Soft Chemical Treatment Options for Varroa Control & Shrew Research Opportunities

Thursday 22 October 2020

Last week's blog talked about synthetic acaricides as part of an IPM approach to managing Varroa mites.  In order to prevent resistance and maintain efficacy, additional methods must be employed and many beekeepers are looking to non-synthetic compounds as alternatives.  Some of these options are discussed below.

More about those tiny, hive invading shrews this week!  Read on to find out about CSI "Operation Shrew"!

Soft Chemical Treatment Options for Varroa Control

In our regions, oxalic acid is often used as an autumn treatment for Varroa mites.  This is done as a stand alone or a late season supplement to some other earlier treatment.  The vapour, or sublimation, application seems to work well in our region as it is less dependent on ambient temperature and humidity.  Oxalic acid vapour is also most effective on a colony with no brood and another reason for using it later in the beekeeping year.  A team of researchers from the University of Guelph has just published a report on a range of soft chemicals to treat Varroa mites which includes some new ideas for the use of oxalic acid.  One of the limitations of vaporized varroacides is the delivery mechanism and possible improvements need to be explored, as has been done by this research team.  This week we will look at this research and some other options available to beekeepers.

Substances like organic acids and essential oils to treat Varroa mites are currently of importance, and poised to become more so, to beekeepers rotating acaricides as part of a IPM program.  The environmental persistence of these chemicals is less, therefore they are viewed as more natural but this does not mean that they are necessarily less potent acaricides.  The essential oil, thymol, derived from the herb thyme is an excellent example.  Work done by ATTTA in 2017 reported that Thymovar® (active ingredient: thymol) was an effective treatment for Varroa mites in our region.  Recent work by a research team led by Dr. Ernesto Guzman-Novoa out of the University of Guelph, reported that other methods of application for thymol were also effective.  This group has reported that thymol, as either a wet or dry (dust) treatment, achieved up to 96.6% efficacy.  The most effective application method was thymol dust.  These workers also reported that oxalic acid and oregano essential oil were effective but less than thymol as applied in this trial (the efficacy range for all three treatments across two types of application was 21 – 96%).  It must be noted that this work did not include oxalic acid vapour as one of the experimental delivery methods.  This is interesting and necessary work as often times new, sometimes dubious treatments, may be introduced to market with unproven efficacy.  It is necessary to prove new treatments and applications!

The success of essential oil and organic acid treatments is highly dependent on the type of application and the ambient conditions.  This would indicate that these methods of Varroa mite control need more knowledge and expertise than do synthetic acaricides.  These soft chemical treatments are favored by some beekeepers due to them leaving no residues and therefore may have a reduced environmental impact.  This brief overview by no means provides the full picture when it comes to soft chemical Varroa controls, so you are encouraged to find out more...

See ATTTA's report which includes work on the efficacy of Thymol and other miticides: Report - Initial Findings on Miticide Efficacy in the Maritimes

Additional details and the abstract of the research work discussed this week can be found here: Evaluation of Dry and Wet Formulations of Oxalic Acid, Thymol, and Oregano Oil for Varroa Mite Control in Honey Bee Colonies

Further information on Varroa mite management is available through ATTTA's website:

Opportunity for Atlantic Canadian Beekeepers to take part in shrew research!

Do you have shrews in your apiaries?  A research team, led by Professor Don Stewart, based at Acadia University, Wolfville, NS is collecting data from beekeepers who place specially designed devices in their bee yards.  These devices will allow for the identification, through DNA analysis, of shrew species using the collected scat.

A system to track shrews using feeding tubes has been used in Great Britain for many years. The feeding tubes consist of short lengths of plastic tube containing insect larvae as shrew food. These tubes do not catch or hold the shrews. The shrews enter to feed, and because of their high metabolic activity, immediately deposit scats. This system was developed by Dr. Sara Churchfield in the UK to identify rare water shrews in that country. The UK team could use size, shape and contents to identify the type of shrew because they only have three species each with quite distinct feces. In contrast, this project uses “DNA Barcoding” to identify which of our seven species of shrew has deposited the feces in the trap (see image below). Feeding tubes can be placed in various habitats, or around bee hives, and feces collected and sent to Acadia for analysis.  If the quality of the sample is sufficient, the beekeepers will then be informed which species of shrew was identified in their bee yards!

Contact ATTTA for details of how to receive a shrew feeding tube to place in, or around, your apiaries and participate in this research project.  Use the email contact below!

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