The Bee-Files

page 4

Integrated Pest Management Varroa destructor in the Northeastern United States
Using Drone Brood Removal and Formic Acid

Modified Traditional Program [without drone brood removal and without economic thresholds]: If you do not base your treatment decisions on an estimate of pest density, you will need to treat your colonies twice each year: once in the late winter or early spring and once near or immediately after the end of the goldenrod flow. However, even that may not be sufficient. Therefore, inspection for evidence of parasitic mite syndrome prior to the start of the fall flow is highly recommended, although it is not as effective as estimating pest density.


  • Late winter or early spring:
    • Treat colonies with Mite-Away II™, Apistan® or CheckMite+®.
  • Late summer (about 2 weeks before start of goldenrod flow):
    • Inspect colonies for symptoms of parasitic mite syndrome. Remove all marketable honey from colonies with symptoms and initiate treatment with Apistan® or CheckMite+®. Mite-Away II™ (formic acid) will not work well at this time due to the presence of large quantities of brood. Procrastination at this stage will result in the loss of your colony.
    • Provide treated colonies with empty supers for fall honey production. Honey produced while pesticides are present in the hive may not be used for human consumption. However, it may be used as feed for other colonies. This allows a beekeeper to remove both the surplus honey and the winter stores from healthy colonies that were not treated during the fall flow and to replace their winter stores with surplus honey from colonies that were treated. Using this method, you save the bees and harvest the same amount of honey.
  • Late summer - early fall (when the goldenrod flow is about 80% complete):
    • Remove surplus honey.
    • Reduce colony to two, full depth hive bodies.
    • Treat with an approved pesticide. Note! Mite-Away II® should be applied after the majority of brood rearing has ended but while daytime temperatures range between 50 and 79 °F. In Ithaca, NY we initiate treatment with formic acid during the last week of September or first week of October, but not earlier and not later than that.

Basic IPM Program [without drone brood removal but with economic thresholds]:
The best strategy for using a pesticide is to use it only when the pest density reaches the economic threshold, that is, the level at which you must control the pest or expect to experience damage to your colonies.

  • Late winter or early spring:
    • Treat colonies with Mite-Away II®, Apistan® or CheckMite+®.
  • Late summer (about 2 weeks before start of goldenrod flow):
    • Estimate pest density in each colony with the ether roll.
    • If an ether roll count is = 3, or if you observe any symptoms of parasitic mite syndrome, remove all marketable honey from that colony and initiate treatment with Apistan® or CheckMite+®. Mite-Away II® (formic acid) will not work well at this time due to the presence of large quantities of brood. Procrastination at this stage will result in the loss of your colony.
    • Provide treated colonies with empty supers for fall honey production. Honey produced while pesticides are present in the hive may not be used for human consumption. However, it may be used as feed for other colonies. This allows a beekeeper to remove both the surplus honey and the winter stores from healthy colonies that were not treated during the flow and to replace their winter stores with surplus honey from colonies that were treated. Using this method, you save the bees and harvest the same amount of honey.
  • Late summer - early fall (when the goldenrod flow is about 80% complete):
    • Remove surplus honey.
    • Reduce colony to two, full depth hive bodies.
    • Estimate pest density in each colony with the ether roll.
    • If an ether roll count is = 2, treat that colony with an approved pesticide. Note! Mite-Away II® should be applied after the majority of brood rearing has ended but while daytime temperatures range between 50 and 79 °F. In Ithaca, NY we initiate treatment with formic acid during the last week of September or first week of October, but not earlier and not later than that.

Intensive IPM Program [with drone brood removal, formic acid and economic thresholds]: The best strategy is to suppress mite populations during the summer with a non-chemical method, and then to treat with a natural product in the fall if the pest density exceeds the economic threshold. Drone brood removal can eliminate the need for a spring treatment and prevent fall collapse. Occasionally, it will result in the fall ether roll count being below the economic threshold level, eliminating the need for that treatment as well. Incorporating both drone brood removal and mite resistant stock into your management program may increase the number of colonies that do not require a fall treatment. At this time, it is recommended that you use a spring treatment if you did not use a treatment the preceding fall.

  • Late winter or early spring:
    • Make sure two empty drone combs are present in the upper brood chamber.
    • No chemical treatment is necessary at this time if the colony was effectively treated with a miticide the previous fall.
    • Apple blossom until just before the end of the goldenrod flow:
    • Use drone brood removal every 26-28 days with the last exchange taking place when surplus honey is removed just before the end of the goldenrod flow. If a drone comb becomes filled with honey, replace it with an empty comb and extract the honey before reusing it.
  • Late summer (about 2 weeks before start of goldenrod flow):
    • Requeen with mite resistant stock and check for acceptance in 7 days.
    • Late summer - early fall (when the goldenrod flow is about 80% complete):
    • Remove surplus honey from colonies.
    • Reduce colonies to two full depth hive bodies.
    • Determine pest density in each colony with the ether roll.
    • If an ether roll count is = 2, treat that colony with Mite-Away II® [Fig. 12].
    • Note! Mite-Away II® should be applied after the majority of brood rearing has ended but while daytime temperatures range between 50 and 79 °F. In Ithaca, NY we initiate treatment with formic acid during the last week of September or first week of October, but not earlier and not later than that.
    • If you do not need to treat a colony in the fall, you should treat it the following spring.

Notes on Treatment Regime

  • Be sure to determine if the mites in your colonies are resistant to Apistan® or CheckMite+® before applying either of those products. Always use the appropriate product. There is no known resistance to formic acid (Mite-Away II) at this time.
  • Sucrocide™ and Api-Life VAR® are not included in the treatment regimes at this time because there is insufficient data available on which to base such recommendations. Preliminary tests have found Sucrocide™ to be ineffective in the northeast. It is also very labor intensive. Previous work with Api-Life VAR® was based on a single application and yielded highly variable results. Current label instructions call for three applications at 7-10 day intervals. This may prove more effective, but confirming studies have not been published. Treatment regimes will be updated as information becomes available.
Fig. 12: A formic acid pad similar to the
Mite-Away II™ pad.
 
  • The drone comb exchange method must be used as indicated above in the ‘Implementation’ section. NEVER leave drone combs in colonies unless you are going to exchange them at least every 28 days.
  • Ether roll counts given above are 300-bee counts.
  • Other treatment regimes for V. destructor are constantly being evaluated by a number of researchers, and the number of available options is increasing rapidly. Check with your local extension apiculturist for the most recent updates before implementing any IPM program.
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© Copyright 2008, All rights reserved, Nicholas W. Calderone, Associate Professor,
Department of Entomology, Cornell University, Ithaca, NY 14853 

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Updated July 2006
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