Those beekeepers using Apiguard for varroa are also getting some protection for tracheal as the website illustrates. 

http://www.vita-europe.com/Map_enscript/frmbuilder.php?dateiname=%2Fen%2Fdisease%2Ftrachea.htm

I hear of more and more beekeepers using thymol in syrup for preventative varroa treatment. This more recent study below gives some credence to this practice. While the study did not look at tracheal one could infer from the apiguard claims that feeding thymol in syrup may also be beneficial to prevent tracheal infestations. 

http://www.ars.usda.gov/research/publications/publications.htm?seq_no_115=230111 

These treatments though would just prolong the susceptible lines and I like Mike Palmers approach of grafting from survivors as a better solution. 

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