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  • From: Greg Vydra <gregvydra AT gmail.com>
  • To: Orange County Bees <ocba AT lists.ibiblio.org>, "NaturalBeesinNC AT yahoogroups.com" <NaturalBeesinNC AT yahoogroups.com>
  • Subject: Re: [ocba] Interesting article
  • Date: Thu, 12 Sep 2013 20:06:40 -0400

The author(s) admit that the study design does not support inferring causality.  Regarding the higher mortality rate in the subgroup that fed with frames of honey, the author(s) state:
"This result warrants more investigation. It could be that beekeepers who lost more colonies simply had more frames of honey to feed."

So, among the sample of 2,883 colonies that were fed carbohydrate and 726 who were not, it is true that the subgroup that were fed frames of honey had the highest mortality.

BUT,
  1. There may very well be factors other than the type of carbohydrate that caused mortality.  The author(s) do not discuss or control for: geographic region and weather conditions where the colonies were located, Varroa levels, pesticide use in surrounding fields, etc.
  2. The author(s) concede that if a beekeeper were experiencing high mortality rates due to any cause, that might leave the beekeeper with plenty of frames of honey to feed the remaining colonies.  Thus, it's a chicken-and-egg dynamic.  Feeding frames of honey may have been the consequence of the colonies dying for other reasons.
  3. The statistical results indicate that, with the exception of the candy board method, the other 5 feeding methods have overlapping ranges of significance, meaning that statistically, we can't infer a difference.

For any other stat geeks out there, I have another issue with the study design.  The author(s) compare colonies with each method of feeding to ALL the other colonies, including those fed by a different method, AND the colonies not fed at all.  The author(s) do not even report the mortality rate of the "not fed" group of 726, apart from the other colonies.  In my opinion, it would have been better to compare each of the 6 feeding methods to the control group of no feeding, and then compare each of the methods with each other.  But this issue is minor when compared to the huge issue of not controlling for other factors that might have influenced mortality.

Greg


On Thu, Sep 12, 2013 at 7:19 PM, Valerie Bateman <vbateman AT aol.com> wrote:
Why would one think that feeding frames of honey would result in higher bee mortality?

On Sep 12, 2013, at 5:12 PM, Marty Hanks <marty AT justbeenc.com> wrote:

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