The Content Of The Article:
- What are bark beetles and what are they looking for in the garden?
- The "most dangerous" bark beetle
- Damage potential, detection of infestation
- Fight bark beetle
- Prevent bark beetle infestation
Bark beetles are actually quite normal "forest clearing beetles" that process deadwood into soil so that there is room for young trees. In forest monocultures, they can propagate so freely in favorable weather that half of the living forest is eaten apart from dead wood. If garden trees lure at the edges of the forest, the gardener and tree owner has a real problem because he can not do much more than to strengthen his trees against colonization. Below you will learn when bark beetles are dangerous and how to best arm your trees:
What are bark beetles and what are they looking for in the garden?
Bark beetles are a subfamily of the weevil family, which bears the botanical name Scolytinae and consists of numerous genera with an estimated 5000 species. These 5000 species are scattered all over the world and can be found all over the world, whether deciduous or coniferous.
In a natural environment, bark beetles do not bother to kill living forest trees. On the contrary, they play an important role in the constant renewal of the forest ecosystem because they act as destructors: hard-working crushers of out-of-date biomass that "shred" degraded trees so finely that they become forest soil for the seeds of young trees. This function of the bark beetle is hardly noticed in the public, because bark beetles became famous for the mass propagation of some species, which then "quickly eat half a forest". However, this development was not heralded by bark beetles with omnipotence fantasies - the useful disposal companies have developed into pests, because humans first acted and then grasped the connections:
The bark beetles do not eat mixed wood, as it occurs naturally (in Germany there are no more natural forests, but only jungle-like relics tiny size), but a spruce forest, as he would of course never originated. Spruce trees in concentrated stands are only to be found in the mountain forests of the Alps, but grow very fast and can be harvested profitably from younger stands. For this reason, the German forest owners and foresters long ago chose spruce as their "bread tree" and for centuries planted pure spruce forests outside the natural range. Even in the second half of the last century large areas were reforested with spruce stands, spruce with 26% area is still the most common tree in the German forest, although for years (increasing, but too low) efforts are registered, spruce stands in mixed forests convert.
These extensive spruce stands are the optimal bark-beetle habitats, while bark-beetle predators seldom become happy with the one-sided plant population. The ecological balance in such monotonous plant communities is more than susceptible to disturbances. Every climatic extremity brings with it the danger that the bark beetles multiply explosively (as was the case eg 1994/95, 1999 and 2003/2004). At least only about 150 species eat in Europe, of which only a few under the bark (which makes them first potential pests of living trees), even less in Germany and on trees, which we "eat ready to eat" in ecologically susceptible gatherings.
However, if these species "make" a mass increase, the path from the forest to the garden is not far, so you should know the bark beetles that might climb into trees near forested land:
Tip: Waldnah is relatively reliant on a hungry or bark beetle willing to reproduce because, after successful conquest of a weakened tree, the beetles also approach the neighboring trees and move from tree to tree. This can take them from forest far into populated areas; if there "the trees are tight", but the beetles can also fly about three kilometers. If the light-weighted insects fall into the right wind, they can carry them much further into the middle of inhabited areas. So that does not sound too threatening: Bork beetles can only cause real damage to weakened trees.
The "most dangerous" bark beetleThere are still pure spruce forests; In forestry, many forests are still not managed properly and sustainably in accordance with § 11 of the Federal Forest Act, but with a sustainable view of economic interests.Bark beetle infestation is usually not followed by an increase in biodiversity that could control the threat, but rather "forest clearing up to clinical purity"; Immediate removal of all dangling and breaking wood, so that the forest becomes even more unnatural and unecological. As long as profit-oriented companies continue to romp unchecked in areas of society with more important tasks as profit / growth, phenomena such as masses of bark beetles and other harmful human development will be part of our lives.
Therefore, garden owners must be prepared to deal with bark beetles that have been bred in a near or distant forest to plague. Only the "bark breeders" among them, whose larvae feed on the sapling bark layers of the tree (there are also wood breeders, but these are limited even in times of need on already lying on the ground wood). In a mass infestation, they mutate from instructors of the resistance forces to tree-threatening pests, and they not only colonize spruce trees. Here is an overview of the potentially threatening beetles and their favorite tree species:
Letterpress, Ips typographus4-5 mm tiny, brownish, hairy, roller-shaped beetles whose larvae cut pretty letterpress templates under the bark: bit.ly/2eq76vb. In addition to the beloved spruce he climbs Douglas fir, larch, black pines, white fir and Weymouth pine, from whose strong representatives he is thrown out before "completion of the print preparation" by means of resin separation.
For ailing trees, the bark beetle can be dangerous, because their smell animates him to mass attack: Beetle 1 drills or eats himself and falls victim to the poisonous resin flow. Before it kills him, he transforms the ingredients of the resin into perfumes that attract more beetles - if there are a lot of bark beetles and few bark beetle enemies nearby, a weak tree will soon stop creating the defense.
Engraver, Pityogenes chalcographusThe engraver looks like a too small book printer without hair. He got his name because he produces intriguing pictures that are reminiscent of copper engravings.
The engraver takes care of spruce and sometimes Douglas firs, pines, larches and firs. It populates the bark of the trees and feeds on bast and bark tissue. Preference for young trees damaged by wind or snow, whose bark tissue is beautifully tender everywhere; in older trees the beetle picks up the upper parts of the trunk, where twigs with thinner bark are found.
Other native bark breeders
- Large forest gardener, Tomicus piniperda, about 0.5 cm, black-brown + hairy, goes on pines and rarely on spruces and larches
- Small Woodland Gardener, Tomicus minor, 3.5 - 4 mm, black-brown + less hairy, inhabited a. bark and young shoots of pine, spruce, larch on wooden storage bins
- Oak chip beetle, Scolytus intricatus, 2.5 - 3.5 mm and black, prefers to eat on oak, willow, poplar, elm, red and hornbeam, chestnut + hazel at the base of the youngest shoots
- Beechbark beetle, Taphrorychus bicolor, hardly distinguishable from the engraver, but on beech, hornbeam, oak and birch on the way
- Involve all rather dead wood, in extremely dry and hot summers but also living trees
- So z. B. from the beech bark beetle expects that it becomes more annoying as the climate warms
- These bark breeders only develop one generation each year, which makes mass reproduction unlikely
Damage potential, detection of infestationBark beetle populations can grow to problematic strength under certain favorable (weather) conditions: For years warm spring and autumn weather with temperatures above 17 degrees, in which three generations of bark beetles hatched each year; best in a monoculture forest, where those responsible take little care of the consequences of the disrupted ecological balance.
The more a formerly functioning ecological structure is destroyed, the more work human beings must invest in order to contain the unfavorable consequences. Garden owners working with insecticides, fungicides and Co. can sing a song of it; a forest is only infinitely larger than the garden in front of the home, the replacement of millions of industrious working Borkenkäfer enemies by human labor infinitely more laborious.
The "unnatural forest" must be kept virtually "clean", no damaged tree may be left to itself, no broken branches may remain lying, and the dead wood must be constantly cleared. If this fails for cost reasons, the hour has struck by Borkenkäfer and Co. in the so-called "beetle years" explosive propagation and garden trees are threatened.
When the time comes, there is talk of increased bark-beetle emergence in the region's media. Then you should be the more vigilant the closer your house is near an infested forest.Watchful means that from the middle of April to the end of April, when book printers and engravers swarm out of their winter quarters (their "start signal is dry weather at a temperature of at least 16.5° C), they must be more attentive.
The book printer leaves traces from the beginning of the infestation: When the incubator chambers are created under the bark, he throws brown drill dust, which collects in bark scales and spider webs, on soil plants and at the foot of the tree. Both species produce small boreholes, which are anyway not visible at all with the magnifying glass and the engraver, because they sit high up in the crown area.
Practically, it looks rather so that tree professionals usually recognize an infestation on the garden tree only when woodpeckers remove the loosely grown bark in large plumps or it falls off by itself, the crown of the tree from bottom to top turns brown or the crown in the green state throws needles at once. This happens months after the infestation begins, when the tree shows these first signs of dying, the beetles are long gone and the tree is beyond saving. What does not have to make you look at the endangered trees in the spring even more attentive or with a magnifying glass, because that does not help you at all: If the approaching bark beetles have got under the bark, they can not be expelled.
Tip: Bark beetle infestations also report special bark beetle warning services in many regions. In Bavaria z. For example, the Landesanstalt für Wald und Forstwirtschaft has been running a Bavaria-wide monitoring system since 2004, and the Infoportal can be found at borkenkaefer.org. Other federal states carry out a similar bark beetle monitoring, you can find out more from the local environmental office.
Fight bark beetle
Beetle insecticides are natural (any creature can be killed by any poison), but when applied to living trees, there is always a risk that the poison will produce more resistance than effect, which would only worsen the problem. Therefore, the use of insecticides against bark beetles in the home garden is generally prohibited, in the commercial sector, they may be used only in a limited range and only under complicated conditions (and should bring even little success).
Pheromone traps are not a useful defense, but only the monitoring. In this regard, you do not need to act as a home gardener, in case of threatening infestation enough pheromone traps will be in the surrounding forests.
For the home gardener, combating the bark beetle infestation is under control to saw or ax. The official recommendation is to fell the affected tree as quickly as possible and to dispose of it far from any contact with natural products because the bark beetles attract more species. If the infestation is detected, it should also be reported to the municipality or city council and the lower forestry authority, and you must contact your plant protection agency / environmental office for the legal regulations to be followed during the tree fall.
A consultation with a tree care specialist may be worthwhile if there are reasonable indications that only individual branches are populated on the edge of an infested area. Maybe here is something to save by quick cut; You can also get advice from a specialist about which trees you can plant when the bark beetle plague is approaching.
Prevent bark beetle infestationThe defense against bark beetles can only come from the tree itself, and you can help it: Maintain your trees so well that they are healthy, strong and full of defenses.
This includes a good water supply: Bark beetle infested trees such as spruce, etc. are usually not additionally watered; If massive bark beetle infestation threatens, which is anyway associated with exceptionally warm and dry weather, you should treat your tree but a little "extra water" - he also needs "extra powers" to ward off the infestation.
That's exactly what it looks like with the nutrient supply, a threatened tree can use a little "super-food" well.
If you plant vegetable manure instead of artificial fertilizer, the tree will be supplied with various fortifying ingredients in addition to the "pure calories".
Furthermore, you should invite the enemies of the bark beetles into your garden by a generally close-to-nature gardening: ore wasps, parasitic beetles, beetles and woodpeckers; the most successful bark beetle killers are entomophagous ("insectivorous") fungi in the soil. If a garden soil is cultivated and planted in a variety of ways, soil life will also promote the variety of mushrooms. Then a garden floor also contains such fungi that decimate larvae / beetles so significantly that the remaining bark beetles are satisfied with the deadwood.
That these Barkenkäfer enemies in a mass increase is not sufficient to bring about their collapse is not an argument.Because it is at least a step in the right direction; only when many gardeners promote bark-beetle enemies (which also keep other beneficial insects out of keeping the populations in a beneficial environment) and more forests are converted back to sensible biodiversity can we control bark beetles and other unnatural plagues to get.