Deformed Wing Virus

Deformed Wing Virus. Plus you can see the Varroa mites on the bee.

This is an article about Deformed Wing Virus or DWV. This article explains the importance of treating colonies before winter bees are being produced. By having low mite levels by around August 1st helps prevent the transmission of DWV into winter bees. By treating colonies later in the season, the mite level drops significantly, but there is a possibility that DWV is still a factor that leads to the colony's demise later in winter.
https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0180910