The decline in many insect populations across the globe is worrying, threatening economies and ecosystems.  A German study in 2017 indicated that the mass of flying insects (in various natural areas) had fallen by some 70%+.  The decline in insect populations has been associated with habitat fragmentation, the spread of agriculture and the use of pesticides, with the neonicotinoids being particularly associated with damage to bee and bumblebee populations. Recent work at the University of Konstanz suggests that when bumblebee colonies are exposed to limited resources of nectar and exposure to the herbicide - glyphosate,  then their colonies may fail.  Bumblebee colonies need a good supply of nectar as a ‘fuel’ in order to maintain a constant brood temperature (of approximately 32oC).  Only at this sort of temperature does the eggs & larvae develop quickly from egg to adult, and the colony grow from a single queen to several hundred bees.  If the temperature is not maintained, then the brood develops slowly or not at all.  The loss of wild flowers (and their nectar) plus the use of the herbicide (in agricultural areas) looks to be a problem for the bumblebees. Just as bumblebees are facing problems, so are honey bees.  The bees have faced infections with a variety of viruses, such as the deformed wing virus.  This virus affects wing development so that the wings are 'stubby' and useless, plus they may be deformities of the abdomen and leg paralysis;  the insect cannot function and dies.  The virus is transmitted by the Varroa mite - a parasite (that also feeds on the bees’ tissues).  The virus was originally identified in Japan in 1980’s and is referred to as DWV-A.  However, a new form of the virus (DWV-B) was identified in the Netherlands in 2001 and it is spreading across Europe, and to other continents.  Sadly, this variant of the virus kills bees faster and is more easily transmitted (according to research at the Martin Luther University).

Honey bees are often infected by the mite - Varroa.  Mites are small arachnids.  The varroa mite is an external  parasite, attaching to the body of the bee and feeding from it.  It also infects honey bees with various viruses, which further harm the bees.  One such virus is the deformed wing virus.  Bees that are severely infected with this virus die within days, some have such poorly developed wings that they cannot properly forage for nectar and pollen.  The virus also affects their ability to learn, so that if they forage they may not be able to find their way ‘home’.  Lost bees die, the colony is deprived of food collected by such bees and the colony may collapse. Eliminating the mite is difficult and the use of chemicals risks contaminating any honey collected from treated colonies / hives.  However, researchers at the National Taiwan University have found a naturally occurring compound that may help alleviate the effects of the virus.  The compound in question is sodium butyrate Na(C3H7COO).  In a series of experiments, the research team found that bees that were fed sugar-water laced with butyrate were better able to resist the effects of subsequent viral infection.  Compared to a control group that did not have butyrate, some 90% were still alive five days after infection whereas 90% of the control group died.  The butyrate treatment also improved the bees’ ability to forage and return to the hive.   Further details of this work here. Sodium butyrate is an inexpensive chemical, and if its benefits are substantiated then it could provide an affordable solution to the mite and virus problem that honey bees face.

The woodland’s blog has repeatedly reported on the state of honeybee populations and the phenomenon of colony collapse disorder / syndrome.  Three principal factors have been held responsible for the decline in honey bee numbers : Pesticides - notably the neonicotinoids Poor nutrition Parasites. Amongst the parasites, various viruses have been associated with decline - such as deformed wing virus (DWV), sacbrood virus (SBV) and black queen cell virus (BQCV).  These viruses are spread within the colonies (hives) by the activity of mites, specifically the varroa mite.  It has generally been assumed that whilst the mite feeds off of a honeybee (by hitching a ride on the bee), it did no great harm.   However, recent work by Samuel Ramsey et al (formerly at the University of Maryland) suggest that it is the mites’ feeding activities that are ultimately responsible for the death of the bees. Read more...

The woodlands blog has previously posted about hygienic behaviour that is seen in some bee colonies, this involves the removal of dead bee larvae and pupae. These could act as breeding grounds for mites and other insects that make “their home” in a hive. Mites, such as the varroa mite, are small spider-like creatures that attach to bees and ‘suck their blood’ and in so doing inoculate the bees with various viruses such as acute bee paralysis virus, deformed wing virus, and slow paralysis virus etc.   Mites are endemic to both wild and domestic bee colonies, as are insects such as wax moth larvae.  Wax moth larvae can burrow into the combs of a hive / colony destroying the cells where the larvae etc. are developing and growing, and where honey is stored. Read more...