Ontario Honey Bee Colony Winter Loss Survey Report for 2014

Paul Kozak, OMAFRA
February 2, 2015

Please contact apiary@ontario.ca for the report in PDF format.

Introduction

During the spring of 2014, the Ontario Ministry of Agriculture, Food and Rural Affairs (OMAFRA) surveyed Ontario beekeepers to estimate honey bee colony mortality over the winter of 2013/2014.

As in previous years, the survey was mailed to all registered commercial beekeepers (defined for this purpose as those with 50 or more hives). The survey had a 40 per cent response rate; 100 of the 247 commercial beekeepers contacted responded to the survey.

For the first time, the survey was also sent to 399 non-commercial beekeepers, randomly selected from the ministry's registry. Their feedback will help provide further insight into Ontario's beekeeping industry. Of the non-commercial beekeepers surveyed, 32 per cent (129 beekeepers) responded.

Because commercial beekeepers represent the majority of managed honey bee colonies, when survey findings were reported to the Canadian Association of Professional Apiculturists (CAPA), only commercial beekeepers' results were used. The average winter loss statistic is also based solely on commercial beekeepers' response. Reporting only commercial beekeepers' results to CAPA and for the average winter loss statistic for 2013/2014 keeps the reporting consistent with previous years when non-commercial beekeepers were not surveyed.

In total, the survey results represent 53,000 colonies (53 per cent) of the 100,000 colonies operated in Ontario.

Methodology:

This report is based on responses provided by all beekeepers, as well as data from targeted ministry inspections conducted in 2013 and early spring 2014. Data from commercial and non-commercial beekeepers was analyzed separately.

Statistical analysis was conducted on the responses beekeepers provided through the winter loss survey.

There are limitations to survey and inspection data. The information provided was voluntary, self-reported, and in some cases, a best estimate by beekeepers. For some questions, response rates were low or there was a wide variation in responses. Data for those questions is difficult to analyze. For more accurate analysis in the future, more commercial beekeepers would need to participate and complete all questions in the survey.

Regardless of the data's limitations, the survey captures beekeepers' specific management practices and their health concerns for their colonies.

The anonymous survey followed the same template as the National Apiculture Survey conducted through CAPA, and included additional questions specific to Ontario. OMAFRA's survey tracked mortality levels as well as some colony management practices for pests and diseases in honey bees.

Bee Mortality:

Through the survey, Ontario commercial beekeepers reported a 58 per cent overall approximate honey bee colony mortality rate for winter 2013/2014. Since 2010, a commercially viable hive has been defined in Ontario's survey as having four or more viable frames of bees in the spring.

The mortality rate was based on reported info and was calculated by dividing the total number of colonies that died during the winter by the total number of colonies that were alive at the start of winter.

Half of the beekeepers who responded lost less than 54 per cent of their hives; the other half lost more than 54 per cent of their hives. There was a large variability in losses, with some beekeepers reporting no colony deaths and others reporting all of their colonies had died. The standard deviation for the survey results was 27.6 per cent.

The estimated 58 per cent overall winter loss is substantially higher than in any previous year. In Canada overall, a normal level of winter mortality is up to 15 per cent (Furgala and McCutcheon, 1992; CAPA, 2007 to 2014).

Although beekeepers reported a wide variation in hive mortality, overall survey results indicated high loss levels. Many of Ontario's honey bee colonies did not survive into spring 2014.

The apiary program conducted approximately 140 beeyard inspections in spring 2014 to validate the over winter losses reported by beekeepers. Some beeyards had high levels of mortality and others had low levels. Of the beeyards inspected, the overall average level of loss was high at 45.1 per cent.

This is the first year that the apiary program has conducted this scale of field validation. The effort was important to help compare and validate beekeepers' survey responses.

Loss by Region of Ontario:

The following table presents regional survey responses. It shows the number of beekeepers who responded and overall winter loss rates for each region. There was no significant difference in mortality rates among the regions.

Region
Commercial Beekeepers
Non-Commercial Beekeepers
Number of Beekeepers Responding
Overall Loss Rate
Number of Beekeepers Responding
Overall Loss Rate
North
3
45.5%
9
61.9%
East
16
42.7%
25
51.4%
Central
18
58.5%
22
44.3%
South
48
59.7%
41
34.9%
Southwest
8
57.5%
15
61.8%
No County Listed
4
46.4%
10
40.7%

Table 1. Overall Winter Mortality by Region

Overall Winter Loss By Region (Commercial Beekeepers)

Figure 1: Overall Winter Loss By Region (Commercial Beekeepers)

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Overall Winter Loss By Region (Non-Commercial Beekeepers)

Figure 2: Overall Winter Loss By Region (Non-Commercial Beekeepers)

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The high level of estimated mortality in 2007 was a major concern for the industry. This was followed by two more consecutive years (2008 and 2009) of high winter mortality for an estimated overall winter mortality average of 33 percent over the three years.

Winter Loss of Ontario Honey Bee Colonies by Year (Commercial Beekeepers).
Figure 3: Winter Loss of Ontario Honey Bee Colonies by Year (Commercial Beekeepers).

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The red horizontal line represents the 15% normal winter loss threshold

Variation in winter loss for individual commercial beekeepers. The patterned bars represent beekeeping operations at or near the level of acceptable level of winter loss (15% mortality).

Figure 4: Variation in winter loss for individual commercial beekeepers. The patterned bars represent beekeeping operations at or near the level of acceptable level of winter loss (15% mortality).

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Mortality by scale of operation:

  • When beekeepers were grouped by operation size (i.e., number of colonies managed) the differences among winter loss rates were not significant
Number of Beekeepers
Number of Hives Put into Winter
Beekeeper Average Loss (%)
36
< 10
51.3
88
10-49
46.5
56
50-200
49.1
28
201-500
49.8
10
501-1000
49.0
11
>1000
55.4

No significant difference among groups of beekeepers

Table 2: Winter loss rates by size of beekeeping operation (i.e., number of colonies operated), Commercial and Non-Commercial Beekeepers

  • When the largest beekeepers (i.e., those with more than 1,000 colonies) were removed from the statistics, the overall average level of over-winter loss in Ontario was still high at 48.1 per cent.
  • The average over-winter loss for large commercial beekeepers (i.e., those with more than 1,000 colonies) was 55.4 per cent, however, some of those beekeepers had much lower levels of over-winter loss at 9 to 17 per cent mortality.
  • When non-commercial beekeepers (i.e., those with 50 colonies or less) were analyzed together, their overall over-winter loss was high at 43.9 per cent.
  • Based on survey results for winter 2013/2014, there is no clear relationship between size of beekeeping operation and over-winter loss.

Management Practices and Treatments

Colonies may not survive winter for a variety of reasons. Hives can be killed by varroa infestation, starvation, small cluster size and environmental stressors.

There are many theories on why honey bee colony mortality has increased. Ineffective varroa control, new pathogens, pesticides and a combination of those factors are all possible contributors.

A study from the University of Guelph (Guzman et al., 2010) identified Varroa destructor as the primary pest and disease factor in winter mortality for Ontario honey bee colonies. For this reason, OMAFRA's survey focused on beekeepers' management techniques and varroa treatments.

Treatments

Varroa are relatively large external parasites that feed on the body fluids of adult and developing honey bees. Varroa cause physical damage, weaken bees and transmit a variety of pathogens, particularly viruses. In almost all cases, when varroa infestations are not effectively managed they will eventually result in the death of the entire honey bee colony. In OMAFRA's survey, beekeepers were asked how they manage varroa levels in their colonies and the treatments they used for spring and fall 2013.

Ontario beekeepers use a variety of options to manage varroa. In spring and fall 2013, the two most common methods of treatment were Apivar® and 65% liquid formic acid (small pads - 40 ml). To date, there have been no documented cases of Apivar®-resistant varroa in Ontario. The active ingredient in Apivar® is amitraz.

The two least commonly used synthetic acaricides (known as "strip treatments") were Apistan®, and Checkmite+™. There are varroa in Ontario that have developed resistance to both Apistan® and Checkmite+™. This is likely why these two treatments are used cautiously.

The Technology Transfer Program administered by the Ontario Beekeepers' Association has conducted field trials to test varroa treatments. Checkmite+TM is effective approximately 40 per cent of the time. Apistan® is effective approximately 70 to 90 per cent of the time. Apistan® can work some of the time against varroa while varroa are resistant to the active ingredient in Checkmite+™ in most situations in Ontario.

When beekeepers suspected that a treatment had failed, the Technology Transfer Program conducted tests to see if varroa were resistant to the treatment. The tests confirmed that Apistan® and Checkmite+™ are still effective in managing varroa.

Recent data from the U.S. showed that varroa there have developed serious resistance to all three synthetic acaricide treatments: Apistan®, Checkmite+™ and Apivar®. To delay varroa in Canada from developing a resistance to chemical treatments, Canadian beekeepers must rotate treatment types as part of an Integrated Pest Management (IPM) strategy.

Varroa levels are constantly rising in honey bee colonies. In both spring and fall 2013, some beekeepers chose not to treat for varroa mites. Choosing not to control varroa will eventually kill the colony, but as long as varroa levels remain low and can be verified through monitoring, beekeepers may be able to justify periods of not treating the colony. Treating only when required and monitoring for pest levels are key practices of IPM.

Treatments used to control varroa mites in spring 2013 (Commercial Beekeepers)

Figure 5: Treatments used to control varroa mites in spring 2013 (Commercial Beekeepers)

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Figure 6. Treatments used to control varroa mites in fall 2013 (Commercial Beekeepers)

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Treatments used to control varroa mites in spring 2013 (Non-Commercial Beekeepers)

Figure 7. Treatments used to control varroa mites in spring 2013 (Non-Commercial Beekeepers)

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Treatments used to control varroa mites in fall 2013 (Non-Commercial Beekeepers)

Figure 8. Treatments used to control varroa mites in fall 2013 (Non-Commercial Beekeepers)

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Data From Field Inspections:

During their field checks in the 2013 season, apiary inspectors gathered data on varroa levels. To give an accurate picture of the conditions leading into winter 2013/2014, this field data should be considered along with responses from the over winter loss survey.

Throughout the beekeeping season, planned and random inspections fulfilled regulatory requirements, provided targeted pest and disease surveillance, and addressed requests from beekeepers.

In commercial beekeepers' colonies, levels of varroa were well below the spring and fall treatment thresholds established by Ontario researchers (Ernesto Guzman, et al., 2010). There were anecdotal reports that varroa levels were low throughout most of the 2013 season. Evidence shows many beekeepers in Ontario are effectively controlling varroa in their colonies.

In non-commercial beekeepers' colonies, levels of varroa were below the treatment threshold in the spring, but above the treatment threshold in the fall. It should be noted that fall had a low sample size.

The type of varroa treatment used and when the treatment was applied did not appear to influence winter mortalities.

Beekeepers must choose treatments carefully and treat their colonies well before varroa reach damaging levels, especially in preparation for winter. All varroa treatments have limitations (e.g., timing, temperature thresholds, etc.). Rather than relying on one type of treatment all the time, beekeepers must understand the limitations of the treatments and ensure the treatments are working to control varroa.

Monitoring and managing varroa levels in colonies will always be an essential task in beekeeping.

Varroa levels documented in commercial beekeeping operations by apiary inspectors

Figure 9: Varroa levels documented in commercial beekeeping operations by apiary inspectors

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Varroa levels documented in non-commercial beekeeping operations by apiary inspectors

Figure 10: Varroa levels documented in non-commercial beekeeping operations by apiary inspectors

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Nosema

Nosema (N. ceranae and N. apis) is a fungal pathogen that infects the digestive system of honey bees. The majority of Ontario beekeepers did not treat for nosema in fall 2013 (61 per cent of all survey respondents indicated no treatment used). The survey did not ask beekeepers to indicate why they did or did not treat for nosema.

Nosema can be an added stress on colonies, depending on the time of year and the species of honey bee. However, recent research from Ontario (Guzman, et al., 2010) did not determine a correlation between nosema levels and winter loss.

Queen Management and Colony Replacement

On average, commercial beekeepers replace 44 per cent of their honey bee queens as part of their regular management. This level of queen replacement is considered the ideal when colonies have healthy, effective queens.

On average, non-commercial beekeepers replace only 21 per cent of their honey bee queens.

Regularly replacing old queens with new, healthy queens is an important strategy for healthy honey bee colonies.

Percentage of honey bee queens replaced by beekeeper as part of regular management

Figure 11: Percentage of honey bee queens replaced by beekeeper as part of regular management

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Beekeepers were asked to report the level of queens they had to replace as a result of queens' health problems or failure. Anecdotal and documented reports in recent years show an increased number of queen deaths and failures.

Commercial beekeepers reported an average of 22 per cent of their colonies suffered from queen problems. Non-commercial beekeepers reported an average of eight per cent of their colonies suffered from queen problems. When analyzed by region, more colonies in Southern Ontario were experiencing queen problems than elsewhere in the province. In Southern Ontario, an average of 28 per cent of colonies experienced problems. This was statistically significant when compared with the rest of the province.

Ontario beekeepers access honey bee queens from a variety of sources, including Ontario, California, Hawaii, Australia, and Chile among others. Many queens are produced locally in Ontario.

Origin of honey bee queens used by commercial beekeepers in Ontario.

Figure 12: Origin of honey bee queens used by commercial beekeepers in Ontario.

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Abnormal mortality

In the OMAFRA survey, beekeepers were asked whether they had experienced abnormal mortality or abnormal decline in bee population during the regular beekeeping season. Stressors that impact a honey bee colony may ultimately impact the long-term survival of that colony. However, long-term impacts of stressors and their possible link to winter loss was outside the scope of this survey.

Of commercial beekeepers, 46 per cent reported some sort of abnormal mortality or decline in bee population.

Estimated or Suspected Reasons for Winter Mortality Self-Identified by Beekeepers

Beekeepers were asked what they thought was causing colony mortality. Their opinions may have been based on symptoms, beekeeper experience and judgment, or speculation.

In order from most common to least common response, the reasons for winter loss cited by commercial beekeepers were:

  • starvation
  • weather
  • chronic pesticide exposure
  • unknown
  • weak colonies
  • acute pesticide exposure
  • other
  • nosema
  • ineffective varroa control.

Most beekeepers suggested a combination of reasons for their winter loss.

A single honey bee colony can be impacted by multiple stressors. Similarly, in a beeyard or beekeeping operation, each colony can be impacted by different stressors. For example, in a beeyard, where clusters in a hive are positioned in different ways, several colonies may die due to starvation while the other colonies survive.

Beekeepers' opinions on suspected causes of hive mortality were not further verified, so they cannot be taken as established facts. However, these opinions have value and could indicate real issues. Responses to this type of survey question should be considered together with field data and may prove useful for directing future research.

Few beekeepers blamed varroa control for colony mortality, perhaps because those beekeepers were having success with controlling varroa in their colonies.

Many beekeepers believed starvation was causing winter mortality, which is likely because of the very harsh and long winter conditions in 2013/2014. Honey bee colonies will starve to death when they do not have enough food stores to last the winter. In some cases, weakened colonies and the position of the colony cluster within the hive can result in starvation even when colonies are sufficiently fed.

Reasons for winter mortality reported by commercial beekeepers

Figure 13: Reasons for winter mortality reported by commercial beekeepers

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Weighted reasons for winter loss reported by commercial beekeepers (the proportion of importance that beekeepers assigned to this type of loss by %)

Figure 14: Weighted reasons for winter loss reported by commercial beekeepers (the proportion of importance that beekeepers assigned to this type of loss by %)

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General Comments and Discussion

  • Based on research from the University of Guelph (Guzman et al., 2010), as well as reports and field observation from other provinces (Currie et al., 2010), varroa is still the main pest factor associated with winter mortality. Although varroa may have been an issue in some operations, data from the field showed that varroa levels were low in many operations.
  • The overall ability of Nosema ceranae to cause disease in honey bees is somewhat unclear. However, recent research from the University of Guelph shows there is not a clear correlation between nosema and winter loss under Ontario conditions.
  • While there is not enough evidence to establish a direct link, weather patterns likely impacted the survival of some colonies. Last year, most parts of the province had a very long and cold winter. The harsh winter may have resulted in more honey bee colonies starving, regardless of hive management. Anecdotal reports from some operations revealed that the cool, rainy spring further stressed colonies that were recovering from winter. This too could have caused significant colony losses well into mid-spring. In contrast, 2012 had one of the mildest winters in recent years and the over-winter loss reported for that year was only 12 per cent.
  • A number of beekeepers reported chronic pesticide issues as a cause for increased colony mortality. This concern is likely linked to reports of mid-season pesticide incidents and further impacts on colonies. The effect of chronic pesticide exposure on honey bee mortality will require further research and data from the field to determine its influence on winter mortality.
  • The winter loss survey is a valuable tool for gathering information on colony mortality, on the concerns of beekeepers, and on the type of management practices they use. However, the winter loss survey cannot provide all the answers on honey bee health. Results must be combined with data gathered in the field, mid-season reports of honey bee health, and research prompted by the concerns of beekeepers to give a comprehensive understanding of honey bee health.
  • In 2013/2014 Ontario had its highest ever level of documented winter loss. This is especially concerning as the demand for honey bee pollination services increases. The sector is growing, although it is not yet back to historic levels. When colony losses force beekeepers to rebuild, this growth is restricted. Slower growth affects business profits and beekeepers' ability to provide more colonies to meet the growing demand for pollination services.
  • The strategy for improving honey bee health in Ontario will take a comprehensive approach that includes continued development of integrated pest management practices by beekeepers and growers, safe areas for foraging, research on honey bee health, documentation of incidents from the field and further work relating to long term colony health.

References:

Canadian Association of Professional Apiculturists (CAPA) Statement on honey bee losses in Canada. 2007, 2008, 2009, 2010, 2011, 2012, 2013 and 2014.

Currie R., Guzman E. and Pernal, S. 2010. Honey bee colony losses in Canada. Journal of Apicultural Research. 49 (1): 104-106.

Furgala B., and McCutcheon, D.M. 1992. Wintering productive colonies. In Graham J M (Ed). The hive and the honey bee (revised edition). Dadant and Sons; Hamilton, IL, USA pp. 829-868.

Guzman-Novoa E., Eccles L., Calvete Y., McGowan J., Kelly P. and Correa-Benitez A. 2010. Varroa destructor is the main culprit for death and reduced populations of overwintered honey bees in Ontario, Canada. Apidologie. 4 (4) 443-451.

Kozak, P. 2011. Beekeeper Survey - 2011 Winter Loss Report for Apiculture in Ontario. Ontario Ministry of Agriculture and Rural Affairs.


For more information:
Toll Free: 1-877-424-1300
E-mail: ag.info.omafra@ontario.ca
Author: Paul Kozak, Provincial Apiarist/OMAFRA
Creation Date: 12 March 2015
Last Reviewed: 22 October 2015