Presentation on theme: "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."— Presentation transcript:
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: o Hygienic behaviour o Innate immunity o Pesticide Sensitivity o Nutrition o Adult age o Temperature Colony Collapse Disorder
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 o Followed 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 success o This 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): o Acute Paralysis Virus (IAPV) o Deformed Wing Virus (DWV) Both these viruses are transferred to the bee’s through the Varroa mite Disease Transmission
In the case of DWV, the mite transmits the virus to the pupae while feeding o When the infected pupae metamorphosis to an adult, they emerge with a wing deformity o Adult 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 o Impairing the bee’s immune response o Impairing 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 o The 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 o The 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 o This 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 o The mean intensity and abundance of the mites was similar in both sizes of brood cells o However, 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 o Very 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 o Acetone 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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