Mortality factors and age-specific mortality rates of Chionaspis salicis L. (Hom.: Diaspididae) on poplar trees in Van, Turkey 1 Remzi ATLIHAN 2 M.Salih ÖZGÖKÇE 2 Abstract: Willow scale, Chionaspis salicis L. (Hom.: Diaspididae) is a major pest of poplar trees in Van. To understand population structure and density, and to determine reasons for population fluctuation of C. salicis, its population dynamics were investigated and a life table was constructed in 2000. Data were collected in three poplar tree plantations. Sampling was carried out every fortnight and 5 cm 2 parts of the stem of poplar trees were used as sampling units. C. salicis had one generation per year in Van. Generation mortality was extremely high and approximately 71% of it occurred during the egg-crawler stage. Egg and crawler deaths caused by various factors were the most important mortality factors underlying fluctuations in the population. Parasitism and predation contributed to total generation mortality at the pre-ovipositing female stage and caused mortality rates of 14.7% and 18.6% respectively. Zaomma lambinus (Walker) (Hym.: Encyrtidae) and Inostemma sp. (Hym.: Platygasteridae) were found as parasitoids, and Chilocorus bipustulatus L. (Col: Coccinellidae) and Temnostethus sp. (Hem.: Anthocoridae) as predators. Key words: Chionaspis salicis; life table; poplar trees Chionaspis salicis L. (Hom.: Diaspididae)’in Van’da kavak ağaçları üzerindeki ölüm faktörleri ve yaşa bağlı ölüm oranları Özet: Chionaspis salicis L. (Hom.: Diaspididae) Van (Türkiye)’da kavak ağaçlarının önemli bir zararlısıdır. C. salicis’in populasyon yapısı ve yoğunluğu hakkında bilgi edinmek ve populasyon değişimlerinde rol oynayan faktörleri belirlemek için 2000 yılında Van’da zararlının populasyon gelişmesi izlenmiş ve yaşam çizelgesi oluşturulmuştur. Örneklemeler üç kavak plantasyonunda 15 günde bir yapılmış ve kavak ağalarının gövdesi üzerinde 5 cm 2 lik alanlar örnekleme ünitesi olarak kullanılmıştır. C. salicis’in Van’da yılda bir döl verdiği belirlenmiştir. Bir döldeki ölüm oranı oldukça yüksek olarak bulunmuş ve bunun yaklaşık %71’i yumurta - hareketli larva döneminde meydana gelmiştir. Çeşitli faktörler tarafından meydana getirilen yumurta - hareketli larva ölümlerinin zararlı populasyonundaki değişmelere neden olan ana faktör olduğu belirlenmiştir. Parazitizm ve predasyon pre-ovipozisyon döneminde görülmüş ve bu dönemde meydana getirdikleri ölüm oranları sırasıyla %14.7 ve %18.6 olarak bulunmuştur. Zararlının parazitoidleri olarak Zaomma lambinus (Walker) (Hym.: Encyrtidae) ve Inostemma sp. (Hym.: Platygasteridae), predatörleri olarak ise Chilocorus bipustulatus L. (Col: Coccinellidae) ve Temnostethus sp. (Hem.: Anthocoridae) bulunmuştur. Anahtar kelimeler: Chionaspis salicis, yaşam çizelgesi, kavak ağacı 1 Y.Y.Ü Araştırma Fonu tarafından desteklenmiştir. 2 Yüzüncü Yıl Üniversitesi, Ziraat Fakültesi, Bitki Koruma Bölümü, 65080 VAN Introduction Scale insects are important pests of many annual and perennial plants in and out of agricultural areas all over the world (Borchsenius, 1966; Yanin, 1976; Kozstarab and Kozar, 1988). One of them, Chionaspis salicis L. (Hom.: Diaspididae), is widely distributed and is an important pest of various shrubs and trees in Turkey (Bodenheimer, 1949; Yıldız, 1972; Çanakçıoğlu, 1977). It is especially a pest of poplar trees (Populus spp.) in Van in eastern Turkey where these trees are widely grown and important for the local economy (Yaşar et al., 1995). Its feeding activity (sucking plant sap) causes stunted growth and dying of young trees in heavy infestations. There is no empirical information about the population dynamics of C. salicis or about the factors which are responsible for the variation in its population density. In order to devise a sound management plan, it is important to understand the population structure and dynamics of any pest species and to determine factors (biological and physical mortality factors) causing the population fluctuation. For this reason the population dynamics of C. salics was investigated and a life table was constructed in order to determine the temporal variation in population density and the reasons for population fluctuations. Important data, which could be used for developing descriptive models and control strategies for C. salicis, were obtained by determining age-specific mortality rates and mortality factors. The contribution of various mortality factors to generation mortality of C. salicis was calculated and mortality factors were determined. Material and Methods The study was carried out in three poplar (Populus nigra L.) plantations of the same age located in different places in Van region: Akköprü which is on North Hemp., Hatuniye on South Hemp., and İskele on West Hemp. during 2000. No control practices were applied for C. salicis during the study. Four trees were selected randomly for sampling in each of plantation. Due to the fact that C. salicis prefers the stem of the tree, one stem part with a surface area of 5 cm 2 was selected randomly as a sampling unit from all four sides of each selected tree. Sampling was carried out every fortnight and the number of dead and alive individuals of C. salicis in the sampling unit was counted for each stage (egg, crawler, first and second instars, male, pre-ovipositing female and ovipositing female) and the causes of mortality were recorded. The number of eggs, first instar, second instar, pre-ovipositing female and ovipositing female was counted on sampling units directly. But the number of crawlers was