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

Colony Collapse DisorderColony Collapse Disorder

Varroa Destructor MiteVarroa 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 non-

feeding 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

successoThis 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

•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

Disease TransmissionDisease Transmission

•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 UsePesticide 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 mitesThis 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 GroomingSocial 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

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

Being able to breed bee’s with an innate higher resistance to the mites?

•The colonies that were bred for higher grooming behaviours had

showed no reduction in honey production

The impact was miniscule, and not feasible as a

control strategy

•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 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 eco-friendly way do

deal with pests. Plant derived substances, many from South America, have been shown to have toxicity, repellence, anti-feedant 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.

• Araneda, X., Bernales, M., Solano, J., & Mansilla, K. (2010). Grooming behaviour of honey bees (Hymenoptera: Apidae) on varroa (Mesostigmata: varroidae). Revista Colombiana De Entomologia, 36(2), 232-234.

• Calderone, N.W. (2001). Behavioural responses of Varroa destructor (Acarii Varraidae) to extracts of larvae, cocoons and brood food of worker and drone honey bees, Apis mellifera (Hymenoptera: Apidae). Physiological Entomology, 26, 341-350.

• Coffey, M.F., Breen, J., Brown, M.J.F., & McMullan, J.B. (2010). Brood-cell size has no influence on the population dynamics of Varroa destructor mites in the native Western honey bee, Apis mellifera mellifera. Apidologie, 41(5), 522-530.

• Damiani, N., Gende, L.B., Maggi, M.D., Palacios, S., Marcangeli, J.A., & Eguaras, M.J. (2011). Repellant and acaricidal effects of botanical extracts on Varroa destructor. Parasitol Res, 108, 79-86.

• Di Prisco, G., Pennacchio, F., Caprio, E., Boncristianai, H.F., Evans, J.D., & Chen, Y.P. (2011). Varroa destructor is an effective vector of Israeli acute paralysis viros in the honeybee, Apis mellifera. Journal of General Virology, 92(1), 151-155.

• Guzman-Novoa, E., Eccles, L., Culvete, Y., Mcgowan, J., Kelly, P.G., & Correa-Benitez, A. (2010). Varroa destructor is the main culprit for the death and reduced populations of overwintered honey bee (Apis mellifera) colonies in Ontario, Canada. Apidologie, 41(4), 443-450.

• Le Conte, Y., Ellis, M., & Ritter, W. (2010). Varroa mites and honey bee health: can Varroa explain part of the colony losses?. Apidologie, 41(3), 353-363.

• Mockel, N., Gisder, S., & Genersch, E. (2011). Horizontal transmission of deformed wing virus pathological consequences in adult bees (Apis mellifera) depend on the transmission route. Journal of General Virology, 92(2), 370-377.

• Mullin, C.A., Frazier, M., Frazier, J.L., Ashcroft, S., Simonds, R., van Engelsdrop, D., & Pettis, J.S. (2010). High Levels of Miticides and Agrochemicals in North American Apiaries: Implications for Honey Bee Health. PLoS ONE, 5(3), 1-19.

• Stanimirovic, Z., Stevanovic, J., Aleksic, N., & Stojce, V. (2010). Heritability of Grooming Behaviour in Grey Honey Bees (Apis mellifera carnica). Acta Veterinaria (Beograd), 60(2-3), 313-323.

• Wu, J.Y., Anelli, C.M., &Sheppard, W.S. (2011). Sub-Lethal Effects of Pesticide Residues in Brood Comb on Worker Honey Bee (Apis Mellifera) Development and Longevity. PLoS ONE, 6(2), 1-11.