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CONTRIBUTION TO THE STUDY OF BIOLOGY OF ASH WEEVIL (Stereonychus fraxini De Geer) PRILOG POZNAVANJU BIOLOGIJE JASENOVE PIPE (Stereonychus fraxini De Geer) Milan DREKIĆ1, Leopold POLJAKOVIĆ PAJNIK1, Verica VASIĆ1, Predrag PAP1, Andrej PILIPOVIĆ1 Abstract One of the most harmful defoliating insects on ash species in Southeast Europe is the ash weevil (Stereonychus fraxini De Geer). Frequent occurrence of ash weevil outbreaks initiated research of the biology of this insect. The aim was to study the less known parts of insect biology, such as time of the insects development in natural conditions, fertility and fecundity of females, the duration of the embryonic, larval and pupal development, the amount of food consumed by larvae and adults. Research of insect development in nature conditions were carried out during 2008 and 2009 in the forests Branjevina near the town Odžaci in Serbia. This research was carried out by observation on 15 permanently labeled lower branches, every 6–9 days. Growing of insects in order to determine fertility and fecundity of females, the duration of developmental stages and the amount of food consumed by larvae and adults was carried out in a building with outdoor conditions. Results are showing that overwintered adults become active from the beginning of the second decade of March until beginning of April. Female fertility was ranged from 30 to 104 eggs, and total fecundity from 58 to 109 eggs. Embryonic development was in range from 9 to 11 days. First larvae were found on leaves in the second decade of April, and the last are observed at the end of June. Ash weevil larvae undergo three larval stages. The entire larval stage development lasts 16–20 days. Larvae consumed average 3.3 cm2 of narrow – leaved ash leaves. Pupal stage lasts from 6 to 8 days. Adults of new generation occur in the same year from the beginning of the second decade of May to the beginning of July, and immediately after eclosion starts with additional feeding for overwintering and each adult feeds on average 2.5 cm2 of narrow leaved ash leaves. Key words: Stereonychus fraxini, ash, biology 1. INTRODUCTION Uvod Among insects defoliators feeding on ash, the ash weevil (Stereonychus fraxini De Geer) is famous for its harmfulness and frequency of occurrence in South – East European countries (Mikloš 1954,1977, Marović 1963, Tsankov et al. 1990, Pojras 1993, Mihajlović and Ristić 1995, Ciesla and Moore 2007, Avramović et al. 2008, Glavendekić 2010). Ash weevil is common in Europe, North Africa and Asia Minor (Wingelmüller 1921). Ash weevil is oligophagus species feeding on: Fraxinus excelsior L., Fraxinus angustifolia Vahl., Olea europea L. and Phyllirea media L. (Mikloš 1954, Scherf 1964, Lemperiere and Malphettes 1983, Hrašovec and Harapin 1999, Blando and Mineo 2004). Ash weevil is harmful both as larva and adults. Overwintered adults in early spring |