I agree with Justin's observations and would add a fifth in that their dosage at 1 g was too small to draw a conclusion either way unless, as they mention,  the point was to encourage revisiting efficacy at low dosages. 

Also, in my opinion, trying to kill varroa using forced broodless periods is different compared to natural broodless periods because the starting point of the phoretic population may be much higher. The period leading to a natural broodless condition eliminates mites along the way.


>Our inability to control Varroa effectively regardless of OA treatment suggests that the current labeled dose of 1 g per brood chamber was ineffective, at least under the conditions we maintained in our study.

>The lowest effective dose of OA sublimation in the United Kingdom was found to be 2.25 g (Al Toufailia et al. 2015), which is more than twice the label rate in the United States. Therefore, researchers should focus future efforts on determining the effective dose for OA vaporization and seek changes to legislation allowing beekeepers to apply the effective dose.


Bill Hesbach
Cheshire CT

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