The decline of bees continues to make headlines

Posted 2 May 2013

The decline of bees has been making headlines worldwide. Staff at Harper Adams have provided a summary to explain why, and the latest view from a conservation perspective.

Research Entomologist, Dr Tom Pope and Associate Head of Department - Crop & Environment Sciences, Simon Irvin:

“As the countryside gradually emerges from a long cold winter, we begin to look forward to the summer ahead - surely this year has to be better than last! With the warmer weather, beekeepers will be checking their hives and if all is well will see bees returning to the hive carrying pollen collected from flowering plants growing in the surrounding area. In addition to the pollen, the bees will also be collecting nectar, which they will convert to honey inside the hive and which the beekeeper will hope to harvest later in the year.

The past few years have seen a massive increase in the number of people interested in beekeeping. This increased interest was evident at the recent British Beekeepers Association – Spring Convention held at Harper Adams University. While beekeeping is undoubtedly a fascinating hobby in its own right, a significant number of people have become involved in beekeeping in response to reports that honey bee numbers are in decline.

Indeed, the latest winter-loss survey for honeybees in the UK (2011 – 2012), suggests that on average, 20% of all honey bee colonies died out over the winter period in the UK. Many of the threats facing the honey bee were explained in lectures given as part of the Spring Convention. Topics covered included, pollinator health, managing honey bee mites and diseases, honey bee nutrition, UK climate change and its effect on beekeeping and the impact of pesticides.

Recently, the threats facing honeybees and other pollinating insects, such as bumblebees, have been the focus of much research. The importance of this work is clear when we consider that pollination is needed for about three-quarters of global food crops. Threats such as the parasitic mite Varroa destructor are well known to beekeepers, who use a range of techniques to reduce mite populations within the hive. Beekeepers know only too well that if left unmanaged, Varroa is capable of devastating honey bee colonies. 

While Varroa is a key pest affecting honey bees, it is likely that a combination of factors is behind the decline in pollinators as whole. The role of one of these factors, insecticides, has recently been at the centre of much debate. Insecticides have long been used by farmers to control pests of crops; however, attention has focused on a group of insecticides, known as the neonicotinoids. Of particular concern is the use of these insecticides in seed coatings in crops, such as oilseed rape, that are visited by pollinators.

As a plant germinates, neonicotinoid in the seed coating moves into the stem and leaves of the growing plant. Later as the plant flowers the insecticide is found in tiny amounts in the pollen and nectar. The neonicotinoid in the stem and leaves of the plant provides protection against important pests, such as the peach-potato aphid, but once in the pollen and nectar, the insecticide may be eaten by insect pollinators. It is this final point that has raised concerns that these insecticides may be harming pollinating insects. Other concerns have focused on dusts produced when neonicotinoid coated seeds are drilled and the presence of neonicotinoid insecticides in guttation fluids (water droplets produced by a plant).

This week the European Union announced that the use of three neonicotinoids; clothianidin, imidacloprid and thiamethoxam, will be restricted for a period of two years. The decision has been taken following publication of a report by the European Food Safety Agency, which concluded that these insecticides posed a "high acute risk" to pollinators.

Restricting the use of neonicotinoid insecticides will have important implications for UK agriculture. These challenges will include, continuing to effectively control key pests while at the same time managing insecticide resistance with a reduced range of insecticides. Farmers have until December 1 to reassess their pest management options in light of the announcement on neonicotinoid insecticides this week."