I have posted in this blog section about monitoring and treating for varroa mites before – It’s something that all beekeepers need to be doing in order to keep from killing hives. Dave Pehling was good enough to forward me this pdf on varroa put out by Veto-Pharma. It has some really good information on varroa including some information on the lifecycle that I had been looking for and having trouble finding. Specifically, a new varroa mite emerging from a closed cell for the first time must spend from 5-14 days in the phoretic stage before she can enter a cell and start her reproductive cycle. HOWEVER, a mother mite who has just completed a reproductive cycle can come out of that cell and immediately go back into another cell to reproduce again. Also, a typical mother mite will undergo 3-4 successive reproductive cycles before she dies. I highlight this information because it shows that even when the mites are reproducing in worker brood where they don’t produce many offspring, they are STILL able to expand their population significantly (over a mite’s reproductive lifecycle she is capable of producing 4-6 daughters just from worker brood, and if she reproduced in drone brood she would produce 6-9 daughters!). This explains how fast mite populations can expand and also how long a mite can be feeding on adult bees and larvae and spreading viruses! There is tons of good information in this pdf (with references!) so please take the time to read it yourself.
Before I post the pdf, however, I want to include a disclaimer on the use of the mitecide ApiVar that is being advertised in the pdf – ApiVar has two problems: 1) while the compound itself doesn’t build up in wax, it’s breakdown products do and that is of some concern 2) mites are developing resistance to ApiVar so it might not work terribly well on your mites.
Here is the pdf:guide-varroa-usa-2015