Varroa Destructor is a parasitic mite and is the most insidious pest affecting the honey bee. We do not address treatments here because there is already so much written on the topic. Instead we recommend useful links to help with treating and monitoring Varroa mites.
“Varroa mites are the number one problem for beekeepers!” – Lyle Johnston, March, 2015
“It is critical to monitor and treat, if necessary, before the end of August in Colorado. The most damage from Varroa usually occurs in late summer and is the primary reason colonies don’t overwinter successfully.” – Integrated Hive Management for Colorado Beekeepers
A new study (Flores, J. M., Gil, S., & Padilla, F. (2015). Reliability of the main field diagnostic methods of Varroa in honey bee colonies. Archivos de zootecnia, 64 (246), 161-166. Chicago) appears to contradict other studies regarding accuracy of the different mite monitoring methods. According to the recent thread on BEE-L the accuracy of the Varroa mite monitoring method and having a hard number threshold are less important than understanding the overall trend of your mite population. If mite levels are staying the same or going down that is good. If mite levels are on the rise, however, then that may warrant treatment.