Özet:

Birch tree Betula pendula Roth. is an important ornamental and forest plant, which has a distribution in many parts of the world and has about 40 species. In Turkey, it is frequently encountered in North Anatolia and East Anatolia regions. There are many harmful insect species known to damage birch trees. Samples of the pest species that are the subject of this study were taken from Erzurum Center, Atatürk University Campus, Merkez Teke Stream and Aziziye Campus. The aim of the study is to determine the biology and damage of Nematus (=Croesus) septentrionalis (L., 1758) on birch trees. Samples were collected between 20 June and 20 September 2019 and 2020. A preliminary assessment study was conducted in 2018 to determine the pest's ecology. The adult specimen of the insect was collected from birch trees on sunny days. The larvae were collected by cutting with the help of pruning shears together with the leaves of the branches they ate. Pupae were obtained by digging the soil to a depth of 4 fingers (10-15 cm) with the help of a hoe. The collected adults were placed in jars and killed with ethyl acetate. Dead samples were transferred to a small cardboard box, brought to the laboratory, taped and labeled with the location, size and date of sample collection written on the box. The larvae were placed in a desiccator with the soil at the bottom together with the leaves they will feed on, absorbent cotton moistened with water was left on the ground and fresh leaves were brought to the laboratory every other day to feed and mature the larvae. As a result of the research, spawning time, larval stage and number of generations of Nematus (=Croesus) septentrionalis were determined under natural living conditions. While the number of damaged trees was determined to obtain the parasitism ratio, the damaged leaves on the branches of randomly selected trees were also counted to determine the number of eggs and larvae on the leaves. In this study, the biology of Nematus (=Croesus) septentrionalis and its damage to birch trees were investigated. Useful information has been uncovered for future researchers working on this topic. It was determined that the pest gave one generation per year in Erzurum conditions.