Almost all living creatures require sleep in some form to function properly, and insects are no exception.
But new research warns exposure to a common insecticide, banned in the EU but set for reintroduction to the UK, impacts the sleep of bumblebees and fruit flies, and “may help us understand why insect pollinators are vanishing from the wild”.
Following pressure from the National Farmers’ Union, the UK is now set to allow the use of neonicotinoid insecticides, which were effectively banned in 2018 after numerous studies linked their use with a range of impacts on bees, as well as loss of birds due to a reduction in insect populations.
Two similar studies by academics at the University of Bristol allowed researchers to look at how the insecticide affected fruit flies’ and bumblebees’ brains.
Dr Kiah Tasman, from the university’s School of Physiology, Pharmacology and Neuroscience and lead author of both studies, said: “The neonicotinoids we tested had a big effect on the amount of sleep taken by both flies and bees.
“If an insect was exposed to a similar amount as it might experience on a farm where the pesticide had been applied, it slept less, and its daily behavioural rhythms were knocked out of sync with the normal 24-hour cycle of day and night.”
The fruit fly study found typical agricultural concentrations of neonicotinoids ruined the insects’ memories and the researchers also saw changes in the flies’ brains which also meant their 24-hour cycle became unpredictable.
Dr James Hodge, associate professor in Neuroscience in the School of Physiology, Pharmacology and Neuroscience and senior author for the study, said: “Being able to tell time is important for knowing when to be awake and forage, and it looked like these drugged insects were unable to sleep.
“We know quality sleep is important for insects, just as it is for humans, for their health and forming lasting memories.”
Dr Sean Rands, of the School of Biological Sciences and co-author, said: “Bees and flies have similar structures in their brains, and this suggests one reason why these drugs are so bad for bees is they stop the bees from sleeping properly and then being able to learn where food is in their environment.
“Neonicotinoids are currently banned in the EU, and we hope that this continues in the UK as we leave EU legislation.”
In 2018 the UK government supported the EU restrictions, and then environment secretary, Michael Gove, promised the government would maintain the rules unless the scientific evidence changed.
The decision to overturn the ban despite no new evidence of their safety emerging has alarmed wildlife organisations which have warned the impacts of the poison’s use is far-reaching as it not only kills the aphids and other small insects it is aimed at, but is absorbed into the soil where it kills wildflowers, and is washed into waterways where it can harm thousands of species.
Dave Goulson, a professor of biology at the University of Sussex, has warned one teaspoon of neonicotinoid insecticide is enough to kill 1.25 billion honeybees, equivalent to four lorryloads.
A government statement announcing how the insecticide will be authorised, said: “After careful consideration of all the issues, the government has decided to grant an application for emergency authorisation to allow use of a product containing the neonicotinoid thiamethoxam for the treatment of sugar beet seed in 2021.”
In response, the Wildlife Trusts said the proposed method of application “results in only 5 per cent of the pesticide going where it is targeted, in the crop. The rest ends up accumulating in the soil.”
The organisation added: “The authorisation also proposes adding weed killer to sugar beet fields to ‘protect’ bees by killing wildflowers that grow alongside the sugar beet - because beneficial ‘weeds’ will have absorbed neonicotinoids through the contaminated soil. Doing so would seriously harm already-threatened populations of wildflowers and the insects that depend on them.”
The NFU has said it has been “actively lobbying” to have the ban lifted, and said not doing so “will bring costs for the supply chain and the risk of unintended consequences for the environment.”