It is interesting to read a lots of good information and sharing
experiences about the use of oxalic acid.
I would like to add some information based on my research over the past
several years, specially in the last three years in Alberta, Canada. I
gave a talk at California State beekeeping meeting about "Soft Chemicals".
I did not like the labeling of oxalic acid, formic, etc. as soft
chemicals. This is a turn off for use of these chemicals to control mites.
If you have varroa infestation and you need an immediate control method,
would you resort to soft chemicals or look for the nearest gun to
shoot'em? I like to call these chemicals "Alternative Chemicals"
Mites have become resistant to conventional chemicals (pesticides) and we
are left with alternative chemicals. In fact, the so called soft chemicals
which we are using, are harsh, corrosive, toxic and kill. I would rather
to call these chemicals "alternative chemicals". These chemicals require
specific conditions to achieve acceptable efficacy levels. It also
requires special handling to be safe for bees and applicators.
few comments:
1. Oxalic acid used for treatment of varroa is Oxalic acid dihydrate
2. Oxalic acid can be trickled or sublimated in bee hives for treatment of
mites. Concentrations of applied acid for various geographic locations
have been published. Warm climate areas, according to research from
Italy, it is recommended to use high doses. In cold climate areas, it is
recommended low doses. Please use the proper dose recommended for your
location. It does not mean more is better. The less chemicals thrown in
the hive is good for the bees.
3. It is safe to handle the acid with the use of chemical resistant gloves
and mask. It was mentioned earlier by Keating "a good mask for vapor is
highly recommended". These safety gears are recommended for a purpose. If
the oxalic acid spilled or the syringe broken, the gloves will be handy
protecting your hands and goggles protecting the eyes from splashed acid.
In addition, for those who use OA to treat thousands of colonies, the risk
is higher for exposure and accidents. Please use the proper safety gear
when handling these products. So, you stay healthy to enjoy your alive
healthy bees. No point to keep healthy bees and you suffer and don't get a
chance to enjoy them!!!!
4. We tried feeding caged bees OA in sugar solution at very low to high
concentrations. Bees did not even touch the lowest concentration of OA
sugar solution. This experiment confirmed that bees don't ingest that
applied OA for varroa treatment. It is a contact miticide. When OA dripped
or sublimated in the hives OA crystals will cover the bees and mites.
Mites will be killed as the dose is high enough to kill mites, but not
bees.
5. To get consistent results, OA should be applied when their is a minimal
brood/broodless conditions. keep in mind not all the hives will shut down
the brood production at the same time. Too many variables will determine
when a colony will shut down brood production. Just think of these
variables; queen age, strain of bees, colony size, pollen availability,
feeding, day light length, etc.
6. In Alberta, we found that application of oxalic in a liquid form late
in the season requires too much work. You need to break the two boxes to
get to the bottom box to treat it first. After feeding bees, Good LUCK
breaking these boxes apart. Therefore, we are recommending using
sublimation for late fall treatment.
7. The most interesting challenge is "how will a beekeeper treat 2000,
5000, 15,000, or more colonies with OA?" These number of colonies can be
typical numbers in commercial beekeeping operations in North America. The
question is: how many syringes will be needed to finish the application in
a reasonable time? The use of garden sprayer will never deliver the
recommended 5 ml/ bee space occupied with bees. We tested this delivery
method. We found more than 5 ml were applied and caused killing a large
amount of bees. It also decreased the brood production. Please use the
recommended dose 5ml/ occupied bee space. I understand these type of
questions have not been addressed by any research. It is left to
beekeepers to figure it out.
In my research program, I have been working on finding a simple, efficient
and reliable method to deliver the recommended dose for commercial
operations. We are getting there.
The same challenge is applied to the use of sublimation tools
"Evaporizers" applicators. We have too many models out in the market and
many more home made. The question is are these tools standardized in terms
of heating temperature. Oxalic acid applied to these hot plates will
produce fumes that could contain oxalic acid, water and carbon dioxide. We
need to maintain the integrity of oxalic acid that applied to the hive,
not to break it down all the way to water and carbon dioxide. Imdorf from
Switzerland tested different evalprizers, and reported variable efficacy
results ranged from 20-95%. Therefore, tested applicators are important to
use to achieve good control. Additionally, How many kids should we hire to
do the application in commercial operations in a reasonable time and
safely? These are the kind of problems that need to be addressed and
standardized.
8. Yes: Oxalic acid is not the silver bullet. It will work nicely with
other tested methods for controlling mites such as; resistant bees, formic
acid, Apilife var, etc. Think integration!!!! What is important? Monitor
and make decisions? What is the appropriate method to use. Don't forget to
monitor after you treat to know if you have achieved good results or you
need to retreat.
Medhat
Medhat Nasr, Ph. D.
Provincial Apiculturist
Crop Diversification Centre North
17507 Fort Road
Edmonton, AB, Canada T5Y 6H3
Tel: (780) 415-2314 Fax: (780) 422-6096
Mailto:[log in to unmask]
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