I WAS carrying out a routine inspection of pathside trees the other day, checking for broken limbs or diseased or dying individuals that may become dangerous.

Along one particular trail I noticed a tangle of recently fallen elms. There must have been four. Once these were pulled to the ground, I walked a little further, only to find more of the same.

The trees where all around the same age and height, an obvious indication of them being infected by the fungi Ophiostoma novo-ulmi, or Dutch Elm disease. The disease affects the outer growth ring of the tree, essentially starving it of water. Eventually they become brittle and can fall quite easily.

Why is the height of the trees so important? The fungi is transported between host trees by the Elm bark beetle. The insect lays its eggs under the bark of dying elms. When the larva hatch they feed on the decaying wood, creating a network of tunnels. These passages are the perfect place for the spores of the fungi that cause dutch elm disease to propagate.

Once pupated, the adult beetles leave their tree and fly to a healthy elm to feed on living bark, thus spreading the fungi to healthy trees. The trees of choice are those that are around, or over the four metre tall mark. Hence, affected specimens appear to be of about the same age.

The beetles are native to the UK and have been feeding on elms for tens of thousands of years and they have done so without causing death to the tree. Indeed they have always carried and spread a form of fungi, but it was a relatively harmless type until the 1960s when the more virulent Ophiostoma novo-ulmi arrived, probably from un-quarantined, imported timber from the States. The disease is now widespread and there are only a few free from the disease.

If it where not for the infection, the elm is capable of becoming one of the tallest of our native trees. It was once a much revered tree, and has much folklore surrounding it. Some of this is negative, and probably stems from the fact that timber from the elm was used to make coffins.

However, the elm is also renowned for dropping large limbs, often without warning, and resulted in the death of many weary travellers who rested beneath its crown. It is perhaps a little surprising then that lay preachers regularly selected the majestic elm as a backdrop to their sermons.

The tree also was the timber of choice for medieval Welsh archers to create their bows. It was an excellent material for this as it bends well; the same property however makes it useless as a building material. It also has the ability to withstand moisture.

Luckily, the elm is not totally lost. It produces ‘suckers’ or underground shoots which can produce new trees. Because of this, the tree is still fairly common within our woodlands and as hedge trees, it is however disappointing that it is unlikely we will see another statuesque example on our landscape.