Lloyd writes:
> 
Peter Borst tantalized us by reporting this paper.  Dare I ask...what timing seems successful, and what timing does not seem successful?

Me:
I am afraid I opened up a can of worms here. I fully support this sort of project but reading thru the thesis revealed several problems. 

Here is what they say:

Our project aimed to address these hypotheses:

1. Spring or early summer splitting of a honey bee colony (disrupting
the brood cycle) will reduce varroa mite numbers.

2. Spring or early summer splitting of a honey bee colony will not
reduce seasonal honey productivity or affect pollen collection.

3. The splitting of colonies will have a significant effect on viral
presence.

4. Combining drone brood removal and brood cycle interruptions
(splitting) will complement each other and overall have a greater
impact on mite reduction in a colony than either method used
independently.

* * *

2013 field season

The 2013 season began with 21 colonies. In late June, after splitting there
were 32 colonies total. One control colony was diagnosed with European
foulbrood early in the season and removed from the study; seven colonies died
throughout the sampling season and were removed from data analyses. 

Four colonies survived through winter 2013/2014 (1 control, 1 daughter, 2 parent)
and the remaining 20 colonies died during mid-late winter. The causes of death
are unknown, although environmental stresses including a cooler and longer
winter are thought to have played a significant role.

In this study we found a temporary reduction in varroa mite populations
after the colonies were split. The colonies were split in early summer, at the
beginning of the swarming season in the mid-Atlantic, when colonies began to
show signs of swarming. Immediately after the colonies were split (parents and
daughters) there was a noticeable decrease in varroa mites; however, toward the
end of the season (early fall) the varroa mite averages for all colonies were about equal. 

Bee population and brood area also decreased in split colonies temporally
after they were split but by the end of the season colony populations were all
similar and brood area eventually ceased. Control colonies were not split and
continued to grow without interruption, which led to a significant increase in
bees, almost double that of splits in July, and mites during mid-summer.

The results did not support our hypothesis that spring splitting will not
affect seasonal honey productivity. Over the course of the season there were
noticeable decreases in honey productivity among split colonies, while control
colonies had consistently higher averages of pollen, nectar and honey.

Splitting colonies in late summer or fall will allow colonies to
build up bee populations to take advantage of the spring nectar flow (the most
predominant nectar flow in the mid-Atlantic) and thereby increase honey production.

Splitting of a colony does affect varroa mite populations as predicted by
our hypothesis; however, timing of the split is critical. Early spring splitting
allows sufficient time for the mites to rebound and reduces the productivity in
the parent and daughter colonies during important nectar flows. Late-summer splits
will also allow full colonies to reap the benefits of early summer nectar flows, and
increase the number of colonies going into winter leading to the maintenance of
sustainable colony numbers within an apiary.

Our results showed that the timing of a split
during the season, early summer through fall, is critical to long term reductions in
varroa mites and increased colony survival. Based upon the strong correlations
we found between bee populations, brood area and varroa mite numbers in mid-late
summer, we predict that late summer splits will produce the best results.

* * *

My comments:

First, they split the colonies early but not late; their results are based on the early splits. They have no data on late splits so what they say about them is purely conjecture. They claim that late season splitting will ensure more colonies alive in spring, but have no data to support this. 

I would say that survival of late splits is worse than large colonies, provided mites are under control. They fail to acknowledge the possibility that the fact that mite levels were the same in split and unsplit colonies can be attributed to reinfestation by mites in late summer. Any study that fails to take this into account is missing a key factor. 

In sum, they state that splitting temporarily reduces mite levels, that if it’s done in spring you lose a lot of the summer honey crop, and mite levels by late summer are the same as if they hadn’t been split. Therefore, they recommend splitting later in the season but they didn’t actually do it.

PLB

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