Conference time is here again! Beekeepers are keen to hear about the progress we are making on selecting and breeding bees for hygienic behaviour in Australia. Jody Gerdts will be speaking first at the Tasmanian conference May 29-30 and then at the Queensland conference 11-12 June to share the results of the past year’s tests.
Originally Printed in the Australian Bee Journal February 2015
With the absence of Varroa, access to quality nutrition and no harsh winters, Australian honey bees are faring quite well compared to their counterparts around the world. We haven’t seen major colony losses and haven’t had to conduct wide-scale investigations into “what’s killing our bees” because, for the most part, our honey bees are doing just fine.
Meanwhile, in the rest of the world, untold amounts of money and time have been invested into understanding the reasons behind the global decline of pollinators. Honey bees seem to get the most attention serving as the poster child for all pollinators, for better or worse. This is partly because humans have been engaged with honey bees for many thousands of years, partly because they are fascinating social insects that are accessible to study and partly because we are reliant on them to pollinate our intensively planted food crops.
Because the European honey bee (Apis mellifera) is not native to many of the geographic regions (including Australia) that it now inhabits there is great controversy within the scientific community including conservationists, agriculturalists/ horticulturalists and apiarists over where honey bees should and shouldn’t live. The argument is that honey bees displace native pollinators because of their adaptability to different environments and climates. Strict conservationists would like to send all honey bees back to Europe or Africa freeing up resources for native wildlife. However, native pollinators aren’t up to the task to pollinate 1000’s of hectares of agricultural crops nor do they make honey. So unfortunately for them, honey bees aren’t being deported any time soon.
In Europe however, Apis mellifera is native with about 10 subspecies represented, so saving the honey bee is not only a matter of pollination security or saving an apicultural industry, but it is fundamentally a matter of conservation. These subspecies were influenced by the last glacial period when the mountain chains of the Pyrenees, the Alps and the Balkans acted as geographic barriers preventing the free movement of honey bee genes. Because of this isolation, populations of honey bees (subspecies) have developed distinct characteristics adapting them to the local climactic and disease pressures.
People around the world understand the important place that honey bees play in our modern life and when faced with global honey bee decline, researchers from 69 countries from across the world joined together forming an organization called COLOSS (Prevention of honey bee COlony LOSSes-www.coloss.org), an “international non-profit focused on improving the well-being of bees at a global level”. In 2009 COLOSS commenced, a 2 year Europe-wide research project with the goal of understanding how pests and diseases impacted locally adapted bees in their own environment and in foreign environments.
Altogether 597 colonies were established in 20 test apiaries spread over 11 countries. The genetic strains (subspecies) belonged to Apis mellifera (from now on A. m.) carnica, A. m. ligustica, A. m. macedonica, A. m. mellifera, A. m. siciliana. At each location, the local strain of bees was tested together with two “foreign” strains starting with a minimum of 10 colonies from each origin. Over half of the queens were from established breeding programs selecting for traditional favorable traits such as high honey yield and gentleness. The others were from conservation programs generally managed by a few beekeepers focusing on subspecies closed to extinction and have not been selected for beekeeper-desired traits.
The climates over the study area differed greatly from the cold north in Finland where bees were cooped up for months at a time to warm Greece where bees were able to fly freely all year.
Over the course of the study, colonies were evaluated for Varroa loads, nosema spp. levels, viruses, swarming tendencies, hygienic behaviour, defensiveness, and population dynamics. No colonies were treated with chemicals to combat diseases or Varroa, however in some apiaries, Varroa was controlled by removing the brood from the colony during the summer. Researchers and technicians at participating institutions gathered for several field days to harmonize their evaluation techniques and used identical methods for the course of the study.
Of the 597 colonies observed, only 94 (15.7%) survived until the end of the study (March 2012). The main cause of loss was Varroa infestations (38.4%), followed by queen problems (16.9%) and nosema (7.3%). Other causes lumped together including weakness, starvation, winter death, robbing, etc. caused 33.8% of colony deaths. Only 3.4% of colony deaths were unknown.
Overall, no particular strain proved to be the best across all environments- said another way- there was no super bee. Interestingly, the locally adapted strains survived longer in each apiary on average compared to the non-local strains but no specific cause of death impacted the non-local strains more than the local strains.
Climactic conditions influence factors such as length of brood season, amount of brood carried and colony bee density. All of which impact Varroa infestation levels and viral loads and have cascading effects for the colony down the track. Not surprisingly, the location of the apiary impacted overall colony mortality providing not only different climactic stressors (cold vs warm winters) but differing pathogen associations and potentially different pathogen strains.
The locally adapted strains of honey bees have evolved survival strategies to deal with all of these pressures in concert. Remove a strain from their environment and they don’t necessarily fare as well. Even colonies from “survivor stock” that exhibit Varroa tolerance on their home turf did not show an overall improved survivorship or resistance to Varroa once they left home.
This research gives much food for thought as it is the first large scale project that acknowledges the positive influence that local adaptation has on colony health.
As beekeepers, we make management decisions to keep our colonies healthy and diseases low. This may mean feeding them sugar or protein or antibiotics or moving them to better forage. We also breed off of bees with desirable traits (good temperament, honey production). This is because we need them to do a job for us- make bees to pollinate plants or to make honey and we want to enjoy working with them. In doing so, we remove many selective pressures and that would otherwise shape their behaviour, disease resistance and synchronization with the local flora in other words- make them independent of us.
Honey bees will never be a domesticated animal; there will always be some bit out of our control, and this is a good thing. Australia is not necessarily an easy place to live as a feral honey bee but is perhaps one of the last places on the planet with a significant feral honey bee population. Localized populations are adapting to their unique environment as you read this article. Marrying the survival capacity of local strains with the traits essential for a thriving beekeeping operation will make great strides in creating a resilient apicultural industry.
Hatjina, F., Costa, C., Büchler, R., Uzunov, A., Drazic, M., Filipi, J., … & Kezic, N. (2014). Population dynamics of European honey bee genotypes under different environmental conditions. Journal of Apicultural Research, 53(2), 233-247.
Uzunov, A., Costa, C., Panasiuk, B., Meixner, M., Kryger, P., Hatjina, F., … & Büchler, R. (2014). Swarming, defensive and hygienic behaviour in honey bee colonies of different genetic origin in a pan-European experiment. Journal of Apicultural Research, 53(2), 248-260.
Büchler, R., Costa, C., Hatjina, F., Andonov, S., Meixner, M., Conte, Y., Uzunov, A., Berg, S. et al (2014). The influence of genetic origin and its interaction with environmental effects on the survival of Apis mellifera L. colonies in Europe. Journal of Apicultural Research, 53(2), 205-214.
Costa, C., Büchler, R., Berg, S., Bienkowska, M., Bouga, M., Bubalo, D., … & Wilde, J. (2012). A Europe-wide experiment for assessing the impact of genotype-environment interactions on the vitality and performance of honey bee colonies: experimental design and trait evaluation. Journal of Apicultural Science, 56(1), 147-158.
Meixner, M. D., Francis, R. M., Gajda, A., Kryger, P., Andonov, S., Uzunov, A., … & Wilde, J. (2014). Occurrence of parasites and pathogens in honey bee colonies used in a European genotype–environment interactions experiment. Journal of Apicultural Research, 53(2), 215-229.
Printed in the Australian Bee Journal December 2014
For those of you just joining in, this column is about on honey bee self defence traits and what beekeepers can do to help optimise honey bee health. The first three articles have focused on the benefits of hygienic behaviour and how beekeepers can incorporate this important genetic bee self defense trait into their operations through testing and breeding for this trait.
Please take note, however, that even the best of genetics cannot entirely prevent the spread of diseases
brought on by environmental stresses, poor nutrition, poor beekeeper management, or a combination of these. In fact, even the most hygienic of colonies can be susceptible disease when stressed.
Chalkbrood is caused by the fungal pathogen Ascophaera apis and can be transmitted by spores found on pollen, in honey, and moved about the colony by house bees. Up to about the 3rd instar, larvae are fed royal then worker jelly from the brood food glands located in nurse bees’ heads. After the 3rd instar, the larvae begin to be fed small amounts of pollen and honey potentially containing chalkbrood spores. Adult bees or pupae are not susceptible to infection but can infect larvae with spores. Beekeepers can also spread the disease by moving infected equipment between colonies.
The infection begins in the gut of the larva and slowly grows out until it penetrates the cuticle, which happens during the 5th instar. Larvae are capped over during the 5th instar as they are preparing to spin a cocoon for pupation. A larva dying from chalkbrood becomes mummified and appears white. However,
once the transmittable spores are formed, the mummy becomes grey or black. Chalkbrood kills the larva just as it is being capped over, commonly the cells containing chalkbrood mummies will appear perforated having a hole in the center- similar to AFB. Viable spores have been cultured from honey after two years of storage and can remain viable for 15 years. More importantly, spores can remain viable in bee bread for up to 12 months.
If chalkbrood spores are so abundant, and can be transmitted so easily, why isn’t the infection more rampant? It turns out that honey bees have a number of ways of resisting infection.
Individual Immune Response
Healthy bees, larvae included have immune systems that can fight pathogens including the fungus A. apis. Similar to our white blood cells haemocytes in honey bees can directly kill the invading pathogen. These systems, however will only function properly when the nutritional needs of the larvae have been met.
As we have already covered, hygienic behaviour is a trait whereby house bees can smell dead or diseased brood and remove it from the colony before the pathogen becomes infectious.
When a larva is in the early stages of succumbing to a chalkbrood infection prior to mummification and spore formation, it releases three volatile compounds (smells) that are different than the smell of a healthy developing larva.
Of these compounds, one specifically, phenethyl acetate, was shown to illicit a hygienic response from nurse bees. When placed on healthy non-infected brood, hygienic nurse bees removed the brood from the colony. The key message here is that the infected pupa was removed from the colony prior to spore formation.
A. Apis is quite sensitive to temperature, thriving at lower nest temperatures (30 C) and dying at elevated nest temperatures (35.5 C). It has been observed that colonies newly infected with an A. apis infection can elevate the temperature of the brood nest inducing a colony fever and preventing the spread of infection.
Other Biotic Factors
Recent research conducted on bee gut microflora suggests that several types of beneficial bacterial also have an antagonistic effect on the development and sporation of A. apis.
However, despite the bee’s best self defense strategies, colonies can still be decimated by chalkbrood and it may be directly related to common beekeeping practices. A. apis is an opportunistic pathogen that kills larvae only when subjected to predisposing conditions.
An infected larva can generally prevent a chalkbrood spore from germinating causing infection and eventually death, but if the larvae is chilled as little as 5 C for 6-12 hours (ideal brood nest temp is approximately 35 C) while in the fifth instar, just capped over and beginning to extend in the cell, the fungal infection can rapidly spread and kill the pupa.
Although this type of chilling is unlikely to occur in a healthy, functioning, stationary hives because the bees can regulate the temperature of the nest, common beekeeping practices can influence the otherwise stable nest environment. For example, reducing the number of adult bees by making splits or changing the arrangement of the brood frames within the nest or shifting bees creating drafts through the colony could result in the critical cooling episode necessary for A. apis infection to take hold.
Remembering that spores can remain viable in bee bread for 12 months and are present in wax and honey, subjecting a colony to a cooling event may trigger an outbreak. As more and more larvae succumb to the infection, the spore count in the colony increases hastening the spread of the disease to other larvae.
Management through Prevention
Since no chemical treatments, natural or synthetic have been shown to be an effective treatment against chalkbrood, it is up to beekeepers to be diligent about reducing modes and methods of transmission and keep that brood nest warm.
• Resist moving infected frames between colonies, spreading spores around your apiary
• If equipment is highly infected, get it irradiated before giving it back to your bees
• Keep your bees well fed, warm, and dry
• Be conscientious when making splits or nucs that enough bees are left in both the old and new colonies to keep the brood warm
• Don’t inspect brood on cold or windy days
• Keep just the right amount of space on the colony- not too many boxes
• Requeen with hygienic stock
But remember even the most hygienic of bees will not be able to overcome a severe chalkbrood infestation brought on by poor management.
And the jury is still out about the bananas…..
Aronstein, K. A., and K. D. Murray. “Chalkbrood disease in honey bees.” Journal of invertebrate pathology 103 (2010): S20-S29.
Flores, J. M., et al. “Effect of temperature and humidity of sealed brood on chalkbrood development under controlled conditions.” Apidologie 27 (1996): 185-1922.
Omar, Mohamed OM, et al. “Antagonistic Effect of Gut Bacteria in the Hybrid Carniolan Honey Bee, Apis Mellifera Carnica, Against Ascosphaera Apis, the Causal Organism of Chalkbrood Disease.” Journal of Apicultural Science 58.1 (2014): 17-27.
Starks, Philip T., Caroline A. Blackie, and Thomas D. Seeley. “Fever in honeybee colonies.” Naturwissenschaften 87.5 (2000): 229-231.
Swanson, Jodi AI, et al. “Odorants that induce hygienic behavior in honeybees: identification of volatile compounds in chalkbrood-infected honeybee larvae.” Journal of chemical ecology 35.9 (2009): 1108-1116.
We are excited to announce our next learning opportunity for people interested in becoming beekeepers! This long course will be delivered over 6 sessions- 5 in the classroom and one in a bee hive.
Visit the registration page for more details
Bee Self Defence- Hygienic Behaviour
Originally printed in the October 2014 issue of the Australian Bee Journal
Humans and Bees
Humans have had a relationship with honey bees (Apis mellifera) for a long time. From the earliest honey hunters to beekeepers managing apiaries, we have used their honey and propolis as food and medicine and their wax for industry. Now we rely on them to pollinate our intensive food system essential to feeding the world’s people. Only healthy honey bees can grow colonies to produce profitable quantities of hive products and provide pollination services that are essential to our lives.
Honey Bee Self Defense
Honey bees colonies can be thought as a super organism, each bee having a role and contributing to the greater fitness of the whole. As such, these super organisms have evolved for millions of years, developing behavioural and biological defenses against pests and diseases, keeping the colony healthy and productive. By understanding bee self defense behaviours and biological processes beekeepers can use both breeding and management decisions to optimize honey bee health.
This article provides a background on hygienic behaviour, an important bee self defense behaviour. It is the first of a series of articles on self-defense traits aimed at helping beekeepers maintain optimum health in their apiaries.
Hygienic behaviour is a heritable genetic trait and a specific type of nest hygiene triggered by smell where 15-18 day old workers can detect, uncap, and remove dead or diseased brood from the nest before the disease enters into a transmittable stage (Arathi et al. 2000, Masterman et al. 2001). Some bees are able to detect diseased brood shortly after it is infected and remove it before the pathogen becomes contagious. Slow removal of diseased brood (after it is contagious) may actually aid the spread of disease in the nest.
Two equally beautiful brood frames. The frame on the left is from a hygienic colony whereas the frame on the right is from a non hygienic colony
Hygienic behaviour was first noted in the 1930’s during efforts to determine if some honey bee colonies were resistant to American Foulbrood (ABF) caused by the bacteria Paennibacillus larvae. Interest in this behavioural trait continued through the 1960 and 1970’s as a mechanism for resistance to AFB. However, with the advent of sulfa drugs and antibiotics used to treat AFB, research was not sustained. In the late 1950’s Walter Rothenbueler coined the term “hygienic behaviour” while studying the heritability of the trait.
During the past 30 years in most of the world, AFB developed resistance to a commonly used chemical, oxytetracyclene (OTC), chalkbrood posed serious negative effects on colony health and Varroa emerged as a major threat to most of the world’s honey bee populations. As bee pests and diseases either developed resistance to chemicals, or the effective chemicals used have shown to have negative effects on honey bee health, beekeepers and researchers are again examining bee’s own self defense mechanisms.
In 1941 A.W. Woodrow (USDA in Laramie Wyoming, USA) fed sugar syrup inoculated with p. larvae spores to experimental colonies and discovered that some colonies removed infected brood before it formed contagious spores (Spivak and Gilliam 1998, I). In fact, the faster the diseased brood was removed, the fewer additional larvae were infected. The most rapid removers showed no signs of AFB infection even through spores were found in brood cells and honey. Those rapid removers were resistant to AFB (Sturtevant 1953 as reviewed in Spivak and Gilliam 1998, I).
Chalkbrood (caused by the fungus Ascosphaera aphis) was discovered in the USA in 1968 in California and spread rapidly across the North America. When USDA researchers Steve Taber and Martha Gilliam found chalkbrood in Arizona, they began looking closer at the pathology of the fungal infection.
They observed that some colonies removed larvae infected with chalkbrood within 24 hours. Through subsequent studies Gilliam and coworkers determined it was possible to breed for resistance to chalkbrood. Hygienic behaviour was found to be the primary factor that led to chalkbrood resistance however, there are other factors that help a colony resist the infection. Interestingly, “friendly” moulds and beneficial bacteria found in bee bread can inhibit A. apis growth (more information on beneficial microbes in a future article) (Spivak and Gilliam 1998, II).
Tests for selecting for hygienic behaviour were devised and refined. Colonies were presented with a section of frozen brood and the time to uncap and remove the dead pupae was monitored. Colonies that quickly removed dead frozen pupae were also colonies that showed resistance to chalkbrood. This process showed that using freeze killed brood could serve as a test to gauge the colony’s propensity for hygienic behaviour and thus resistance to chalkbrood.
When faced with Varroa infestation, colonies bred for hygienic behaviour have been observed to remove mite infested pupae, interrupting the mite’s reproductive cycle. However, at low infestation rates, the chemical cues may not be strong enough for the hygiene bees to detect the parasitized larvae. Only at high infestation rates (two or more mites per brood cell) is the pupae damaged enough to alert the hygiene bees (Boecking 1992). But if the colony is faced with an infestation that severe, the colony is probably beyond saving. Hygienic behaviour alone is not the silver bullet for Varroa tolerance.
Breeding for Hygienic Behaviour
Breeding for hygienic behaviour is easily performed. It is being implemented worldwide in countries with substantive apicultural industries.
In populations of honey bees that have not been selected specifically for rapid hygienic behaviour, around 10% of the colonies will carry this trait (Spivak personal comm). From the research done in Australia on hygienic behaviour, just over 15% of tested colonies meet the requirement for rapid hygienic behaviour. These data demonstrate that Australian Honey bee stocks do exhibit rapid hygienic behaviour useful for combating diseases such as AFB and chalkbrood and pests such as future populations of Varroa. These stocks can be improved on with selective breeding.
Stock improvement: Selecting and Breeding for Hygienic Behaviour
Arathi, H. S., and Marla Spivak. “Influence of colony genotypic composition on the performance of hygienic behaviour in the honeybee,< i> Apis mellifera L.” Animal Behaviour 62.1 (2001): 57-66.
Boecking, O., and W. Drescher. “The removal response ofApis mellifera L. colonies to brood in wax and plastic cells after artificial and natural infestation withVarroa jacobsoni Oud. and to freeze-killed brood.” Experimental & applied acarology 16.4 (1992): 321-329.
Masterman, R., et al. “Olfactory and behavioral response thresholds to odors of diseased brood differ between hygienic and non-hygienic honey bees (Apis mellifera L.).” Journal of Comparative Physiology A 187.6 (2001): 441-452.
Spivak, M. and M. A. Gilliam. “Hygienic behaviour of honey bees and its application for control of brood diseases and varroa.” Part I Bee World 79.3 (1998): 124-134.
Spivak, M. and M. A. Gilliam. “Hygienic behavior of honey bees and its application for control of brood diseases and varroa.” Part II Bee World 79.4 (1998): 169-186.
What’s red and white and has buzz all over it? Onion pollination in Riverina, Victoria of course!
Onions grown for seed are quite a sight-long rows of green stems with tufted white inflorescences (a group of flowers) on top. In order for these inflorescences to shoot up in early summer making flowers and seeds, the onion plant has to be chilled for about a month during the winter. Without adequate chilling, onion flower development will be poor with low seed set.
Two different “types” of onions are planted in these rows. About 9 rows contain male sterile plants that produce only nectar and no pollen. These are alternated with 1-3 rows of male fertile plants that contain both nectar and pollen.
Honey bees collect both nectar and pollen from onion flowers but only nectar foragers will visit both male sterile and male fertile flowers providing cross pollination essential for hybrid seed production. This nectar is extremely high in potassium sometimes making the nectar unpalatable to bees.
Without the great efforts of bees and beekeepers, French onion soup wouldn’t be quite as tasty.
To find out more about onion pollination check out these sites:
Published Bee Picture!
The latest issue of the Australian Bee Journal is quite special for Bee Scientifics! The cover features a photo called “waiting for rain to end” taken by the company’s proprietor, Jody Gerdts, in her apiary in Minnesota. The picture was one of two award winning photos from the Victorian Apiarist’s Association annual meeting in Melbourne last June. Inside the journal is also an article introducing Jody to the Apiculture industry!
Click here to read the on-line Journal.
The Australian Bee Journal is a monthly journal produced by the Victorian Apiarist Association. Inside is a wealth of information on beekeeping and the beekeeping industry in Victoria, Australia and around the world. Give it a read!
Here is a nice article by the Age- a prominent Australian paper that I was interviewed for and some of my photos were published! For now, Australia remains Varroa Free. Check it out!
Bee careful out there – a parasitic marauder is nearly at our shores
The biggest pest threat is from a pinhead-sized parasite, Varroa destructor, an oval-shaped, reddish-brown mite that sucks the blood from bees and inflicts upon them a suite of virulent diseases, such as deformed-wing virus.
Read more: http://www.smh.com.au/national/education/bee-careful-out-there–a-parasitic-marauder-is-nearly-at-our-shores-20140828-109ics.html#ixzz3DNhKmCHI
We are excited to announce the first beekeeping course of the season! Four Tuesday evenings in October with one Saturday field day.
This course covers both the science and the art behind beekeeping. Check out our Education Page for more details and to register!