The Natural Enemies of Bark Beetles
Fact sheet for the
The biology and the environmental needs of bark beetles are already well known. The knowledge about their antagonistic agents however is limited. The fact sheet describes in detail the natural
enemies (antagonists) of the spruce bark beetles (Ips typographus und Ips
amitinus) and other bark beetles in Central
Europe. The enemies of bark beetles may be
classified in three superordinate groups: pathogens, predators, and parasites.
Fig. 1 - Three-toed woodpecker
Photo: A. Aichhorn
- Bacteria are taken up by the beetle with food. The body content turns
into a bad smelling-decayed pulp.
- Under humid, warm
conditions, fungi have
a significant influence on the mass reproduction of numerous bark beetle
- Protozoa mainly
attack the larvae stages of the hosts. However, there is little known
about the effect of protozoa on bark beetles.
- Nematode worms can
usually be found in the breeding system of the bark beetles. There is,
however, still too little known about their effects.
- According to the newest state of
art, viruses also
occur but play a secondary role as pathogens of bark beetles.
- Mites can be found in almost all bark beetle breeding systems. The
suck on the eggs, larvae, and cocoons of the bark beetles. However, there
is still little known about their effect.
- Among the beetles, there are numerous species
which are as larvae and/or in the adult stage important predators for bark
beetles. The most conspicuous one is the checkered-beetle (see photo).
- The snakeflies also play a role
with the natural regulation of the population density of various bark
beetles. However, it is only the larvae which are feeding on bark beetles.
true flies play an important role as
predators of bark beetles. The larvae of the long legged flies (Dolichopodidae)
and lance flies (Lonchaeidae) are particularly important predators.
- Birds can intervene in a regulatory manner in bark beetle
populations, as long as these are not too large. The black woodpecker, the
lesser spotted woodpecker and, in particular, the three-toed woodpecker
are important enemies.
- Various parasitic wasps among the Hymenoptera, contribute as
parasititoids of bark beetles significantly to the maintenance and the
reestablishment of the natural balance.
Fig. 2 - European
checkered-beetle (Thanasimus formicarius) eats a bark beetle.
Photo: Beat Fecker (WSL)
Fig. 3 - Parasitic wasp laying eggs onto a bark beetle.
Photo: Beat Wermelinger (WSL)
- This fact sheet, issued by the Swiss Federal Institute for Forest, Snow and Landscape Research WSL, is not available in English language.
- You can order a paper copy free of charge in German or French.
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