In 2015-2016, a study was performed examining the distribution, colony dispersion in tree canopies, occurrence rate in shoots at different ages, morphology, and the damage of the cedar aphid (Cinara cedri Mimeur 1936) (Hemiptera: Aphididae) This study was completed alongside biological observations in the Isparta Regional Forest Directorate. This study was conducted across 46 sites at an elevation of 820-1738 meter (m) and the distribution of this species was determined by a survey. Compared to other sites, the Cinara cedri (C cedri) population was found to be higher in 10 sites with young stands with an average height of 1000-1200 m. These sites were established through plantation. Colonies were typically observed on the shoots from the previous year and on branch axils. They were found to feed on shoot tips and trunks of young trees and preferred shoots with a diameter of 1.0-1.5 centimeter (cm) on the southern and eastern aspects of the trees. It was observed that C cedri mostly fed on shoots of the previous year, which caused the needles to dry and turn red. Damage was observed especially on young trees from which the dried needles fell and defoliation was concentrated particularly on the shoot tips and tops of the trees. It was found that honeydew was secreted by those insects fed with sap, and this secretion then covered the needles, shoots and branches, resulting in fumagine. The populations overwintered as eggs and then nymphs hatched during the first week of April. The adult stage was reached after completing four nymph periods over a time span of between one week and 10 days. These adults then reproduced parthenogenetically, with winged viviparous individuals appearing between May and June, and oviparous emerging in October. The final stage of the cycle was a period of mating and then egg-laying. Keywords: Cedar aphid, Cinara cedri, damage, Isparta, life cycle Çalisma, 2015-2016 yillarinda Isparta Orman Bölge Müdürlügü'nde, sedir yaprak biti (Cinara cedir Mimeur 1936) (Hemiptera: Aphididae)'nin yayilisi, türün agaç tepe tacindaki koloni dagilimi ve farkli yaslardaki sürgünlerde bulunma orani, morfolojisi, biyolojisi ile zarari tespit edilmistir. Çalisma, 820-1738 m arasinda yükseltiye sahip 46 alanda gerçeklestirilmistir. Plantasyon sahalari, genç mescere ve ortalama 1000 m yükseltide bulunan 10 alanda diger alanlara göre C cedri'nin popülasyonunun daha fazla oldugu belirlenmistir. Kolonilerin genellikle bir önceki yila ait sürgünlerde ve dal koltugunda bulundugu, ayrica sürgün ucu ile genç agaçlarin gövdesinde de beslendikleri, agacin güney ve dogu bakidaki 1,0-1,5 cm çapindaki sürgünleri tercih ettigi görülmüstür. C cec/r/'nin çogunlukla bir önceki yila ait sürgünlerde beslendigi ve ibrelerin kuruyup kizarmasina yol açtigi gözlenmistir. Zararin özellikle genç agaçlarda oldugu, kuruyan ibrelerin döküldügü ve yapraksizlasmanin agacin sürgün uçlari ile tepe kisminda oldugu görülmüstür. Zararlinin öz suyu ile beslenmesi nedeniyle balli madde salgiladigi ve balli maddenin dallarin üzerini kapladigi ve fumajin olusumuna neden oldugu belirlenmistir. Popülasyonlar kisi yumurta döneminde geçirmis, Nisan ayinin ilk haftasinda yumurtadan çikan kanatsiz viviparlarin yaklasik bir hafta ile 10 günlük sürede dört nimf dönemini tamamlayarak erginlige ulasmislardir. Mayis-Haziran aylarinda kanatli viviparlarin görüldügü, ekim ayinin son haftasinda oviparlarin ortaya çiktigi ve çiftleserek yumurta biraktiklari gözlenmistir. Anahtar Kelimeler: Onara cedri, Isparta, sedir yaprak biti, yasam döngüsü, zarar