Hickory bark beetle (Scolytus quadrispinosus (Say.)) L. Tucker

L. Tucker, E. Czerwinski, T. Scarr
Ontario Ministry of Natural Resources, Forest Health and Silviculture Section
Background
The native hickory bark beetle is considered the
most destructive pest of hickories. Like other
bark beetles native to Ontario, it is attracted to
trees previously weakened by other factors such
as drought. Hickory is an important forest
ecosystem component in southern Ontario. This
insect attacks and kills hickory trees and has
been a serious forest health issue in recent
years.
Hosts
In Ontario, hosts are primarily bitternut hickory,
Carya cordiformis (Wangenh.) and shagbark
hickory, Carya ovata (Mill.). Elsewhere, pecans,
Carya sp., and butternut, Juglans cinerea (L.) are
also attacked.
Current Situation
The recent population increase of hickory bark
beetle in southern Ontario is likely linked to the
drought conditions experienced in 2001, 2002
and 2005. The hickory bark beetle tunnels in the
bark and sapwood of hickory trees which can
cause rapid decline in tree health. Larval galleries
(Figure 1) in the main stem and large branches
disrupt the host tree’s ability to transport
nutrients and water. Heavy shoot damage and
foliage feeding by adults severs the leaves and
twigs which hang or drop to the ground.
Range
Hickory bark beetle occurs throughout the
natural range of hickory, Carya sp. (Figure 2).
HICKORY BARK BEETLE
Scolytus quadrispinosus (Say.)
Figure 1 Hickory bark beetle larval galleries.
Figure 2 North American range of hickory species
(Map courtesy of the USDA).

FOREST HEALTH ALERT – HICKORY BARK BEETLE June 2006
Description
Adults are short (4 to 5mm long), stout,
cylindrical, and dark brown to black (Figure 3).
Larvae are short (5 to 8mm long), curved,
and yellowish-white, legless with a wrinkled
appearance. Pupae are compact and white.
Eggs are not usually visible to the naked eye.
Figure 3 Adult hickory bark beetle with exit holes.
Life Cycle
Adult beetles emerge from tiny round exit holes,
roughly 3mm in diameter (Figure 4), May to
August and begin feeding in the crown at the
base of leaf petioles and twigs. Once mature,
adult females are attracted to weakened trees
where they bore into the bark of the main stem
and branches. Here they construct vertical
galleries in the phloem and deposit between 20
to 60 eggs. Newly hatched larvae feed just
beneath the bark, in individual feeding galleries
radiating from the original egg gallery
constructed by the adult female. Larvae
overwinter under the bark at various stages of
development.
Figure 4 Adult exit holes.
Figure 5 Thinning hickory crown.
Signs and Symptoms
Signs and symptoms include: thinning crown,
wilted leaves (Figure 5), dead twigs and limbs,
leaf yellowing and premature dropping of leaves,
epicormic shoots, hanging (broken) twigs in
crown, tiny borer holes approximately 3mm in
diameter (Figure 4), fine boring dust on bark and
at base of tree, presence of parasitic wasps
around host tree, and an increase of woodpecker
activity on host tree. Foliage of heavily infested
trees turns yellow then red within a few weeks.
Management and Control
Once infested with the hickory bark beetle, a
tree usually dies rapidly. Preventative measures
include maintaining healthy, vigorous woodlands
by following Best Management Practices outlined
in the Extension Note: Do You Have a Healthy
Woodlot? It is available on-line at:
http://www.lrconline.com/Extension_Notes_
English/pdf/hlthywdlt.pdf.
For additional copies of this publication contact
the Ontario Ministry of Natural Resources
Information Centre at the number listed below.
2
FHA-1-2006