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 Ontariofootnote 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 efficacyfootnote 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.

Technique Timing Actions
Drone trapping All season
  • Insert 1-2 frames with drone foundation or empty drone comb into the brood chamber to attract varroa mites. Varroa mites are more attracted to drone brood, so a higher proportion of varroa mites in the colony will enter the drone brood and be concentrated in these 1-2 frames in the brood nest.
  • Remove the frames of comb containing drone cells from the brood chambers after the cells are capped and before adult drones emerge (approximately 21 days).
  • Scrape out the removed drone frames (away from the colonies) or freeze so that the drones are not able to hatch and release the live varroa mites within the colony.
  • Varroa mite reproduction is higher in drone brood because they produce more offspring in drone brood than in worker bee brood. Beekeepers must take care to not let the drones emerge. Failure to remove these frames from the colony in a timely manner will result in an even greater number of varroa mites in the colony.
  • Repeat until early fall when drone production tapers off.
New queens Throughout beekeeping season, as needed
  • Re-queen colonies with new queens from hygienic stock that may have some mite and disease tolerance.
Screened bottom board All season
  • Incorporate #8 mesh screen (8 squares per 2.54 cm) onto bottom boards. Approximately 3 cm spacing is needed between the screen and bottom board to separate varroa mites from the bees.
  • Add a sticky material to a paper or thin cardboard insert below the screen. Mites that fall onto the sticky surface are less likely to crawl back into the colony.
  • This method may enhance varroa mite monitoring but will not substantially reduce mite infestations without additional treatment methods.

Chemical control methods

Refer to the disclaimer when using chemical control methods.

Chemical type Product and application method Active ingredient Timing and temperature considerations Use with honey supers present Application factors
Organic acid Liquid formic acid – single application

 

  • 250 mL pad per colony
 65% formic acid Spring and/or fall when ambient daytime temperatures are between 10-26°C on day of application.

Remove pads if daily temperature exceeds 30°C.		 No, not permitted
  • Colonies must have 6 or more frames of brood covered with bees to use this treatment.
  • Place pad on the top bars close to the brood area.
  • One treatment is applied for a period of 21 to 30 days.
Organic acid Liquid formic acid – multiple applications

 

  • 15-20 mL pad for 1-story colony
  • 30-40 mL pad for 2-story colony
 65% formic acid Spring and/or fall when ambient daytime temperatures are between 10-26°C on day of application.

Remove pads if daily temperature exceeds 30°C.		 No, not permitted
  • Up to 6 applications, repeated at 3 to 5-day intervals, can be used.
  • For really small colonies, move the brood to the side of the colony and place pad on top of the middle frame(s) in the brood chamber.
Organic acid Mite Away Quick Strips™ (MAQS™) 46.7% formic acid Anytime during the active beekeeping season, including summer and during a honey flow, when ambient daytime temperatures are between 10–29.5°C on day of application. Yes, consult label
  • Colonies must have 6 or more frames of brood covered with bees to use this treatment.
  • Apply MAQS™ every 2 to 6 weeks as needed throughout the beekeeping season.
  • Treatment duration is 7 days.
  • Refer to the label for dosage and placement instructions.
Organic acid Formic Pro™ Strips 42.25% formic acid Anytime during the active beekeeping season, including summer and during a honey flow, when ambient daytime temperatures are between 10–29.5°C on day of application. Yes, consult label
  • Colonies must have 6 or more frames of brood covered with bees to use this treatment. 
  • For colonies with single or double brood chambers, place the strip on the top bars of the frames of the lower brood chamber.
  • Strips can be applied for either a 14-day treatment or a 20-day treatment (consult label for proper dosage and timing).
  • Allow 1 month between applications.
Organic acid Oxalic acid – drizzle method Oxalic acid Early spring or late fall on a cool day when little to no brood is present and bees are clustered in the colony. No, not permitted
  • Use in brood-free periods (very early spring or late fall or during a break in brood cycle).
  • The maximum dose is 50 mL per colony (same dose for nucleus colonies, single or multiple brood chambers).
  • Only has the capacity to kill varroa mites on adult bees.
Organic acid Oxalic acid – vaporizer method Oxalic acid Use at times when colonies are broodless.

No temperature specified.		 No, not permitted
  • Treatment is intended for broodless colonies.
  • There is a risk of damage to colonies with a high number of repeated applications.
Synthetic acaricide Apivar® strips Amitraz Spring and/or fall No, not permitted
  • If treating when colony is clustered (ambient daytime temperatures are low), ensure the strips are positioned in the colony in contact with the cluster.
  • 1 strip for every 5 frames of bees, but refer to label to confirm dosage and placement instructions.
  • Remove strips at the conclusion of the treatment and do not reuse strips.
Synthetic acaricide Apistan® strips Tau-fluvalinate Spring and/or fall No, not permitted
  • If treating when colony is clustered (ambient daytime temperatures are low), ensure the strips are positioned in the colony in contact with the cluster.
  • Strips can be applied for 42 to 56 days. Refer to label to confirm dosage and placement instructions.
  • Remove strips at the conclusion of the treatment and do not reuse strips.
Synthetic acaricide Bayvarol® strips Flumethrin Spring and/or fall No, not permitted
  • If treating when colony is clustered (ambient daytime temperatures are low), ensure the strips are positioned in the colony in contact with the cluster. 
  • Use 4 strips per brood chamber for 42 days. Refer to label to confirm dosage and placement instructions.
  • Remove strips at the conclusion of the treatment and do not reuse strips.
Essential oil Thymovar® strips Thymol Spring and/or fall when ambient daytime temperatures are between 13-30°C on day of application.

Best results are seen at 20-25°C.

Start with reduced dose if daytime temperatures are greater than 30°C.		 No, not permitted
  • Place strips 4–10 cm from brood cells.
  • Leave 1–2 cm space over the strips to allow good evaporation of the thymol.
  • Cut strips into 2 pieces for easy placement.
Essential oil Api Life Var tablets Thymol, camphor, levomenthol and eucalyptus oils Use when ambient daytime temperatures are between 13-35°C on day of application. No, not permitted
  • Colonies must have 8 to 20 frames of bees to use this treatment.
  • 2 treatments per year may be made.
  • Place tablet portions around edge of brood nest on top of top bars. Avoid placing tablet portions directly above brood nest.
Beta hop acid HopGuard® III strips Potassium salts from hop beta acids Anytime during the active beekeeping season, including summer and during a honey flow, when ambient daytime temperatures are above 10°C on day of application. Yes, consult label
  • Hang strips between the brood frames.

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

Technique Timing Actions
New queens Throughout beekeeping season, as needed
  • Re-queen colonies with new queens from hygienic stock that may have some mite and disease tolerance.

Chemical control methods

Refer to the disclaimer when using chemical control methods.

Chemical type Product and application method Active ingredient Timing and temperature considerations Use with honey supers present Application factors
Organic acid Liquid formic acid – multiple applications

 

  • 35 mL pad per colony
 65% formic acid Spring and/or fall No, not permitted
  • Colonies must have 6 or more frames of brood covered with bees to use this treatment.
  • 3 consecutive applications at 4 days apart.
  • For really small colonies, move the brood to the side of the colony and place pad on top of the middle frame(s) in the brood chamber.
Organic acid MAQS™ 46.7% formic acid Anytime during the active beekeeping season, including summer and during a honey flow, when ambient daytime temperatures are between 10–29.5°C on day of application. Yes, consult label
  • Colonies must have 6 or more frames of brood covered with bees to use this treatment.
  • Apply MAQS™ every 2 to 6 weeks as needed throughout the beekeeping season.
  • Treatment period is 7 days in length.
  • Refer to the label for dosage and placement instructions.

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

Technique Timing Actions
Maintain queenright colonies (presence of a functional queen) Throughout beekeeping season
  • Monitor colonies to ensure a functional queen is present and re-queen colonies with new queens as needed.
  • Colonies may be overrun by SHB when they are “queenless”.
Maintain populous, healthy colonies and reduce excessive space Throughout beekeeping season
  • Colonies without enough bees to protect the space/area inside the colony will not be able to effectively prevent SHB egg laying and production of larvae, which is the damaging stage of SHB.
SHB traps Throughout beekeeping season
  • Place physical traps (baited with food grade oil or a material the beetles can get entangled in) in colonies to trap and kill some individual SHB.
  • These traps can also be effective in monitoring for SHB in bee yards.

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.

Treatment type Product Active ingredient and application method Timing Use with honey supers present Application factors
Antibiotic Oxytet 62.5 Oxytetracycline mixed with powdered sugar according to the label instructions or veterinary prescription. Spring and/or fall No, not permitted

If treatment must occur during the honey flow, honey supers must be removed first and the withholding period/residual of the antibiotic must be accounted for before supers can be replaced.
  • Label must indicate it can be used for honey bees unless a veterinarian directs otherwise.
  • Typically, colonies receive 3 applications at 4 to 5-day intervals in the spring and in the fall.
  • Stop treating 4 weeks before the main honey flow.
  • Honey from the brood chambers of treated colonies must not be harvested for human consumption.
Antibiotic Tylosin Powdered Tylan mixed with powdered sugar according to the label instructions or veterinary prescription. Fall only (after honey flow)

Do not use in the spring and summer as product may contaminate honey.		 No, not permitted
  • Label must indicate it can be used for honey bees unless a veterinarian directs otherwise.
  • Typically, colonies receive 3 consecutive applications.
  • Honey from the brood chambers of treated colonies must not be harvested for human consumption.
Antibiotic Lincomycin Powdered Lincomix mixed with powdered sugar according to the label instructions or veterinary prescription.  Fall only (after honey flow)

Do not use in the spring and summer as product may contaminate honey.		 No, not permitted
  • Label must indicate it can be used for honey bees unless a veterinarian directs otherwise.
  • Typically colonies receive 1 application weekly for 3 consecutive weeks.
  • Honey from the brood chambers of treated colonies must not be harvested for human consumption.

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

Technique Timing Actions
Destroy infected frames Anytime
  • Destroy infected comb and replace with new, non-infected comb or foundation.
  • Destroy an entire colony in severe cases.
New queens Throughout beekeeping season, as needed
  • Re-queen colonies with new queens from hygienic stock that may have some mite and disease tolerance.
Pollen supplements Spring and fall
  • Provide supplemental feed after intensive berry pollination or other periods of extreme pollen shortages.
Cull old frames Anytime
  • On a regular basis, remove and dispose of older frames from the brood nest.

Preventative treatment methods

Refer to the disclaimer when using antibiotics.

Treatment type Product Active ingredient and application method Timing Use with honey supers present Application factors
Antibiotic Oxytetracycline Oxytetracycline mixed with powdered sugar according to the label instructions or veterinary prescription. Spring and/or fall No, not permitted

If treatment must occur during the honey flow, honey supers must be removed first and the withholding period/residual of the antibiotic must be accounted for before supers can be replaced.
  • Label must indicate it can be used for honey bees unless a veterinarian directs otherwise.
  • Typically, colonies receive 3 treatments at 4 to 5-day intervals in the spring and in the fall.
  • Stop treating 4 weeks before the main honey flow.
  • Honey from the brood chambers of treated colonies must not be harvested for human consumption.

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

Technique Timing Actions
New queens Throughout beekeeping season, as needed
  • Re-queen colonies with new queens from hygienic stock that may have some mite and disease tolerance.
Control varroa mites Throughout the active beekeeping season

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

Technique Timing Actions
New queens Throughout beekeeping season, as needed
  • Re-queen colonies with new queens from hygienic stock that may have some mite and disease tolerance.
Cull old frames Anytime
  • On a regular basis, remove and dispose of older frames from the brood nest.
Destroy infected frames Anytime
  • Destroy infected comb and replace with new, non-infected comb or foundation.

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 coloniesfootnote 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

Technique Timing Actions
Cull old frames Anytime
  • On a regular basis, remove and dispose of older frames from the brood nest.

Preventative treatment methods

Refer to the disclaimer when using antibiotics.

Treatment type Product Active ingredient and application method Timing Use with honey supers present Application factors
Antibiotic Fumagilin-B Fumagilin dicyclohexylamine

Fumagilin-B mixed with sugar syrup and delivered via a method whereby each colony in the bee yard receives a standard dose (for example, feeder bag).		 Spring and fall No, not permitted
  • Label must indicate it can be used for honey bees.
  • Use if a qualified laboratory (or sampling from a trained beekeeper) determines that colonies are exhibiting a significant infection (an average of > 1 million spores/bee).
  • Avoid applying the treatment using barrel feeding as this method will cause the Fumagilin-B to settle at the bottom of the barrel and each colony will receive a different dose.