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This varmint and controlling it using oxalic acid fogging (evaporation) is the focus of my study these days

This photo was shot with my point and shoot Fujifilm FinePix XP15 waterproof camera
through the eyepiece of a 40x dissecting microscope

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Thursday December 1st 2011
Click to visit December pages from previous years: 2010, 2009, 2008, 2005, 2004, 2003, 2002, 2001, 2000, 1999

First thing today, I looked at yesterday's post and noticed that there was an error in the hive six record.  I had somehow over-written the last several weeks of data for that hive with "26".  That is a problem since I had saved the accidental changes on top of the previous version of the file. 

Fortunately, Dropbox saved me.  I keep the working file in my Dropbox and share it at this link.  So, I just right clicked the file and looked at the previous versions that Dropbox automatically makes each time I save the file.  I found a previous version with the original, correct data and pasted those data into the latest version and am back on the rails.  I updated and corrected the diary post. 

I always look back to check for and correct errors in recent posts, but don't edit older posts in any material way since I don't want to alter the record.

Back in May, I wrote about Dropbox and I am quoting that post below.  I highly recommend Dropbox as a way to back up, access and share your files and pictures securely in the cloud.  If you use the Dropbox links here, I get a small reward -- some additional free space.

Dropbox - Free file sync and off-site backupI use the Dropbox free storage and synchronization service many times a day and have for years now, without a hitch. 

My Dropbox folder is a normal documents folder I create once on each computer that I own and use for important files I need to access everywhere.  Any time I am connected to the Internet, Dropbox automatically and silently syncs my important files between all my various computers.  Any file I create or change on any of my four active computers appears also on my other computers -- and my phone as well as my Galaxy Tab -- assuming I do put that particular file into my Dropbox folder.  Since I have limited bandwidth and limited Dropbox storage, I don't do that with all my files, but I do that with all the files I use often and my photos.

Putting files into Dropbox also provides me with a free automatic, secure off-site backup.  In addition, I can access my files from any computer if I know my username and password.

I started with 2 GB free storage, but recommended Dropbox to a few people and received additional free storage from Dropbox for doing so.  I'm have3GB at present and have used 2.72 GB, so I am now reaching my free limit. and it occurs to me to recommend it here to get some more.  I could pay the $9.99 per month for paid service, but that gives me 50 GB and that is far more than I could ever use since my ISP charges  me $5 per GB  beyond my basic quota of bandwidth.  A few more free GB would keep me happy for quite a while.  My present allotment has been fine for the last several years.

Synching files between machines on a local wired or wi-fi network does not use much bandwidth, though, since Dropbox used the local network for most of the transfer, but each file added uses the Internet for upload once.  Changes to files are accomplished by a 'patch' method and only the changes are transferred in updating large files.

You might find Dropbox essential, too, if you have not already discovered it.   Check Dropbox out and sign up if you like by clicking here.  Try it out with a few files to see what you think.  If you do sign up, at no risk or obligation, you get a free 2GB account to experiment with and when you use any of the links here, I should automatically get another free 1/4 GB added to my quota, regardless whether you decide to keep using Dropbox

I'm sure you will find Dropbox indispensible, though, and everybody wins.

Dropbox is also a superior way to share photos.  Forget about PhotoBucket and all those other photo sites.  This is far better.  You have full control, easy access on your own computer and no special uploads.  Everything is automatic.

The thumbnail at left right shows a screenshot of a public shared example of some random pictures I took last month.  Don't sign up from there, though, please use this link so I get credit.  Then you can recommend it to your friends and get extra space -- as long as they use your links.

To create that excellent example gallery, I simply dragged a folder on my computer into the Public Photos folder in my Dropbox folder and published the link here.  The files in my Dropbox folder are also in the same folder on all my devices, including my phone.

Evaluation of Small-Cell Combs for Control of Varroa Mites in New York Honey Bees - CORNELL UNIVERSITY -- http://www.reeis.usda.gov/web/crisprojectpages/211868.html

"IMPACT: 2008-10-01 TO 2009-09-30 The work supported by the grant has now shown conclusively that providing honey bee colonies with frames of small-cell (4.9 mm) combs does not depress the reproduction of Varroa mites relative to giving colonies frames of standard-cell (5.4 mm) combs. These results match those of parallel investigations on this topic that were conducted independently in Georgia and Florida. It seems clear, therefore, that despite much interest by and discussion among beekeepers in using small-cell combs to control the nites without chemical, this approach is ineffective. The studies that have been supported by this grant will be reported through a publication in a peer-reviewed scientific journal (Apidologie) and a beekeepers' magazine (Bee Culture).

I am starting to see increased drops again.  It could be that it takes time for the oxalic acid to act.  Yesterday's count was made only about 12 hours after the application, so for a 24-hour number one would have to double it.  I do the counts just after 9AM and the application was done at around 9PM the night before..

Looking at the individual charts above, it appears that the applications were not uniformly successful.  Some hives did not spike after the first application and some did not respond much to the second.  I am thinking that this could be due to how the evaporator was operated, and that some investigation is required to understand how to ensure uniform dosing.

Click on each image to enlarge, or here for all the data on one page

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Friday December 2nd 2011
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We are off to Calgary again today for another appointment.  The snow has been melting as the Chinook winds continue, but the temperature is dropping.  The roads are icy.

I went out to get the drop boards this morning and found the mailbox had blown over again, as had a burning barrel.  We had very strong winds during the night and I notice it had been powerful enough to blow the drop board drawers an inch further under two hives, and for a moment I thought they were missing.  I also notice that wind blowing in the cracks had blown a few mites across the boards a bit and they were up against the far rim, but most were stuck down.  Nonetheless, the strong wind may have affected the drop count a bit by blowing some mites away and by forcing the bees to cluster more tightly.

Click on each image to enlarge, or here for all the data on one page

It seems that all the hives are broodless, or close to it, judging by the lack of pale mites dropping, so this confirms that December 1st has to be about the best time to treat. 

A problem, of course arises in waiting until; now if the hives have been allowed to accumulate high mite levels, as apparently several of the hives under observation did.  The solution, I'm guessing is to do what I did and treat early to knock them back, but be sure to do a final application in early December to clean up the mites in hives that raised brood late.  It will be interesting to see how these hives do next spring after all the treatments.

How long the hives will remain broodless is always a good question., but I'm thinking there should be at least a one-month window.  Seems to me that I noticed that the brood rearing got going in the second or third week of January when I was watching the hive scale the other year.

For those who worry about oxalic acid exposure, I should mention that quite a bit of the dust winds up on the drop boards.  I have yet to experience a burn from it or see any bleaching of clothes from treating it like any other debris on the boards.  I have taken no special precautions in handling the drop boards.

How does the Heilyser device stack up against the Cowen machine when treating three and four-storey hives?  We'll soon see, since Meijers will be over tomorrow and we'll do a repeat treatment on the test hives and a third treatment on the rest of the hives, which I did not treat when I did the third and repeat treatments with the Heilyser devices earlier this week.

So far, the spike in the graphs following the Heilyser treatment has been lower than the Cowan peaks, but that could be because we have already killed off a lot of mites.  If not, then we should see when we re-treat the test hives.  I suspect that the blower assisted application has to be better for large hives or colonies that are clustered in the top boxes.

I also am wondering if injecting oxalic vapour on the floor is the best plan.  Some are injecting through the auger holes and there is the lid idea mentioned here previously.  Working upright and at the top of the hive instead of down at the ground makes a lot of sense to me.  Of course, at this time of year in doubles, the bees are near the floor.  Not so with my hives.  I know since I placed a box or two of honey under many of them.  My bees are clustered in the second and third boxes, and some are into the fourth.

We drove to Calgary and back, then ran up to Three Hills for some supplies.  We expect a lot of company tomorrow.

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Saturday December 3rd 2011
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Today: Cloudy. Flurries beginning this morning. Amount 2 cm. Blowing snow with near zero visibility at times this afternoon. Wind becoming west 20 km/h this morning then north 40 gusting to 80 this afternoon. High plus 3.
: Flurries ending early this evening then cloudy with 40 percent chance of flurries. Blowing snow with near zero visibility at times early this evening. Wind north 40 km/h gusting to 80 becoming light this evening. Low minus 13.

It is minus seven this morning, just before sunrise.  We are expecting visitors today, so I have quite a few chores to get done early.

Meijers are planning to come over with their oxalic vaporizer to give all the colonies their final (I hope) treatment for this fall.  I'm looking at the forecast and wondering how pleasant this will be  if the forecast is correct and there is blowing snow, and if we should put the job off until Tuesday, when we will again have settled weather -- again if the forecast is correct.

I thought to look further at P-O's website and came across this mention of his oxalic vaporization experiment.

Here are today's results.  We can see that the effects of the last treatment are wearing off.  From past experience, we know that it is entirely dissipated after two weeks.

There was snow on some of the drop boards, having filtered in through a crack.  That does not affect the drops as far as I can figure.

Click on each image to enlarge, or here for all the data on one page

We had people lined up for supper tonight and a friend planning to stay over, but a light snow is falling, the roads are icy, and wind is predicted.  As a result, all except one who is nearby cancelled.  We have a big roast in the oven to share among three of us.

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Sunday December 4th 2011
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It's minus eight this morning, with fresh snow on the ground.  I went out to get the drop boards and se there are large drops from some hives still.  I see a bit of oxalic ash(?) has dropped onto one board (picture).   It must have been stuck to the screen.  I don't know what to think of it.  Does it represent un-evaporated OA?  I can't see how it would not.

The temperature is now down to minus twelve.  I'm thinking of going out to fix the mailbox and clear the driveway and pond.  With no wind, this may be quite pleasant if I'm dressed for it.

Click on each image to enlarge, or here for all the data on one page

Scrutinizing the charts and drop histories of the six different hives, all treated in the same way at the same times, we see some interesting patterns and also lack of pattern.  I think we can make some tentative conclusions. 

  1. Both the Cowan machine and the Heilyser devices drop varroa mites quite significantly.  I have no way to compare their effectiveness in the present tests.

  2. I did not get as big a spike in drops from the Heilyser units, but they were employed after two previous treatments with the Cowan machine had presumably reduced the mite populations, leaving fewer mites to kill.

  3. Three OA applications on October 13, November 10, and November 28 did not reduce the varroa loads to zero in any hive by Day 50, but have reduced several hives to very low levels.

  4. Several other hives are still dropping large numbers of mites 50 days after beginning treatment.

  5. I can't see a mathematical correlation between current drops and evidence of brood rearing over the treatment period, however there is obviously a positive relationship of some sort.

  6. Each time we treated, each hive responded differently, both in terms of numbers of mites dropping, and the timing of the peaks in drop counts over succeeding days.

  7. Presence of brood impacts the response to treatment negatively.

  8. Some hives seemed to have lower response to one or more of the treatments than to subsequent treatments. Could this show problems with the evenness of the application or convection of the oxalic acid vapours, or perhaps differences in the amount of brood present?

  9. Some hives in any yard are far more responsive to OA evaporation treatment than others.  This may be due to brood rearing, cluster location, or other factors.

  10. It is apparent that the background counts -- as represented by the low points in the daily charts -- have not gone down significantly from the initial drop levels by Day 50.  This does not mean that the varroa loads have not been seriously reduced by treatments, however, as all the mites are now assumed to be phoretic and are much more vulnerable than when in brood.

  11. November 24 was the first date after which no evidence of brood emergence is seen in the six hives observed.  Most hives were clear of emerging brood two weeks earlier.  This confirms that the most likely dates for treatment without brood in the hives are from mid-November on here in South Central Alberta, as previously suggested by numerous observers.

  12. Note, though, that some hives in a yard may never cease brood rearing and that will affect the response to OA treatment, and therefore the mite load of the entire yard in subsequent seasons.

  13. October applications on hives with brood were beneficial in that they did reduce varroa levels drastically and earlier than if we waited -- even if they did not eliminate the mites or reduce them to target levels (< 1 mite/day).

  14. It appears that I allowed the mite levels to get too high earlier in the season.  I have no baseline data, but several hives were over threshold (24/day) at the beginning of my observations.

  15. We do not know what harm if any is done to the hives by treating.  All reports I have seen seem to indicate that any harm to bees is minimal.

  16. Counting mites is not as easy as it may seem on the surface.  Careful counts made using only reading glasses were typically 10 to 20% under the true number reported when using bright light and a magnifier.

Note that my hives are three and four stories high and in EPS boxes.  This may affect the cluster location in relation to the treatment and also the timing of the end date for brood emergence.

Dropbox - Free file sync and off-site backupThanks to those who signed up for Dropbox, using the link I provided previously.  I notice I have a bit more space there now.  I'm up to 4.25 4.75 GB of free storage!

So far, I have not needed more than I have been given and earned, but if I do need more, I would not hesitate to pay the fee.   It would be worth it.   Until recently, I have been restricted from cloud storage due to my ISP, but the limits have been raised recently.

In the meantime, until I do decide to pay and jump to 50 GB for $99/yr, please do give it a try.  I get even more space and you get a really handy service for free.

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Monday December 5th 2011
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We made the drive to Calgary again today and were back around 3:15.  I had big plans, but lay down for a nap and did not wake up until almost five.  When I woke up, all ambition had faded.

*   *   *   *   *   *

Here are today's counts.  The drops are diminishing and we are planning to give them all another blast tomorrow, this time with the Cowan machine.  If we don't, then the next temperature window will be Friday, since the forecast is for minus temperatures until then. 

Click on each image to enlarge, or here for all the data on one page

I am undecided though, since the effect from the last treatment has not entirely worn off, judging by the charts.  Adding pressure to do the hives, though, is the fact that the other nineteen hives have not had a third treatment.   If the six I am profiling are representative, then the others do need a shot, and  I'd like to do it before the snow gets too deep. or we get into a prolonged cold spell.

Are the six hives representative of the entire twenty-five?  That is the sort of question that many smart people think can be answered by statistics.  Can it?   Not really, IMO, but stats can give us a good guess -- if the group is homogeneous, and that is something we cannot often know for sure.   If the group is reasonably homogeneous, then stats can give us an estimate of how many fall inside or outside the range of numbers shown by my charts, but only with a degree of confidence, not a certainty.

Common sense says that if I picked six hives at random from twenty-five, that there is a very good chance that at least one of the remainder is freer of mites than the best sample hive, and at least one of the remainder has more mites than the worst of these samples.  The chances are also pretty fair that there is one hive which has not yet quit rearing brood.

I found another small error in my spreadsheet.  Excel can be really tricky that way.  I insert a column at right inside the last data column, then copy and paste it over, enter the new data in the last column, and then check and correct in order that I don't have to reassign the data range for each graph each time. 

Columns inserted into chart data ranges are always included in existing charts, but any new columns outside the old ranges are not and the charts have to be reconfigured any time new data is added on the end.  That's probably more than most people want to know, but it makes ten or fifteen minutes a day difference to me.  At any rate, I have the data all OK and checked, but did not notice that I had pasted the day number and had several duplicates, resulting in thinking today was Day 51, when it is actually Day 53.  Big deal, I know, but that affects my reports a tiny bit if a day or tow here and there matters.

This also goes to illustrate a major point of this site, which is how easy it is to make mistakes, and how hard it is to do science.  The mistake was not material, but I wonder how often serious errors are made in data recording and reporting and never noticed.  Am I that more error-prone than others, or just more diligent in pointing out my errors?

*   *   *   *   *   *

I did my duty and went to Beebiosecurity.ca and filled in the form.  I can understand that the intentions behind this initiative is good, but I also recall something people say about the road to hell.  Here comes more empire building, regulation and expense.

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Tuesday December 6th 2011
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Today: A mix of sun and cloud. Becoming cloudy this afternoon. Wind becoming north 20 km/h gusting to 40 late this morning. High plus 2 with temperature falling to minus 6 this afternoon.

We have an appointment at 1:15 today and were planning to treat the remaining hives this afternoon after returning.  Judging by the forecast, though, we won't be treating the hives this afternoon.  Recommendations are to treat when it is above freezing.

Here are today's counts. 

Click on each image to enlarge, or here for all the data on one page

Since the last day we saw evidence of emerging brood was November 24 and the last treatment was November 28/29, we should expect efficacy approaching 90% after two to three weeks.  This is yet to be proven in my hives, but has been the pattern in other broodless hives. (See charts at left and right).

We are assuming from the lack of immature mites on the drop boards that the hives are broodless, however this indicator does not show brood other than emerging brood and if there are few mites, emerging brood might present without its presence being revealed by dead immatures.

Mite drops are tapering down again, as expected, with an average of 23 today.  Two boards are showing zero for several days in a row now.  This last treatment has so far dropped half the total mites that the two previous treatments had each dropped eight days after.  This is a good sign, assuming the treatments are all equally efficacious, which is also yet to be proven.

*   *   *   *   *   *

We were home at three, having taken slightly over three hours for the entire trip.  The weather was holding, so I decided to go out and do the treatments with the Heilyser units I purchased previously and not wait for the blower units to be available.

The job went quite well, and took about an hour and a half to do the twenty-five hives.  It would have taken less, but a second unit unit failed, in addition to the one which arrived damaged, leaving me with six working units out of the two sets of four.  I also decided to use two units per hive, having found that if I put the required amount -- 3g -- into one unit, that it was inclined to boil over.  That also slowed me down, since I was short one pair.

However, the units did fit into all my hives and worked quite well.  I probably used about four grams per hive, as each hive has four boxes, with several exceptions that have three.  I don't know if I melted any plastic frame bottoms, but did not smell any plastic.  The units are not recommended for EPS boxes, but the hot units cleared the EPS boxes when I pulled them out, and I saw no melting.   I did get a few bees and some wax in the cups, though.  I really should have smoked the hives first, but was short of time.  As it was, I finished at dusk.

It took about two minutes of electric heat per cycle and about an extra minute of waiting to allow the evaporation to finish, and since it took me 90 minutes to do 25 hives, then that works out to about four minutes a hive.  Fiddling with the wiring wasted quite a bit of time andI can see several ways to improve the setup once I get the two defective units repaired.  I can see having a spare unit is also a good idea if the plan is to run four units at a time, since they have so far proven to be subject to failure.  I'm down to 6 out of 8.

I discovered that using these electric hand units exposes the applicator to far more oxalic fumes than the blowers, contrary to what one might think, since there is a need to lean over to retrieve these little units after fogging each hive and there is residual OA vapour in the air down there unless one wishes to wait a long time.  Also, having a vehicle in the middle of the yard for battery charging disrupts the breeze that would ensure clean air upwind and causes eddies. 

I can also see how the wiring could be improved to provide greater flexibility by lengthening the leads and changing the battery clamps for eyes that could be screwed to the side of the battery.  Longer booster cables are called for as well.  The three-prong 110 volt type plugs work, but are awkward to insert and the covers on the boxes impede that even further. 

The plug-in aspect is important, though, so that units can be exchanged when they act up.  If I had two full sets, I would not have had to plug and unplug at all unless there was a problem.  Nonetheless, this arrangement is awkward to use and could be refined to be less tangled and clunky.  Even then, though, there is no practical way to incorporate swivels into electrical cables and that would prevent some of the tangling.

I may have been a little early treating this time for best evaluating how the last treatment worked, but I was eager to get this job done and all the hives treated.  So, tomorrow morning's drops should be interesting to see.  Stay tuned.

*   *   *   *   *   *

I got curious why the Heilyser unit failed.  The vaporizers had proven more durable in service than I first thought, and so I troubleshot the problem after watching TV.

The open-circuit turned out to be at a crimp-on connector in the wiring harness (non-Heilyser).  Those connectors can be very useful, but are also a frequent cause of trouble, especially where they are used on stranded wire that is flexed or where corrosion can get going.  In this case, the wire broke off at the connector.   I'll solder the connection and tape it up and be back in business.  I ordered a replacement pan from Heilyser and it should arrive soon.  Then I will have two complete four-unit setups. 

When will I need them again?  I don't know, but I'll be ready.

The green wire in the picture is unused.  The beekeeper who made up the harness used three-wire cord and plugs.  Only two wires are required, but three-wire extension cord is easier to find and the plugs chosen are a three-wire type.  I'd choose two-wire myself since it is lighter and far more flexible.  Non-polarized two-prong plugs would also be much easier to handle in service, but they may be impossible to find these days.  One could file the fat blade on the currently available two-prong plugs, though.  That way no time is wasted turning plugs around to find the proper position.  Polarity does not matter in this application, and there is no ground wire needed.

*   *   *   *   *   *

I mentioned some time back that we bought an LG SmartTV and that I subscribe to Netflix streaming video.  I have to say it is a pleasure to watch.  We watched an episode of Monk tonight followed by an episode of Murder She Wrote.  There are no commercials, the quality is good and we can start and stop as we please.

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Wednesday December 7th 2011
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The morning is cool at minus 6 and snow is drifting down.  We have drive to the city and back again today.

Here are today's drops.  It is only a half-day since the treatment, but the drops are up a bit.  I'm not seeing much OA on the boards.  I think the trick is not to overfill the evaporation pans.  Using two units per hive allows placing one on each side and that should ensure more even application.

Click on each image to enlarge, or here for all the data on one page

Here is a something new.  I have kept the same axes on all the charts so far in order that a comparison can be made visually without having to check the scales on the axes each time, but have decide to keep a separate set with the axes adjusted to the individual charts so that each plot reaches the top of the chart at some point and patterns can be seen better.  NB: I did not maintain the same ratio of left to right axes as I did in the unadjusted charts above, so be careful not to assume that relationship from chart to chart..  The adjusted set is at right and may give a different perspective.  As always, click to enlarge.

What can we see better from these versions?  We can see what proportion of the total drops happened during each treatment and after, and the duration of the treatment effects in each hive.  Surprisingly, some hives dropped the mites right at the time of treatment and others had slower, but significant response.

Ellen is very tired and the roads are bad, so we cancelled the appointment and I am at home today.  I'm exhausted, too and slept an hour and a half after lunch.  I don't seem to be able to anything too mentally challenging, like the advertisements I have promised and which are several days late.

*   *   *   *   *   *

Thanks to readers signing up for Dropbox from my links here, I now have 5GB of free storage.  Thanks, folks.

I've now treated my hives four times with oxalic vapour.  Is that good?  Is that bad for the bees?  I really do not know.  Looking at the daily drops as of yesterday, several were over the 24-mite threshold, but that reading appears to have been elevated since the last treatment did not wear off completely before I did this one.  Maybe I jumped the gun and maybe I overdid it.  We'll see in the next few weeks and next spring.

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Thursday December 8th 2011
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It's minus twenty and dropping here this morning at 6 AM.  At four, when I got up, it was only minus fifteen.  We have to make the trek to Calgary and back again today, and leave earlier than usual, so I decided to make an early start.  I had gone to bed early last night and slept well.  When I awoke at 3:30, I found I was not sleepy, so I got up, had breakfast, and got to work.

In the interval from four to six, I managed to get the ad finished, submitted, and accepted and that is a huge relief.  Finishing was not actually a massive job, but a creative one that required getting back into the right state of mind and using some complex software.

I had come within a hairsbreadth of completing on my last attempt, but I ran right out of time and had to drop it.  It might seem to some to be a simple thing to just pick up where I left off, but those of you who do creative work know how hard it can be to get back into the groove when the job is interrupted.  To do so often requires hours of procrastination, and then a lot of fiddling before things suddenly fall into place.

I use The Gimp, a free open-source image manipulation program that is extremely capable, but also has a very steep learning curve, steep enough to daunt most who try it.  I don't use it often enough to stay in the groove and it took me a few hours to remember all the ins and outs when I began this project.  I have created coffee cups and full colour magazine ads with it in the past, but I have gotten rusty.  No matter.  The job is done -- for now.

FWIW, I appreciate comments pro and con about any of my work.  I realize that I am often too close to what I am doing to see obvious errors and oversights, so please feel free to make constructive comments using the links above and below every daily entry. 

Click on each image to enlarge, or here for all the data on one page

Above is a chart that shows the average of all six hives under observation.  Each is shown individually below in two separate views

The charts above all use the same scale on the right and left axes and are thus directly comparable as to magnitudes of daily and total drops.

These same charts above have had the axes adjusted arbitrarily so that each plot reaches roughly full scale and the plots are therefore not directly comparable.  The purpose of these latter charts is to reveal patterns of response.

What do you make of the results?  It's actually looking as if we are gaining control.  The drops, for the most part, are less than from previous treatments.  Two hives still seem to have some, though.  This is quite intriguing.

Most studies concentrate on the averages, but I am more interested in the individual response, because IMO, that is where the weaknesses are.  As they say, "The devil is in the details".

*   *   *   *   *   *

We made the trip again today, the 80 miles from Swalwell to the Tom Baker Cancer Clinic in Calgary, then back.   I'm getting to know the route and the maze of halls there quite well.  Today, we had two meetings and spent over three hours at the hospital, so the round trip took about six hours, but it was a good day.

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Friday December 9th 2011
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Off to Calgary again, today.  Then Jean and family are coming for a visit.

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What can I say about the mite drop counts today except that they are not at all what I expected.  On day three fogging broodless colonies, we should have dropped about 40% of the remaining mites according to our guideline charts from other studies. 

If so, we have two hives approaching zero mites and, surprisingly, hive three is well below threshold for natural drop (24/day), and this is not a natural drop, this is accelerated due to two recent treatments.   That was the hive we figured would be a problem, but it appears to be responding very well.  Another look at the young/total mite drop chart (right) may shed some light on what we are seeing now.

Hive two is a bit of a surprise, too, providing a heavy drop.  Looking at the individual  chart, I suspect we flubbed the second treatment or for some reason, hive two did not respond at that time as well as the others and therefore is one treatment behind.

What can we conclude at this point?

I guess we can conclude that three oxalic acid vapour treatments beginning mid-October and repeated every three weeks or so until mid-December should provide very good varroa control.

The earlier treatments would not be required if the mite drops were lower than what I saw and very possibly, only two treatments would do.  If any hive in a yard dropped more than five or ten mites a day, I would treat the whole yard early to knock back the populations.  Otherwise I would wait until the brood is al hatched on November 25th to treat, as only one or two treatments on broodless hives would do the job, judging by what I see.

I would not try to get by with only one treatment at this point in my understanding.  Although most hives would be fine,  from what I see here, the way we did it at least, sometimes a hive does not respond to a treatment while the others do.  It seems the next treatment works OK, however.  This may be due to operator error or it could be due to something we do not understand, but treating twice should ensure that varroa populations in all hives are reduced to near zero.

The broodless date may be earlier in unwrapped wooden hives.  The date can be determined reasonably well by looking for immature mites on the drop boards. 

If there are few mites in a hive, and there is brood, looking for immatures may not work well as an indicator, but in that case, there are few mites in the brood anyhow, so there are also probably few mites dropping, and therefore treatment may not be indicated until later anyhow.

All this is assuming that the Heilyser units are as effective as the Cowan machine.
This should become clearer over the next week or two as the treatment wears off
and drops return to natural levels.

Although the day was predicted to have a high of minus two, we saw temperatures as high as plus eight during the day.  If this affects the mite drops we will see.  It could be that tight clusters keep mites from dropping as freely as looser clusters.  We'll see.

We made the trek to Calgary and back again and returned in time to put a roast into the oven.  Jean and family arrived at 6:30 and we had a pleasant evening.

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