Experience following storm calamities of the last decades has shown that forest protection problems – mostly bark beetle calamities - always follow such events. The rise in bark breeding insect populations is usually followed by a proliferation of wood breeding species. Though secondary damage after storm events can not be avoided completely, it can be considerably influenced.
- Emphasis on prevention
- Combination of silvicultural, biological, mechanical/technical and chemical measures
- Utilisation of all ecological effects
- Minimise insecticide demand by tapping the full potential of all non-chemical methods.
Insecticides should only be used if all other means to avert damage are exhausted and extensive damage is expected. In certified stands, application of insecticides may possibly be ruled out. Integrated Forest Protection encompasses three different goals. They have to be distinguished clearly when planning protection measures:
- Prevention (Prophylaxis): Measures to minimise the risk of damage occurring (e.g. 'clean' forestry practise, close-to-nature silviculture). In the event of storm calamities, this refers to the chosen strategy and/or succession of salvage logging.
- Control: Proactive measures to minimise imminent damage and prevent directly impending secondary damage to remaining stands (e.g. quick logging and debarking of standing infested trees). Control aiming for the fast lowering of local beetle populations and thereby the prevention of further damage.
- Protection of individual objects: Defensive measures to prevent immediate impending damage to goods worth protecting (e.g. timber storage sites, edges of high value stands). Examples are massive deployment of pheromone traps in beetle hotspots or application of insecticides to timber stacks.
Choice and intensity of forest protection measures must be goal-oriented. Protection of single objects and control are differing goals. Insecticides are used only as a last resort for the urgent protection of single valuable objects.
Other than those factors mentioned, successful control of wood and bark breeding insects is critically dependent on prevailing local conditions.
Future Central European weather conditions won’t prevent an outbreak after high-impact storm calamities. Ips typographus (Eight toothed spruce bark beetle) outbreaks always occur after locally significant storm events in spruce stands.
The following factors determine whether the population development may endanger the whole region:
- Date/ season in which the storm occurs
- Amount of windthrow
- Tree species composition in the stands and proportions within windthrow
- Density of pest population
- Weather development especially after the calamity
- Overall state of forest health
- 'early' storms (winter storms: before mid-January)
- 'low' amount of windthrow (e.g. up to normal annual cut)
- bark beetles on conifers: low proportion of spruce (in windthrow and remaining stands)
- low population density of wood and bark breeding insects at the time of the storm event
- cool temperatures and high precipitation during the following summers (April - September) reduce the insects' chances of successful propagation
- damage occurring at higher altitudes (also lower chances of successful propagation)
- windthrow on even sites is easier to remove (also, monitoring is easier)
Economic losses due to outbreaks of wood and bark breeding insects are manifold and complex. The direct damage caused by Ips typographus to roundwood alone amounts to at least 20 – 25 € per m³ of beetle damaged timber harvested.
The full potential of all three dimensions of Integrated Forest Protection has to be utilised right from the start of an outbreak. In this phase, measures taken are most likely to be effective. If infested timber is not detected and removed early enough, the damage will multiply considerably. Costs of forest protection measures, especially during the first few years after storm calamities, will therefore pay off in the long run due to their prophylactic effects, even though they might initially seem disproportionate compared to immediate effects.
|Tab. 1: Overview Effects of insect calamities.
|Price decline due to congestion of the timber market and exhaustion of storage capacities
|Increased time and effort for forest protection (e.g. more thorough monitoring, burning of infested material, debarking, insecticide application etc.)
|Restricted choice of tree species (e.g. avoidance of host species etc.)
|Technical damage and staining due to insects and fungi infection -> further drop in prices
|Stand-by and maintenance of labour and machine capacities
|Losses in volume and value increment
|Loss of protective functions of the forest (e.g. erosion control, wind-break, etc.)
|Higher organisational effort (e.g. updating cutting plans, provision of labour capacities, work plans/ holiday organisation, paperwork, etc.)
|Sustainability at risk (especially severe for small enterprises)
|Higher logging and transportation costs due to scattered felling volume (possibly out of season), e.g. longer set-up time, logging and hauling damage to the remaining stand, etc.
|Establishment costs for required infrastructure (e.g. opening up, machinery, training, etc.)
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Back to the article overview in the: Storm Topic Collection – Coping with Storm Damaged Timber