Pests and diseases of interest

Whilst Observatree focuses on 21 different priority pests and diseases there are many others out there just as threatening and important. We'd like to raise your awareness of the following so that you can help keep an eye out for these whilst at work or leisure.  If you believe you have spotted a tree pest or disease double check signs and symptoms using our resources and report via Tree Alert or TreeCheck in Northern Ireland.

Dutch elm disease

  • Targets: elm
  • Spread by elm bark beetles
  • Symptoms first appear early summer
  • In the 1960’s England suffered an epidemic outbreak
  • 1n 1985 it was estimated that 30 million elms had died in Britain from the disease

Brown spruce longhorn beetle

  • Targets: spruce
  • Adults are 8-18mm long
  • Believed to target trees already ‘stressed’ by other factors
  • Known to be in Great Britain, mainly reported in Scotland
  • Establishment across the UK seen as ‘very likely’ due to climate and hosts

Pine looper moth

  • Targets: pine (mainly scots pine)
  • Adult moth wingspan is 28-35mm
  • Defoliates and weakens trees leaving them susceptable to attack
  • Large numbers cause serious economic damage to trees
  • Most common in Scotland, found occasionally in Britain

Pine beauty moth

  • Targets: scots pine (most damaging on lodgepole)
  • Caterpillars have distinct orange stripes on either side
  • Adult moth wingspan is 30-33mm
  • Flies in March and April
  • Most common in Northern Scotland, found occasionally in Britain

Pine sawfly

  • Targets: pine
  • Larvae live in large colonies of 60-100
  • Adults reach 10mm, more closely related to bees, ants and wasps
  • Heavy infestations can considerably defoliate trees
  • Egg clusters can be seen laid within the previous year's needles

Gypsy moth

  • Targets: Broadleaf tree leaves and shrubs
  • Large caterpillars have distinct blue and red spots on the body
  • Larvae disperse in the wind on silk threads (‘ballooning’)
  • Heavy infestations can considerably defoliate trees
  • Repeated attacks can cause tree death

Phytophthora ramorum

  • Targets: numerous trees and shrubs (larch, sweet chestnut, rhododendron, beech)
  • First found in the UK in 2002
  • In many cases the spread to larch may have come from infected rhododendron
  • Spore movement is easily spread over several miles in mists, air currents, watercourses and rain splash
  • Symptoms include lesions/bleeding cankers - extensive trunk lesions cause tree death

Xylella fastidiosa

  • Targets: economically important crops, woody commercial plants (eg olives), broadleaf trees and herbaceous plants
  • Not currently present in the UK but high risk of possible accidental introduction
  • Restricts and blocks water and nutrients from plants
  • Spread occurs from movement of plants or insects feeding on plants’ xylem fluid
  • Symptoms are leaf scorching, dieback and tree death