This schedule was created by Bill Hesbach to help teach other backyard beekeepers techniques for seasonal varroa management. Included are treatment options, timing, and safety measures to keep your colonies healthy and address the issue of varroa mites.
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Seasonal Varroa Management - Starting with a package in late March or early April
When starting a three-pound package with or without foundation in a Langstroth style box, Top Bar, or Warre’ hive, the bees can be treated before brood occurs with oxalic acid (OA) vaporization or dibble. HopGuard3 can also be used, assuming the minimum daytime temperature limits on the label are occurring.
Initial Treatment Options:
Option 1- OA Pre-Installation
A liquid OA spray treatment can be done while the bees remain in the package. Be sure to read the label thoroughly since this option requires two steps. First is a generous plain 1:1 sugar water spray so the bees fill their honey stomach. Then, the treatment mixture is sprayed after the bees have consumed the plain sugar spray. The first spray minimizes the consumption of the OA spray that follows.
Option 2 - OA After Installation
A vaporization treatment after the package installation is effective once the bees release the queen and she is laying, but before any brood is capped—about day five after package installation. It’s important to note that this treatment is done after the queen is laying but before any brood is capped. The presence of uncapped brood will keep the bees from absconding, which can occur if we apply the treatment before the colony has open brood to care for.
Option 3 - HopGuard After Installation
To get the most out of HopGuard3, it should be done under the same brood requirements outlined above for the OA after installation. The difference is the minimum temperature requirements. OA has no low daytime temperature limit, but HopGuard has a daytime high-temperature minimum of 50 degrees, so check the HopGuard Instructions.
VarroxSan, a slow-release oxalic acid strip, was recently approved for use in the US by the EPA but will require CT state approval before it is legal to use in our state.
Additional Necessary Treatments:
June - The colony should be close to full strength about ten weeks after the package installation, likely mid-June. The initial treatment should have produced adequate temporary control, but some varroa are still reproducing. A 14-day treatment of Formic Pro or a 7-day treatment using Mite Away Quick Strips is recommended now. (See Note 1)
August/September - Colonies will need an 80% kill treatment at the end of August or the first week in September. You now have two options - a thymol-based product like Apiguard or one of the formic acid products mentioned above. Follow the label instructions carefully since Apiguard cannot be used if your colonies have honey supers you intend to extract. Also, daytime highs may prohibit using both products, so it’s important to watch the weather for an appropriate daytime high treatment window. The first three days after the start of treatment are the most critical.
November Broodless Treatment - Treatment is required when the colony is broodless, and the best option is an OA dibble or vaporization, possibly in late November. OA is very effective without brood when all the mites in the colony are out in the open (dispersal stage).
December - Finally, as a precaution, vaporization of OA at the end of December will help kill most of the remaining varroa. A tightly packed cluster may not benefit as much as a loose one, so wait for a 50-degree day before treatment for better acid dispersal.
General Note:
The guiding principle when using oxalic acid is that the colony must be broodless. There can be other times during the season when a colony no longer has brood, like when a colony swarms, during walkaway splits, or intentionally during beekeeper-initiated brood breaks. Anytime there is no brood, oxalic acid is a good choice.
Safety Note:
Polystyrene hives cannot tolerate the heat generated with vaporization equipment and may get damaged or ignite, so oxalic acid dribble, VarroxSan, when approved, or HopGuard3 are your only safe alternatives.
Seasonal Varroa Management - Nucleus Colonies
Starting with a nucleus colony in May or early June
Initial Treatment:
Nucleus colonies come with brood and varroa. So, it’s a good practice to give them an initial treatment. Since they are small, using formic acid may be harmful since it is not recommended until a colony has at least six brood frames. HopGuard3 is a good option since in May or June, the daytime high temps of 50 degrees are in range for a HopGuard treatment. OA is not a good option since the colony has brood.
Additional Necessary Treatments:
July - The colony should be gaining strength and, about six weeks after installation, should be sized right for a formic acid treatment. The initial treatment should have produced adequate temporary control, but varroa are still reproducing. A 14-day treatment of Formic Pro or a 7-day treatment using Mite Away Quick Strips is recommended now. (See Note 1)
September - Developing nucs will need an 80% kill treatment at the end of August or the first week in September. You now have two options - a thymol-based product like Apiguard or one of the formic acid products mentioned above. Follow the label instructions carefully. If you choose Apiguard, be aware that it cannot be used if your colonies still have honey supers you intend to extract.
November Broodless Treatment - Treatment is ideal when the colony is broodless, and the best option is an OA dibble or vaporization, possibly in late November. OA is very effective without brood. A colony must be inspected thoroughly to determine if it is broodless. Wait until you know for certain before treatment.
December - Finally, as a precaution, vaporization of OA near the end of December will help kill most of the remaining varroa. A tight cluster may not benefit as much as a looser one, so wait for a 50-degree day before treatment for better acid dispersal.
Treatment Rotations - The above treatments deploy a rotation strategy using three or four separate treatment products. Rotation delays resistance to a single product and should be part of your treatment practice. Follow the label instructions for all treatments.
Seasonal Varroa Management - Overwintered Colonies
Treatment Schedule:
Healthy overwintered colonies treated the previous year using the above schedule will have a significant amount of brood but a lower varroa population. The goal is to keep the population low all year.
Early Assessment - We don’t have an accurate measurement tool to assess total varroa populations in early spring. However, using a sticky board for a three-day drop in early March will help identify a colony with unusually high varroa. OA vaporization or a dribble combined with a sticky board drop will help assess varroa populations, but they are not considered treatments with brood present. The technique provides an accelerated drop of dispersal mites, those out of cells riding or feeding on bees, and is only used to identify a colony that will soon be in trouble. A colony in early spring with high varroa drops requires special treatment like immediate brood reduction or isolation in another yard until treatments can be applied. Another consideration is elimination. The best practice is to take appropriate action quickly, or the varroa will infest other colonies and spread viruses. Varroxsan, if approved, may also help once the colony is isolated since it’s a long-term treatment.
For all other overwintered colonies, the treatment schedule is like what was described for nucs, with timing differences since overwintered colonies are generally close to full strength, have more brood, and likely more reproducing varroa.
April - A 14-day treatment of Formic Pro or a 7-day treatment using Mite Away Quick Strips is recommended now. Follow the label for treatment placements and timing.
June - A second treatment with formic acid in early June will keep mite counts low until late August or early September. Apiguard is also an option, but only if the colony does not have harvestable honey supers that you intend to extract.
August - Colonies will need an 80% kill treatment at the end of August or the first week in September. You now have two options - a thymol-based product like Apiguard or one of the formic acid products mentioned above. Follow the label instructions carefully. Again, if you choose Apiguard, be aware that it cannot be used if your colonies still have honey supers you intend to extract. Also, daytime highs may prohibit using both products, so it’s important to watch the weather for an appropriate daytime high treatment window. The first three days after the start of treatment are the most critical.
November Broodless Treatment - Treatment is ideal when the colony is broodless, and the best option is an OA dibble or vaporization, possibly in late November. OA is very effective without brood. A colony must be inspected thoroughly to determine if it is broodless. Wait until you know for certain before treatment.
December - Finally, vaporization of OA near the end of December will help kill most of the remaining varroa. A tight cluster may not benefit as much as a looser one, so wait for a 50-degree day before treatment for better acid dispersal.
End Notes:
A week or ten days after all treatments, the colony must be inspected to ensure the queen is still laying.
Under no circumstances should you use harsh chemicals like Apistan (tau-fluvalinate) or Checkmite (coumaphos).
Alcohol washes should be used after treatments to determine efficacy but are not being used to establish treatment thresholds.
Following the above treatment regimen will minimize varroa damage and allow your bees to live a healthy and productive life.
References & Links:
About the Author:
Bill Hesbach
Bill Hesbach is a Connecticut beekeeper with a background in engineering. He's an Eastern Apicultural Society Certified Master Beekeeper, a graduate of the University of Montana's Master Beekeeping Program, and the President of the Connecticut Beekeepers Association. Bill operates Wing Dance Apiary in Cheshire, CT., producing artisanal raw honey and other natural hive products.