A horsewoman from Hundleton is warning of the dangers of sycamore seeds after one of her ponies died suddenly after eating them this week.

In 50 years of looking after horses Sue Scourfield, of Pembrokeshire Riding Centre, said this is the first time she has come across a case of poisoning by sycamore seeds.

If eaten it can cause a condition which attacks the horse’s nervous system call Atypical Myopothy.

There has been a marked increase in seeds – known as ‘helicopters’ – this season following a good summer and they can be extremely dangerous for horses. It is thought that high winds and wet weather has dispersed the seeds over wider areas than usual.

Sue was shocked at the speed in which her two and half year-old Highland pony Ghillie became ill, with a vet having to put him to sleep within 48 hours.

“I’ve never seen anything like this before. This is very quick and it’s lethal,” said Sue “People are very unaware of it. We’ve never come across it before – we’ve grazed the same fields for 35 years.

“He looked a little bit less lively on the Sunday but didn’t look ill but by Monday morning he couldn’t move, he was rooted to the spot. We couldn’t move him from the field so the vet attended and straight away gave him an injection of anti inflammatory, pain killers and fluids, all things to try and preserve life.

“Apparently one horse could eat just two or three of the helicopters and it will kill them but other horses seem to be able to eat more. It seems to be a particularly bad year this year,” said Sue.

Horse owners are recommended to move horses out of fields where sycamore seeds may be a problem or sweep up the leaves and helicopters if possible.

“We are surrounded by sycamore trees – 40 acres – it’s just not possible so we have brought all the horses in and someone has let us use some grazing away from the trees. Unless you are incredible lucky and check within five or six hours of them eating it there don’t seem to that many treatments.

“We are crossing fingers and toes that the others are ok and are watching them closely,” she added.

The Farmers’ Union of Wales has also issued a warning about sycamore seeds and said the number of cases had increased significantly over the past year.

It is warning owners to vigilant for any signs of muscle weakness or stiffness, colic like symptoms, sweating or trembling which could be symptoms.

Early diagnosis can meant that treatments such as the ones received by Ghillie can help in recovery but deputy director of agricultural policy Rhian Nowell-Phillips said that there is no cure and the mortality rate is more than 75 per cent.