“The Virus, Mite And Model: A Useful Approach Towards Varroa Control,” is the title of a provocative paper delivered in Vancouver (Proceedings of the 36th Apimondia Congress, pp. 141-142, September, 1999) by Dr. S.J. Martin. He says that in spite of treatments, many colonies continue to be lost to Varroa for two reasons. One is that controls are implemented “blind,” without being based on any kind of monitoring for either threshold levels and/or treatment effectiveness. Another is that the mechanism by which colonies perish is not understood. For despite information to the contrary, according to Dr. Martin, the presence of the mite alone often does not cause colony death. As an example, he cites information from South Africa that colonies may be supporting as many as 60,000 mites without collapsing.
There appears to be a link between certain bee viruses that really are responsible for colony loss, according to Dr. Martin. These are delivered (vectored) by Varroa. Some of them may not be immediately fatal, but can affect bee longevity or cause the insects to emerge with deformed wings or other abnormalities.
Most recently, viruses have indeed become the issue main issue as Varroa is an excellent vector. In conclusion, Varroa has evolved from a simple parasite into something much more complex that beekeepers have to face. The mite as a virus vector no doubt has increased the honey bee’s dependency on humans, contributing to further domestication of this important insect.
Fortunately, new technologies in identifying and treating viruses appear to be on the verge of development. Most significantly is the promise of something called RNAi in viral control.