Forest Pests: Insects, Diseases & Other Damage Agents

Pityogenes chalcographus

Translation of French document (Jean-Pierre Renaud)

Pityogenes chalcographus is a small (2-3 mm) bark beetle. Adults have a bicolor aspect; with their thorax being black; and their elytra reddish brown. The elytra declivity of the males has three spines that are bigger than those of the females.

Life cycle

Norway spruce (Picea abies) is the preferred host of Pityogenes chalcographus. Nevertheless, Fir, Douglas-fir, pine and other spruce species could also be attacked. This beetle prefers the thin bark of branches and trunk of young trees, but can still be found on older trees in association with the European spruce bark beetle.

Initial adult flight takes place in spring during the first warm days (only a few consecutive days with temperature higher than 18-20°C are required). Pityogenes chalcographus is a polygamous species. Male bores a mating chamber within the bark, where he is joined by 3 to 7 females. Once fecundated, each female bores a gallery underneath the bark. Eggs are laid alternately along opposite sides of the gallery. Newly hatched larvae mine outward and perpendicularly to the main gallery, creating sinuous galleries which are widening out and ending in a nymphal chamber.

The annual life cycle largely depends on local climate: in the French plain locations, two generations per year are usually occurring, whereas at higher altitudes, only one generation can be observed. Flights are occurring all year long, from early spring to October, whenever meteorological conditions are suitable (no rain and temperature warmer than 20°C). Therefore, at a given time, individuals from different generations can be observed.

Damages

Pityogenes chalcographus normally concentrates on weakened and unhealthy trees. However, during drought periods, it can cause significant damages to young stands, and could become more aggressive wherever windthrown trees or large stocks of attractive logs are left in the forest.

Attacks of Pityogenes chalcographus on spruce are usually associated with those of the European spruce bark beetle. Both beetles cause tree death by the destruction of the sap conducting tissues.

External evidence of infestation

1st picture: Typical galleries underneath the bark: Star shaped egg gallery (3-7 arms; length = 2-7 cm; width = 0.8-1 mm)

2nd picture: if massively attacked, a tree can turn from yellow to completely reddish.