This comes from the April Issue of APIS, newsletter of the
Florida Cooperative Extension Service and is in response to
detection/treatment levels.  As S. Bambara says, it's best
to determine a ball park figure and not treat when only very
few mites are detected.
 
 
 
                        VARROA DETECTION
 
The rest of the United States is starting to realize what many
beekeepers in Florida have learned in the last two years.  Varroa
mites are here to stay and monitoring the mite population is the
best way to keep parasite populations low.
 
Dr. Eric Mussen in his January/February 1992 issue of From the UC
Apiaries published a piece called "Varroa Getting Nasty."  It seems
many beekeepers in California got a surprise when their colonies
collapsed last fall.  The symptoms at first seemed to be classical
for tracheal mites:  1. rapid loss of adults;  2.  tiny clusters of
bees with a queen; and 3. abundance of stored honey and pollen.
Not characteristic was varying amounts of capped brood.  The latter
revealed that something else was going on; the adults were not
being replaced.  Developing pupae were killed in their capped cells
by mites and never emerged.
 
To prevent colony collapse, Dr. Mussen suggests checking bees for
Varroa two to four times per year.  Finding a mite or two doesn't
mean the colony is in immediate jeopardy, but it will require
treatment sooner or later.  And if another check, not too much
later, turns up a lot of mites, then you are the unlucky recipient
of someone else's failure to detect a problem.  Choose your method
of colony examination (ether roll, tobacco smoke, Apistan), he
concludes, early detection is critical to colony protection.
 
"Looking for trouble," is the way Dr. Roger Morse categorizes the
perpetual hunt for Varroa in the April, 1992 issue of Gleanings in
Bee Culture.  He concludes, "...in all probability every beekeeper
in the continental U.S. and Canada will have infested hives within
two to four years."  He recommends, therefore, that beekeepers in
the U.S., Canada and Mexico check colonies for Varroa at least
twice a year.
 
Although it has been reported that colonies sometimes take years to
die after being infested with Varroa, there are exceptions.  Dr.
Morse speaks of a New York beekeeper whose hives produced over 100
pounds of honey in July and August, yet were dead by late fall.
And Dr. Mussen describes a California beekeeper, who after a good
producing season, saw 75% of his colonies severely damaged or dead
by Christmas.  That beekeeper is no longer in business and had to
sell out at submarket prices.  These cases may be because of drift
by bees from nearby heavily infested apiaries that were not
treated.  Also the fact that mites are hidden and protected in
capped brood cells may mean a serious undercount in those found on
adults or in bottomboard debris.
 
Fortunately, detecting Varroa is a fairly simple process.  A number
of methods are described by Dr. Morse, including:  examining brood
or adults; sorting through bottomboard debris; and using the ether
roll.  These are well documented in Varroa Mite Detection, VT 249,
produced here at the University of Florida.  I can have a copy made
and sent upon receipt of a blank VHS videotape.
 
The technology to determine when a Varroa infestation reaches a
treatable level by any detection method currently in use has not
been well worked out.  Detection results may vary and are dependent
on bee/mite population dynamics.  For example, in the fall, Dr.
Morse says, with little or no brood, you are more likely to find
mites on adults, whereas in the spring they will be easier to find
in brood.  Practical experience by the Florida Division of Plant
Industry indicates that when 20 mites in an ether roll of
approximately 300 adult bees are found, a colony should be treated
with Apistan.   However, Dr. Harvey Cromroy of the Entomology-
Nematology faculty, University of Florida, believes more than five
mites is a treatable level.  Dr. Morse concludes finding 30 to 40
mites per hundred bees (ether roll) is serious and the colony may
be beyond saving.  The ability to correlate ether roll with other
detection methods is not presently available.
 
++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
Tom Sanford       Extension Apiculturist   University of Florida
Mailing Address:  Bldg 970, Hull Rd., Gainesville, FL 32611-0620
Voice phone  904/392-1801, Ext. 143
FAX  904/392-0190
INTERNET:  [log in to unmask]
BITNET:  MTS@IFASGNV
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