Thanks for the input Jim & Tim.
I realize that my question was a bit over-simplified, but I guess we all
long for simplistic solutions to Varroa.
As to threshold evaluation, it seems to me that a simple 9-celled matrix of
approximate mite thresholds could be developed easily with the available
data. As discussed in numerous threads and studies, there are three primary
seasons of concern: Winter (Nov-Feb), Summer (May-Aug), and Spring/Fall
(Mar/Apr or Sep/Oct). Likewise, there are ostensibly three primary size
groups for hives: 1) Nuc or package 2) Intermediate (single
story/developing nuc) 3) Mature Hive.
Using Delaplane/Hood's data (1 story Langstroth, 24,000 bees +/-, lower mite
"Action" threshold of 3,172 mites), the following matrix appears:
Hive Size --> 1 2 3
-----------------------------
Summer | 52 | 105 | 210 |
|----------------------------
Spring/Fall | 15 | 31 | 62 |
|----------------------------
Winter | 4 | 8 | 16 |
------------------------------
The resultant numbers are 24 hr natural drop, based on an averaged ratio of:
1 mite drop = 30 mites in the hive, Summer.
1 mite drop = 100 in hive Spring/Fall
1 mite drop = 400 in hive Winter.
Hive sizes are 12,000/24,000/48,000 bees, respectively. Obviously, we can
adjust the matrix for differing populations. Obviously, mitigating factors
would have to be considered (e.g. overwintered hives hit by a hard winter
might fall back to a category 2 or 1 hive), but I would think that such a
system would allow for quick *reasonable* asessments.
These ratios come from both Delaplane/Hood's data, as well as numbers used
in Bee-L archives. This is just a *very* quick arrangement of data. With a
little careful analysis, I should think that a very useable guideline matrix
should come out of the wealth of knowledge and experience on this list. At
the least, it would be of value to beginners who don't have a feel for what
"looks" right.
I also found Jim's references to Wyatt Mangum's comparison of natural drop
vs. Apistan drop interesting - I was thinking of doing the same. I was also
considering a two day study - 1) natural 24 hr drop 2) comparison of 24 hr
drop w/Apistan vs. Oxalic acid vapor application between hives of similar
size and infestation based on previous 24 hr natural drop (caveat - oxalic
acid drops would be monitored over longer period due to acid's slower
action).
any thoughts? (a dangerous question, I know :))
Todd.
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