Spring worm warning as 2026 Nematodirus forecast goes live

A potentially costly spring parasite threat is looming for lamb producers as the 2026 Nematodirus Hatching Forecast goes live.

The Sustainable Control of Parasites in Sheep (SCOPS) group has launched its updated online tool, designed to help farmers judge if — and crucially when — lambs may need treatment to avoid losses.

Heavy Nematodirus infections can cause severe scour, dehydration and rapid setbacks in young lambs, with the risk heightened if a sudden ‘mass hatch’ catches flocks off guard.

Kevin Harrison, SCOPS chair and South Gloucestershire sheep farmer, said the forecast has become a key part of seasonal flock planning.

“This free online tool has proved to be an invaluable resource for many producers, vets and advisers for a number of years,” he said.

“For 2026 we have made some improvements, which we hope will make it even more helpful when deciding if, and when lambs may need a treatment.”

Nematodirus battus behaves differently to most other worm species. Eggs passed by lambs the previous season overwinter on pasture and hatch the following spring once air temperatures rise above 10°C.

Independent sheep consultant Lesley Stubbings warned that when conditions align, hatching can happen rapidly.

“Nematodirus battus, the parasite that causes nematodirosis, can be a tricky call for sheep farmers because it has a different lifecycle to other worms,” she said.

“If this happens, we can see a ‘mass hatch’ and farmers must act quickly to avoid losses in groups of vulnerable lambs.”

Timing can vary significantly from year to year, sometimes by several weeks, making close monitoring essential.

“The Hatching Forecast provides warning of when this is likely to occur and because this can vary by several weeks between years, the forecast is an essential tool,” Ms Stubbings added.

The interactive forecast map is updated daily using data from 140 weather stations across the UK. Users can select their nearest station and assess risk through a colour-coded warning system, alongside guidance on management and treatment options.

For 2026, the tool has been enhanced with clearer visual indicators, additional guidance beneath each warning symbol and a new symbol shape to indicate when peak hatching has passed. A short explainer video and links to more detailed advice have also been added.

SCOPS advises producers to carry out a risk assessment of lamb groups before consulting the forecast, ensuring treatments are targeted rather than routine.

A recent webinar covering how to use the forecast, alongside background on Nematodirus and practical case studies, is available online.

With lambing under way across much of the country, early awareness and timely action could prove critical in preventing avoidable losses this spring.

The SCOPS Nematodirus Forecast is supported by Bimeda and Techion (FECPAK).