LANDOWNERS and conservationists are warning of the dangers of ragwort, a plant fatal to horses which is spreading because of the dry summer.

Wilf Dimsdale, chairman of the Hertfordshire Country Landowners Association whofarms near Buntingford, said: "It causes liver failure but remains undetected until it has done irreversible damage.

"It affects horses most of all, but also sheep and cattle as well as rodents and invertebrates.

"This is why draconian measures are in place to require the occupiers of land to control it.

"Defra can serve enforcement notices but a glance at our highways and byways will tell you that this is not being done.

"There are vast amounts of ragwort alongside roads, particularly motorways and dual-carriageways and along railway lines.

"It takes only one individual - one landowner, one utility company, one highway authority, one horse owner - to fail to deal with the weed and they will create appalling problems for everyone else.

"Ragwort may appear attractive and even add a splash of colour to verges, but it is a killer weed that spreads across the countryside like wildfire, causing serious problems for animal owners.

"It's no good just pulling it up - the dead plants are just as deadly.

"The authorities need to act now and I ask everyone to report it when they see it."

Defra minister Barry Gardiner has said that controlling Ragwort has to be done in a balanced way, as it is a valuable food plant for the caterpillars of the cinnabar and four-spotted burnet moth.

The caterpillars feed on the noxious weeds as the toxins they ingest make them unpalatable to birds.

But a spokesman for the St Albans-based Hertfordshire and Middlesex Trust, which always removes ragwort from its reserves, advised other landowners to do the same.

She said: "It does cause liver damage to horses, particularly if it gets mixed with hay.

"It should be handled with gloves.

"Ragwort does have wildlife value, but the cinnabar moth caterpillars can also feed on groundsel, a very common weed."

Ragwort along Hertfordshire roads should be reported to the county council or the Highways Agency.

Landowners who fail to remove it can be reported to Defra on 08459 335577.