Based on what I have been seeing in the past few weeks of peeking in and checking for signs of life and food stores both in my own apiaries and in many others, I am seeing the signs of nosema ceranae in about 25% of the dead outs. This supports the recent findings from Cornell indicating a rise in this spore born intestinal disease by about 10% statewide.
After doing some Web trolling, hitting the books, and consulting with our state apiarist Paul Cappy, I have the following to share. Recognizing nosema ceranae is difficult with out a microscope. It is generally omnipresent in colonies, and affects the lower intestinal tract of the honeybee.
What causes it to become deadly to a colony?
The wintering conditions during clustering are moist and warm which is a prime environmental cause. If bees were fed lots of sugar syrup and are now getting into those stores, the obvious lack of nutrients also contribute. Further, pollen stored from last fall in the dearth, also deficient in nutrients was packed away probably with spores in it and now released or activated at a time when the natural defenses and supporting fresh nectar and pollen are not available.
What to look for
When doing your dead out forensics you should be looking for small clusters of bees in the far corners of the hive, especially at the top, away from the current brood frames. While this is an indication of ceranae infection, it may or may not be the primary reason for collapse. All of our colony pathogens seem to have a common symbiosis when once the immune system is weakened, it is a free for all of sorts. If your mite load was high in Aug and Sept, your bees were compromised, and not able to live as long as they should have. This got the brood rearing started earlier than usual and that required using up more stores than normal contributing to light stores in March or starvation.
Once the spinning away from health begins it is never one thing that brings a collapse, but rather a combination. Imperfect nutrition in fall, stored and relied upon in late winter, a compromised digestive track from nosema, shorter than normal life span from mites, throw in a virus or bacterial vector and Voila, dead hive syndrome.
Treating for mites and nosema are essential, unless of course you are ‘going native’ and well that’s for a different posting, but for now let’s address nosema treatments.
I cannot stress enough the value of your spring honey as a nutritive antidote later in the winter. Locust honey in particular is rated as one of the top 5 nutritive nectars. Coincidentally one of our tastiest spring varietals. I would suggest you leave as much of this stored away in the outer regions of your brood boxes and move to the top boxes in sept, to make available when they need it late winter.
Since this may not be practical for some, my suggestion is treat with NOSEVIT PLUS and not use Fumagilin-B, or any antibiotic. Research concluded that while a short term reduction on the nosema counts was noted, long term, nosema returned with an exponentially larger number, I think over 1,000%. The treatment mentioned applied as per directions works quite well and causes no harm and Treating prophylactically as a bit of insurance. Why continue treating through out the year? Chances are you will be doing some feeding each year so as an additive to sugar syrup, it will help on mold in containers as well as make sure the sugar ingested doesn’t create a relapse.
If you are a bit more serious you should requeen as soon as possible as it is spread invitro as well.
Equipment
Equipment should get a scrub down of bleach solution and dried out prior to reuse. Since replacing infected equipment is not always possible, again I suggest Nosevit when feeding again. To really get spore counts down stop smashing bees, as one smashed worker can dump a huge fresh load of spores out to the house bees and fed back to larvae. You will need to be vigilant for several years, generally 3, to really have an impact to get to very low spore counts.
This is best done in spring before build up occurs, although this mild winter is redefining our usual dates by at least 2 weeks earlier. If some of your colonies are dwindling while others are booming it very well could be nosema, or a combination of pathogens.
Lastly a small 2 inch square should be removed from a brood frame and sent the the usda lab in Beltsville, MD. to get an idea of the spore count in your hives.
In conclusion, this is an easy pathogen to reel in and should not be a reason of why your losing colonies.
-Tom