# When best time to use Oxalic vaporizer?



## Michael Bush (Aug 2, 2002)

I just did mine when I could get to it, usually in the middle of the day. It worked great. An inspection this spring by the Nebraska Dept. of Agriculture found NO mites.


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## BerkeyDavid (Jan 29, 2004)

Great news Michael! Did you hit them more than once? Do you think it is the small cell?


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## Michael Bush (Aug 2, 2002)

Here's the sequence of events and you can draw your own conclusions. I started trying to regress in 2002 but started late and didn't get any regressed past 5.1mm and lost them all to mites despite using Apistan when the mite counts skyrocketed in the fall (as they had with large cell as well). The next year I started with 20 hives of feral bees that had been treated only with FGMO fog. While regressing I treated also with only FGMO fog. Since I "cheated" by using the wax coated PermaComb, most were regressed by fall. Since I wanted to sell bees without having to ship with Apistan, and I wanted to see how the FGMO fog had worked, I treated with OA after brood rearing had stopped. Twice two weeks apart. The total mite drop from that was about 200 per hive average. I treated one more time in the spring (late winter really) before brood rearing started again and only got a few (5 or 6 mites) from most hives. One had 30, if I remember right. An inspection in April by the Nebraska Dept. of Agriculture found no mites at all. We did sugar rolls and (mostly because of the PermaComb) uncapped quite a bit of drone brood and found no mites.

What was the cause of no mites? The count was pretty low in the fall when I treated with OA and during the previous spring they were not at all regressed yet so I'd have to give credit to the FGMO for keeping the mites down during regression. After regression I'm sure the small cell contributed. 

This year I have done nothing except try to keep them on natural size cells. I will probably do the OA treatment this fall and see what the mite count is total per hive with no treatments whatsoever since the OA treatment in early March, which killed almost no mites at all.

I will probably not treat my outyard at all since I don't ship bees from there, so I can see how it does on just natural sized cells.


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## BWrangler (Aug 14, 2002)

Hi Guys,

I like to treat them when they are all home and not too active. At this time of the year that's early in the morning. The main reason has nothing to do with the effectiveness of the treatment, but for the convience. There are just fewer bees flying at that time.

If you use the vent type evaporator, the time or flight doesn't make much difference. But if you use the entrance evaporator and plug the entrance when lots of bees are out, a lot of confused bees end up loitering around the flame. 

In my tbhs, I use the entrance evaporator and don't plug the entrance when the bees are flying.

I speculate that most of the oxalic powder is transferred among the bees by electrostatic charge rather than deposited as a coating on affected bees. It takes time for the process to occur so timing isn't much of a factor impacting treatment effectiveness. Just get the fine OA dust in the hive and the bees will do the rest.

On another thought, vaporizing OA reduces the partical size allowing this transfer to occur. If OA could be mechanically 'micronized', it could be blown into a hive using compressed air, etc., rather than using heat. Treating a hive with this type of equipment might require less than 10 seconds, rather than 4 minutes, and be a viable option for the commercial beekeeper.

Regards
Dennis 

[This message has been edited by topbarguy (edited October 07, 2004).]


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## BerkeyDavid (Jan 29, 2004)

Thanks Dennis and Michael. Interesting. I had thought that the Oxalic was converted to a gas. I had not considered that it might be ionized or whatever the right term is and attach to bees who come in to the hive after the treatment.
david


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## chemistbert (Mar 4, 2004)

If I were to hazard a guess about what happens when OA is heated I would say that some of the acid is degraded into water and CO2. However some would remain as an aerosol of OA. There would probably be some side reactions also, though I doubt any polmerization would occur like some organic decompositions. Being a solid acid does allow it to become charged but it is probably not "ionized" in the true sense of the word. Dunno, guess I am going to have to make a visit to the analytical lab.


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## BWrangler (Aug 14, 2002)

Hi Guys,

It will be interesting to hear what actually happens. I know that some of the acid decomposes into steam and formic, but most of it sublimates, then condenses as a very fine, white powder insided the hive.

I seen only a few unfortunate bees coated during the application. And the initial application, whether done at the top or bottom of the hive, isn't uniformly distributed throughout the hive. The frames, cluster, etc. greatly inhibit the distribution. Yet, the treatment are very effective.

Regards
Dennis
Wishing I had a chem lab to play in and am thankful I know someone who has :> )


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## BerkeyDavid (Jan 29, 2004)

Hey Bert, give us all the details will ya? Flashbacks to high school chem lab! 
cool!


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## Guest (Oct 9, 2004)

This "coating" side-effect is bothersome,
in that it seems at first glance to indicate
and uneven heating of the crystals.

Has anyone tried grinding the crystals into
a less "chunky" powder? The size of the
clumps may be part of the problem, as in
both the "crack pipe" and the battery-powered
units, one is heating SURFACES, which then
heat the OA crystals that are in contact
with the surfaces. 

Looks like I should build one and watch
the fumes fill a single and double deep.
(We have plexiglass brood boxes for our
testing of application techniques for 
Bee-Quick, so the issue of "even" 
distribution can be answered fairly
quickly.)


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## BWrangler (Aug 14, 2002)

Hi Guys,

A 3-D plex view, neat!

Regards
Dennis
Thinking an elephant is like a tree, from all I see :> )


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## chemistbert (Mar 4, 2004)

BerkeyDavid: Flashbacks to last year... I worked as a chemist before I got the Systems Admin gig.

On the heating of the crystals issue. The OA I have seen is very pure and hence sublimates all at once. The heating inside the pipe vaporizer is very intense and my guess is it is rather even due to the small size. All this means is the OA should sublimate all at once. This is more or less what I have observed. A very large jet of gasses in a very short time span. 

I will fill everyone in on my findings in the lab once I have time too actually run some tests. I have to get the OK from the college to use the IR and the gas sampling equiptment anyhow. I can run a few simpler test in my basement though. Look for a report sometime before spring.


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## chemistbert (Mar 4, 2004)

Ok, instead of reinventing the wheel I hit the journals to see if others had done decomp studies on OA. They had. When heated to 100 C the solid begins to sublimate. Total sublimation occurs at about 150 C It decomposes at 189 C At higher temperature it will decompsoe into CO CO2 Formic acid (Hmmm...) and water. Nothing there harful to bees but the formic is certainly toxic to mites. So the mystery is solved and I didn't have to lift a beaker or IR cell to do it.


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## BerkeyDavid (Jan 29, 2004)

Bert

so is it vaporized then? In micro-droplets? Or is it in a gaseous form?

david


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## chemistbert (Mar 4, 2004)

It sublimates. Meaning like dry ice it goes directly from a solid to a gas. So no microparticles or anything. Just gaseous OA. No of course it condenses on everything in the hive that is lower in temperature than 150 C. That is to say everything the gas comes in contact with. I would think that the OA begins to condense immediatly after leave the evaporator so perhaps it is better to think of it as being microcrystals. This also explains the white residue left in the end of the pipe. While it may be some decomp products it is more likely to be regular old OA that never made it out of the pipe.

The more I look nto this the more questions I have. Maybe a trip to the lab is in order after all. I'll have to take an empty hive with me.


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