I would like to take this opportunity to alert/caution you regarding high mite populations in honey bee colonies this year due to an unusually long bee season similar to past year. We had another long bee season this year similar to past year (2015) due to prevailing warm weather of about seven 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. Our PNW Tech Transfer Team has also reported higher mite intensities in samples of participating beekeepers for the month of July when compared to past two years. Some beekeepers had to treat their colonies three times this year in order to get adequate mite control. If you treated your colonies for Varroa on time during July or first half of August, then probably you may have your mite populations somewhat under control, but still I urge you to monitor mites one more time before overwintering to make sure that the treatments that you used were effective and your current mite populations are not at damaging levels. If your mite levels are still high, then please consider using a suitable mite control product immediately before the weather gets cold, and use an oxalic acid treatment if feasible 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:
a) Bee population may decline significantly or the colonies might totally collapse.
b) 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.
c) 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 a few other locations in Oregon when the weather is still okay (temperatures around 55 to 60°F).
Small Hive Beetle (SHB)
I would also like to alert you regarding occurrence of small hive beetle in Oregon. This year we have received more reports of small hive beetle than in the past six years and plan to explore this issue in more detail. Todd Balsiger has written a nice article regarding this beetle in a past issue of The Bee Line [March 2013].
Current climatic and soil conditions may not be ideal for SHB overwintering/pupation/establishment in most of Oregon, but future changes in climate, such as frequent mild winters, could aid in establishment of SHB populations in Oregon. Early detection, reporting, and control of SHB may help mitigate its establishment in Oregon. Hence, we urge you to keep an eye on this beetle, report its occurrence, and take appropriate control measures when detected.
Further, we suggest you to be cautious when purchasing package bees, nucleus colonies, or queens from locations in the US where SHB is well established. Also, please monitor your colonies for small hive beetles during summer and fall if you regularly transport your bees across state lines for pollination, especially to California (almond pollination). Please refer to our recent extension publication on SHB for more information. Following is the link to access this publication: https://catalog.extension.oregonstate.edu/em9143. You can also access it here: The Small Hive Beetle: A Potential Pest in Honey Bee Colonies in Oregon.
Sap Beetle (Brachypeplus basalis)
Finally, I would like to make you aware of another beetle that has been recently documented in empty honey bee hives in Oregon that were stored outside. These sap beetles have been reported to feed on stored pollen in honey bee colonies. Very little is known about the biology of this beetle. This beetle has the potential to become a nuisance/problem for beekeepers, especially with regards to stored bee equipment (frames). Please watch for this beetle infestation and report its incidence. You can find a picture of this beetle in the above extension publication.
Thank you and good luck.