The main culprit is coumaphos and to a lesser degree the other
miticides used to control Varroa. Most, if not all, beeswax sold in the
USA has some coumaphos residue. It causes "Intercaste Syndrome" where
queens reared in colonies where coumaphos residues are present emerge as
adults which have a varying degree of worker characteristics instead of
being 100% queen. 

I published about this in the Beekeepers Quarterly
about 10 years ago. 

Miticides such as fluvalinate, flumethrin and
thymol affect drone fertility. 

Best regards 

Roger White 

Cyprus. 

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