Ari Seppala writes:  “Beekeepers shifted to thymol and oxalic because 
formic is more diffucult to use. We have ready made formic acid gel packets 
for sale, but still they are 
a bit more work.”

     I haven’t used oxalic acid or thymol yet.  In my experience with 
Formic acid to get good results you do have to take several things into 
consideration and deal with them accordingly.  Temperature and relative 
humidity are important factors as everyone here probably knows.  The colony 
population is another factor that can affect the effectiveness with which 
the fumes are circulated throughout the hive.  Too few bees results in poor 
circulation.  I imagine an over crowded hive can have the same problem.  
Formic acid fumes are heavier than air so the fumes can easily escape out 
the entrance or cracks between the bottom box and bottom board and not be 
circulated back up to the top.  To avoid this I tape the cracks and I put a 
block in front of and across the entrance that is a little higher than the 
entrance but has a three or four inch wide quarter inch deep notch in the 
side that faces the entrance so the bees have to go out the entrance and up 
through the notch.   This acts as a dam for the fumes.  Air can still be 
pulled in for circulation, bees can still come and go, but the fume layer 
at the bottom stays at least enough to get sufficient concentration to kill 
mites.  A spacer has to go between the top box and the inner cover with 
small slats under the presoaked pads to keep them a quarter inch up off the 
frames.  I realize this is probably too much work for anyone with very many 
hives, but it, especially the taping and the dam, does seem to make a 
significant difference in the mite drop I get.  I got a lot of this info 
off of Bill Ruzicka’s MiteGone web site.  I highly recommend anyone 
thinking about using Formic Acid consult that site.

 http://www.mitegone.com/

     Most recently I’ve been using the MiteAway presoaked pads as described 
above.  It saves me having to buy and store my own formic acid and I have 
less exposure due to dipping dry pads into a tub of acid.  It is 
considerably more expensive than MiteGone pads or paper towels or shop rags 
or what ever though.
     For those of us who are still dependent on treating for mites, I have 
always heard (mainly on this list) that using formic or Thymol in the 
spring and oxalic in the fall is an effective way to go.  
     The fact that formic kills two mites with one stone is definitely a 
factor that I consider.  Now I am wondering if there is any evidence that 
formic acid kills Nosema spores.  Seems like if acetic acid works so would 
formic acid.  Anyone know? 

Steve Noble      

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