Hi all
Supposedly African and Africanized bees are naturally resistant to varroa. I guess it's not the case in Mexico: 

(Excerpts for review purposes only)

> With the appearance of resistance to pyrethroids in varroa from Mexico, several beekeepers indicated a decrease in honey production

> New alternative treatments based on thymol crystals, thymol in vermiculite and oxalic acid amongst others, have been implemented

> the purpose of this study was to evaluate the efficacy of Apilife Var® and Hive Clean® on the control of varroa under the tropical sub humid climate condition of Veracruz, Mexico, on colonies of Africanized hybrid bees.

> Apilife Var® was clearly effective under tropical conditions ...  median treatment efficacy of 95.8% ... In contrast, Hive Clean® presented a very limited efficacy with a median of 19.7%

> No negative impact of both products on bee population of the treated hives was observed. Bees followed their normal development during all treatment period.

Journal of Apicultural Research: Vol 54, No 5 - Taylor & Francis Online
www.tandfonline.com/toc/tjar20/54/5
Two commercial formulations of natural compounds for Varroa destructor (Acari: Varroidae) control on Africanized bees under tropical climatic conditions.

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