Dear friends

There are many factors causing decline in bee populations, and these include habitat loss and nutritional stress, while the role of pesticides in bee decline is ferociously contested between environmentalists, agriculturalists, and industry lobbyists.

As we go to press important research concerning the effect of neonicotinoid pesticides is published by the UK’s Centre for Ecology and Hydrology 1 .

Neonicotinoids (or ‘Neonics’ for short) are neurotoxin insecticides developed in the 1990s which are now the biggest-selling type, widely used in agriculture and horticulture. Neonics are sprayed on to leaves, watered into the soil, or used as a coating for seeds. They are designed to kill insect pests which feed on plants, and they work systemically, which means that they are present throughout all the tissues of a plant, including its sap, nectar, and pollen. They are persistent: once in the soil they remain there for years, and they are highly toxic to aquatic life.

The research findings now published in Science add to the accumulating body of evidence suggesting that neonics contribute to the decline in bee populations. The US$3m field study was funded by the chemical companies Bayer CropScience and Syngenta which produce neonics, and took place at 33 sites, each of around 60 hectares, in Germany, Hungary and UK.

The study considered prevalence of bee disease and landscape quality, colony growth rate, worker mortality and overwinter survival. Three bee species were exposed to crops of oilseed rape treated with seed coatings containing the neonic clothianidin from Bayer CropScience, or Syngenta’s thiamethoxam.

The researchers found that exposure to treated crops reduced overwintering success of honey bee colonies in two of the three countries. In Hungary colony numbers fell by 24% in the following spring. In the UK honey bee colony survival was very low, and lowest where bees fed on clothianidin-treated oilseed rape in the previous year. No harmful effects on overwintering honey bees were found in Germany.

Lower reproductive success – reflected in queen numbers of bumblebee Bombus terrestris and egg production in solitary bee Osmia bicornis – was linked with increasing levels of neonicotinoid residues in the nests of these wild bee species in all three countries.

According to lead author Dr Ben Woodcock: “The neonicotinoids caused a reduced capacity for the three bee species to establish new populations in the following year.” He suggested that the differing impact on honey bees between countries may be associated with factors including the availability of alternative flowering resources for bees to feed on in the farmed landscape, as well as general colony health.

Bayer and Syngenta have both dismissed the research findings as simplistic.

In 2013 the EU banned the use of neonics. This will be debated again this year and based on latest evidence, must be continued.

Dr Nicola Bradbear Director, Bees for Development

Woodcock, B A, Bullock, J M, Shore, R F, Heard, M S, Pereira, M G, Redhead, J, Ridding, L, Dean, H, Sleep, D, Henrys, P, Peyton, J, Hulmes, S, Hulmes, L, Sárosspataki, M, Saure, C & Pywell, R F. Countryspecific effects of neonicotinoid pesticides on honeybees and wild bees, Science, VOL 356, ISSUE 6345.

Read the paper online: http://science.sciencemag. org/cgi/doi/10.1126/science.aaa1190