Dendroctonus armandi (Tsai & Li) - Large pitch tube bark beetle

Coleoptera: Scolytidae

IDENTIFICATION

Adults are cylindrical beetles that are 3.5 to 6.8 mm long.⁶² Newly emerged beetles are initially light-yellow but gradually become light-brown, black-brown and finally black upon maturation.⁶²

HOST TREES

Pinus.^{62, 101}

LOCATION OF INFESTATION WITHIN THE TREE

Larvae feed on the inner bark along the lower three-quarters of the bole.⁶²

HOST CONDITION

Healthy or recently felled trees, greater than 30 years old are attacked.⁶² Outbreaks generally initiate in pine forests growing in nutritionally poor, steep, dry sites, with thin soil layers.^{62, 69} This insect prefers to attack trees growing in sparsely stocked forests and trees growing on southern aspects.⁶²

DISTRIBUTION

Central China (Gansu, Henan, Hubei, Shaanxi, Sichuan and Yunnan provinces).^{62, 69, 106}

SIGNS AND SYMPTOMS

Adult females mine monoramous, longitudinal egg galleries that are 10 to 60 cm long (30 to 40 cm average).⁶² Females lay eggs in niches on both sides of the egg gallery.⁶² The average distance between egg niches is 8 mm.⁶² Larval galleries are perpendicular to the egg gallery and are usually 2 to 3 cm long, but may reach lengths up to 5 cm.⁶² Elliptical pupal chambers are formed at the end of larval galleries.⁶² Maturing beetles feed within the pupal chamber, greatly enlarging it and increasing the damage to the phloem tissue.⁶²

Evidence of attack includes red to grey-brown pitch tubes (10 to 20 mm in diameter), reddish frass around entrance holes on the trunk, loose frass in bark crevices and fading of the foliage from yellow to yellow-brown.^{62, 65, 67} Trees girdled by larvae will eventually die.⁶²

A - Adult D. armandi (3.5-6.8 mm long).

B - Pitch tubes on host tree attacked by D. armandi.

C - Pitch tube surrounding the entrance hole of D. armandi.

D - Drawing of D. armandi egg (10-60 cm long) and larval galleries (2-3 cm long).

Photo credits

• A Klaus Bolte, Natural Resources Canada, Canadian Forest Service
• B Zhang Zheng, Research Institute of Forest Protection, Chinese Academy of Forestry
• C Zhang Zheng, Research Institute of Forest Protection, Chinese Academy of Forestry
• D Drawing from Li, K. and J. Zhou. 1980, Forest Insects in China, Chinese Forestry Press