We have five species of bumblebees (Bombus) and two species of solitary mining bees (Colletes) in the Outer Hebrides, some of which are rarely found on the mainland; including the lovely Great Yellow Bumblebee (Bombus distinguendus) which I rely on to pollinate my broad beans. In the absence of honey bees, our bumbles, aided and abetted by the hoverflies, other pollinating flies and beetles, are kept busy during the summer.
Crofting is low intensity agriculture which uses no agricultural chemical, only small amounts of artificial fertilisers and a system of growing cereals involving a two year cycle of fallow and cultivation. This system of land management has helped to create the perfect environment for bees and other insects, but we have to be vigilant if we wish to ensure that our precious bees remain safe. It is possible to keep honey bees (Apis mellifera) here but the flowering season is very short and it is difficult to keep the hives going through the long winter period. The absence of commercially introduced bees may also have helped keep our local populations safe. Bumblebees do not carry the varroa mite but they are susceptible to deformed wing virus and a fungal parasite called Nosema ceranae which are carried by honey bees.
Bumblebees are used to pollinate horticultural crops in the UK and it is estimated some 60,000 nests are imported annually, 45,000 of which are for glasshouse crops (e.g. tomatoes or cucumbers) and 15,000 for soft fruit. Since 1988 commercially reared bumblebees (mainly Bombus terrestris dalmatius and Bombus terrestris terrestris) have been shipped around the world. Despite reassurance by producers, research has shown that commercially produced bumblebee colonies may carry multiple parasites that are viable and can infect other species of bumblebees and bees.
It has been possible for gardeners to buy Bombus terrestris (Buff-tailed Bumblebee) in the UK for sometime. This is a native species, but there is no guarantee that they are of British origin, or free from disease or parasites. With respect to claims that they will “reward you with increased pollination of fruits, flowers and vegetables” this at best doubtful. If you have pollination problems it is probably due to the absence of the right kind of flowers in your garden rather than a lack of pollinators, so releasing a few bees won’t really help. It would be better to spend the money on buying some bee-friendly plants.
Several species of our native bumblebees are declining, but Bombus terrestris is one of the most common species and is not threatened. Therefore, the release of commercially reared bees in gardens may do more harm than good. Bombus terrestris is scarce in the Scottish Highlands and only occur in any numbers around the Moray Firth. It is not native to the Outer Hebrides and an introduction could have serious consequences for our local bees. Island ecosystems are particularly vulnerable to introduced species, even when they are native on the mainland. Even a well intention introduction can have disastrous consequences as we have experienced following the release of hedgehogs on the South Uist in 1983.
So if you would really like to help our wild populations of bees and other pollinators it would be better to plant more insect friendly plants and send a donation to Bumblebee Conservation Trust.