The British Equine Veterinary Association (BEVA) is calling for renewed vigilance to prevent outbreaks of a fatal horse disease.
BEVA says at this time of year while trees are in full leaf and the seeds clearly visible, it should be easier to identify sycamore seeds and take steps to minimise the risk of horses eating them.
SPM is an often fatal muscle disease in horses that, until recently, was of unknown origin. Research in 2013 and 2014 showed it to be caused by the toxin hypoglycin A contained in tree seeds, including that of the sycamore.
High winds last autumn resulted in considerable contamination of pastures with sycamore seeds and saw veterinary practices across the UK managing large numbers of horses with the condition. Data from the National Equine Health Survey showed a four-fold increase in cases last year.
Horses that develop SPM are usually kept in sparse pastures with an accumulation of dead leaves, dead wood and trees in or around the pasture and are often not fed any supplementary hay or feed.
While the seeds may not be directly palatable, horses grazing on poor-quality pasture may ingest considerable numbers of them.
Horse owners are advised to identify sycamore trees on or near grazing land and take steps before the autumn to prevent the seeds falling where they are in reach of horses.
BEVA president-elect Mark Bowen said the association was urging horse owners to try to reduce the impact of this devastating condition.
“We would urge horse owners to resist the natural urge to fell trees, since doing so can lead to massive pasture contamination further increasing the risks to their horses,” he said.