Solving colony collapse disorder probably can't be just better bee husbandry

The problem of 'emerging infectious diseases' (EID) is well-recognized in humans and other vertebrates but less so among invertebrates.  Colony collapse disorder (CCD) is an ongoing and serious problem among honeybees that are used to pollinate food crops, but a new study published in Nature ("Disease associations between honeybees and bumblebees as a threat to wild pollinators", Fürst et al.) reports that whatever is killing managed pollinators is spreading to wild bumblebees and killing them too.  Indeed, wild bumblebee populations are in decline around the world.

Wild and managed bees already share some diseases, including deformed wing virus (DWV) and infestation with the fungal parasite Nosema ceranae.  Varroa mites seem to be among the causes of CCD, but they are not being found in wild bees.  Fürst et al. suggest that, as with vertebrates in which 'spillover' from domesticated animals to wild sympatric species, wild bees readily become infected with diseases that managed bees carry because they visit the same flowers.  Whether wild bees are as vulnerable as honeybees have been to the causes of CCD is yet to be seen.  

Source: BBC

Fürst et al. tested the infectivity of several diseases found in honeybees, DWV and Nosema ceranae, by inoculating bumblebees with the virus and infecting them with the fungus.  They found that these infections are indeed devastating to bumblebees, infected wild bees had non-viable offspring and shorter lifespans than uninfected bees.  

They then surveyed bumblebees throughout the UK and found evidence of active infection by both mites and DWV, although currently at lower levels than among honeybees -- 11% of bumblebees and 35% of honeybees had DWV, and 7 and 11% respectively had the fungus.  

They further found that prevalence of these infections was not uniform among their sampled wild bees but that it was correlated with prevalence in nearby honeybees. They further tested the strain of infection among wild and managed bees and determined that they shared the same strains. While they couldn't confirm the direction of infection, they suggest that it's likely to be honeybees to bumblebees since prevalence of DWV and fungal infection is higher in honeybees.  

The global trade in honeybees and the worldwide prevalence of CCD mean, to Fürst et al., that beekeepers need ways to reduce infection rates in managed bees, both for the health of these bees as well as for the health of wild bees.  But, as they point out, 'reducing the pathogen burden is not easy.'  They suggest that beekeepers should learn from experience with infection control in vertebrates.

Lessons learned from vertebrates highlight the need for increased pathogen control in managed bee species to maintain wild pollinators, as declines in native pollinators may be caused by interspecies pathogen transmission originating from managed pollinators.

A piece on the BBC website on Thursday includes this quote:

Dr David Aston, president of the British Beekeepers Association (BBKA), said: "By employing good husbandry practices, beekeepers can take steps to reduce the impact of pests and diseases on honeybee colonies using biotechnical controls and practices such as apiary hygiene, regular brood comb changes, ensuring the colonies are strong and well-nourished and the use of authorised treatments."

In other words, good husbandry can reduce the disease load on managed bees, and thus on wild bees, and knowing specific causes of CCD isn't as important as simple hygiene.  This may be true as far as it goes, but if pesticides and herbicides are part of what seems to be a complex chain of causation this problem can't be solved from hive to hive, but instead controlling use of toxic chemicals must be part of the solution.