Asian Journal of Chemistry Vol. 19, No. 3 (2007), 2285-2294 Comparative Toxicity of Neem and Seven Insecticides on Hazelnut Weevil (Curculio nucum Col.: Curculionidae) with Laboratory Bioassays CELAL TUNCER*, ISLAM SARUHAN† and IZZET AKÇA† Department of Plant Protection, Selçuk University, Konya, Türkey E-mail: isaruhan@omu.edu.tr Hazelnut weevil (Curculio nucum L. Col., Curculionidae) is common pest in hazelnut (Corylus avellanae) and insecti- cides are the primary tool used to manage infestation of it. The insecticides are applied for its control for many years; therefore, to evaluate their effectiveness and establishing base- line insecticide mortality for future resistance monitoring programs are needed. In this study, efficacy of 7 insecticides including benfurocarb, carbaryl, carbosulfan, furathiocarb, lambda-cyhalothrin, methiocarb and 1 botanical pesticide with azadirachtin were evaluated in laboratory bioassays and lethal concentrations were determined against hazelnut weevil. There was no acute toxicity of azadirachtin on hazel- nut weevil in 72 h. The highest toxicity based on LC50 values was observed in lambda-cyhalothrin (3.06 mg AI/L) and followed by carbosulfan (12.4 mg AI/L). The LC50's (mg AI/ L) for furathiocarb, methiocarb and benfurocarb in residual filter paper method were 36, 44.5 and 90.2, respectively. The least efficacy were determined in carbaryl, LC50's were 224.3 and 277.5 mg AI/L for two carbaryl preparations. The lowest slopes of probit lines were determined for carbaryl whereas it was steepest for carbosulfan. LC99's were close or upper than recommended field doses in carbaryl while they were lower for other compounds. Key Words: Hazelnut weevil, Curculio nucum, insecticides, azadirachtin, toxicity, hazelnut. INTRODUCTION Hazelnut is one of the main agricultural export products of Turkey, drives hundred millions dollars of income each year. About 400,000 families live on hazelnut and about 70 % of the worldwide hazelnut production is supplied by Turkey. Almost 584000 hectare land is used for hazelnut production in Turkey 1 . Hazelnut weevil (HW) (Curculio nucum L. Col.: Curculionidae) is the most serious pest of hazelnut in Turkey as well as other hazelnut growing countries 2-10 . Hazelnut weevil cause †Department of Plant Protection, Ondokuz Mayis University, Samsun, Türkey.