Live adult Varroa jacobsoni from different geographic locations within
and outside the U.S. were tested for resistance to the acaricide fluv
alinate. Mites were exposed to technical grade fluvalinate using a gla
ss vial technique similar to standard toxicological methods. A single
concentration of fluvalinate causing approximately 80% mortality of su
sceptible mites was used. Mites from Texas showed no resistance to flu
valinate, with mortality ranging from 70.7% to 80.8% after 24 hours of
exposure. Mites from migratory beekeeping operations tested in Califo
rnia showed moderate to no resistance to fluvalinate, ranging from 48.
9% to 80.8% mortality. Mites tested in Florida showed moderate to high
levels of resistance, with mortality ranging from 5.1% to 61.6% morta
lity. Mites tested in Mexico showed the greatest susceptibility of any
location surveyed. Resistance in a Florida beekeeping operation was f
urther confirmed by using a glass jar technique developed by Pettis wh
ere live bees with mites are placed in contact with small sections of
Apistan((R)) strips. The current toxicological studies support previou
s field research which demonstrated failure of Apistan((R)) to provide
anticipated control (> 90%), due to changes in varroa susceptibility
to fluvalinate.