07554     Revised 2010

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Our Philosophy

• In this manual, we advocate using as few chemical treatments as possible in bee colonies to control diseases and parasitic mites for the following reasons:
• Bees should not be dependent on our treatments for their survival. Bees can develop natural resistance to disease and mites through careful selection and breeding.
• Antibiotics, particularly pesticides can contaminate honey, beeswax and other hive products.
• Diseases and mites can develop resistance to antibiotics and some pesticides with prolonged use, rendering treatments ineffective.
• Combinations of chemical compounds can lead to potentially toxic effects on bees, in the same way that combinations of drugs used for human health can have synergistic and negative side effects.

Knowledge, Prevention, Control

Our strategy for keeping bees healthy and reducing chemical treatments follows three deliberate steps: Knowledge, Prevention and Control. We want all beekeepers to be educated about the diseases and pests that bees face and to use the best beekeeping management practices to control them. The use of chemical treatments should be considered only as an absolute last resort.

1. Knowledge:
   Learn about bee diseases and mite pests.
   Be able to recognize clinical symptoms of diseases and understand the life-cycle of the mites.
2. Prevention:
   Implement sound beekeeping practices to avoid getting and spreading diseases and mites.
   Sample your colonies for diseases and mites to know the degree of infection or infestation.
   Bee self-defense! Use stocks of bees that demonstrate some resistance to diseases and mites.
   Resistant Bees & Resistance Management
3. Control:
   Use cultural / mechanical / non-chemical control techniques to reduce transmission if your bees do have diseases or mites.
   Last resort: Use chemical treatments only when absolutely necessary and according to label.

Healthy Bee Course

For more information on controlling diseases and pests, we encourage you to take our on-line course called “Healthy Bees.” You can register through
our web site: http://www.extension.umn.edu/honeybees

Resistant Bees

Currently, bees are being bred in the U.S. that are resistant to American foulbrood (AFB) and chalkbrood diseases and to the parasitic mites, Varroa destructor (the varroa mite) and Acarapis woodi (the tracheal mite). We encourage you to try these different lines of bees.

Bees bred for hygienic behavior demonstrate good resistance to AFB and chalkbrood and partial resistance to varroa mites. Our Minnesota Hygienic stock, bred at the University of Minnesota, is commercially available. These bees will require periodic treatments for varroa, but may not require treatments for AFB or chalkbrood.

Bees bred by Drs. Harbo and Jeff Harris at the USDA Baton Rouge lab for Varroa Sensitive Hygiene (VSH) have very good resistance to varroa, but they have not been tested for disease resistance. They are best used as hybrids, when VSH queens are mated to local drones.

Russian bees, imported from Russia by the USDA Bee Research Lab in Baton Rouge, have demonstrated resistance to both varroa and tracheal mites but not to diseases.

Resistance Management

For many years beekeepers have been giving treatments of oxytetracycline (an antibiotic, trade name Terramycin® or TM) to prevent and treat the highly infectious and devastating disease, American foulbrood (AFB). In most cases, TM is no longer effective in treating AFB because the bacterium that causes AFB has developed resistance to the antibiotic. This problem has forced us to think of resistance management strategies that do not involve the use of antibiotics. Please read and follow the section in this booklet on prevention and control of AFB carefully.

Also, in recent years, varroa mites have developed resistance to the pesticide fluvalinate (a synthetic pyrethroid, trade name Apistan®). This pesticide was used very successfully for 10 years to control varroa. When it became ineffective, a new compound, coumaphos (an organophosphate, trade name CheckMite+®) was given Section 18 (temporary-emergency) registration for use in many states. Coumaphos has a different mode of action than fluvalinate, so it kills mites that are resistant to fluvalinate. The mites also developed resistance to coumaphos rendering it ineffective. Importantly, wax samples throughout the U.S. show high residue amounts of both fluvalinate and coumaphos, and we are uncertain as to the health risk this poses to bees.

It is very important to employ resistance management strategies in our treatment of bees to avoid allowing the mites to develop resistance to the treatments, and to avoid contaminating beeswax! What do you do?

To control varroa mites, the best resistant strategy is to use Integrated Pest Management. The idea is that beekeepers sample their colonies regularly for varroa mites (spring and late summer). When the number of mites exceeds a threshold range, or Economic Threshold, the beekeeper must decide what kind of treatment is appropriate and rotate among treatments so that the mites don’t develop resistance to them. It is very important that beekeepers do not just assume their colonies have or do not have mites! All beekeepers must learn to sample their colonies to know how serious the mite infestation is, and then must learn to make the best treatment decision. In some cases, the mite levels may not be high enough to initiate treatment, but the colonies should be monitored closely for changes in mite levels. In other cases, the beekeeper may opt to use a treatment that the mites cannot develop resistance to, such as formic acid or thymol botanical oils. In all situations, the beekeeper should sample the mite levels after treatment to ensure the treatment was effective. If it was 4 Resistant Bees & Resistance Management not (because the mites were resistant to the chemicals, or the treatment was not applied properly), a different treatment will have to be used. See page 18 for more information on varroa.

Final Note

It is the responsibility of every beekeeper to be able to recognize symptoms of disease and to know how to sample colonies for mites and other bee pests. It is very important to maintain healthy bee colonies for pollination and honey production. Please subscribe to one of the beekeeping trade journals, and/or join a beekeeping association to keep informed of the latest developments. When in doubt, ask national and state beekeeping extension, research, and regulatory personnel a lot of questions. It is their job to help you find correct answers.

Comb Replacement

Beeswax and Pesticides

The properties of beeswax are such that it absorbs many chemicals such as pesticides. With the increased use of pesticides in the colonies to treat for mites, beekeepers run the risk of contaminating honey and wax. Good beekeepers will avoid having pesticides in the colony when honey supers are placed on the colony and will not extract honey from the brood chamber where pesticides were applied.

Beeswax and Disease

Old combs may also harbor disease spores, such as foulbrood, chalkbrood, and nosema (Figure 1). American foulbrood (AFB) spores remain viable in combs indefinitely. Many beekeepers have had the unfortunate experience of purchasing used equipment from a beekeeper, or hiving a new package of bees in used equipment, and having the bees die from AFB. Experienced beekeepers will be able to spot combs containing AFB scales and should burn contaminated combs and equipment.

Old Combs

Old combs accumulate cast off cocoons and larval feces causing the cells in the combs to become shallower and smaller. Larvae that develop in old combs with smaller cells emerge slightly smaller than they do in new combs with normal size cells. It is not necessarily true that bigger bees produce more honey and smaller bees less honey, so having smaller cells is not as damaging to a bee colony as the preceding two problems. Some people claim that smaller cells prevent varroa mites from reproducing successfully. This claim is not substantiated by research.

Replace Your Old Combs

• Traditionally, beekeepers do not replace combs because it is costly to replace the foundation, and it is energetically costly for the bees to draw out new comb. Some beekeepers have combs that are over 30 years old. It is now time to reconsider this old practice of not replacing combs. It is essential for beekeepers to prevent pesticides from contaminating wax and honey. It is critical for the survival of the beekeeping industry to maintain pure, wholesome products.
• In Europe, many beekeepers insist on replacing up to 1/2 of the combs in each of their colonies every year. However, this practice may not be feasible for many beekeepers.
• We recommend that every beekeeper replace 1-2 combs per brood box in each colony, every year.
• Every comb should be replaced every 5-10 years, depending on your situation and finances. If you follow the Horizontal 2-Queen method described in this manual, replacing combs will not be a problem if you depopulate the honey producing colonies every fall. You can easily replace combs in the empty equipment at your leisure during the winter.
• To help recognize old combs from new combs, consider using a system to track them. The date can be put on the top bars by scratching, burning, paint, thumbtacks, or magic marker.

See the related program: Honey bees in Northern Climates

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