Pests, Diseases & Ivy

Trees can suffer from a range of pest and disease problems which can seriously weaken or kill them. In many cases pest and disease are often the results of poor planting selection or practice or where a tree has suffered construction injury within the last ten or more years. Maintaining a trees’ vigour, for example, by avoiding close regular mowing under the canopy and the judicious use of good mulch will often prevent the premature onset of pest and disease problems.

Honey fungus (Armillaria mellea) is probably the best known and most feared of all tree diseases and is incurable. It is both a pathogen (disease causing), which can quickly kill a tree and a decay agent which can, in time, cause instability and may result in the tree falling over. Prevention is better than cure through good hygiene prior to planting, selecting resistant species, avoiding irrigation and excessive fertilisation after establishment and the use of good quality mulch.

Goat moth (Cossus cossus) larvae attack already weakened trees and is a common pest in Guernsey. The grubs or larvae reach tunnel their way through the stems of trees and can cause weakening of the tree to such an extent they become hazardous

There are many other pest and diseases which affect trees. For more information or advice contact

Ivy on trees seems to be a much talked about and, at times, controversial subject. Many people believe that ivy kills trees and should be removed in every situation. Others believe in non intervention because ivy is a valuable habitat and food source for wildlife. The recommended approach is as always somewhere between these two extremes.

The facts about ivy:

Ivy is not parasitic on the tree – it merely uses the tree as a support to climb up

Ivy is often a symptom of problems not a cause of them.

Generally ivy should only be killed or controlled in trees growing near risk areas eg roads, properties, playgrounds, well used footpaths where you need to manage risk accordingly. In most other situations ivy can be left or at least managed so it can provide a source of pollen and nectar early in the year.