|
|
Ichneumons are natural enemies of elm bark beetles. A female wasp oviposits her egs in a developing bark beetle larva/pupa
(Fragment of the film “Threatened Species: The Elm”, COM4HD,
Madrid, Spain)
|
Elm bark beetles have several natural enemies. Of these, wasps and woodpeckers
appear to be the most significant (see Enemies of the elm bark beetle). Control of DED vector populations using these enemies is highly attractive
from an environmental point of view. However, in contrast to the situation in a greenhouse, a field system is never ‘closed'. For this reason,
full elimination of a elm bark beetle population will probably fail under natural conditions, e.g., wasps and woodpeckers will never fully eliminate the vector population at a location {[381]}. The use of such biological
control agents as entomopathogenic fungi, nematodes, and mites has not yet been thoroughly exploited and awaits further development {[522],[523],[524],[574],[641],[784]}. Selecting a control pathogen that exhibits high specificity for the DED vector may not be easy {[231]}. Competitive replacement
of the aggressive elm bark beetle by a secondary beetle species—a method which has successfully reduced the number of mountain pine engravers in lodgepole pine—may offer a unique form of biological DED control {[807]}.
| 
