Migrant insect

Bug turns out to be an “oak leaf vampire”

Sap-sucking bugs prey on the greenery of oak trees in native forests.(Bild: Krone KREATIV/Gernot Hoch Rubina Bergauer)

The oak net bug is spreading. The introduced insect sucks plant sap from certain trees, but also stings humans.  

Observant walkers in local mixed and deciduous forests will notice that oak leaves are already changing color and even unripe acorns have long since fallen to the ground. This is not due to the effects of the summer weather, but to an insect that has migrated from the south - the oak weevil is making masses of its way across the forest canopy.

Semmering crossed
The insects, which are only up to three millimetres in size, were introduced from North America to Turkey and Italy at the beginning of this millennium. They were first detected in Austria five years ago and have now also crossed the Semmering and are occurring in the Wechsel region as well as in other areas of Lower Austria.

The bug does not disdain blackberry leaves either.(Bild: Veronika Brudl)

Oak leaves and other greenery
"The bugs feed primarily on oak leaves, which they suck on with their proboscises," explains Gernot Hoch from the Federal Research Center for Forests. However, the insects do not disdain the greenery of beeches, elms or blackberry bushes.

Heavy sucking activity causes leaf damage, which weakens the tree and can also disrupt seed production.

Gernot Hoch, Waldschutzexperte

Bild: zVg

Skin irritation after a sting
When Corythucha arcuata - the Latin name for the small "leaf vampire" - flutters from tree to tree, it may land on people. And dig its proboscis into their skin. "But that's more of an accident," emphasizes Hoch: "The bugs are interested in plant juices, not human blood." In any case, a bite is harmless and at most causes skin irritation. And the oak web bug's sucking is not lethal for forests either - but it can weaken trees.