11/11/2026
⚠️ SYCAMORE POISONING: A POTENTIALLY FATAL AUTUMN DANGER TO HORSES 🍂
The HPA would like to remind all horse owners of the potentially fatal dangers of sycamore poisoning, which causes Atypical Myopathy; a life-threatening condition with an estimated mortality rate of over 70%.
Many affected horses die despite intensive veterinary treatment, and horses of all ages and breeds can be affected. Prevention is essential.
Sycamore seeds or "helicopters” contain hypoglycin A, which can cause severe, often fatal, muscle damage in horses. Many UK sycamores are experiencing a mast year after high summer temperatures, producing unusually large numbers of seeds and increasing the risk.
🔎 Know the signs: Affected horses may show sudden weakness, muscle stiffness, trembling, reluctance to move, sweating, or dark brown or red urine. Some horses may initially appear unusually quiet or depressed.
🚨 Atypical Myopathy is a veterinary emergency and can progress rapidly. If you suspect poisoning, contact your vet immediately. Do not force the horse to walk or exercise.
How can you protect your horses?
🍁 Check paddocks regularly for seeds, including those blown in from neighbouring land.
🍁 Avoid grazing where seeds are present. Fencing off the tree canopy may not be enough; seeds can travel at least 500m in high winds.
🍁 Don’t assume a field is safe because it has been used for years. Cases have occurred in horses grazing the same fields for decades.
🍁 Provide adequate supplementary forage and avoid overgrazing, which increases the risk of horses ingesting seeds. Place forage away from areas where seeds may blow in.
🍁 Sycamores vary in toxin levels, and it’s impossible to tell the risk by appearance. Testing is available, but levels can change each year.
🍁 In spring, remove or mow seedlings and keep horses off the area. Where possible, remove seeds in autumn to prevent germination.
🍁 Learn to identify sycamore (Acer pseudoplatanus), which is toxic, and distinguish it from Field and Norway Maple, considered non-toxic. If unsure, take suitable precautions.
Please take a few minutes to check your grazing and share this warning.