement with results of Richi et al., (1991) found
that the colonies treated by Apilife – Var ( Thymol represent the most
content) for a total 38 days resulted in 96.4% of the mites mortality and in
colonies treated for 79 days, 99.00%. Allam, (1999) found that the
essential oils treatments had higher effect on the Varroa mite, Less side
effect on brood rearing and Less hazards towards bees and queens, in spite
of some lost colonies during treatments. Imdorf et al., (1999) mentioned
that Thymol and Thymol blended with essential oils or essential oil
components provided the best results as mite mortality approached 100%.
Khattab (2001) found that the efficacy of the volatile oils were tested
against Varroa mite in Egypt i.e. Thymol and Clove oils as Varroacids in
controlling the Varroa mite were found to be highly effective in reducing
the Varroa mite infestation on the honeybee colonies.
Serag El- Dien and Eissa (2003) found that Clove oil ( 2 cm3/ hive) gave
the highest reduction ( 91.00%) of Varroa mite in comparing to menthol,
anise, citrus and camphor after four weeks of treatment.
Many essential oils are known to possess various bioefficacies such as
ovicidal, repllent, antifeeding and biocidial activities various arthropod
pests (Isman, 1999). Additionally, some plant extracts or phytochemicals
are found to be highly effective against insecticide – resistant mite and
insect pests. (Ahn et al., 1997) A carcidal activity has been reported from
some essential oils against V. destructor (Imdorf et al., 1999) and
Dermatophgoides fasinae and D. Pteronyssinus mites (Kim et al., 2003).
In this study, potencies varied according to oil type, concentration and
number of treatments. Additionally, differential susceptibility of the
essential oils from the same plant species to the adult mite was observed
in the two seasons. These differences may be due to the different in a
climatic conditions of the hive, and ecosystem. Thus the essential oils i.e.
( Majoroum oil, Thymol oil, and cinnamon oils gave highly average
reduction % on adult i.e 89.15, 87.56 and 87.22 % respectively.) and the
mixtures ( Cinnamon + clove, Majoroum + Cinnamon and Majoroum +
Clove)gave average reduction % 95.29, 84.72 and 84.47 % on adult)
might be good elements for naturally occurring varroa mite control agent
in honey bee colonies. Also from the general results Cinnamon oil gave
the highest aveg. Reductin % in mites in Adult and brood and gave the
highest aveg. Fallen no. of mite. And its mixture with Euchlyptous oil.
Investigation on mode of action of essential oils or chemical is important
for mite control because it may give useful information on the most
appropriate formulation and delivery means. Volatile compounds of many
plant extracts and essential oils are composed alkanes, alcohols, aldehydes
and terpenoids, particularly mono-terpenoids, and exhibit fumigant
activity Coats et al., 1991, Kown and Ahn, 2002 andf Kim et al., 2003).
Isman and Machial 2006 Bakkali et al., (2008) indicated that aromatic
plants and their essential oils have been used as antimicrobial, acaricidal
and insecticidal agents and to repel insect and mites or protect stored
products. These constitute effective alternatives to synthetic pesticides
without producing adverse effects or the environment (Isman 2000,
Isman and Machial, 2006). Moreover, the interest is essential oils has
regained momentum during the last decade primary due to their fumigant
and contact pesticidal activities and the less stringent regulatory approval
mechanisms for their exploration due to long history of use ( Isman,
2006).
the future potential of plant essential oils as an alternative to synthetic
acaricides for the control of this pest seems promising.
This variability could be overcome through careful sourcing of products,
identification of essential oils that are generally reliable in their toxicity or
controlled production practices. For example work suggests that the
techniques such as micro propagation and used it as dust application may
be use in reducing essential oil variability, through encouraging the
proliferation of selected, reliable plant genotypes (Garddulf et al. 2004).
In general New alternatives for the control of V. destractor are necessary
because of the rapid and widespread development of pythroid and organo-
phosphate resistant mite population and because of the potential for
contamination of hive products by these chemicals ( Hussein 2009)
Essentials, and especially components of essential oils, may serve as
alternatives or as adjuncts to traditional treatment measures. In our
screening tests, many oils and their mixtures show significant acaricide
activity against varroa mites. Some the them may be repellent to V
destructor, others may be alternative and majority of their caused mite
mortality and varied from season to another. This variation may be due to
variation in local environmental and colony conditions effect efficacy and
make it difficult to predict the outcome of many treatments. Only a
combination of Cinnamon and Clove has been successfully used for mite
control with minimum site effect on the bees. Also oils Clove, Thymol and
marjoram were highly effect against Varroa mite on adult and brood with
less effect on honey bee individuals and gave highly honey production with
highly annual profit colony.
Identifying compounds from these oils with acceptable acaricidal activity
with low toxicity to honey bees is essential for providing candidate
compounds for field trails.
Future research can assist in this effect by focusing on the characterization
of the dose response relationships between essential oils and mite /bee
toxicity and effects on mite behaviours. This procedure can serve as a
powerful screening technique because it guides subsequent field researches
into the most productive a venues.
Most essential oils are mixtures of more than 50 components (Imdorf,
1999). The depending on the individual partition coefficient of the
constituents, residues in honey and wax are to be expected. Residues in
honey can lead to adverse effects on taste, while residues in wax can render
it unsuitable for some applications.
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