Transcript Honey Bee Colony Collapse Disorder

Colony Collapse Disorder
Population crashes have been common place since the 1980’s but have
become disastrous since 2006, with 1/3 of honeybee colonies being lost
each winter since.
•These collapses happen during overwintering
•Honey bee colony health can be impacted by many things including:
oHygienic behaviour
oInnate immunity
oPesticide Sensitivity
oNutrition
oAdult age
oTemperature
Varroa Destructor Mite
•The Varroa Destructor is a parasitic mite of Western/European Honey
Bees (Apis Mellifera) which is considered a severe pest.
•The mites presence in a hive puts pressure on the health of the colony
•The leading cause of colony overwintering mortality is an infestation by
these mites
oFollowed by bee populations and food reserves of the colony going
into winter
•The mite is nonfeeding while being
carried around on
adult bees
•Contradictory?
•Mite is only reproductive while living within the brood cell and feeding on
the bee larvae
•In Apis Mellifera bees, the mite can reproduce on the both worker and
drone brood, not so on it’s other bee host
Immature drone bees are more likely to be infected than worker bees,
while queen cells are almost never infected
•A mite can produce 2.2 -2.6 viable female offspring on average when on a
drone larvae
•Only 1.3 – 1.4 viable offspring are produced per worker larvae
•Those mites that do enter queen cells have zero reproductive success
oThis could be due to the
amount of care and
attention given to
different classes of larvae
by nurse bees
•Mites enter drone cells
40 – 50 hours prior to
capping
•Enter worker cells 15 –
20 hours prior to
capping
It is believed that the mites are responding to aliphatic esters being released by
the larvae
•The drones produce much more of these compounds than either workers or
queens
•As the larvae progress before capping, all increase production
•Even at peak production workers and queens never match drone
production
Disease Transmission
•Bee’s have fewer immune response proteins than many other insects
•Two viruses are significant markers of colony collapse disorder (CCD):
oAcute Paralysis Virus (IAPV)
oDeformed Wing Virus (DWV)
•Both these viruses are transferred to the bee’s through the Varroa mite
•In the case of DWV, the mite transmits the virus to the pupae while
feeding
oWhen the infected pupae metamorphosis to an adult, they emerge
with a wing deformity
oAdult nurse bees can be infected as well if they cannibalize infected
pupae
Pesticide Use
If the mite populations within
a colony are not kept in check
by a beekeeper, the colony will
collapse within a few years.
•Traditionally the hives are treated with chemically synthesized pesticides
•Apis Mellifera have only half as many detoxifying enzymes as pesticide resistant
insects do
•Chemical pesticides have sub lethal effects, impairing the bee as opposed to
killing it outright
oImpairing the bee’s immune response
oImpairing learning and memory in individuals
•Bee mites in Argentina are showing resistance to synthetic compounds
The sub lethal effects of the pesticides on bees can help
the Varroa mite
•The pesticides can cause delayed emergence of the pupated bees
•Gravid female mites lay four eggs every thirty hours within the sealed
brood cell
oThe first egg laid is male, while all others following are females
In control bees the third daughter would only have a 13% chance of
reaching maturity before the host emerges from it’s cell
oThe longer emergence is delayed, the higher the chance that
female will be able to reach maturity in time
This leads to higher fecundity of the Varroa mites
This also leads to further damage to the honeybee
individuals
•The mites inflict direct damage on the larvae while feeding
•The more mites on a larvae, the more damage they do
•Bees will emerge small, with low metabolic reserves,
sometimes even with physical deformities
Social Grooming
•Bees are able to locate and remove mites from there’s and other bees
bodies using their mandibles
oThis can significantly reduce the impact of the pest on the colony
Generally hygienic and grooming behaviour
is the most significant mechanism that
contributes to a colonies resistance to the
mites
Even in immaculate colonies, hygiene is not
going to be adequate to maintain the pest on
it’s own
Being able to breed bee’s with an innate higher resistance to
the mites?
Experiments have been performed to look
into long-term solutions through breeding
high grooming strains of bees.
•Looking at grooming behaviours in
individuals of different levels of relatedness,
and different colonies with different queens,
they determined that grooming behaviour is
genetically determined, but also influenced
by environmental factors
•The colonies that were bred for higher grooming behaviours had showed no
reduction in honey production
•The test colonies did show slight improvement in grooming behaviours, but
only between close relatives
•The slight increase did not increase the removal of mites or reduce the
population densities of the mites within the colonies
The impact was miniscule, and not feasible as a control strategy
The impact of brood cell size on the effect of mites within the colony
was also tested:
•The small test brood cells were compared with control regular sized
brood cells
oThe mean intensity and abundance of the mites was similar in
both sizes of brood cells
oHowever, the smaller brood cells were actually more likely to be
infected
In the wake of alternative strategies failing testing and chemical
pesticide use having damaging effects not only on the bees but the rest
of the environment around them, people are beginning to look at
substances derived from plants as natural pesticides. A safe and ecofriendly way do deal with pests.
Plant derived
substances, many
from South America,
have been shown to
have toxicity,
repellence, antifeedant and growth
regulatory affects
against insect pests.
•Apis Mellifera hives are
conventionally treated with
synthetic acaricides
•Some essential oils affect mite
reproduction and have repellent
actions
oVery low concentrations of monoterpenes and phenolic
compounds can induce a reduction in the fecundity of the mite,
preventing high levels of parasitism within treated colonies
oAcetone extracts have been shown to have remarkable toxicity for
the mites in laboratory settings
Ethanolic extracts from Baccharis
flabellata and minthostachys
verticillata have been shown to have
high levels of toxicity to Varroa mites,
but be completely harmless to Apis
Mellifera hosts.
•This effect is due to different terpenes
and phenolic compounds in the
extracts from these plants
•Increasing the concentration of these
compounds and exposure time of the
mites to the compounds only increases
their toxicity
Baccharis flabellata has been shown to have
further repellatory affects on Varroa.
•A simple olfactory stimulus from extracts of
this plant is powerful enough to cause a
disturbance in the mites behaviour, keeping it
away from the ‘smell’
Sub-lethal effects such as this are just as
useful in controlling the mites, anything that
can interfere with the mites ability to locate
it’s host prevents it from reproducing.
The mixture of Baccharis flabellatas extracts to both prove toxic
to and repel the mites simply by the smell of it makes it a
promising control agent.
Like any control strategy, botanical extracts have their difficulties
•Even once you’ve discovered your target extract, you must be precise in
gathering it
•The same herbal extract may vary depending upon things such as
the season you harvest it in, the origin of the plant you’re harvesting
from or the process you use to dry it
A single botanical extract may be composed
of over 150 chemical constituents
•Even the Minthostachys
extract has very little know
about it’s chemical
constitution
These mites are a major pest posed to initiate an
economic disaster if they are not controlled.
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