Sub-lethal effects of imidacloprid on bumblebees,Bombus terrestris (Hymenoptera: Apidae), during a laboratory feeding test

Abstract

A laboratory feeding test was conducted on queenless micro-colonies of three bumblebee workers (Bombus terrestris L) to study the effects of low doses of imidacloprid on pollen and syrup consumption, worker survival, brood size and larval development. Two doses were used: D1 = 10 mg AI kg À1 in syrup and 6 mg AI kg À1 in pollen; D2 was 2.5 times higher in syrup and 2.7 higher in pollen. During 85 days 27, 30 and 29 micro-colonies were reared for control, D1 and D2 treatments respectively.Food consumption was not affected by either dose. During the 5-day pre-oviposition period the mean insecticide intake was 4.8 ng per day per worker in treatment D2. Both doses slightly but signi®cantly affected worker survival rate by 10% during the ®rst month, without any dose-effect relationship. Brood production was signi®cantly reduced in D1 treatment and larval ejection by workers was signi®cantly lower in D1 and D2 than in control. No signi®cant effect of D1 and D2 treatments on the duration of larval development was revealed. No residue could be detected in workers still alive after 85 days.It was concluded that the survival rate and reproductive capacity of B terrestris was not likely to be affected by prolonged ingestion of nectar produced by sun¯ower after seed-dressing treatment with imidacloprid (Gaucho), since honey or pollen collected by honeybees foraging treated sun¯ower never revealed concentrations of imidacloprid higher than 10 mg kg À1 .

Herbivore Defence Compounds Occur in Pollen and Reduce Bumblebee Colony Fitness

“…We have found that split colonies tend to be more successful than worker-founded microcolonies not provided with brood (e.g. as used by Tasei et al (2000)) and produce new brood more quickly. Each microcolony was randomly allocated to one of the four D-lupanine concentration treatments.…”

“…However, one must consider that pollinators are also herbivores, and exposure to some secondary compounds in nectar affects adult pollinators (Wright et al 2013), sometimes in similar ways to the effects of insecticide exposure via pollen or nectar (Bryden et al 2013;Tasei et al 2000). Few studies have examined the effect of naturally-occurring plant compounds in the larval food of pollinators, or determined how larval feeding may impact on offspring production or fitness, i.e.…”

The neonicotinoid clothianidin interferes with navigation of the solitary bee Osmia cornuta in a laboratory test

“…Residue intake has been estimated to range from 4.27 to 13.65 ng per bee day −1 (Authority, 2013). Similar doses during chronic exposure to a different neonicotinoid (imidacloprid) were used by Tasei et al (2000), who found in bumblebees reduced survival of workers and less brood production. Rundlöf et al (2015) found 6.7-16 ng ml −1 clothianidin in the nectar store of honeybees foraging in oil rape fields that grow from seeds coated with clothianidin.…”

Risk assessment for side-effects of neonicotinoids against bumblebees with and without impairing foraging behavior

“…Moreover, the risks as scored in the behavior test agree with experiments by other investigators in bumblebees and also in honeybees. Tasei et al (2000) reported in B. terrestris colonies a loss of 10% in worker survival and a significant decline of about 40% in the numbers of adults produced upon exposure to imidacloprid at 6-10 ppb in the syrup and pollen. Similar sublethal effects were also seen in other bumblebee species like Bombus occidentalis and Bombus impatiens: exposure to 30 ppb imidacloprid had a significant negative effect on the foraging rates (Morandin and Winston 2003).…”