Strange Suspect
There has been a lot of talk on this blog about colony collapse, pollinator problems and the various causal factors. It would seem there is a convergence of issues affecting pollinator populations today, which may on their own or, more likely, combined, are contributing to the stress and reduction of honey bees and pollinator populations. Climate change, habitat destruction and 
overuse of pesticides are all known to be impacting these animals in some way, but now there may be a new suspect on the scene. It appears that a virus that for the past 1.6 billion years has only affected plants has made the jump across the species boundary and is now infecting hives.
Tobacco Ringspot Virus
Tobacco Ringspot Virus is a new culprit for hive collapse, it is so named due to the circular discoloration it produces on plant leaves. With over 90 known host plants, Tobacco Ringspot is very hard to control, many farmers have discontinued susceptible crops. It is spread from plant to plant on pollen hitching a ride in the guts of insects, where it usually remains. However, recent research has revealed the virus spread throughout the animals’ bodies, in wings, antennae, trachea, nervous system and blood. This species boundary transference is not unheard of, shorter transfers are made by influenza strains, but it is not an everyday occurrence. This virus has also be found in varroa mites which parasitize honeybees, aiding in the spread of the virus. What makes these diseases so successfully virulent is the use of RNA encoding, which allows for mutations more often.
Tobacco Ringspot Virus on a leaves of a peony.
Virus Verdict
The verdict is far from in when it comes to the ultimate malefactor of colony collapse, research continues along all avenues. The primary suspect remains neonicotinoid pesticides which are under review by the FDA and have been banned in the European Union. But the search for any and all possible candidates and how to combat and control them is ongoing and will be for some time. Viruses just add flame to the fire, are they contributing, causing or just enjoying the fruits of a weakened host? This remains to be seen. Keeping informed and staying up to date with current research will inform the choices you make for your landscape. Using integrated pest management on your property as advised by your arborist will help protect and preserve the pollinator community.
