> Charles do you know of cases where Apivar has failed and is known and proven? I have had a case where this maybe the case here and want to generate as much information on the failure as possible. 

¶

Apidologie Volume 31, Number 3, May-June 2000

> We conducted laboratory tests investigating the mortality of mites infesting honey bee colonies in Minnesota after exposure to fluvalinate, amitraz, or coumaphos. Results indicated that these mites were not only resistant to fluvalinate, but also to amitraz. Coumaphos was effective against these resistant mites. A separate field trial was conducted with the same hives as those used in the laboratory test. The field trial supported the laboratory results, showing that mites in Minnesota are resistant to both fluvalinate and amitraz, and that coumaphos is effective in controlling these mites. This represents the first known reported case of amitraz resistance in Varroa jacobsoni in the U.S.A.

> Field studies further supported the laboratory findings (Tab. III). There was an increase of 89.1% over the treatment period for colonies exposed to Apistan, indicating little/no control, and thus very high resistance. The control obtained with amitraz was only 75.4%, which significantly differed from the expected 98% control using the same strip form of amitraz as used in previous studies in Guatemala

¶

Journal of Invertebrate Pathology 149 (2017) 119–126

> this study found that exposure to a formamidine acaricide [Apivar®] may have a negative impact on the ability of honey bees to tolerate viral infection. Furthermore, this work has demonstrated that amitraz and its metabolite significantly alter honey bee cardiac function, most likely through interaction with octopamine receptors. The results suggest a potential drawback to the in-hive use of amitraz and raise intriguing questions about the relationship between insect cardiac function and disease tolerance.

> These findings have some immediate implications for apiculture practices, as there is likely a trade-off to be considered when the decision is being made to treat a mite-infested hive with amitraz.

PLB

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