Glue rings on oak trees catch caterpillars
In the oak-dominated forest of Am Schnellen Markt and Zeisigwald, caterpillars of the small and large frost moth had stripped the treetops bare in spring, causing worried forest visitors to fear for the survival of the trees. The caterpillars then retreated into the ground to pupate at the end of May. A short time later, at the end of June, even bare trees were covered in leaves again, so that walkers can now enjoy their autumnal colouring.
After the butterflies hatch at the beginning of October, the wingless females begin to crawl up the trunks of the oaks to lay their eggs in the crowns, from which caterpillars hatch again the following spring. As part of a standard procedure for frost moth monitoring, glue rings have now been installed in a red oak stand in Zeisigwald to intercept the females crawling upwards. At the end of December, when the glue ring monitoring is completed, it will be possible to estimate the intensity with which the frost moth caterpillars will infest the oak crowns in the coming spring.
This monitoring helps foresters to estimate the following year's seed harvest. Even if the caterpillars strip entire trees bare, there is no need for a poisoned club to combat them. This is because, on the one hand, the easy-to-capture caterpillars are ideal food for birds and, on the other hand, the trees develop a second shoot - the so-called St John's shoot - which provides effective protection against clear feeding.
Incidentally, the name of the forest pest is due to the fact that the flight time of the moths begins in autumn around the same time as the first night frosts.