Bumblebees

Imidacloprid, developed by Bayer CropScience in 1985, is an insecticide, a seed treatment insecticide and seed treatment insecticide/fungicide combination. Bayer still holds patents on the active for some formulations, specifically when combined with fertilizer. Its mode of action is nicotine acetylcholine receptor agonist/antagonist, and it is registered in more than 100 countries worldwide for use on more than 140 crops. It is used primarily on canola, cereals, corn, cotton, oil seed rape, pastures, potatoes, rice, sorghum, sugarbeet and sunflowers for approved control of aphids, fruit flies, leafhoppers, grubs, termites, thrips, white fly, wireworms, various beetles (including flea beetle and pygmy beetle), various weevils, nematodes and various fungal diseases. It also has widespread applications in noncrop, including nursery, landscape, forestry, pest control and veterinary applications. Bayer Animal Health has been using a 10% imidacloprid formulation for its popular Advantage/Advantix flea treatments for dogs and cats as early as 1986.

There are multiple ways that plants in urban landscapes can contain imidacloprid-contaminated nectar, since it is commonly applied in the landscape for many pests and many greenhouse plants are treated with prior to sale and transplanting. Imidacloprid may persist in nectar for a long time, since soil applications were effective against foliar pests for 1 to 2 years in containers and landscape trees. Injections of concentrated volumes of imidacloprid applied to trees trunks and roots were effective for 12 months for ash and linden. A soil application of imidacloprid to Eucalyptus tree resulted in 500 ppb in nectar and pollen, which will kill any insect feeding on nectar and pollen. Tree injections of imidacloprid at flowering are cause for concern, since linden flowers are a good source of nectar and pollen for bees, butterflies, and other beneficial insects.

The British public has helped scientists uncover what looks like a substantial decline in one of the UK's most common bumblebees over the last 20 years. By gathering valuable information about the insects, citizen scientists from across Britain have shown that the common carder-bee made up less than 10 per cent of bumblebee colonies from 2007 to 2009. Just 20 years previously, they made up a whopping 21 per cent. This is the first time anyone has shown that one of the UK's big six common bumblebees may be in decline. 'There seems to be a clear shift in how common different species in the UK are,' says Dr Gillian Lye from the University of Stirling, lead author of the study, published in the Journal of Insect Conservation. Professor Dave Goulson from the University of Stirling and Lye came up with the idea of getting enthusiastic members of the public to help them get to grips with bumblebee nesting ecology when they realised they could get a lot more information than they could on their own. 'People tend to spend quite a lot of time in their gardens, so spotting bumblebees and following them to their nests is a real possibility,' says Goulson. In this latest study, Goulson, Lye and colleagues asked members of the public to send information about which species they saw and what type of nest the bees used to the Bumblebee Conservation Trust. They encouraged people to send photographs, so that Lye could confirm the species. In total, over a thousand people sent information about the nests in their gardens.

While the decline of B. franklini in southwestern U.S.A. and B. affinis in eastern North America have been well documented and quantified, there are few baseline data for comparing previous and current abundances of B. occidentalis, the Western Bumblebee. Here we provide a comparison of the relative abundance of B. occidentalis after 20 years in the Fraser Valley of British Columbia, Canada. Bombus occidentalis was the second most abundant bumble bee in blueberry fields in 1981 (27% of collected bumble bees), and it was the second most common Bombus species, overall, collected in berry fields and natural vegetation (approx 22%) in 1982. In 2003–2004, this species represented less than 1% of the Bombus collected (26 individuals of the 2738 total). Likewise B. occidentalis was the most abundant bee (55% of bumble bees, 312 individuals) in cranberry fields in 1982 and second most abundant bee in 1981 (41% of bumble bees, 104 individuals) but was represented by 2 individuals (0.3% of bumble bees) in cranberry fields in 2003 and was absent from cranberry fields in 2004. Bombus occidentalis was also very low in abundance in urban habitats adjacent to this region in a survey performed during the same time period (2 individuals, 0.1% of bumble bees). These results provide quantitative evidence that wild populations of B. occidentalis have declined in western Canada.

We quantified the relative value of native and long-established plant species as forage (nectar and pollen) resources for bumblebees by collating visitation data from 14 field sites across Britain. Twentieth Century changes in range and frequency of these forage plants were assessed using data from the New Atlas of the British and Irish Flora (1930–1969 to 1987–1999) and the Countryside Surveys of Britain (1978–1998). Forage plants declined in both large-scale range and local-scale frequency between the two survey periods. These changes were of greater magnitude than changes in other native plant species, reflecting serious reductions in quality of foraging habitats for bees as well as a general decline in insect-pollinated plants. Seventy-six percent of forage plants declined in frequency within 1-km squares, including those (e.g. Trifolium pratense) of particular value for threatened bumblebee species.