I experienced the same thing 2 winters ago after feeding HBH in the fall. Although it might not be much EO, EO's are still oils and probable not suitable for bees when confined in the hive for long periods in the winter. In circumstances like this I think the oils give the bees the screaming 'you-know-whats'. this past fall I fed without EO's adding the recommended dosage per gallon of fumigillin and now I have the best bees I've had in a long time.
Originally Posted by Gregg
I still spray a medicated syrup on the bees in the fall with EO's that are different from what you would find in HBH but there is to little for them to store.
I found using HBH, or the EO's that make it up, in the syrup in the late spring has good results and using it as a spray for when applying formic acid like wise.
Will Gruenwald Chilliwack BC