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.