Hello James & All,
Excellent post James! I agree with the points made and respect the advice of
the CSL/DEFRA. but will add a couple opinions.

James said:
Advice from CSL/DEFRA (Bee Inspection, testing and research, UK) is to
multiply the daily mite fall by 30 to get a reasonable estimate of the
total mite population during brood rearing; 400 without brood - once
everything has settled.

The above figures cover all bases but the range is too wide in my  opinion
for the average beekeeper ( and certainly the commercial beekeeper dealing
with thousands of hives) and I will tell you why.

Reason is to use the above figures you need (as Jim pointed out in his post)
the figure for the amount of brood. To get the brood number figure one has
to disassemble much of the hive. The whole purpose of sticky board tests is
*you do not need to open the hive* and the draw back is you need to make two
trips to the apiary.
With a *roll* you can get a better idea of the amount of brood but the hive
needs opened and at least one frame pulled (to be done correctly).

There are those researchers which say that you multiply the natural mite
drop after brood rearing by 200. If so then a figure of 400 dead varroa on a
sticky board in 24 hours would indicate a varroa population of 80,000  .
Hmmm.

James said:
How you get a threshold is another matter. The size of the colony and
its susceptibility to viruses are variables. Our Regional Bee Inspector
suggested (for a typical UK colony) that we revise down the previously
recommended threshold of 2500 to 1000.

Surely you are not talking about the number of natural fall mites on the
sticky board but the amount of varroa in the hive?

James said:
- perhaps the viruses are now endemic and kick in earlier.

Bringing viruses into the issue or (P.M.S.) as we call the virus situation
brought on by advance stages of varroa infestation (U.S.A.) opens another
can of worms. Waiting for two high a varroa infestation to treat invites
viruses (in my opinion).

James said:
Our RBO has given us a table for urgent treatment, delayed or less
potent treatment and no treatment. One figure given was that if there
were more than 15% drone brood with mites, we should use an appropriate
treatment immediately.

Sounds primative as all drone brood would have to be opened and a count made
to figure a percentage and the drone brood could be on each frame of the
hive.  Not something I would be interested in doing with my limited time.

James said:
This seems to be getting towards your approach, where, if my memory serves
me, Bob, you referred a year or two ago to % mites being a better guide to
the need for treatment. Absolute numbers are not reliable, since they must
be interpreted. % cells infested is perhaps rather more reliable.

I can not really remember the post you speak of but varroa testing is easy
as far as doing rolls or board tests but analysis of the results can be
confusing and differ greatly from one area to the next.

I will say that every beekeeper looks for a once a year fail proof way to
control mites. Now that we are going into a new era of U.S. beekeeping we
are faced with only trying to knock back the varroa load. FGMO only knocks
down varroa load and efforts need to be done all season. Even drone brood
removal might help with knocking down varroa load if the beekeeper wants to
spend every Saturday pulling drone brood through the brood rearing season.

A control which only provides a 50-60% control and many temperature and
humidity dependent chemicals have shown *at times* control in this range
will seem like they are working great but over a year or so the varroa load
will climb to a level at which *in my opinion* they will not produce the
results wanted and low honey crops will results combined with poor wintering
.

When we move into a use of a control dropping from 98% to possibly *at
times* 50-60% varroa is winning. Eventually ( several years) varroa will win
and the hive will die. Many have posted that from personal experience that
formic acid ( both gel & liquid) is not as effective when the hive is
approaching threshold as Apistan or Checkmite.

complicated subject. Those which are confused by now either ask questions or
search the archives as a wealth of testing information exists in the
archives.

Sincerely,
Bob Harrison
Odessa, Missouri

Ps. many of you in the U.S. might have read in your beekeeping assn.
newsletters that I will be in St. Louis, Missouri at the meeting of the
Missouri State Beekeepers  showing slides of California Almond pollination.
I regret to say I will not be attending as I will be enroute to California
to remove hives from Almond groves. My partner will be at the meeting
showing the slides. I will be off BEE-L for about three weeks.

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