Bark Beetle Situation in Austria’s Forests
The favourable weather resulted in an alarming increase of the bark beetle population in Austria. The forest owners are called upon to remove the infested wood from the forest as quickly as possible.
The prophylactic and combating measures already initiated are associated with an increase in domestic wood production. However, there is absolutely no reason for panic as it is sometimes instigated by some daily news media. According to surveys by the Federal Office and Research Centre for Forests and the provincial forestry services, the current extent of damage is under prognose. Even if this means disaster for the individual forest owner concerned, it is nonetheless of a magnitude that the market can cope with easily and that does not give rise to market problems.The main causes of this bark beetle explosion are the high bark beetle base populations in low-standing secondary spruce forests. Currently, small beetle nests are usually the starting point for gigantic beetle populations. Storm damage (wind-throw and breakage) as a result of the last foehn storm. As a result of ideal conditions for the bark beetle broods, 4 instead of the usual 2 (3) complete bark beetle generations will grow this year. The beetles will fly again in the low stands from the middle to the end of September. And the problem will not be over with the onset of cold weather this year. Next spring the bark beetle will again start out with a high population. The difficult situation will continue for some years, even if the weather returns to normal again.
The bark beetle is the most dangerous forest pest in our region. To be precise, it is not just one species, there are some 120 species of bark beetles. The most harmful to our domestic spruce trees is the so-called “printer beetle”, but the “copper engraver” also causes considerable damage. Normally, the beetles infest mainly diseased trees, but newly fallen trees with a bark that is still intact are also particularly attractive.
Within the shortest time, a tree can be completely infested with bark beetles. In the live bast beneath the dead bark, the beetles and their larvae create typical feeding tunnels that also give the printer beetle (Ips typographus) and the copper engraver (Pityogenes chalcographus) their names. As a result of destruction of the conductors in the bast that transport assimilates, the tree dies as a result of severe infestation.
As a result of the prevailing drought, even apparently vital spruces with dense needles are no longer able to fight of the beetles’ attempts to penetrate their bark by secreting more resin. Due to the high temperatures and lack of precipitation, these beetle attacks are no longer limited to trees with southern exposure, but have spread throughout the entire forest stand as a result of the trees being weakened and suffering from lack of water.
Due to the enormous number of newly infested trees, the supreme principle of the fight to prevent a further spread must be to remove these trees from the stands or strip their bark as quickly as possible. The infested trees display fresh, brown sawdust all over their trunks, but their needles are still the normal green.
Trees with yellowing or brown needles have already been killed by the beetle infestation. Most of the beetles have already left these host trees (numerous holes). If there are still light-brown young beetles in these trees, these trees must also be removed. Stripping the bark would not kill off the young beetles. The important thing is also to remove the surrounding green trees that do not appear to be infested.
Since the copper engraver, like the printer beetle, occurs in masses, infested branch material and logging waste must also be treated. Here, shredding with mobile machinery is the most suitable option. Piling wood in locations exposed to the sun also promotes rapid drying of the wood and thus prevents the beetle broods from maturing.
In addition to the economic impacts for the forest owner, the fact that the extreme infestation of spruce forests in low and medium stands can result in a loss of all the forest functions and in particular the protection function in these regions must be regarded as a major problem. Therefore, reforestation of these areas must be oriented towards the natural forest communities with a view to the comprehensive and sustainable safeguarding of all forest functions.
The Ministry, together with the forest supervision officers of the provinces and the consulting institutions of the provincial Chambers of Agriculture are developing effective immediate measures and strategies to solve the acute forest protection problems. The priorities are to remove the infested trees as quickly as possible before the end of autumn, preventive actions as of spring, and the promotion of reforestation with mixed tree species in accordance with the natural forest communities.
Further information is available from the experts at the Federal Office and Research Centre for Forests and the provincial forest inspectors.
21.04.2010,