Every year, the bark beetle (Scolytinae) causes immense damage to the trees in gardens and is responsible for the death of many forests. Natural enemies can keep the plant pest in check.
combat
Fighting bark beetles poses a major challenge for garden owners, because the use of home remedies, classic insecticides and attractant traps (pheromones) has little chance of success as soon as there is a more extensive infestation. The most effective way is to fell the affected trees. In the meantime, experts are also relying on natural enemies of the bark beetle, with which the spread/reproduction of the pests can be prevented.
Recognize
In order to be able to take targeted action against the Scolytinae, a perfect identification of the beetle is necessary. This is based on the appearance, various properties and recognizable damage patterns. There are mainly two types of weevils active in Germany:
Bookprinter (Ips typographus), engraver pine bark beetle forest gardener
- Common name: octagonal spruce bark beetle
- Size: 4.5 to 5.5 mm
- Colour: dark brown, yellowish to brownish hairs
- Body shape: cylindrical, broadening to the rear
- Arched pronotum, humped in front, with long hairs and dots
- Head barely visible, surmounted by pronotum
- Special Features: Serrated elytra (four per side)
copper engraver (Pityogenes chalcographus)
- Common name: six-toothed spruce bark beetle
- Size: 1.6 to 2.9 millimeters
- Colour: copper to reddish brown
- Body shape: cylindrical
- Pronotum wider than long and covers head
- Weak dot drawings
- Special features: red-brown, toothed elytra (three per side), shiny, yellow antennae
properties
Both bark beetle species show the following characteristics:
- Start of activity: from spring around April with temperatures from 16.5 degrees Celsius and dry air
- Duration of activity: until about September, then hibernation
- Prefer weakened and diseased deciduous and coniferous trees
- Egg laying and larvae under the bark
- Mainly infests spruces (Picea), but also:
- Douglasien (Pseudotsuge menziesii)
- Siberian larches (Larix sibirica)
- European larches (Larix decidua)
- Pines (Pinus)
- Silver Fir (Abies alba)
- Siberian firs (Abies sibirica)
- Frequent infestation also on floor wood/fallen branches
Typical features/damages
- Small holes in tree bark
- Usually increased resin formation
- Red instead of grey, beige inner bark
- Late stage whitish trunk
- Wood flour on the floor (only at the printer)
- Brown and red discoloration on treetops
- Blue discoloration of the sapwood (only with letterpress – especially visible with sawn wood)
- Lots of leaf and needle droppings
- dying of branches
- Often associated with fungal infections
Natural predators
Various animals have proven to be ideal predators in forestry. In the garden they serve the same purpose.
- Ameisenbuntkäfer (Thanasimus formicarius)
The ant beetle is very voracious. The bark beetle is one of his favorite foods. When this burrows into the tree, it secretes aggregation pheromones. This creates an odor that attracts other conspecifics, but also natural enemies, such as the ant beetle.
- Langbeinfliegen (Dolichopodidae)
Like the lance flies, the long-legged flies, which are up to 6.4 millimeters in size, feed on the larvae of the bark beetle. They can also settle more in the garden if there is a certain amount of moisture and an insect hotel.
- Lance flies (Lonchopteridae)
The two to four millimeter long lance flies are hungry specimens that attack the larvae of bark beetles. They prefer moist areas. Setting up insect hotels increases the chance of attracting plenty of lance flies to the garden.
- Mites (Acari)
Mites and in particular predatory mites are known for biological pest control. They eat the eggs of bark beetles and are thus able to stop the reproduction. No matter what measure is taken against the pests, mites should always be used in addition. They can be purchased in specialist shops.
- Ichneumonidae (Ichneumonidae)
With parasitic wasps, the bark beetles and larvae can be kept under control and ideally reduced to almost zero. They sit on the adult animals, pierce a hole in it and lay their eggs there. The bugs are dying. Since the adult beetles only survive one winter, parasitic wasps should be active as enemies for at least two seasons in order to eat all the larvae and stop the beetle infestation. You can usually buy them in any well-stocked hardware store and garden center.
- Spechte (Picidae)
If the bark beetle infestation is manageable and there are no masses of beetles, woodpeckers are used to combat it because they eat the beetles and larvae. They tap off the bark to get their “food”. Above all, black, small and three-toed woodpeckers reduce the problem. There are a few tricks you can use to attract woodpeckers to your garden:
- Lay out suitable food, such as seeds, peanuts and black sunflower seeds
- Position feeders close to infested trees where it is light and warm
- Choose upright/hanging feeders (increases feeding comfort)
- Also offer a water point
- Provide nesting boxes
