Acaricides are used to treat honey bee (Apis mellifera L.) colonies to control the varroa mite (Varroa destructor Anderson & Trueman), a worldwide threat to honey bee health. Although
acaricides control a serious honey bee parasite and mitigate bee loss, they may cause harm to bees as well. We topically applied five
acaricides, each with a different mode of action, to young adult queen and worker bees to generate dose-response curves and LD50. Twenty-four hours
after treatment, queens were found to be three-times more tolerant of tau-
fluvalinate and six-times more tolerant of
thymol than workers when adjusted for
body weight differences between workers (108 mg) and queens (180 mg). Queens survived the highest administered doses of
fenpyroximate (1620 microg/g) and
coumaphos (2700 microg/g) indicating that queens are at least 11-fold more tolerant of
coumaphos and at least 54-fold more tolerant of
fenpyroximate than workers. However, queens treated with as little as 54 microg/g of
fenpyroximate exhibited reduced survival over 6 wk
after treatment.
Amitraz was the only
acaricide tested for which queens were not more tolerant than workers. The striking difference in
acaricide tolerance of queen and worker honey bees suggests physiological differences in how the two castes are affected by
xenobiotics.