> What is the threshold for a sugar shake for spring and fall?
> Is this out dated?
> [log in to unmask]" target="_blank">http://www.beelab.umn.edu/prod/groups/cfans/@pub/@[log in to unmask]

Thanks for the links.

I think the thresholds are the same for the Minnesota sugar shake and 
for alcohol wash if they are done correctly. However there are huge 
caveats in using small samples, either in hive numbers or in 
replications, and interpreting the results is about as objective and 
sometimes as meaningful as readings obtained from tea leaves or chicken 
entrails.

I've done a lot of alcohol washes and mite drops and have to say that 
any one reading may not have any direct relationship to another from the 
same hive or to the true situation in any one hive.  Any one reading can 
easily be off by a factor of 10 in high infestations and or even 
infinity where a zero count is found.

This unreliability is due to uneven distribution of varroa in hives and 
to the problem of sampling in the correct area of the hive.  A Bee 
Culture writer I often disagree with said it simply recently and earned 
my respect.  He said that to get an accurate reading, _the sample MUST 
be a sample of young nurse bees which are found directly on an area of 
brood that is about to be capped_.  Any other sample will not compare to 
what most researchers are using for comparison.

Interestingly, though, the Reuter and Spivak poster does not appear to 
specify where in the hive to find the bees to shake.  It also suggests a 
threshold that makes me shudder: The Minnesota poster says "If your 
colony has over 10-12 mites/100 bees, you should consider treatment.

On the other band, the Ontario table says 2 or 3 mites/100 depending on 
season.  I am far more comfortable with that.

I guess it all depends on where you live how lucky you feel.  I have the 
greatest respect for both Marla and Gary, but where I live, in my 
opinion and the opinion of successful beekeepers I know, the Minnesota 
recommendation would, with great probability, lead to disaster in a 
large outfit -- especially if that was a spring count, and far less so 
if that count was found after all brood had hatched in fall.

I would love to hear Medhat's comments on this since he brought Alberta 
losses down from unbearable levels to near-normal by advocating very low 
thresholds, similar to Ontario's.  Most Alberta commercial beekeepers 
take Medhat's thresholds as an upper limit and if any hives in a yard 
show the threshold, they treat all hives in that yard at the next window 
of opportunity.  We are lucky to have Apivar and it is highly effective 
if properly used.

> I recently read that the threshold numbers have been changed to a lower
> mite count. They do not include a sugar shake on the Varroa Mite Threshold
> Levels table posted here.
> http://www.omafra.gov.on.ca/english/food/inspection/bees/11-treatment-recomms.htm#Monitor%20Varroa

I think it is safe to use the alcohol wash numbers with the sugar shake, 
but I would be sure first to verify for myself that several of my sugar 
shakes get the same results as alcohol wash by putting the sugar shake 
bees and the sugar shaken out through an alcohol wash using isopropyl 
alcohol (98%) available at pharmacies (not washer fluid)

Sadly, no test is idiot-proof and there are many details to observe. 
Fore one thing, in an alcohol wash, make sure the alcohol is at room 
temp or higher or the mites may not release in the one-minute shake.

Also the 300 bees recommended is slightly too many for the standard 
shaker jar screen and will filter some mites from running into the lower 
jar if the operator technique is not perfect.  I prefer 250 or 200 bees. 
  The lower number results in less mathematical certainty, but the lower 
number also gives higher accuracy for the sample since mites are not 
caught in the mass of dead bees.

Anyhow, this is big topic. My advice is to be conservative and take 
measures any time you see varroa in any numbers.  Once they get above a 
low threshold, they balloon in numbers and the effect on the hives is 
IMO geometrically -- not linearly -- related to the number of mites/bee.

Levels of other pathogens tend to build after several years at threshold 
and then collapses can occur at below-threshold levels.

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