Varroa and the Honey Bee Understanding the Dynamics
- How does an infestation of Varroa affect honeybees throughout a
season and what can be done about it?
You will have to refer to this chart to understand the following
I originally wrote this for the biobees web site, This article was
reviewed and edited by Phil Chandler and Norm Weston
The following is based on various research and years of observing
mites decimate untreated colonies. The Biobees team does not claim to
have all the answers nor do we wish to give the impression that our
recommended methods are absolute doctrine. We only wish to share
experience with the bee keeping community in order to show that there
are ways to combat this parasite without the use of poisons within
Understanding the Basics
Making simple assumptions for this scenario, assume the colony went
into the winter healthy OR we have a new package, first season
colony. At this point, the colony is assumed to be healthy! This
colony is not treated with anything.
The colony population is a cycle of rises and declines in both Bee
and mite. Starting in spring; the time of year when the colony is
building up its work force, the queen begins to lay eggs in the core
brood nest as cells are emptied of honey and become available. At
this time worker bees are preparing these cells for the queen to lay
in which includes cleansing debris and any lingering pests! The mite
population for a healthy colony is in check at this point. Looking at
the graph you can see the bees maintain a relatively higher
population than the mites. This is the host parasite ratio the colony
CAN exist with, provided there are no additional stressors placed on
it. A stressor can be anything from pesticide problems to bee keepers
that need to play with their bees every chance they get!
In this scenario after mid April the converging lines show what can
happen if an additional stressor is placed on the colony. This can
happen anywhere along the time line! Proceeding along the time line
the two populations are beginning to close in on each other, this is
where the danger begins.
A probable cause is the bees change in focus to preparing for the
winter. Part of their preparation is a reduction in colony population
to optimize their use of winter stores. The mite population is still
increasing No longer are they picky about drone cells now, it's a
matter of survival, so any cell will do for mite reproduction. Where
the two lines cross marks the economic threshold (the point at which
the host can no longer support itself and the parasite.) After this
point has been reached, you will see bees emerge from the colony with
deformed wings (DWV) deformed wing virus and a host of other nasty
viruses known as PMS (parasitic mite syndrome) as the mites
parasitize what little brood is left. As long as there is brood this
will continue and eventually result in the failure of the colony.
Identifying the Change of Focus
A decrease in bee population in a colony occurs naturally on two
occasions, the first being reproductive swarming and the latter being
preparation for winter. This change in focus is marked by a decrease
in laying by the queen and the back filling of the brood nest with
nectar/honey. When we treat a hive we knock down the mite population
and keep the two lines from crossing thus maintaining the host
parasite ratio the colony can sustain!
Our aim is to create conditions in which our bees can attain a state
of sustainable, dynamic balance with the mites and other invaders
that will always be present in and around a colony. One way in which
we can help them is to reduce the mite load at critical points using
a treatment that has significant impact on the mites and minimal
impact on the bees.
There are several treatment options that do not require the use of
synthetic miticides, such as organic acids, sugar dusting and 'shook
swarm'. While organic acids (such as formic, lactic, acetic and
oxalic) are widely regarded as effective and 'natural' compared with
synthetics (such as pyrethroids and organo-phosphates) they
nevertheless pose a health risk for the beekeeper and are not
entirely benign towards the bees. Sugar dusting is, we believe,
entirely harmless for the bees and has a significant knock-down
effect on mites, caused by interference with their ability to cling
to their hosts. The bees clean the powdered sugar from each other and
thus may physically assist in the mite drop.
Shook swarm has been practiced for many years by beekeepers as a
control for European Foul Brood. Done at the right time - in spring,
as the colony is building up strongly and may be making swarm
preparations - it can be an effective way to both radically reduce
the mite load and to propel the bees into 'new swarm' mode, when they
will work with renewed vigor as if they had, in fact, swarmed.
Nevertheless, there are risks with this procedure and if the timing
is wrong, the bees may abscond or fail to thrive.
Overall, it is important to remember that we, as beekeepers, can be
the primary cause of stress to the bees in our care and that it is an
important part of good husbandry to strike the right balance between
correct monitoring and too much interference. The bees know what they
are doing: our job is mostly to keep out of the way.
What to Look For
The signal that it is time to do something is an increase in natural
mite fall. This signals a stressor that the colony encountered and
cannot handle at this point. A smart chemical free beekeeper should
break out the powdered sugar and dust each frame, repeating two weeks
later to ensure you get as much of the mite cycle you can! Should you
have a bar of capped drone brood you can pull it out, freeze it, and
return it to the colony to be cleaned.
Why is the TBH Hive conducive to Sustainability?
A proven contributor to the survival of the colony is natural comb.
Natural comb allows the free building of comb by bees at the bees
will. This in turn allows the construction of âthe core brood
nestâ this is the part of the nest constructed with smaller cells.
It is the part of the nest that is reserved and cleaned for periods
of reduced brood rearing. This is why small cell worked so well. The
theory of small cell (first mentioned by the Lusbys) was just never
thought through to the end until Dennis Murrell came along and
finished it. We have Dennis to thank for all the references to the
core brood nest contained here in. The cleaning of this part of the
brood nest keeps the mite load in check at crucial times of colony
Anything extraneous added by the beekeeper i.e. foundation, frames
and artificial feed can be grouped into the category of stressors. So
use a Varroa screen w/sticky board to monitor mites and remember it
was never intended to be a ventilation device!
Anything you do that decreases the mite population keeps the two
lines on the graph from crossing which translates to maintaining a
higher bee population. Using sugar dusting and drone comb trapping
methods are the softest non chemical approaches available today. The
most efficient times to treat are the periods just before the mite
population reaches the bee population or the economic threshold A
colony just beyond this point can be saved, however, the chances for
survival decrease every day left untreated there after.
The colonies that need least treatment should be the ones to select
A few of many references for this research are:-