The weather still shows its wintry side with cold nights and cool temperatures even during the day. Therefore, the bark beetle still remains in its winter dormancy, either under the bark of infested spruce trees, or in the ground in the litter layer. But already in march the first warm days can occur. At daytime temperatures above 15 degrees, the bark beetle begins to develop a new generation. The first swarm flight can be expected from the middle to the end of april.
"There is little we can do about the grapes in the ground. Affected trees, on the other hand, can be. Must be taken quickly by the forest owner", according to bernhard zurner of the amt fur ernahrung landwirtschaft und forsten in bad kissingen. Already in the months of november and december, forest owners were contacted in whose forests infested spruce trees were discovered. You have been asked to remove these spruces by the end of february 2019. If the forest owner did not take on this work himself, this was not always possible due to a lack of entrepreneurial capacity.
"If the infested spruces are still in the forest, we are running out of time", zurner continues. Every effort must be made to remove these trees immediately and to reprocess them. Possible storage sites for infested wood may only be selected at a sufficient distance from other spruce stands – i.E. At least 500 meters apart. Crown material is best to chop. This is the only way to minimize the pressure of the infestation in spring.
In addition to trees that are already completely dead, spruces with red or yellow discolored crowns and fallen bark in particular must be removed in a draughty manner. The transition to apparently uninfested spruce trees should be made roughly to prevent further spreading.
Another sure sign of fresh infestation is brown drill dust. However, this can be found at the earliest in april on the trunk of infested trees, when the oats have drilled into the bark after their first swarming flight. Particularly after the extremely dry summer of 2018, the spruce is heavily water-stressed and often defenseless against a possible bark beetle infestation. Natural defense mechanisms, such as the resinification of the kafer, will no longer be possible for many spruce trees after this summer.
As a possible partner for the removal of the infested trees, besides the local forestry companies, the responsible forestry association in oberthulba is also available for support.
Against the background of this development, the government of lower franconia issued an "order for the monitoring and control of conifer bark beetles" at the end of january enacted. As a result, all forest owners will be obliged to clean their forests from the 1. October until 31. March at least once, and in the period from 1. April to 31. October for bark beetle infestation at intervals of at least four weeks. Moreover, the bark beetle infestation must be controlled either by oneself or by third parties.
The exact wording of the ordinance, valid until 31. December 2023, can be found on the homepage of the government of lower franconia. Additional information can also be found here on the internet.