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Neodiprion nanulus contortae Ross

  • Latin name: Neodiprion nanulus contortae Ross
  • French name:
  • Order: Hymenoptera
  • Family: Diprionidae


Alberta, British Columbia

This species occurs throughout British Columbia; it also occurs in mountainous western Alberta and south to Oregon and Montana.

Damage, symptoms and biology

Neodiprion nanulus contortae is a common colonial defoliator and occasionally reaches epidemic levels causing significant defoliation. A major outbreak covering over 14,000 ha was recorded along the North Thompson north of Vavenby from 1976-78, smaller scale outbreaks occurred near Chilliwack Lake in 1960, Campbell River in 1963, on several outer islands south of Prince Rupert in 1975-76, Nadu Creek on the Queen Charlotte Islands in 1983-84 and on the Winchelsea Islands near Nanoose Bay in 2001.

During outbreaks, some trees defoliated for 2 or more years may be killed or suffer growth loss.

Mature larva up to 21 mm long. Head, brown with black eye spots. Body, green to grey, light green middorsal stripe bordered with darker green subdorsal stripes; spiracular stripe dark bordered by light green supraspiracular stripe and light grey subspiracular stripe. Prepupal larvae similarly marked except brown. Eight pairs of abdominal prolegs.

Overwinters in the egg stage. Larvae feed on foliage of the previous year or older from late May to early July; mature larvae spin cocoons in the duff. A variable percentage of larvae may diapause in the cocoons for 2 or more years. Adults emerge from September to October and lay eggs in slits along the margin of a needle.

Other information

Other Neodiprion species appear similar but feed on different host trees.

Canadian Forest Service Publications

Information on host(s)

The principal host of Neodiprion nanulus contortae is lodgepole pine; it also occurs on ponderosa pine.

Main host(s)

Lodgepole pine, ponderosa pine


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