As Canadian beekeepers work to rebuild after the unusually high overwintering losses of the winter of 2006-2007, what should be done to promote bee health and reduce future winterkill?

Medhat Nasr has prepared a fact sheet, Honey Bees and Winterkill, for the Alberta Department of Agriculture. It outlines the best management practices developed in Alberta to address the several possible causes that contribute to winterkill, and provides beekeepers with options to minimize the amount of winterfill in future.

In general:

Best Management Practices

• Keep bee colonies strong — avoid over-splitting.
• Send bees into winter with a healthy, mated young queen.
• Make room for the queen to lay eggs to make winter bees.
• Feed the bees as needed.

Following is a summary of highlights from the Alberta beekeeping factsheet.

Beekeepers will find it useful to read the original factsheet on the Alberta Departmant of Agriculture website, however. It has much more detailed information — including the fascinating fact that winter bees are physiologically different from summer bees, and thus better suited to withstand winter weather — to help beekeepers in making sound management choices in caring for our bees.

Pest Management

Sighting a single pest does not always mean control is needed.

Check with your Department of Agriculture for up-to-date recommendations and information on pest management. The incorrect application of chemicals can cause high kill and sub-lethal effects on honey bees, so it is important to follow the label instructions and apply only the recommended dose at the proper time.

Use an Integrated Pest Management (IPM) approach for pest control in honey bee colonies, which begins with identifying the pest and monitoring its population levels, as well as the hive’s general health.

IPM first sets an action threshold — a point at which pest populations or environmental conditions indicate that pest control action must be taken. When identification, monitoring, and action thresholds come together to indicate that preventive methods are no longer effective or available, effective pest controls are chosen to ensure the protection of bee health with the minimum of risk.

Varroa mites

Varroa remains the most destructive honey bee pest. Recently, varroa mites have been implicated in transmitting viruses that could cause seriously high colony kill. Many of the pesticides currently used are failing, and mites are out of control in some regions.

The Alberta factsheet advises beekeepers to keep varroa under control by taking the following steps:

• Monitor the mite population in bee colonies to determine mite levels reaching defined thresholds, treatment time and control methods.
• Monitor before and after treatment to compare results and ensure that treatment was effective.
• Test varroa mites for resistance to Apistan and CheckMite before using either one for control of mites.
• Choose a combination of effective control methods as needed.
• Do not delay treatment. It is important to protect winter bees from any damage caused by mites.

Nosema

Nosema is another possible serious cause of high winterkill. Beekeepers need to examine their bees for nosema and determine the infection levels, and should consider taking serious steps to control nosema in their bee colonies throughout the year.

Honey Bees and Winterkill recommends the following steps:

• Survey bee colonies to determine nosema infection levels.
• Feeding fumagillin in sugar syrup in spring and fall should be considered by all beekeepers to keep the nosema levels below the economic threshold. Ensure that bees will take all medicated feed before wintering.
• Disinfect dead outs using irradiation or acetic acid before using the equipment again. Dead outs could have combs infected with nosema and other pathogens, so it is possible that re-using infected dead out boxes will infect the new colonies.

Acetic Acid Fumigation of Dead Outs

Acetic acid is known to be effective as a sterilizing agent against nosema and also helps with the problem of waxmoth. The acid will kill both the eggs and adult waxmoth, but not necessarily the bigger larvae. Acetic acid fumigation is the simplest way for beekeepers to sterilize combs contaminated with nosema spores. It is suggested that beekeepers use acetic acid as a normal routine preventative method to help guard against nosema.

American Foul Brood (AFB)

Do not let neighboring colonies rob out AFB-infected colonies. Remove dead outs as soon as possible from apiaries to reduce the chance of robbing these hives. AFB-infected colonies are on the rise, and neglected dead outs are scatted throughout the countryside. Antibiotics are only used to treat the active form of AFB, which does not affect spores. Consider burning infected hives, irradiation and shaking bees on new foundations as a long-term solution to the problem.

• Do not combine a sick colony with a healthy one. The sick colony will contaminate or infect the strong, healthy colony. Treat and strengthen the sick colony until it is cured.
• As a general role of thumb, use alternative management approaches to minimize the use of chemicals in bee colonies, to lessen bee exposure to potentially toxic chemicals and to reduce the risk of contaminating honey with antibiotic residues.

This integrated approach of recommendations will reduce any stress or combination of stresses (pathogens, chemicals, genetics, varroa, etc.) on bee colonies, Dr. Nasr says. These stressors can suppress a bee’s immune system and potentially cause high winterkill. By addressing all aspects of colony health, on the other hand, honey bees will have a better chance to survive and be productive.

See:
Honey Bees and Winterkill
Medhat Nasr, Ph.D.
Pest Management Branch
Alberta Agriculture and Food
Source: Agdex 616-24. November 2007.

See also:
In Response to Winterkill Advice (on this website)
for a note on New Brunswick recommendations.