ABSTRACT

The development time, survivoship and reproduction of Tuberolachnus salignus (Gmelin)(Lachninae: Lachnini) were studied on Salix alba at five constant temperatures (17.5°C 20°C 22.5°C 25°C and 27.5°C). The developmental time of immature stages ranged from 17.00 days at 17.5°C to 12.21 days at 25°C on Salix alba. The total percentage of survivorship of immature stages varied from 50% and 70% 17.5°C-20°C on S. alba. The largest [r.sub.m] valueoccurred with 0.2540 at 20°C on S. alba. The mean generation time of the population ranged from 13.595 days at 22.5°C to 19.60 days at 17.5°C on S. alba. The optimal temperature for Tuberolachnus salignus was 20°C.

KEYWORDS: Tuberolachnus salignus, Developmental time, Survival, Life table

INTRODUCTION

The giant willow aphid, Tuberolachnus salignus Gmelin (Lachninae: Lachnini) is the largest of the over 120 species of aphid that feed on willows (Salix spp.) and longest-lived aphids ever recorded [6,16,9]. This species has an almost cosmopolitan distribution [9] and is present in Turkey [8,21,2]. It occurs visibly on host trees from mid-summer until January or February. As this species is apomictic and cannot generate an egg stage by sexual reproduction [5].

Temperature is the most important abiotic factor affecting development and reproduction of aphids, geographically separated populations of aphid may differ with respect to the influence of temperature on development and population growth [7]. Temperature influences both aphid development and mortality and is a fundamental feature of its life history [19,20]. Temperature influences both aphid development and mortality rates therefore, knowledge of the effects of temperature on the biological parameters is essential to investigate aphid population dynamics.

The present study was designed to provide data on the developmental rate and fecundity of T. salignus at different constant temperatures than might be used for developing control models.

MATERIAL AND METHODS

Aphid and plant source

The T. salignus clone used was originally collected from Salix alba in Tekirdag, Turkey. The aphids were raised on potted, growing willow trees maintained a climatic room held at 25 ± 1°C a relative humidity 65 ± 5%, and a light regime (16 h light; 8 h dark).

Development and survival

Nymphal development duration was estimated on Salix alba grown at five different temperatures (17.5 ± 1, 20 ± 1, 22.5 ± 1, 25 ± 1 and 27.5 ± 1°C ambient temperature) under conditions of controlled day length (16 h light; 8 h dark).

For each of 40 replicates per temperature on Salix alba, apterous adult were placed on an isolated cutting of the willow species. Observations were made until the adult established and each twig hosted one progeny the adults removed. The time on each twig underwent ecdysis at each instar change was noted. The nymph and adult on each Petri dish were checked daily under stereoscopic microscope and their...