ARS | Publication request: Hygienic Activity Toward Varroa Mites in Capped Brood is not Dependent on Mite Reproductive Status

Submitted to: American Bee Journal
Publication Type: Abstract Only
Publication Acceptance Date: March 15, 2009
Publication Date: June 15, 2009
Citation: Harris, J.W., Danka, R.G., Villa, J.D. 2009. Hygienic Activity Toward Varroa Mites in Capped Brood is not Dependent on Mite Reproductive Status. American Bee Journal. 149(6):587-588.

Technical Abstract: - The varroa resistance of bees selectively bred for high levels of varroa sensitive hygiene (VSH) is characterized by a reduction of (1) the mite infestation rate (Harris 2007 J. Apic. Res. / Bee World 46: 134-139) and (2) the percentage of fertile mites (Harris and Harbo 1999 J. Econ. Entomol. 92: 83-90) after naturally infested capped brood is exposed to the bees. Selective removal of pupae that are infested with fertile mites (those with offspring) could explain both results (Harbo and Harris 2005 J. Apic. Res. 44: 21-23). This experiment tested for a bias by VSH bees for chewing pupae infested with fertile mites. Combs of naturally infested worker brood were put into control (n=12), hybrid VSH (n=7), and pure VSH (n=8) colonies for 3 hours. Half of the capped brood on each comb was protected by a screen to prevent hygienic manipulations by the bees. The percentage of fertile mites in protected brood was compared to the percentage fertile mites from chewed pupae at the end. Biased removal of pupae with fertile mites should increase the fertility (i.e. above background levels of protected brood) of mites on chewed pupae that were being removed from capped brood by bees. Exposure of brood to bees was limited to 3 hours so that hygienic bees could uncap mite-infested pupae and begin chewing some of them, but the interval was too short to allow complete removal of most targeted pupae. The percentage of fertile mites on chewed pupae was not significantly different from that of mites from protected brood (a = 0.05). There were no significant differences in percentage of fertile mites on chewed pupae among the three types of bees despite significant differences in overall hygienic activity (hybrid and pure VSH bees chewed more pupae than control bees). These results suggest that VSH bees removed mite-infested pupae independent of the presence of mite offspring (Figure). Thus, other processes related to hygienic behavior of VSH bees must decrease the frequency of fertile mites from capped brood.