I monitor the situation in France with regard to that other pest in the news, the Asian Hornet. Over there, winter colony mortality is at an average of 30% with some of the 96 departments hovering around 40%. Very disturbing for a country that has been down to 5% and more normally at 15%. A French Senate Committee sat in 2017 to examine the multi-factorial decline in honeybees calling on the major bee research institutes and UNAF the French national Union of beekeepers to give evidence. They identified the following as the major causes:
Pathogen load (including pathogens spread by varroa)
Pesticides and pesticide residues (they have banned all the Neonicotinoids)
Loss of forage (due to increasingly intensive agriculture)
Hive Pests with the number one pest still being varroa
Poor apicultural practices (they have had a big loss of beekeepers with the numbers coming back but with beekeepers needing training - big effort to correct that is in force); climate change and the Asian Hornet.
The National Agricultural Institute (INRA) was at pains to point out that all these factors were culumative.
In my area of interest the hornet is the straw that breaks the camel's back.
This has given me a renewed focus on varroa control and an added incentive to rethink my apiary hygeine practices. I am also looking with renewed interest at my bees' diet in our intensive agriculture area.
Bottom-line - no good dealing with one factor we have to look at the wider picture and deal with as many factors as we can