ECWBA club members keep asking what they should do to
control the mites in their hives. At
club meetings we have recommended both a spring and mid-summer (early August)
mite treatment. This article and last
week’s article show in the real world how mite levels respond to treatments or lack thereof.
This past week beekeepers Jon and Fred did another 2 sets of
alcohol wash mite checks. In addition, I
finally finished my comparative test of oxalic alcohol fog and oxalic acid
vaporization.
TEST NO. 1
This mite check was performed on two remote hives that have
not been treated for mites this year.
These two hives were started on May 1st using packages. It’s now been eight weeks plus a few days
that the mites have been allowed to build unimpeded. The alcohol wash of 300 bee (1/2 cup of bees)
samples yielded 2 and 0 mites from the two hives. At the mite level of the first hive the mites
will probably cause a mite related crash this winter without additional beekeeper
intervention. These hives have honey
supers in place so the recommended treatment would be formic acid (MAQS or
FormicPro) ASAP during a cool stretch.
TEST NO. 2
This time it was in Jon’s Apiary. After disastrous results last year when Jon
lost about 95% of his hives in September Jon decided to implement a strict
regimen of applying an oxalic vapor treatment to his hives once per week. He thought the risk of elevated queen loss
due to the repeated treatments was less than the potential loss of the entire
colony due to mite born diseases. Since
installing the new packages of bees on May 1st Jon has treated his
hives every Monday; a total of eight (8) times. The hives have now built up to the point
where a few bees were exploring the honey supers.
It’s now been nine weeks since package installation and we
decided it was time to get an accurate reading on the mite levels in his
hives. We decided that 3 hives should
provide a good measure on the success of this oxalic acid vapor treatment
scheme. Taking ½ cup samples of nurse
bees from frames containing open brood we performed an alcohol wash. From the first hive we washed out a total of
one (1) mite. The second hive was
queenless and had no open brood. We did
see an open queen cell, but did not see the replacement queen. The third hive yielded zero (0) mites. A fourth hive yielded one (1) mite.
So this mite control method appears to be holding the mite
levels at a tolerable level. Although we
did encounter a queenless hive we feel this queen loss level (25%) was no worse
than normally occurring with new packages and the loss might not have been
related to the treatments. In
comparison I had lost 3 of 15 queens (20%) in my packages prior to any mite
treatments.
With the mites at these low levels a break in the treatments
could be in order while the honey flow is
on. Treatments could begin again after the flow without the mites
getting out of control.
EDITORS COMMENT: The EPA has not approved use of oxalic
vaporization while honey supers are in place.
It is common knowledge that beekeepers in Europe and elsewhere use
oxalic vaporization and that this honey is imported into the U.S. If we can import this honey why can’t we use
the same mite control methods? Makes no
sense to me. Ah, the vagaries of big
government.
TEST NO. 3
Two weeks ago, I reported on the alcohol wash mite checks
performed on a few of my hives. My worst
hive, from a mite perspective, yielded 3 mites.
Based on Randy Oliver’s varroa model that means this hive has
approximately 1000 mites; a combination of phoretic mites and those inside
capped brood. Three days after the
alcohol wash mite level check I treated the hive with oxalic alcohol fog and
monitored the mite drop for 4 days. I
mixed the oxalic alcohol solution and used it within 15 minutes in case there
was a tendency for the oxalic acid to breakdown into another substance. Total mite drop in those 4 days was five (5). I was expecting a higher mite drop if the
oxalic alcohol fog was an effective mite control.
Next, I treated the hive with my oxalic acid vaporizer. Total mite drop in the next four days was twelve
(12); 3 mites the first day, 5 mites the 2nd day, 3 mites the 3rd
day, and 1 mite the 4th day. From this comparative test it is easy to see
that oxalic alcohol fogging was NOT as effective in controlling mites as the oxalic vapor (5 vs 12 mite drops).
I had run this comparative test earlier this spring, but I
discovered one of the hives in the test was queenless. During this first test the oxalic alcohol fog
was also not as effective as the oxalic acid vapor treatment. However, I discounted this earlier test due
to the fact that one of the hives went queenless and this may have effected the
test results. Now with this second test
completed and also the warning on the Scientific Beekeeping website (scientificbeekeeping.com/oxalic-dribble-tips/)
that the oxalic acid and alcohol combines into a harmless ester, makes me
conclude that using the oxalic alcohol treatment is simply not worth the
risk. In addition I have heard of
several beekeepers having astounding hives losses in the fall and winter after
utilizing oxalic alcohol treatments.
So remember ITS THE MITES, MITES, MITES.
1 comment:
I think what you have shared is just good practical practice. Beekeepers have to recognize that we can no longer pussy foot around the mite. One thing that comes out of this, is the use of powder sugar for either testing or treatment is best left in the kitchen for making deserts.
Some will question, I'm sure, is, Jon's weekly treatment. My feeling is "so what it you lose a hive or two ?" Based upon our history - The old way of doing things no longer works. - Starting over every spring is not a good way to be a beekeeper. Beekeeper Grandpa Jack
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