Tree Killers: Sirex Wasp

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  • Common English name: Sirex Wasp
  • Other names: Sirex woodwasp
  • Latin (scientific) name: Sirex noctilio

Threat type

150x150 insects

History in Canada

  • introduced from Eurasia in wood packing material
  • first detected in New York State in 2004
  • found in southern Ontario in 2005
  • now known also in Michigan and Pennsylvania


  • life cycle takes one to two years
  • adult wasp has a dark body and wings, and orange-brown legs
  • adult size is quite variable: 9-36 mm (3/8-1 ½ in)
  • adults are strong fliers and can travel several kms after emerging
  • female lays eggs in stems along with toxins and a symbiotic fungus
  • larvae are whitish grubs that grow to 30 mm long (1 ¼ in) and have a distinctive tail spike

Impact on Trees

  • attacks living trees
  • prefers Pine, but will also attack Spruce, Fir, and Douglas Fir
  • causes foliage to wilt and turn yellow
  • in the Southern Hemisphere, the wasp has caused 80% mortality of pines where it is established

What can be done to control this tree killer?

  • a parasitic nematode (Deladenus siricidicola) can be used to infect larvae that then develop into sterile females
  • sterile females spread the nematode when they attempt to lay eggs
  • several species of parasitic wasp that are native to North America have been introduced into South America as control agents there and these should help control the wasp here

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