Responding to your comment about leaving Apistan strips in hives
continuously.  This practice places a continuous selection pressure on
the mite population - only mites that do not respond to Apistan
treatment will live to produce the next generation of mites.
Treatment followed by a period without treatment, as recommended on
the label, allows mites that are not resistant to Apistan to
reproduce.  In addition, mites from the surrounding area are likely to
invade the colony and further dilute the resistant population.  If you
want more information on why this procedure is the recommended
practice look up recent references to "refugia" in entomological
journals.
 
Your acquaintance is doing what is easiest for him by leaving Apistan
strips in his colonies continuously.  He is, however, putting the
entire beekeeping community at risk by applying treatments in a manner
that will shorten the life expectancy for Apistan being a valuable
beekeeping tool.  He should treat according to the label and develop a
sampling or monitoring program for deciding when another treatment is
merited.  This is easier said than done for a commercial beekeeper,
however, we currently have only one option for controlling varroa in
our colonies.  We should do all we can to protect that option.
 
 
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *
 *    Marion D. Ellis               Assistant Professor and          *
 *    University of Nebraska        Extension Apiculture Specialist  *
 *    Department of Entomology      email: [log in to unmask]    *
 *    P.O. Box 830816               Phone: 402-472-2125              *
 *    Lincoln, NE  68583-0816       Fax:   402-472-4687              *
 * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *