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Simplified field methods for diagnosing honey bee diseases and GBPs to prevent them

Dear TECA members,

My name is Giovanni Formato. I am a veterinarian working as Head of the Beekeeping Laboratory, at the Honey Bee Health laboratory of IZSLT (Istituto Zooprofilattico Sperimentale of Latium and Tuscany, a Governmental Regional Institute for Animal Diseases) (Italy). My area of work is mainly linked to the beekeeping sector with a particular focus on honey bee diseases' diagnosis and management. Since January 2017 I’m the scientific coordinator of the EU project “New indicators and on-farm practices to improve honeybee health in the Aethina tumida era in Europe”. This project is focused on a "new approach" to the Good Beekeeping Practices (GBPs), expecially on those practices able to detect the main honey bee diseases before they become "clinically evident" e.g. using debris (or other matrixes) to detect American Foolbrood (AFB), European Foolbrood (EFB) or Small hive beetle (SHB). For this reason we invented the term "pre-clinic indicator", wth the final goal to reduce the impact of the diseases on the colonies and to reduce the impact of veterinary medicines on the hive products.

Finally, I’m President of SVETAP, that is a Scientific Society of Veterinarians specialized in Apiculture.

In 2015, we moderated the TECA discussion on “Veterinary medicines in beekeeping around the world: Which active ingredients are in use and do they respond to the needs of beekeepers?”, in collaboration with APIMONDIA. Moreover, along with the TECA discussion we conducted a survey with the title “Veterinary medicines in beekeeping around the world” which allowed us to have more data about the challenges that beekeepers face in dealing with disease management and control. In particular, the survey showed that some diseases are very well known by beekeepers worldwide but their impact on honey bee colonies is missing/underestimates and there is a lack of knowledge on the instruments available for diagnosis.

We would like to invite you to actively participate in the upcoming discussion on “Simplified field methods for diagnosing honey bee diseases and GBPs to prevent them”. The purpose of this discussion is to list and suggest the best on-field methods to diagnose honey bee diseases worldwide and to underdstand if they are sufficiently accurate. We also want to look at the available procedures/kits/instruments that can be used in the field to detect and monitor all the honey bee pathogens, before or after clinical symptoms appear. We will also talk about the kind of assistance beekeepers can receive in their respective countries (beekeeper self-diagnosis, expert beekeepers, researchers, governmental inspector) and suggest some GBPs to prevent or avoid the bee diseases in order to assist veterinary services or beekeepers where diagnostic tools/kits are unavailable.

Eran Raizman, Head of the Emergency Prevention System for Animal Health in FAO HQ in Rome, which deals with control of economically important diseases that also cross border such as Avian Influenza and food and mouth disease, will be closely following the discussion.  Eran and his team are convinced that they have a lot to contribute to the apiculture sector in improving diseases control and as a consequence people’s livelihoods and food security.  The Emergency Prevention System for Animal Health team is looking forward to working with beekeepers to improve their own source of livelihoods!

This discussion will last for 5 weeks starting from July 6th to August 8th and will be summarized at the end.

It will be divided into five sections answering the following questions:

A.      From July 6th to July 11th: Which are the GBPs able to prevent diseases or avoid their spreading? Comments on results of the 2015-2016 survey on “Veterinary medicines in beekeeping around the world”: beekeepers knowledge and needs. Which are the most known diseases? Is their impact on colonies underestimated?

B.      From July 12th to July 18th: Main tools available on the field to diagnose Varroa destructor and viruses will be described. Moreover, participants will be asked share the methods they adopt. Are they specific? Is it possible to find a practical and valid method to be used by beekeepers without a laboratory?

C.      From July 19th to July 30th: Main tools available on the field to diagnose American Foulbrood (AFB) and European Foulbrood (EFB) will be described. Participants wil be invited to share the methods they adopt to diagnose AFB and EFB. Are they specific? Is it possible to find a practical and valid method to be used by beekeepers without a laboratory?

D.     From July 31st to August 6th: Main tools available on field to diagnose Nosema and chalkbrood will be described. Again, participants will have the opportunity to share the methods they adopt to diagnose Nosema and chalkbrook. Are they specific? Is it possible to find a practical and valid method to be used by beekeepers without a laboratory?

E.      From to August 7th  to August 14th: Main on-field tools available to diagnose Aethina tumida and Tropilaelaps spp. will be described. Participants can share their methods. Are they specific? Is it possible to find a practical and valid method to be used by beekeepers without a laboratory? Conclusions: How do beekeepers diagnose honey bee diseases on field worldwide?

Looking forward to have a lively online discussion!

Giovanni Formato

Comments

European Foul Brood (EFB) and American Foul Brood (AFB) are bacterial diseases able to affect and kill developing and immature stages of honey bees of Apis mellifera. Both of them are a world wide problem for beekeeping.

EFB is caused by Melissococcus plutonius, that is a non-spore forming bacteria (Fig. 1). It infects developing honey bee larvae that are less than 24 hours old and bring to die larvae usually at their 4th or 5th day of life.

 

Figure 1 – Melissococcus plutonius (optical microscopy)

AFB is caused by a spore-forming bacteria named Paenibacillus larvae (P. larvae) (Fig. 2), which through its spores, makes it more devastating and persistent in the colonies than EFB. Bee larvae infected by American Foul Brood die later than EFB, at the stage of pre-pupae or pupae, when the brood cells have already been capped by the worker bees.

 

Figure 2 – Spores of P. larvae

How to recognize EFB and AFB?

To recognize EFB and AFB, the symptomatology is crucial.

Bee larvae infected by European Foul Brood turn yellow or brown (instead of glisten and pearly white like in the healthy larvae) and die twisted in the uncapped cell (Fig. 3).

Figure 3 – EFB affected larvae (arrows)

Moreover, a foul smell of decaying and rotten brood is associated with this disease.

Melissococcus plutonius doesn’t produce spores and honey bees are able to push through the disease with the help of a strong honey flow (or feed supplement administered by the beekeeper) or with the queen replacement.

In the case of AFB, cell cappings of the affected cells turn dark and are usually perforated or sinking (Fig. 4) (instead of having a close dome-shape like in the healthy brood).

Figure 4 – How cell cappings appear in AFB (perforated or sunken cell cappings)

Removing the cap and looking inside of this cell, in the bottom part of the cell it is possible to see a typical, persistent dark scale (Fig. 5) that adult bees are not able to clean.

Figure 5 – Persistent, dark, scales in case of AFB

Moreover, it is possible to see the so called “pupal tongue” that is a typical structure given by the died pupae when shrivel down away from the top of the cell due to the disease (Fig. 6).

Figure 6 – “Pupal tongue” in AFB

Finally, taking a small stick and stirring it in the AFB affected cells we’ll see a typical ripeness or a stringeness when we pull the stick out of the cells. Positive matchstick test: when pulling the stick out from infected brood cell, a brown, ropey slime can be seen (Fig. 7).

Figure 7 - Positive matchstick test

Both in AFB and in EFB diseases, a foul smell of decaying and rotten brood could be recognized.

Commercial Kits

Always at the apiary level, it could be possible for beekeepers, veterinarians and technicians to use some commercial Kits that could enable them to confirm the symptoms observed in the colony (Fig. 8).

Figure 8 – Commercial kit showing positive result (double lines) to AFB

Laboratory

Alternatively to the commercial kits, it is possible for beekeepers to send samples of affected brood to a diagnostic laboratory specialized on the honey bee diseases. Here bacteria will be isolated (Fig. 9) and characterized.

Figure 9 – Isolation of P. larvae on selective media

EFB and AFB are contagious bacterial diseases. After diagnosing EFB or AFB, the beekeeper should take action:

- substitute the queen (to avoid colonies with queens sensitive to the foulbrood diseases);

- shake the bees from the infected combs into a clean hive with new foundation;

- treat the colony with a antibiotic registered for the honey bees (ONLY in countries where this is allowed);

- destroy the family, including the combs (and hive, if necessary) if the disease is in an advanced stage and the colony is very weak (few bees)

The beekeeper should disinfect all beekeeping equipment (hive tool, gloves, etc.) that he used for manipulating the infected hive or touched with the gloves after having opened the hive and contaminated them.

Questions:

What other methods do you adopt to diagnose AFB and EFB?

Do you think is it possible to find a practical and valid method to be used by beekeepers without a laboratory?

Chalkbrood, Stonebrood and Nosema are fungal diseases of honeybees (Apis mellifera) present worldwide.  Chalkbrood is caused by the fungus Ascosphaera apis and affects the brood. Stonebrood is caused by the fungi Aspergillus flavus and Aspergillus fumigatus and affects both the brood and adult bees. Nosemosis is a fungal disease caused by Nosema apis and N. ceranae.

We will first look at the causes and symptoms of Chalkbrood and Stonebrood and how to diagnose the diseases. We will then study a little closer Nosemosis.

Chalkbrood

The fungus rarely kills infected colonies but can weaken it and lead to reduced honey yields and susceptibility to other bee pests and diseases, like for example European Foulbrood.

Bee larvae become infected by ingesting spores of the worldwide present fungae Ascosphera apis with food. The spores germinate in the intestines leading to the death of the larvae.

Each dead larva of chalkbrood produces billions of spores and, if not removed by the worker bees, they can remain infectious for several years within the hive, waiting for the right conditions to grow. The disease is transmitted by spores that are readily moved from colony to colony on infected pollen, on robbing or drifting bees, or beekeeping equipment.

Ascosphera apis grows better in larvae situated more externally in the brood because it is colder. This phenomenon may occur especially during the colony spring growth, when the number of adult bees is not enough to allow an adequate nutrition and to allow an adequate nest temperature control to cover the whole brood. Less populated and weaker colonies are more susceptible as the bees are not able to keep all brood warm. Drone larvae are usually the most affected because located on the outskirts of the brood chamber. Humid and cold locations and climates favour the development of chalkbrood disease. Therefore, it is important to keep only strong colonies with enough bees to keep the brood warm, and place the hives as much as possible in sunny places.

Symptoms and diagnosis

The larvae may be affected in different periods of life, more frequently during the first two days after capping: the larvae become chalk-white and die as pupae. Chalkbrood produces a mummification and/or calcification of the larvae. Worker bees will pierce and uncap the cells to remove the dead larvae, making mummified pupae clearly visible (Fig. 1 and 2). There may not be any symptoms if the infection is less than 12%. Larvae at first appear soft, assuming the hexagonal shape of the cell, then they will dry out and become gummy, then calcify. The majority of the affected larvae appears white, but some become grey or black depending on the life stage of the fungus (Fig. 3). A typical symptom that can be observed by the beekeeper before opening the hive is the presence of dead and hardened larvae like little stones of about 1 cm, referred to as “mummies” at the entrance of the hive. The same mummies can be observed on the bottom of the hive, after opening it for the inspection (Fig. 4).

Figure 1 – Brood affected by chalkbrood (white/yellow larvae)

Figure 2 - Calcification of the larvae (Photo source Dr. Palazzetti - ASL VT, Italy)

Figure 3 - Some larvae appear yellow and white (left), some become grey and white (centre) or black (right).

Figure 4 – Chalkbrood: dead larvae at the hive entrance (left) and on the bottom of the hive (right)

In summary: the beekeeper should check for the presence of any little black or white stones at the hive entrance or in the bottom of the hive and for the presence of yellow/grey larvae or pierced brood.

When the beekeeper suspects chalkbrood he/she can:

  • send suspicious affected brood to the laboratory for diagnosis/confirmation;
  • replace queens of the affected colonies as soon as possible because of poor genetic resistance;
  • avoid to use genetic material from affected hives to produce new queens or royal cells, considering the genetic predisposition to the disease;
  • ensure proper position of the apiary and proper orientation (towards the sun) of the hive entrance;
  • supplement colony with good quality feed (proteic nutrition) to recover from the disease;
  • disinfect beekeeping material (e.g. torching levers with fire) after inspecting the affected hives;
  • replace old, blackened brood combs as these may harbor chalkbrood spores.

To prevent chalkbrood, the beekeeper could verify presence of sufficient amount of storages in spring and select lines of queens resistant to the disease at the apiary level.

Stonebrood

The disease is not difficult to identify. The dead larvae are removed from the cell combs by the adult bees. It is not uncommon to find green mummified larvae on the hive floor or at the entrance of the hive.

There is no chemical treatment for Stonebrood. Thus, prevention is the only solution to have healthy, stonebrood-free colonies. The hives and all the beekeeping tools must be clean so as to prevent infestation. The dead larvae must be removed and the combs that are severely infested must be taken away. The hives have to be well ventilated and equipped with new frames that also have a new foundation. If bees do not produce enough honey they should be given food supplements. Hygiene is the key for having healthy bee families and the only available method to fight Stonebrood and other bee diseases.

Stonebrood is a rare honey bee disease, present worldwide and caused by several fungi of the genus Aspergillus (usually the fungus Aspergillus flavus or, less frequently, Aspergillus fumigatus), that are commonly disseminated in the soil. The temperature limits for its development in the soil is quite large, being between 7° and 40° C.

The spores of Aspergillus spp. might be present within a bee family without causing damage to it. However, the fungi that cause the disease might affect humans or animals. In fact, a major concern with the presence of Aspergillus in honey bees is the production of airborne conidia, which can lead to respiratory diseases (allergic bronchopulmonary aspergillosis, pulmonary aspergilloma, or even invasive aspergillosis in lung tissues) upon inhalation by humans (mainly beekeepers or consumers) and/or animals.

For this reason it is advisable to destroy the heavily infected combs. Moreover, honey or pollen or other hive products that come from infected hives should not be sold for human consumption for the risk of conidia inhalation or for the risk of mycotoxin assumption/ingestion.

Stonebrood affects larvae (capped and uncapped) as well as adult bees. The infection with the spores occurs orally through feeding or by direct contact with the spores (fungus are also able to develop on the surface of the affected bee’s body). At the beginning the infected larvae appear white and fluffy, then they become yellow (when stonebrood is caused by A. flavus fungus) or greenish brown (when affected by A. fumigatus). In fact, the spores of the different species have different colours.

Larvae that died because of this disease are mummified like those that have died because of chalkbrood. The appearance is very similar to the chalkbrood affected larvae (Figure 1, 2, 3 and 4). After death, the larvae turn black and become difficult to crush, hence the name stonebrood. In the end the pathogen fungus comes out from the integument of its host and erupts. In this stage, the larvae are covered with powdery fungal spores. Worker bees clean out the infected brood and the hive may recover depending on factors such as the strength of the colony, the level of infection, and hygienic habits of the strain of bees (variation in the trait occurs among different subspecies/races). The disease is spread outside the hive by drifting, robbing or swarming honey bees. Beekeepers also transmit the disease through the beekeeping tools or by moving combs that contain Aspergillus spp. in healthy families.

When the beekeeper suspect stonebrood, (s)he should apply the same measures already presented for the chalkbrood to preserve honey bee health. Moreover, infected combs should be destroyed and honey or pollen or other hive products that come from infected hives should not be sold for human consumption.

Laboratory analyses will be needed to differentiate the pathogens (Aspergillus fumigatus, A. flavus, or Ascosphaera apis) that are responsible of the disease.

Diagnosing fungal diseases of honeybees: Nosemosis

Nosemosis is a fungal disease caused by Nosema apis and N. ceranae that affects the gut of adult bees.

  • Nosema apis is more common in northern countries with cold and humid climate.
  • Nosema ceranae is much more present in warm areas (e.g. Southern Europe, South Eastern Asia, Latin America and South Africa).

Figure 5 – Spores of Nosema spp. Both species of nosema look similar through the optical microscope.

Both Nosema species cause similar symptoms, but Nosema apis is considered more severe. The spores (Fig. 5) penetrate the gut wall of adult bees, where they are to multiply in the epithelial cells and eliminated outside with the intestinal content.  Through feces the spores are transmitted to other bees. The absorption of nutrients by affected bees is reduced, with presence of diarrhea and abdomen with increased volume. Some bees can be seen at the entrance of the hive trembling and unable to fly. Nosemosis caused by N. apis is more frequent during early spring, while N. ceranae causes the disease during the warmer period of the year.

What are the symptoms of Nosemosis?

Recognition of symptoms at an early stage is essential to control the disease.

Typical symptoms in heavy infections are:

  • Presence of diarrheic feces into the hive (Fig. 6) and in the entrance (Fig. 7). With N. ceranae cases of diarrhea are just sporadic;
  • Bees with enlarged abdomen unable to fly trembling in front of the hive;
  • Progressive decrease of the hive population and loss of the colony.

Figure 6 – Comb with a big amount of feces in the upper part due to nosemosis (Nosema apis)

Figure 7 – Hive entrance spotted with feces due to nosemosis (Nosema apis)

How to diagnose Nosemosis?

When a beekeeper observes some of the above mentioned symptoms and suspects a nosema infection in a hive, (s)he should collect some foragers bees from the entrance of the hive and pull out the intestines together with the last segment of the abdomen and examine them. The nails can be used to tear off the stinger. Diseased bees have a bigger and brown/yellow intestine, full of feces, while healthy bees have a transparent midgut (Fig. 8). To confirm the suspected  nosemosis, the beekeeper can send to the laboratory from 5 to 60 forager bees (depending on the laboratory technique used), where diagnosis will be performed by optical microscopy (spore count) or by biomolecular analysis (Polymerase Chain Reaction - PCR).

Figure 8 - Medium gut of healthy (left) and ill (right) bees. For examination the intestines are extracted together with the last segment of the abdomen. Right: infected. Left: healthy, transparent midgut.

Another way to detect a nosema infection in the hive would be the identification of diarrheic feces inside the hive, mainly on the frames (Fig. 6).

An accurate diagnosis can be carried out with laboratory procedures using a microscope. A simple non-quantitative method for detecting Nosema spp. infection is described in the OIE Terrestrial Manual 2013 Chapter 2.2.4 (www. http://www.oie.int/international-standard-setting/terrestrial-manual/) and is as follows:

1.      Collect in a honey jar at least 60 bees from the hive entrance. This is an important detail because young bees are less likely to be infected, and including them in the sample would give a distorted picture of the infection rate in the hive.

2.      Fill the jar with 4% formol, 70% ethyl alcohol or freeze the bees in a standard freezer in order to prevent them from decomposing (possibly, bees should be kept frozen until they reach the laboratory).

In the lab, the abdomens of the bees to be examined are separated and ground up in 5 ml of water. Then water is added representing a total volume of 1 ml per bee in the sample. A drop of the suspension is placed on a slide under a cover-slip and examined microscopically at ×400 magnification, under bright-field or phase-contrast optics.

To quantify the average infection level, spore counts in a haemacytometer (Fig. 9) can be used or bees can be diagnosed individually to yield the proportion of infected bees.

Figure 9 – Spores of Nosema spp. in the haemacytometerready to be counted

If the beekeeper has positive hives, (s)he should apply proper treatments according to the products that are registered in his/her country. (Administer proper treatment or feed complementary nutrition containing essential oils or plants – e.g. garlic, able to reduce the amount of spores in the hives).

Finally, please, remember that nosemosis is a contagious disease and the infected combs and frames should not be moved to other hives (balancing techniques). Infected hive tools or equipment must be disinfected before use. In the same way, hive-boxes should be disinfected before used with new colonies.

Questions:

Do you want to contribute to this discussion explaining the methods you are adopting into your apiary to diagnose chalkbrood, stonebrood or Nosemosis?

Do you think is it possible to find other practical and valid methods to be used by beekeepers without a laboratory?

Dear Giovanni,

 In connection with the topic of detection of varroa infestation levels, I have three different questions: a) I was wondering if it would make sense to adopt another approach in the sense of using beehives that are known for enabling to keep levels of infestation low and use them as benchmarks. In other words, I think it would be interesting to test such beehives and then compare the level of infestation with common beehives. This comparison should reveal the difference in level of infestation and also evaluate exactly the magnitude of this difference and assess how this actually impacts on the general health of the colony.  The advantage of this comparison should show also how much a natural system should enable the reduction of treatments. How would you see this implemented in actual practice? Do you think beekeepers would benefit from testing this approach? b) another aspect related to this, would be to know the average levels of infestation and also the tytpical patterns of development of varroa and their numbers within a given colony during the season, possibly tabualted in graphical/visual form. I would assume that it would be very interesting and important for beekeepers to know and understand exactly how varroa develops in the colony over the months, the average number of mites likely to be present and how to best intervene for a timely reduction if not total removal of the infestation. Of course, figures would very much depend on the kind of bees used and the different geographical and climatic context. c) in the past I also thought about the viability and impact of a system that would force all the bees of a colony to go through a narrow passage in the hive from which treatment against varroa is dispensed (like in a shower) more or less on the principle of the bee escape board. In this way, there would be the guarantee that all the bees of the colony are checked against varroa and that they all receive the treatment in the same way. If such a system is developed and it works to *% accuracy it would be interesting to see how it impacts on the health of the bees and also if eventually then there is a chance to achieve 100% removal of varroa. Please let me know what you think about these three issues hoping that they can bring some useful contribution to the discussion. With kind regards. Riccardo Jannoni

Dear Riccardo,

Thanks for your comments. I like very much your "preventive" approach! 

I try to answer respecting the order of your questions:

a) Using small cell (4.9mm) foundation (in modified Warré hives), or by buying bees that are more tolerant for varroa and letting them build their own natural cells, it could be possible to keep varroa populations at lower levels than they might otherwise be. However, some number of varroa mites always exists within any colony and, if given the chance, can build up to a high enough population to kill it off. Some strains of bees are more tolerant of varroa than are others, but if you do nothing to treat for mites it is very likely that your colony will die out due to varroosis + virosis (e.g. Deformed Wing Virus - DWV). 

Anycase, it should be kept into mind that even if some more "natural" approach could partially reduce the varroa infestation level, their management is usually more complicated and time-consuming (moreover, some times, even more expensive) respect the "classical/common" approach.

Of course, it would be interesting to test such beehives and/or natural techniques to compare the level of infestation with common beehives. This comparison should reveal the difference in level of infestation and also evaluate exactly the magnitude of this difference and assess how this actually impacts on the general health of the colony. Yes, I agree!

b) Concerning your consideration about the importance to know the average levels of infestation of varroa in a given colony during the season, in my Institute we started to collect the results given by the "icing sugar method" applyed in different months and on several hives categorized according to the climatic context of the apiaries and the subspecie of bees used. Thus, we hope to have these data, soon.

c) Finally, considering the possibility to have a system that would force the bees of a colony to go through some narrow passages in the hive from which treatment against varroa is dispensed, there is a new acaridice product that will be soon on trade, specifically registered for the honey bees: it must be placed on the hive entrance and works exactly in the way you are saying. Of course many studies will be carried out to verify its efficacy against varroa and toxicity for honey bees comparing many geografic ares (researchers are very curious people, right like beekeepers, you know?). Even if it this method will be likely to get high acaricie efficacy, there is unfortunately a very low chance to achieve 100% removal of varroa as you (and all of us, of course") are hoping. 

With kind regards. 

Giovanni

Small Hive Beetle (SHB)

Aethina tumida, also known as “Small Hive Beetle” (SHB), is a beetle from the Order Coleoptera, member of the Family Nitidulidae. SHB is native to Sub-Saharan Africa, where it lives developing most of its life cycle within the honeybee colony, and it has spread mainly due to international trade to other areas: SHB was first discovered in Florida (United States – U.S.) in 1996 and has now spread to many U.S. states including, Georgia, Florida, South Carolina, North Carolina, California, Michigan, Pennsylvania, New Jersey, Ohio, Illinois, Indiana, Louisiana, Minnesota, Maryland, Missouri, New York, Connecticut, Rhode Island, Virginia, Texas, Kansas, Tennessee, Oklahoma, and Hawaii. The movement of migratory beekeepers from Florida may have transported the beetle to other states. Recent findings also indicate transport of the beetles in packages.

Where has the SHB been detected ?

In 2000 SHB has been detected in Egypt and in 2002 in Canada and Australia. In Canada, the small hive beetle has been detected in Manitoba (2002 and 2006), Alberta (2006), Québec (2008, 2009), Ontario (2010), British Columbia (2015), and New Brunswick (2017). In the Prairie Provinces, measures were taken to control the pest and SHB failed to establish a population. It is still to be determined whether the SHB has been able to establish a resident population in Ontario or Québec. In the summer of 2015 the discovery of a number of adult beetles as well as one infestation in all stages of brood in British Columbia's Fraser Valley triggered a temporary quarantine. In 2004, presence of SHB has been detected for the first time in Portugal, where it was quickly eradicated. In 2005, SHB has been found in Jamaica.

In Mexico, the small hive beetle has become established since 2007 in at least eight states. Infestation levels are especially high in tropical areas such as the Yucatán.  In 2012 in Cuba and in 2014 in Nicaragua and in Italy (Calabria region).  The small hive beetle was first detected in Belize in 2016 in the Corozal District. The small hive beetle has now reached the southern Philippines in southern Mindanao Island and there is great concern that it will spread through the country if hives and bees are moved from the southern Mindanao area where the beetle has already been identified.

Life cycle of the SHB

The adult SHBs (Fig. 1) enter the natural or man-kept honeybee colony and reproduce laying eggs in crevices and small spaces where bees cannot remove them.

Adults of SHB are oval-shaped. At first age they are yellow-reddish, then they become gradually brown, and then always darker to reach black with sexual maturity. They can survive inside the hive up to six months. The body is rather flattened, 0.5 - 0.7 cm long and 0.3 - 0.45 cm wide (about 1/3 of the adult bee size). The antennas are club-shaped and the rather long legs enable the SHB to move easily and quickly inside the hives. Its natural armor on the back and the characteristic "turtle position" (retracting head and legs under the body) they assume when attacked, protect them from the honey bee bites and stings.

Larvae (Fig. 1) develop feeding on bee larvae, pollen or honey inside the hive.

The larvae of SHB are responsible for the greater damage inside the hive. They are cream-coloured and about 11 mm long at the end of their development. Typical signs of the larvae are: four rows of dorsal spikes along the back, three pairs of legs (Fig. 2) and two rear spines. A differential diagnosis can occur with the larvae of the wax moth (Galleria melonella), where spikes are absent.

Figure 1 – Adult (left and centre) and larvae (right and centre) of SHB

Figure 2 - Larva head showing the distinctive three pairs of legs at the front end of the body- Simon Hinkley and Ken Walker, Museum Victoria, PADIL

When larvae have finished their development, they come out of the hive for pupation in the soil. After pupation (Fig. 3), SHB adults leave the soil and complete the life cycle as described above.

Figure 3 – SHB pupa 

Table 1 describes the duration of the different life stages of the SHB.

The SHB can causes considerable damage in the hive in different ways:

1.  The SHB larvae feed on honey, pollen and bee brood. The larvae dig galleries in the combs and cause considerable damage to the bee brood;

2. SHB larvae defecate on the combs, honey, pollen and in the brood cells. The faeces contaminate the honey and the honey can start fermentation (Fig. 4);

Figure 4 - SHB larvae massive infestation on honey comb resulting in honey fermentation

3. When the honeybee colony is not strong enough to control the development of SHB larvae, they can entirely destroy the beehive (Fig. 5 and 6);

Fig. 5 – Massive SHB infestation (by the Slimed beehive - http://peacebeefarm.blogspot.it/2011/11/slimed-bee-hive.html)

Fig. 6 - Damage to the hive (http://www.ars.usda.gov/Research/docs.htm?docid=18993)

4. The colony can abscond from the hive due to a large number of SHB;

5. SHB eggs can hatch during super storage before honey extraction. The larvae feed on available honeycombs and as there are no bees present to protect the combs, the larvae can destroy completely the combs (Fig. 4).

How to diagnosw SHB?

Currently, the SHB is only present in the above mentioned Countries. Beekeepers not located in any of these areas, should not worry about the SHB. However, if you suspect SHB in your hives, you should contact immediately the veterinary services so that necessary measures can be taken to promptly stop the SHB spread.

There are several methods to diagnose SHB:

1. direct visual inspection of the hive to search for larvae or adult beetles;

2. use of SHB diagnostic traps at the hive level to search for adult beetles;

3. use of SHB diagnostic traps at the honey house level to search for larvae or adult beetles.

1. Hive inspection method:

Note:  this type of inspection is only possible for movable frame hives (topbar hives or frame hives).

Several types of inspection methods are available depending on the objective. In areas where SHB is known to be present (e.g. South-Africa, USA, etc.) the main target of the beekeeper is to quantify the number of SHBs present and maintain them at a low level (e.g. destroying highly infested combs or using traps containing chemicals).

In areas where SHB is not present but there is the risk of arrival (e.g. areas bordering with infested areas) the objective is to detect the arrival of A. tumida and prevent its establishment and spread in the territory as soon as possible.

To inspect the hive, the frames will have to be removed from the hive to check if there are any adult SHBs present in the hive. The best way to proceed to search for larvae or adult beetles in the hive is as follows:

1) Remove the outer cover and place it on the previous hive; examine the outer surface of the inner cover (Figure 7) to search for adult or larvae of SHB; then remove it and examine the internal surface.

Figure 7 - SHB larva in the outer face of the inner cover
2) Remove and inspect the frames one by one starting from one side of the hive moving to the other side of the hive and put them inside an empty nucleus box. Take the combs out of the hive with slow movements, in order to allow the SHB to move towards the remaining frames escaping from light. Inspect also the corners, walls and bottom of the hive.

3) If a honey super is present, inspect it with the same procedure used for the nest.

4) Observe the content of the bottom board if present.

In case of low infestation levels, in order to move and “concentrate” all adults of SHBs in the same place, to ease the diagnosis, a lateral division board (of wood, felt or cardboard) with the same size of a brood box frame (Fig. 8), should be used. Place the division board at least 2 days before the inspection between the last comb and the lateral wall of the hive (in order to act as hiding place for SHB). During the hive inspection, after moving the last combs, inspect behind that board too.

This inspection method allows the detection of any kind of SHB life stage (even if eggs are difficult to see due to their small size).

The SHB threshold are difficult to define as it depends on many factors: the honey bee subspecies, the climatic conditions of the area and the local apicultural practices. An experienced beekeepers will be able to define the SHB thresholds (number of parasites/hive) that could represent a risk for profit or for the bee hive survival.

2. Use of diagnostic traps at the hive/apiary level

There are several types of traps that can be used both to diagnose the presence of SHB within the hive and outside the hive. The goals could be to diagnose and/or to reduce the number of the parasite.

SHBs look for small spaces in the hive where bees cannot follow them, in order to avoid aggression by the bees. Traps usually provide small, apparent safe hiding places for the adult SHBs: they will enter the trap but will not be able to escape from it anymore. Most of the SHB traps that are used inside the beehive take advantage of this “behaviour” of the SHB. 

Often the traps will allow a visual detection of the SHBs that are inside by the beekeeper. There are many types and models of traps that can be find online or in beekeeping stores. Moreover, there are other types of traps that could be easily made by the beekeeper him/herself.

Some examples:

- Small containers that should be provided with vegetable or mineral oil (Fig. 9 and Fig. 10). This type of trap can be used to monitor SHB presence and development in the hive as well as to control SHB populations in the hive.

Figure 9. A trap provided with oil on the bottom to capture SHB adults

Figure 10. Traps placed between the external frames of the hive

- Polycarbonate trap: a piece of polycarbonate board is placed at the hive entrance. The gaps in this trap allow the SHB (mainly adults) to hide. Beekeepers can extract it from the hive entrance and detect SHB presence (Fig. 11-13). This kind of trap can be used only to monitor SHB presence, not to reduce or control the number of SHBs generating the infestation.

Figure 11 - Polycarbonate trap (view from above)

Figure 12 - Polycarbonate trap (lateral view)

Figure 13 - Polycarbonate trap placed in a bee hive (a part of the trap is outside for easy removal of the trap)

- Fibrose texture material: This trap can be placed in the bottom of the hive or on the top of the frames. The SHB (mainly adults) tries to hide inside and its legs remain trapped in the fibers (Fig. 15 and Fig. 16). This trap can be used both to monitor SHB presence (f.eg. to quantify the infestation rate) and to control the SHB population.

Figure 15. Fibrose texture material

Figure 16. SHB caught in the fibrose texture material

- Traps with chemical products (e.g. coumaphos, fipronil): these traps are provided with one (or more) active principles that kill SHB (usually adults) after it enters the trap looking for a hiding place. The substances used in this kind of traps could be harmful to the bees and to consumers. Active principles must be closed in the traps, where only SHBs can enter (due to the size of the entrances). This type of trap is usually placed in the bottom of the hive (Fig. 17) and can be used to detect SHB presence and to control SHB infestation levels.

Figure 17 - Trap containing a substance that kills entering SHBs, placed on the bottom of the hive

Figure 18 – Home-made SHB trap

- Beetle attractant traps around the hives:  some beetle traps can be used around the hives. They are provided with different range of valatiles, particularly those associated with the SHB driven fermentation of hive products, which are highly attractive to the SHB (Fig. 19).

Fig 19 – Beetle trap in the apiary with attractant substances

3. Use of traps at the honey house level

At the apiary level, the use of queen excluders should be recommended, in order to avoid the presence of brood in the supers stored in the honey house or warehouse: brood could be attracting for SHB.

The presence of SHBs in honey houses and/or storage places indicates the presence of SHB in the area and can be an indicator of insufficient hygiene and maintenance in the beekeeping/honey extraction facilities.

In order to avoid the presence of SHBs in honey houses, maintaining clean the facilities is essential. Thus, clean meticulously the honey house and warehouse. You can use bleach (Sodium hypochlorite) in the cleaning of honey houses and warehouses in order to prevent the development of SHB larvae and microorganisms.

Moreover, honey should be extracted within 2, max 3 days of harvesting the honeycombs from the beehives. Alternatively, if possible:

- stock honey supers and combs in a refrigerated area (at a room temperature under 10°C). This will prevent surviving of SHB eggs and larvae development;

- stock honey supers in a sealed chamber with less than 34% relative humidity (RH) in order to prevent SHB egg development.

Return the extracted supers to the hives, in order to allow the bees to eliminate the remaining honey, before stocking them for next season.

Placing light traps in the honey house and warehouses with beekeeping material could indicate the presence of SHB larvae, as mature SHB larvae are attracted by light.

In case of SHB presence in the honey house bleach can be used; in case of SHB presence in the supers it should be verified that the honey is still good for human consumption and that combs are treated with cold (83 hours at -20°C) before storage or destroyed.

Tropilaelaps spp. (Fig. 1) is a genre of mites native to Asia where it naturally infests the Asian honeybee Apis dorsata.

So far, 4 species of Tropilaelaps have been identified around the world:

  1. Tropilaelaps clareae, that is able to affect Apis mellifera (in Africa, India, Indonesia, Malaya, Nepal, Philippines, Vietnam, Thailandia, Cina, Taiwan, Pakistan Afganistan, Iran, Nepal); Apis dorsata (in India, Indonesia, Nepal, Philippines, Buruna), Apis cerana (in Afganistan, India, Buruna, Malaya, Java, Pakistan, Papua New Guinea), Apis florea (in India) and Apis laboriosa (Himalaya mountains);
  2. Tropilaelaps koenigerum, that is able to affect Apis dorsata (in India, Indonesia, Nepal, Philippines, Buruna) and Apis laboriosa (Himalaya mountains);
  3. Tropilaelaps mercedesae, that is able to affect Apis mellifera (in Africa, India, Indonesia, Malaya, Nepal, Philippines, Vietnam, Thailandia, Cina, Taiwan, Pakistan Afganistan, Iran, Nepal); and Apis dorsata (in India, Indonesia, Nepal, Philippines and Buruna) and Apis laboriosa (Himalaya mountains);
  4. Tropilaelaps thaii, that is able to affect Apis laboriosa (Himalaya mountains).

Even though Tropilaelaps spp. has not spread all around the world as other bee pathogens (such as varroa), it represent a potential pathogen for the Western honeybee Apis mellifera spp.

This mite has some similarities with the mite Varroa destructor. It feeds and reproduces in the bee brood, but unlike the varroa mite, it is unable to feed on adult bees. Tropilaelaps spp. has a faster reproductive cycle and a higher capacity of multiplication, but it is not able to survive brood interruption periods of the honey bees (e.g. natural brood interruption during winter or artificial brood interruption by caging the queen bee).

Tropilaelaps spp. are brown to reddishbrown in color. Comparing Varroa with Tropilaelaps spp., the body of the female Varroa mite is wider than it is long (measuring 1.1 to 1.2 mm in length and 1.5 to 1.6 mm in width) and it moves slowly, whereas the body of Tropilaelaps is elongated (there are small differences among the 4 species, but females measure about 1 mm in lenght and 0.6 mm in width; males are a little smaller) and fast running. (Fig. 1).

Figure 1. Varroa destructor (left) and Tropilaelaps spp. mite (right)

How to diagnose Tropilaelaps spp. ?

At the apiary level it is possible to verify the presence of Tropilaelaps adopting one of the following methods:

a)  Adult honey bee examination

Take a sample of 200 adult bees from suspected infested colonies and put them into a jar (1 Kg jar) with powder sugar (about 30 g), putting a screen on the top of the jar. Then shake the bees and the mites will pass through the screen on to a white paper to count (similarly as it could be done to diagnose and quantify infestation by Varroa).

Otherwise, the 200 adult bees could be put into a container (e.g. 1 Kg jar) with 70% ethyl alcohol or with soapy water. After closing the container, shake them, filter the bees and the fallen mites can be identified and counted on to a white paper.

b)   Brood examination

When monitoring honey bee colonies for the presence of Tropilaelaps (or Varroa), an examination of both drone and worker brood may provide an early indication of infestation. Mites can be observed inside capped bee brood by using a honey scratcher to pull up capped pupae. The mites are clearly visible (Fig. 2).

 

Figure 2. Tropilaelaps spp. mite on larvae of honey bees

c) Sticky board examination

A precise diagnosis can be made using a sticky board covered with a mesh with size of 2mm, that prevents the bees from removing the dislodged mites. The mesh of 2 mm is large enough for mites to pass through. Make a sticky board with poster board, cardboard or other white, stiff paper coated with Vaseline or other sticky substance, or use a sheet of sticky shelf paper. Cut the paper to fit the bottom board of a hive. Leave the bottom board in the colony, under the hive for up to 3 days, collecting and examining the debris for mites.

For faster mite diagnosis, smoke each colony adding 25 g (1 oz) pipe tobacco in the smoker. Puff the bees 6–10 times, close up the hive for 10–20 minutes. Pull out the sticky board after 10 minutes and count the mites.

Questions:

Do you want to contribute to this discussion explaining the methods you are adopting in your apiary to diagnose Tropilaelaps mites?

Is Tropilaelaps mite present in your country ? Do you think is it possible to find other practical and valid methods for monitoring it to be used by beekeepers?

 

Dear TECA members,

It’s now the moment to say goodbye. Before all, I’d like to acknowledge Charlotte Lietaer and the TECA staff for the help with their comments, suggestions and revisions of the documents I posted in this TECA beekeeping exchange group discussion. In fact, taking the chance of this useful tool of FAO that TECA represents, in last month you and I spent together some time considering the good beekeeping practices (GBPs) and the main diagnostic methods for the more important honey bee diseases (varroa, viruses, AFB, EFB, nosemosis, chalkbrood, stonebrood, SHB and Tropilaelapsosis).

Moreover, I would like to refer to the TECA cards on GBPs and on honey bee diseases that are available in the TECA knowledge database:

Good Beekeeping Practices: http://teca.fao.org/read/8409

Main honey bee diseases: http://teca.fao.org/read/8412

Varroa mites (Varroatosis or Varroosis): http://teca.fao.org/read/8416

Nosemosis: http://teca.fao.org/read/8413

European foulbrood: http://teca.fao.org/read/8418

Bee viruses: http://teca.fao.org/read/8419

These TECA cards can help you in the apiary to correctly diagnose a disease and also provide some information on how to treat the disease and/or prevent diseases.

Please, even in the future, if you want, you can share your considerations and experiences with the posted documents at the bottom of each of the different cards. All you have to do is to log in (with your registration email and the chosen password) and write your comments or questions. I am in close contact with the TECA team and will be happy to post an answer or discuss with you your observations.  Alternatively, you can write the TECA team at TECA@fao.org

One last thing: during this discussion, together with my team, we have developed the attached guidance document “Good Beekeeping Practices”.  To produce this document, we have used the FAO Guidelines that I attach hereby. The document provides a set of guidance/advice for good hive management. The “Good Beekeeping Practices” are a first draft version that should be updated to provide the best guidance for all type of beekeeping operations around the world.   If someone of you is interested to collaborate, please contact me by email giovanni.formato@izslt.it

Kind regards.

Giovanni Formato

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