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Description

The poplar borer (Saperda calcarata) is a common insect in natural forest stands around Grande Prairie. Adults are large (20-30mm) long-horned, light blue/gray beetles with orange markings.  Larvae are legless, white, and 30mm long.  The most visible sign is the damage they cause to poplar and aspen trees - boring large holes that then weep sap that stain the bark a dark brown.  The larvae remain inside the trees feeding for two to five years before pupating and then emerging as adults to mate and lay eggs.  High populations of this insect may significantly weaken or stress trees, particularly if they are already under drought stress.  Unlike other long-horned beetles, which only attack stressed trees, the poplar borer frequently attacks healthy, vigorous trees.

Poplar Borer

Large bore holes, varnish streaking on bark, and sawdust
at the base of the tree are the most visible symptoms
of poplar borers.

 Poplar Borer Adult

 Adult poplar borer.  Photo courtesy of Marius Aurelian

 Poplar Borer Larva
 Poplar borer larvaePhoto courtesy of forestpests.org.

Plants Affected

Symptoms

The first signs of this insect will be sap weeping down the side of the tree, staining the bark a dark brown color.  Upon closer inspection you will see holes drilled into the bark with sawdust and frass at the entrance.  Heavy woodpecker damage on your tree may also indicate the presence of these borers.

Controls

Cultural (Non-chemical) Controls:

  • Open-growing and lone trees are more susceptible to attack.  Plant trees in shaded locations or in a stand to help them withstand attack more readily.
  • Remove brood trees - trees that are heavily attacked and serve only to infect other nearby trees. 
  • Burn or bury removed trees immediately - larvae will continue to feed  and may complete their lifecycle in stored firewood.

Biological Controls:

  • As this is a native insect, several natural predators and parasites exist to help keep populations in check.
  • They can kill up to 40% of eggs and 65% of larvae in some areas. 

Chemical Controls:

  • Chemical applications to the bark that target newly emerged adults may be effective.  Timing is very important; aim for the first of June.  Repeated treatments may be called for up to August 1 - read and follow label instructions carefully.  

For more information on chemicals available for control of these pests, call Agriculture Canada's Pesticides Directorate in Ottawa (toll-free) at 1-800-267-6315. Chemical pesticides may be toxic to humans, animals, birds, fish, and beneficial insects. Follow all label instructions and precautions listed by the manufacturer.

Last updated: 4/15/2016 7:45:03 AM