Borkenkäferkatastrophe 2003: Vier Borkenkäfergenerationen in Süd- und Ostösterreich

bark beetle - infested tree

Ips typographus with fresh frass

Frass in a cobweb at the stem base

fresh bore hole

The extremely long drought period of the summer 2003 was responsible for the alarming mass outbreak of bark beetle in Austria. Preliminary estimations suggest an increase in the number of freshly infested trees followed by disturbances in the Federal Provinces of Lower Austria, Upper Austria, Styria and especially in the Burgenland. The insect-damaged wood is expected to reach similar quantities as in the year 1992.

Bark beetle-homepage

What are the causes for the bark beetle explosion?

- High initial infestion with bark beetle in secondary spruce forests in the plains. Generally, small beetle nests are the departure points for enormous beetle populations.

Damages by storms (wind throw and wind break) as a consequence of the Föhnstorm in November in Salzburg, Styria and the Tyrol.

- Ideal conditions for the development of bark beetle breeds have led this year to 4 instead of normally 2 (3) full bark beetle generations:

First flight peak beginning of May,

Second one end of June/beginning of July,

Third one in the second week of August and

Mid to end of September there will be again a beetle flight in the plains.

Due to the prevailing drought, even visibly "vital" spruce trees with healthy looking needles are no more in a position to defend themselves by resin flow against the beetle boring trials.

Due to the high temperatures and the lack of precipitation beetle attacks are no more limited to south exposed marginal trees but they are spread all over the forest stand as even there trees are weakened due to water shortage. Trees exposed to the sun may even be avoided as bark temperatures are much too high for bark beetles.

Control measures

Due to the enormous number of freshly attacked trees it must be stressed that the immediate removal of these trees from the stands or barking has utmost priority. These trees show on the entire stem fresh, brown boring dust despite green foliage.
Trees showing wilted or brown needles are already dead due to beetle infestion. Most of the beetles have already left the host trees (numerous emergence holes). In case of any remaining light brown young beetles those trees have to be removed. Barkening alone would not kill the young beetles.
As in addition to the Ips typographus also Pityogenes chalcographus occurs in mass, infested twig material and logging debris has to be treated. This is best achieved by chipping with mobile machines. Laying out heaps of twigs at sun exposed sites favours quick drying of wood and hinders that the beetle brood hatch.

Bark beetle calamity 2003: four generations of bark beetles in South and East Austria
Krehan H.	German
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