‘Slug sleuth’ farmers in England help develop prediction tool to cut back on pesticide use

Maps created as part of Defra-funded Slimers project allowed test growers to halve amount of slug pellets used

Farmers believe they have a new weapon in their age-old battle against the slugs that destroy their crops: modern technology.

Slug prediction maps, which have been created by computer models as part of a research project, are now helping growers to better target the use of pesticides, saving them money and reducing environmental harm.

Slug damage is not just frustrating – as many gardeners will attest to – but it is also expensive for arable farmers, with damage to wheat and oilseed rape crops estimated to cost almost £44m a year in the UK.

The gastropod mollusc grazes on the young leaves of emerging cereal crops and has been known to eat barley, oat and wheat seeds. Slugs also damage potatoes and can have a huge impact on vegetable crops, as whole fields sometimes have to be abandoned if there are signs of an infestation.

The monitoring work is being carried out as part of the entertainingly named Slimers project – which stands for strategies leading to improved management and enhanced resilience to slugs.

The three-year, £2.6m scheme, which began in 2023 and comes to an end in late August, is funded by the Department for Environment, Food and Rural Affairs and led by the British On-Farm Innovation Network.

A team of 28 “slug sleuth” farmers were recruited to work alongside scientists to increase understanding of the invertebrates’ behaviour by setting up traps – large plastic saucers – on their land. The information collected was fed into a computer model, and an algorithm was used to predict where the slugs would be found in arable fields, while soil samples were also taken.

The resulting slug prediction maps were tested by 16 farmers over the past autumn and winter, and have already helped them to halve the amount of slug pellets they need to use to control the pests.

Charles Paynter, a farmer in Bedfordshire who was involved with Slimers from the start, has already cut back on his use of pesticides.

“My threshold for taking control measures is higher now because I have been able to prove to myself that I can evaluate the risks from slug activity with greater accuracy,” he said.

The chemical metaldehyde, which was commonly used in slug control products in the UK, was banned in 2022, resulting in the increased use of ferric phosphate pellets. There is, however, appetite for alternatives to pesticides.

Prof Keith Walters and a team from Harper Adams University created the slug prediction model. He said they were now confident that it worked.

“We already knew that slugs didn’t occur randomly across fields, but that they form distinct patches according to soil type and climatic conditions,” Walters said.

“The slug sleuths’ data of slug populations across their fields helped us develop that understanding further and allowed us to confirm our hypothesis about how slug patches re-form after waterlogging.

“In waterlogged soils, [slug] patches become unstable and break down, but we have now confirmed that patches re-form temporarily in places we wouldn’t expect in normal conditions and then quickly return to their predicted areas once more typical soil conditions return.”

Another part of the Slimers project has been working to develop slug-resistant wheat varieties. Scientists have identified three areas of the wheat genome that are responsible for resistance to the grey field slug, and it is hoped this finding will pave the way for plant breeders to develop new varieties that will not be damaged by what farmers call one of the most persistent pests.