Alternative Control Measures for Wood and Bark Boring Insects
Alternative control measures were
intensively discussed in the context of tense forest protection situations
during the years after the storms in 1990 and 1999). The target was to reduce
the already low amounts of insecticides used even further. The basic approaches
and the experiences applying them are described here.
Trap trees and mass trapping with pheromone traps
Effective use of bark beetle traps is only possible with a massive labour
effort. (Photo: FVA, Dept. for Forest
- Both measures are basically suitable
means to influence infestation progression on a local level.
- However, they are both not fit for
population regulation during population growth stage and peak in the main
- Trying to reduce population densities
of Ips typographus after large-scale storm calamities requires a massive
personnel and material effort. This can hardly be achieved in today’s business
structure. Additionally, it is out of all proportion to the benefits gained
when compared to available alternatives. Successful realisation of these
measures requires personnel and technical capacities to be flexibly deployable
at all times as well as a high degree of caution, diligence and experience.
- The measures are only suitable for
controlling localised calamities or for accelerating the demise of large-scale
calamities as one of many measures used for the local protection of vulnerable
is expensive. It only makes sense when used to relieve the timber market. Short-term
storage aiming solely at killing beetle broods as a measure of forest
protection is not justifiable from a commercial point of view.
Fig. 2: Wet
storage. (Photo: R. Willmann)
- It can be
assumed that "white stages" (eggs, larvae, pupa) are killed if irrigation is
started immediately. Flying and further breeding can be expected if adult
beetles are present, putting adjacent stands at risk. Furthermore, logs in
which maturation feeding has already taken place will loose a lot of bark when
handled and during transport. Large proportions of the untreated bark
containing the brood and/or adult beetles will therefore remain in the forest. This
can result in a very low degree of effectiveness and does not justify the high
costs involved in wet storage.
wet storage is best for infested trees that were detected early, logged
immediately and dispatched straight away. A consistent and efficient logistics
chain is needed here.
- Wet storage
can not be recommended as a standard forest and wood protection method in the
event of bark beetle calamities.
tests in a hothouse showed that the mortality rate of wood and bark boring
beetle species is very high inside the wrapping. However, individual beetles
repeatedly managed to bore through the plastic film.
and non-infested timber should never be stored together inside the same
wrapping. The tests showed that the beetles react to a deterioration in living
conditions by leaving their burrows and infesting other logs inside the
demanded in terms of timber quality, brood development stage, and thus the
available time frame, correspond to those given for wet storage. Hence the same
problems and consequences can be expected from a forest protection point of
Removal of susceptible or infested logging residues
mulching, etc. is only justified if…
- large amounts of infested material accumulate near adjacent vulnerable
Hazard or not...? (Photo: FVA, Dept. for Forest
material lying close to vulnerable stands must be checked for infestation
- the residue
contains larger diameters,
- and/or is
located predominantly in shadow!
Logging residues dry out relatively quickly
and/or are a much less hazard if...
- the residue
only contains small diameters,
- and/or is
exposed to intensive solar radiation,
- the bark
was removed and/or crushed by a harvester’s processor head,
and twigs are left on treetops to maximise the evaporation surface area,
- the bast
fibre turns into a brownish colour (the bark is comparatively hard to remove)!
and residual timber can alternatively be “striped” (partly debarked, peeled in
strips), but this labour intensive work and therefore high costs, must be
balanced against the benefits.
- Past experience proved motormanually cutting
the residues into 30-50 cm pieces was largely ineffective!
for controlled burning of logging residues
- No burning
during times of atmospheric inversion, wet weather, strong winds or long
- Use dry
wood for kindling.
- Do not use
petrol, waste oil or car tyres to light or maintain the fire (illegal in Germany).
inside the forest should burn at a high heat and as quickly as possible.
- Do not
misuse the fire to dispose of your waste.
- Keep enough
distance to surrounding trees.
- Do not
light fires on steep slopes! Burning material could slide down.
- As a
precaution, the local/ regional forest authorities and fire brigade should (or
must, depending on local laws and regulations) be informed about planned
controlled burnings (time and place) to avoid unnecessary (and possibly
expensive) fire fighting operations.
suitable fire-fighting equipment on hand (water buckets, fire extinguishers).
supervision of the fire by at least two people (at least one of whom should be
- Do not
leave the site before fire and embers have gone out completely. Remnants of
glowing embers must be entirely extinguished.
- Pile up
residues only immediately before burning, as birds and small mammals might
otherwise take shelter inside slash piles.
height of the piles: approx. 3.5 metres.