Varroa control— what’s NEW?

The Varroa mite is a formidable foe? As my April PNW survey shows, our annual loses, most specialists agreeing due to varroa mites, continues around 40%. We need better tools (better bees/weaker mites/better controls) to combat the mite. Here are three promising developments that might help.


  1. Weaker Mites:

Greenlight Biosciences of Rochester, NY presented a seminar recently on their development of a very novel type of miticide,  Vadescana dsRNA. Their public comment period (conducted by EPA, the federal agency that will accept registration of miticides for varroa) was open until mid-January.  This technology “RNA interference,” uses double-stranded RNA molecules to “silence” or decrease activity of specific genes by preventing them from making proteins. They have one product for Colorado potato beetle and this product for varroa mite control.

Vadescana downregulates production of a gene involved in Varroa growth and reproduction, targeting a gene sequence that is not found in honey bees (or humans). When it reaches immature Varroa it reduces varroa reproduction success.  It doesn’t affect the adult varroa.

Vadescana is designed to be fed in sugar syrup. It needs to be applied when bees are actively using sugar syrup to feed their brood and not storing it in the colony. Varroa mites reproducing in capped cells must take up the dsRNA molecules by feeding on developing bee pupae whose larva have been fed the treated sugar syrup. The dsRNA molecules degrade quickly, so stored syrup in the hive may not be effective.

  1. Stronger bees:


Another new high tech company Optera, of Greensboro, NC,  has developed UBeeOTM, that utilizes unhealthy brood odors (UBOs) to enhance worker hygienic behavior, In this instance, hygienic behavior is adult bees that detect, uncap, and remove unhealthy brood from the colony. UBO’s are specific Allemone compounds (4 to date that may work singly or in combination. Middle-aged workers uncap and remove (cannibalize) diseased pupae when they smell this distinctive odor.


The UBeeOTM product is designed to be incorporated into queen rearing so the specialist cannibalizing worker bees become a greater part of the genetic makeup of daughter queens reared from the queen mothers. Since these queens are open mated (it appears the drones may also contribute some genetic material to the behavior of uncapping and removal of diseased pupae), it may take some time to get this behavior firmly established in a queen rearing operation. But this stronger bee approach has short-term possibilities for improving our terrible winter losses due to varroa mites.


  1. improved management approach:


Efforts continue to develop a product that uses oxalic acid extended (OAE) to flatten the annual mite growth curve. Research from Maryland shows that mites selectively use drone brood to grow their population in early spring. Managing drones in the colony can help slow (flatten) their growth curve. In spring we need to allow brood rearing to quickly expand but current chemical miticide might interfere with bee growth. Oxalic acid extended – using oxalic acid crystals dissolved in a solvent (glycerin or canola oil are favorites) – has been shown to keep mite reproduction low when supers are in place without affecting the purity of honey being stored, at least in some instances. Lower mite populations can be  more effectively controlled in the fall to help insure better overwintering.


In January American Bee Journal, Randy Oliver covers OAE trails and has a specific recommendation on how Oxalic Acid can assist in keeping varroa mite populations from exploding during the critical honey storage period.  He also indicated that he has obtained verbal assurances that EPA (Environmental Protection Agency) will not continue to oppose home remedies of OAE (at the Federal level). A recent release from EPA however does not confirm that! Vita (a e
European company) registration of varroxsan has been approved by EPA. This is the OAE product tested by Washington State. It Might be available for purchase by end of year. It remains to be seen if another registered product gets onto the market so we can safely and legally use OAE for mite suppression.


I hope your bees are wintering well. Check stores as our generally mild winter (December was 2nd warmest December month on record) means bees are going through stores at a good clip.