We would like to take this opportunity to alert / caution you regarding high mite populations in honey bee colonies this year due to another unusually long bee season similar to past years (2015 and 2016). We had another long bee season this year due to prevailing warm weather of about 7 months. Longer brood cycle (abundance of larvae) usually results in higher mite populations, as the mites get a greater opportunity to breed and increase their populations compared to bees. It has been reported that mite populations could increase exponentially (up to about 50 fold increase) in years when the brood is present in colonies almost round the year (Martin 1998).
We are observing significantly higher mite intensities this year in both commercial and backyard beekeeping operations. Some beekeepers have treated their colonies several times this year and are still struggling to achieve desired/optimal mite control. Please monitor your mite levels and consider using a suitable mite control product immediately before the weather gets too cold. The next 10 days (Oct 11 to 20) look OK (if not ideal) to use one of the following products: formic acid (FORMIC PRO) or Thymol (Apiguard) to get some last minute mite clean up. Later on please also consider oxalic acid treatment if needed when there is no brood (possibly during November). Oxalic acid is approved by EPA and is available from the bee supplier Brushy Mountain Bee Farm (http://www.brushymountainbeefarm.com/?gclid=CLzrqIrB98cCFUiEfgods-gJ6w).
Following are some consequences of inadequate or no Varroa mite control this fall:
- Bee population may decline significantly or the colonies might totally collapse during December/January.
- Colonies that survive the winter will start upcoming year / season with higher mite loads and hence could reach damaging levels soon by late spring or summer.
- High mite infested colonies may contribute to higher mite drifting via robbing bees to other beekeeper colonies and your existing healthy colonies, as your mite infested dead colonies may be robbed by other strong colonies and aid in greater mite dispersal.
Also, please continue feeding protein to your colonies if pollen stores are not adequate in the colonies. Protein feeding not only helps with brood rearing, but also helps boost the immune system of bees. We have observed colonies to consume protein until October 25 in the Willamette valley and few other locations in Oregon when the weather is still OK (temperatures around 55 to 60° F).
Thank you and good luck.
Ramesh Sagili, Oregon State University