Treatment options for honey bee pests and diseases in Ontario

Introduction

This information is intended to help beekeepers in Ontario with their management of various honey bee pests and diseases using practices and treatments specific for Ontario’s conditions (for example, weather, seasonality). This content has been developed from or reviewed by the Ontario Beekeepers’ Association’s Technology Transfer Program and the University of Guelph’s Honey Bee Research Centre and includes both cultural and chemical control methods for common pests and diseases of honey bees.

Cultural control methods are those that use typical beekeeping practices or manipulation of the living habitat or environment of a colony to suppress a pest population. Chemical control methods are those that use pesticides to kill a pest or antibiotics to kill a disease. Cultural control methods can often be used in conjunction with chemical control methods, where appropriate, for a better outcome.

Treatments

It is important for beekeepers to be familiar with what a healthy colony looks like and the signs and symptoms of pests and diseases that can affect honey bees in Ontario. This knowledge is essential for recognizing problems when they occur and understanding how to resolve them. This base knowledge will assist beekeepers in determining the most appropriate treatment to use to manage the pest or disease found in their colonies. Information, including the methods of application and timing of treatment options for Ontario, is provided on this page for controlling:

• varroa mites
• tracheal mites
• small hive beetle
• American foulbrood
• European foulbrood
• sacbrood virus
• chalkbrood
• Nosema

Disclaimer

The treatments and products included herein are to be used in strict accordance with the label directions or veterinarian instruction (if antibiotics). The label or veterinary instruction supersedes and is the authoritative direction on treatment or product use, should there be discrepancy with this page.

The user assumes responsibility for any risk to persons or property arising from the use of treatments or products. This is not an endorsement, or a list of preferred treatments and products, and they are not shown in any particular order. Beekeepers are responsible for determining what will work best for their own colonies and for compliance with all applicable laws.

Search for product labels and label information using Health Canada’s label transcript service.

Best management practices relating to pest and disease treatments

Beekeepers are advised to implement best management practices (BMPs) when monitoring and using treatments to control pests and disease in Ontario apiaries. Some BMPs specific to treatment use include:

• In late spring to summer, re-queen colonies with new queens from mite and disease resistant hygienic stock. For more information about pest and disease management and to find out where to source queens from mite and disease resistant hygienic stock, visit the Ontario Beekeepers’ Association’s Technology Transfer Program’s website or learn about Ontario’s Resistant Honey Bee Selection Program.
• Treatment timing is important to avoid infestations/infections reaching damaging levels.
• Some treatments are temperature-dependent and their effectiveness will be reduced when used outside the recommended temperature range.
• Some treatments may be needed before recommended pest or disease treatment threshold(s) are reached if multiple pests/diseases are found at one time.
• Treat all colonies in the yard at the same time that require treatment as per monitoring or sampling results.
• Rotate treatments to prevent pests or pathogens developing resistance to any one particular active ingredient.
• Follow the product label instructions (or veterinarian prescription/instruction in the case of antibiotics) for all treatment applications, including:
  • treatment withdrawal times and removal of treatment applications (such as pads and strips)
  • use with honey supers

Refer to general BMPs, integrated pest management and biosecurity practices for managing honey bees in Ontario for more BMPs to employ to assist in reducing the risk of pests or disease in a honey bee operation.

Varroa mites (Varroa destructor)

Varroa mites are an external parasite of honey bees. Varroa mites can weaken, cause physical damage, and transmit a variety of pathogens to bees, particularly viruses. It is crucial that beekeepers manage and suppress the population of varroa mites in all their honey bee colonies throughout the beekeeping season. In almost all cases, when varroa mite infestations are not effectively managed they will eventually result in the death of the entire honey bee colony. Research has demonstrated that inadequate varroa mite control is the primary cause of winter mortality in honey bee colonies in Ontario^{footnote 1[1]}.

Learn more about varroa mite biology, monitoring and sampling.

Varroa mite treatment considerations

• Beekeepers must take an Integrated Pest Management approach to control varroa mites by incorporating chemical and/or cultural control methods, hygienic stock, regular monitoring and sampling, and training through workshops from credible specialists.
• It is likely that beekeepers will need to treat their colonies with chemical treatments at least twice a year (spring and late summer), with the possibility of a third mid-season treatment.
  • Applying a third mid-season treatment is determined by sampling and finding high levels of varroa mites in June, July or August. As mid-season treatments are likely used while honey supers are on the colony, it is important to choose an appropriate product.
• Based on research conducted in Ontario, it is recommended that colonies be treated for varroa mites as follows:

  Monitoring method	Treat in May if the number of varroa mites is:	Treat in August if the number of varroa mites is:
  Alcohol wash	>2 mites/100 bees	>3 mites/100 bees
  Sticky board	>9 mites/24-hour drop	>12 mites/24-hour drop

• Beekeepers may decide to treat their colonies before these thresholds are reached as:
  • treatments earlier in the season will suppress varroa’s capacity to increase their population later in the season
  • many treatments can only be applied outside of a honey flow, limiting the times certain treatments can be applied
  • these thresholds may not take into account additional stressors such as viruses, pesticides and infestation with other pests (for example, tracheal mites)

Efficacy of treatments

Many specialists consider approximately 90% efficacy of a treatment to be ideal for varroa mite control. However, treatments with lower efficacies may still fit within a treatment plan, albeit with further treatments likely needed, such that beekeepers are applying 2 or more treatments per beekeeping season.

The most recent research (2019) in Ontario on efficacy^{footnote 2[2]} of varroa mite treatments demonstrated:

• 72% average efficacy with active ingredient tau-fluvalinate (product Apistan®)
• 78% average efficacy with active ingredient flumethrin (product Bayvarol®)
• 92% average efficacy with active ingredient amitraz (product Apivar®)

Varroa mite treatment options

Cultural control methods

Cultural control methods will enhance varroa mite management but should not be considered as a replacement to chemical treatments.

Chemical control methods

Refer to the disclaimer when using chemical control methods.

Tracheal mites (Acarapis woodi)

Tracheal mites are internal parasites of honey bees that live and reproduce in the tracheae (breathing tubes) of the honey bee. Worker, drone and queen bees can be infected. Infected bees become weakened and sick, which results in a reduced lifespan.

Tracheal mite treatment considerations

• Treatment is recommended for bees when the tracheal mite infestation is ≥10% as an average in the bee yard.
• If colonies are being treated with formic acid for varroa mite management, further treatments for tracheal mites may be unnecessary. Note that formic acid treatments formulated for tracheal mites will not be effective against varroa mites.

Tracheal mite treatment options

Cultural control methods

Chemical control methods

Refer to the disclaimer when using chemical control methods.

Small hive beetle (Aethina tumida)

The small hive beetle (SHB) is a honey bee pest that can cause honey spoilage as well as damage (for example, destroy wax comb and bee brood) and stress colonies. SHB is present in Ontario, but to date its impact on honey bee colonies has been limited. There are no treatments or methods that are guaranteed to eliminate SHB from colonies once present. Managing the pest’s impact depends on the beekeeper’s management practices.

Learn more about small hive beetle biology, monitoring and BMPs.

Cultural control methods

American foulbrood (Paenibacillus larvae)

American foulbrood (AFB) is caused by a spore-forming bacterium, Paenibacillus larvae, and is a serious brood disease of honey bees. This disease is highly contagious, will contaminate beekeeping equipment, bees, and honey, and will weaken, and in most cases, kill a honey bee colony. AFB may be found at any time of the year in honey bee colonies or in used beekeeping equipment. There is no cure for AFB once a colony has developed an observable infection. Beekeepers can take steps to mitigate an infection from establishing itself and should take steps to immediately manage an infection if present in their beekeeping operation to prevent further spread.

Learn more about AFB biology, identification and BMPs.

American foulbrood treatment considerations

• Antibiotics will not cure a colony with an observable AFB infection as treatments will not rid or kill AFB spores in colonies or on equipment.
• Prophylactic or preventative use of antibiotics may provide some protection in preventing an infection from occurring in an uninfected colony at times of increased risk (early spring and fall).
  • If antibiotics are used preventively, all colonies in the yard should be treated at the same time.
• Antibiotics should only be delivered via powdered sugar. Using pollen substitutes as carriers or using the sugar syrup method to apply antibiotics are not recommended since these methods:
  • can contaminate honey
  • are less effective application methods
  • may promote antibiotic resistant AFB strains
• Choice of antibiotic (withdrawal time) and timing of antibiotic applications related to the honey flow needs to be well thought out to prevent contamination of honey with antibiotics.
• Beekeepers require a prescription from a veterinarian to access antibiotics for their honey bees. For general information on antimicrobial use in agriculture visit the Antimicrobial resistance in agriculture webpage. For more specific information on antibiotics for beekeeping in Ontario refer to the Ontario Beekeepers’ Association’s Antibiotic Access Resources for Beekeepers.

American foulbrood treatment options

Preventative treatment methods

Refer to the disclaimer when using antibiotics.

European foulbrood (Melissococcus plutonius)

European foulbrood (EFB) is caused by a non-spore-forming bacterium, Melissococcus plutonius. EFB infects the digestive track of honey bee larvae, with larvae younger than 3 days old being most susceptible. EFB is often associated with poor nutrition or a lack of available forage for the colony. EFB is also thought to be problematic when colonies are under stress, such as during hive movement or poor weather conditions. EFB was prevalent several decades ago in Ontario, followed by a period when EFB was relatively rare and largely addressed through antibiotics. Within the last decade EFB has re-emerged and is much more virulent in many regions of North America, including Ontario. Presently, EFB is considered a serious disease in Ontario that has increased in prevalence.

Learn more about EFB biology, identification and BMPs.

European foulbrood treatment considerations

• Antibiotics may not cure a colony with an observable EFB infection.
• Prophylactic or preventative use of antibiotics may provide some protection in preventing an active infection from taking place in an uninfected colony at times of increased risk (early spring and fall).
  • If antibiotics are used preventively, all colonies in the yard should be treated at the same time.
• Antibiotics should only be delivered via powdered sugar. Using pollen substitutes as carriers or using the sugar syrup method to apply antibiotics are not recommended since these methods:
  • can contaminate honey
  • are less effective application methods
  • may promote antibiotic resistant EFB strains
• Choice of antibiotic (withdrawal time) and timing of antibiotic applications related to the honey flow needs to be well thought out to prevent contamination of honey with antibiotics.
• Beekeepers require a prescription from a veterinarian to access antibiotics for their honey bees. For general information on antimicrobial use in agriculture visit the Antimicrobial resistance in agriculture webpage. For more specific information on antibiotics for beekeeping in Ontario refer to the Ontario Beekeepers’ Association’s Antibiotic Access Resources for Beekeepers.

European foulbrood treatment options

Cultural control methods

Preventative treatment methods

Refer to the disclaimer when using antibiotics.

Sacbrood virus

Sacbrood virus (SBV) is a single stranded ribonucleic acid (RNA) virus that can cause mortality at the larval stage. Affected larvae can be readily identified by the presence of a fluid-filled sac that can be removed from the brood cell, often intact. Adult bees infected with the virus will not demonstrate any outward physical effects but may have a reduced lifespan. Nurse bees infected with SBV may exhibit behavioural changes, including early and preferential pollen foraging and can transmit the virus to young through feeding.

Sacbrood virus treatment considerations

• Registered chemical treatments are not available for SBV. However, timely and effective management of varroa mites will typically maintain honey bee viruses at lower levels within colonies.

Sacbrood virus treatment options

Cultural control methods

Chalkbrood (Ascosphaera apis)

Chalkbrood is a readily transmissible disease caused by the fungus Ascosphaera apis. There is no cure for chalkbrood. Spores are highly infectious and are carried in contaminated pollen by foraging bees. Infection may weaken colonies, reduce honey yields, and increase a colony’s susceptibility to other pests and disease.

Chalkbrood treatment considerations

• Registered chemical treatments are not available for Chalkbrood.
• Beekeepers must take an Integrated Pest Management approach to control chalkbrood by incorporating cultural control methods, regular monitoring and training through workshops from credible specialists.

Chalkbrood treatment options

Cultural control methods

Nosema species (Nosema ceranae and Nosema apis)

Nosema are single-celled parasites of the honey bee that infect and damage the mid-gut tissue. In Ontario, research has demonstrated that Nosema can impact the development of honey bee colonies in spring, but there is not a clear link between infections and winter loss experienced by honey bee colonies^{footnote 3[3]}.

Nosema treatment considerations

• Beekeepers do not require a prescription from a veterinarian to access Fumagilin-B for their honey bees as this product does not fall under the class of antibiotics that require a veterinary prescription.
• Fumagilin-B does not treat the spore stage of Nosema, only the active stage of the parasite.

Nosema treatment options

Cultural control methods

Preventative treatment methods

Refer to the disclaimer when using antibiotics.