Prevention and control of fireblight

The procedures described are equally applicable to organic production and conventional systems.

Fireblight prevention

  • Maintain good disease control in orchard and nursery.
  • Replace nearby hawthorns and susceptible ornamental hosts by non-hosts.
  • Keep remaining hawthorns well trimmed to prevent flowering.
  • Avoid pear and apple varieties which produce late flowers (after the main blossom period) or secondary blossom in summer or autumn.
  • Remove secondary blossom if practical.
  • Do not plant cold-stored trees late, because they may subsequently flower late.
  • Avoid soft shoot growth induced by excessive irrigation, poor soil drainage, or unnecessary use of nitrogen fertilizer.

Fireblight control

  1. Learn to recognise fireblight and distinguish it from other diseases such as Nectria canker (apple and pear), Monilinia blossom wilt (apple) and Pseudomonas blossom wilt (pear).
  2. Make routine inspections at the following time
    • Soon after leaf fall – fireblight-infected shoots do not drop their leaves so are easily visible after leaf fall
    • During winter pruning
    • Soon after bud break – fireblight-infected shoots fail to leaf out
    • About mid-June
    • Late July to early August
  3. Inspect young trees more frquently
  4. Make additional inspections:
    • If there is frost damage to blossom
    • Following damaging storms
    • Following warning of fireblight (some local warnings are issued by East Malling Research via consultants)
    • Following reports of fireblight elsewhere
  5. Limit stem invasion
    • Remove and burn diseased parts of all pear trees and young apple trees as soon as possible.  Cut through healthy wood well below diseased wood to ensure thorough removal.  On mature apple trees this might not be cost effective and is less urgent.
    • On twigs or shoots cut out 12” below stain; on branches (of 1” or more in diameter) cut out at least 18” below stain.
    • Start exploratory knife cuts in healthy tissue first and move up.
    • Mark affected parts of trees with coloured plastic streamers to check the success of control measures later.
    • Disinfect tools between cuts and between trees preferably using a recommended disinfectant (3% Hycolin, Sudol or Clearsol).
    • Thorough removal of plant residues from the tools is essential for maximum effectiveness of disinfectants.

Additional advice:

  • Purchase trees from a reliable source.
  • Avoid planting young trees near hawthorns.
  • Remember that fireblight may be difficult to spot in a hawthorn hedge as only one or a few trees may be diseased.
  • Avoid overhead irrigation as it increases fireblight risk.
  • Avoid pruning young or nursery trees in summer.
  • Summer prune orchards only in dry weather.
  • Cut out diseased parts only in dry weather.
  • Pay particular attention to fireblight warnings if:
    • temperatures are 21oC or more during bloom
    • temperatures during or shortly before bloom are –2oC or less
    • damaging storms occur
  • Check for bark rubbing by tree ties.
  • Limit beehive use.