Öz It is determined that Cytospora canker (Cytospora chrysosperma “Pers.â€? Fr.) was the cause for the death of poplars bred in Çankırı Kenbağ Forest Nursery and Central Anatolia Region. Since the disease was seen for the first time, “restriction and assessment surveyâ€? was conducted for determination of the infection area, infection rate and disease intensity in Çankırı as center, Ankara and Kırıkkale in order to prevent the infection of clean areas and take precautions necessary. Different media (PDA-Potato Dextrose Agar, MEA-Malt Extract Agar, Poplar Bark Extract Agar and SNA-Synthetic Nutrient Agar) were used in order to determine the best development media of C.chrysosperma. Infection status of C.chrysosperma, its disease intensity, its hosts and relationships with Paranthrene tabaniformis (Rott.) (Lepidoptera: Sesiidae) were determined. A significant correlation between C . chrysosperma and P. tabaniformis was determined after survey data. The pathogen made spor secretions which in 2-3 cm length, reddish color, curly filamentous found on pycnidia on oily-grey necrosis in infected poplar trunks from the end of March. Spores of the disease agent are hyaline, single celled, in shape of slightly hunchbacked bow and average dimensions are determined as 2.5-5.0 x 0.5-1.5 µm. As a result of the studies carried out, the pathogen was determined to develop in PDA, MEA and Poplar-Bark Extract Agar nourishing media. At the end of 21-day incubation period, average necrosis dimensions were determined as 3.06x1.73 cm. The infection rates due to C. chrysosperma were found as 15.77%, 14.10% and 9.28% in Çankırı (Center), Ankara and Kırıkkale respectively. Correlations between the disease and P. tabaniformis were 0.5955, 0.6763 and 0.9037 in Ankara, Kırıkkale and Çankırı respectively. In literature, there are certain sources that relate the spread of C. chrysosperma with boring insects, there was not any that specify P. tabaniformis directly. However, the correlation rates in 3 cities a powerful (r>0.50) and significant (p<0.05) relationship between C. chrysosperma and P. tabaniformis. As a result it is determined that P. tabaniformis had an effect on distribution of the disease for the first time.