Hi All

Just when you thought this one had gone away...

I just got my hands on the 'Progress Report' (how it differs from an 'abstract' i don't know)
for the research into small cell size underway here in NZ.  No results yet mind, but this
sets out the methodology.  The research is apparently running behind schedule, as by
the time the combs were drawn out, it was into winter weather here, and the bees weren't
too interested in raising much brood.  I hear that the drawn combs are waiting in the
freezer for our spring to roll around...

While i would have used a different methodology, these folk have great credentials, so
i'll just sit quiet (you learn a thing or 2 as the years go by).  There is also a part B planned
should cell size prove effective against mites, to ensure there are no downsides to
production, from using smaller bees.

I expect 'normal' sized cells refers to comb built on typical 5.4 NZ foundation.  I am
however puzzled over someone's rounding-off efforts...

 FWIW.

-Pav


CAN THE REDUCTION OF CELL SIZE REDUCE THE IMPACT OF VARROA?

M.A. Taylor and R.M Goodwin
April, 2001

Sustainable Farming Quarterly Progress Report
HortResearch Client Report No: 2001/291

Part A: Effect of cell size on the reproductive success of Varroa Destructor

Introduction

Varroa Destructor is a phoretic external parasite of worker and drone honey bees (Apis
mellifera).  Due to the recent introduction of this unwanted mite into New Zealand,
international research is being reviewed to identify appropriate methods of mite control
for New Zealand (Goodwin and Van Eaton, 2001).  However, New Zealand's climatic
conditions, flora and fauna, and unique beekeeping practices mean that much of the
overseas experience is not directly transferable.  Currently, miticides are used to control
varroa world-wide.  However, due to the development of resistance problems, coupled
with the organic image of New Zealand honeys, these control methods may have a
detrimental effect on both New Zealand's beekeeping practices and trade on the
international market.  International research suggests that cell size may reduce the
reproductive rate of varroa (Message and Goncalves, 1995).  If this is the case hive
damage, resulting from varoosis, may be delayed, and the need for miticide use,
reduced.

The aim for this project is to determine whether a reduction in honey bee comb cell size
will reduce the reproductive success of Varroa destuctor in New Zealand.

Methods

This trial is being conducted in an apiary run by HortResearch at the Ruakura Campus,
East Street, Hamilton.  The site was originally to be managed in Auckland but due to the
recent finding of varroa within 2km of Hortresearch's Hamilton apiary the trial has been
relocated for ease of use.

Five different cell sizes, 4.7, 4.8, 5.0, 5.1 and 5.4mm have been selected for analysis.
The 5.0 and 5.4mm foundation were sourced from New Zealand Beeswax Ltd, South
Canterbury New Zealand, in late January 2001.  The 4.7 foundation was sourced from
South Africa, and the 4.8 and 4.9mm foundations were from the United States of
America.  All three international shipments were sent directly to Schering-Plough in
Upper Hutt for irradiation treatment, and then forwarded to HortResearch, Ruakura
Research Centre, in late February 2001.  The ordered cell size varied slightly from the
actual size (Table 1).  Throughout this study the cell sizes will be referred  to as the
actual cell size (1 decimal place).  Six sheets of each foundation were embedded in
frames and placed in hives with large bee populations, for the cell walls to be drawn out.
Twenty frames of normal foundation were also drawn out at the same time.

The late arrival of foundation has resulted in autumn weather patterns effecting the
colonies so that their populations have started to decline and the bees have focussed on
collecting winter stores rather than the establishment of new storage areas.  This means
a delay in the time that the bees are taking to draw out the foundation and has delayed
milestone completion.  In an attempt to schedule each colony was fed sugar syrup every
two days, to aid the foundation-drawing process, and then the undrawn foundation was
shifted to where where a strong flow of rata nectar has lengthened the foraging season.

Table 1.  Actual versus ordered cell size of foundation

Ordered cell size (mm) 4.8   4.9   4.9   5.0   5.4
Actual cell size (mm)   4.71  4.8  5.08  5.11  5.4
Country of Origin        SA   USA   USA   NZ   NZ

Ten nucleus colonies have been established using sister queens and varroa infested
bees from Auckland.  Until the five different sized foundations are fully drawn out and all
mosiac frames constructed, the bees will be managed with two frames of normal sized
brood cells and a feeder.

As each of the full-depth fames, of the different cell sizes, 4.7, 4.8, 5.0, 5.1 and 5.4mm
has been drawn out they have been removed from the colonies, frozen and then cool
stored.


Expected Progress

Once all framesare drawn they will be cut into 5cm x 8cm sections and randomly
inserted in the centre of the newly drawn, normal cell-size frames.  These five sections of
cell sizes, plus a control (normal cell size) section, will replace the normal cells in a 2x3
grid.  Two of these mosiac frames, and a frame of bare foundation, will replace the brood
frames in each of the 10 varroa infested nuc colonies.  This limits the queen's egg laying
space to the constructed frames.  Once she starts to lay, 100 eggs from each of the six
cell size sections will be marked using map pins.

When the pupae in the six sections of cells are 19-20 days old the repructive sucess of
varroa will be analysed.  The brood comb will be removed and frozen to kill the mites.
The sections will then be thawed, and the cells will be uncapped individually to identify
the presence and number of adult females, deutomnymphs, and other offsring of Varroa,
as outlined in Message and Goncalves (1995).

This reproductive data  will be collected and statistically analysed during the next quarter
and used to identify whether any of the cell sizes reduce the reproductive rate of Varroa,
and if so, which has the greatest impact.  This cell size that produces the greatest
impact (Part B) will then be assessed further to determine whether smaller sized cells
result in smaller bees and lower production.

References

Goodwin, M and C. Van Eaton.  2001 Control of varroa - A guide for New Zealand
Beekeepers.  External report by HortResearch to Ministry of Agriculture and Forestry.

Message, D and L.S. Goncalves. 1995.  Effect of the size of worker brood cells of
Africanised honey bees on infestation and reproduction of the ectoparasitic mite Varroa
jacobsoni Oud. Apidologie 26:381-386


www.hortresearch.co.nz

Head Office
The Horticulture & Food Research Institute of NZ Ltd
Batchelor Research Centre
Private Bag 11030
Palmerston North
Telephone: +64-6-356 8080
Facsimile: +64-6-354 0075

Ruakura Research Centre
The Horticulture & Research Institute of NZ Ltd
Private Bag 3123
Hamilton
Telephone: +64-7-858 4728
Facsimile: +64-7-858 4704




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  (\      Pav                                          [log in to unmask]
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