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ŠUMARSKI LIST 7-8/2014 str. 34     <-- 34 -->        PDF

for additional feeding and oviposition damage the buds, shoots and leaves. In case of heavy attacks can cause a complete destruction of buds and consequently the absence of normal spring development of leafs. Larvae firstly skeletonize then completely eat the leaves, while the new generation of adults, because of additional feeding, make damage on the leaves. Lemperiere and Malphettes (1983) reports ash weevil damages on ash seedlings as a very considerable due to destruction of terminal buds. Outbreaks occur frequently and last 4–5 years, or longer (Mihajlović 2008). Frequent defoliations of ash trees cause loss of growth, physiological weakness and creation of favorable conditions for the attack of secondary insects. Vajda (1974) determined that dry vegetation periods, waterlogging of soil and attack of ash weevil play an important role in ash dieback by weakening trees and creating predisposition for the attack of bark beetles Hylesinus fraxini Panz. and Hylesinus crenatus Fab. Ash dieback in the lowland forests around the river Sava is mentioned by several authors (Vajda 1974, Janeš 2004, Medarević et al. 2009). A particular problem in the cultivation of ash in Europe is the occurrence of new pathogen Hymenoscyphus pseudoalbidus Roberge ex Desm. (anamorph Chalara fraxinea T. Kowalski) which causes ash dieback (Kowalski 2006, Queloz et al. 2010) and which is recorded in numerous European countries. This pathogen in Southeast Europe has been recorded and confirmed in Hungary (Szabó 2008), Slovenia (Ogris et al., 2009) and Croatia (Barić and Diminić 2010, Županić et al. 2012) and represents a threat for narrow - leaved and European ash. This imposes a need for research of the adverse factors that threaten the development of these ash species. Among them, ash weevil is one of the most important. There is a lack of results of ash weevil research and available data are generally older and that was the reason and encouragement for our research group to explore some parts of the insect biology which are insufficiently explored. Data on the biology of this insect are provided by many authors (Nüsslin 1913, Nüsslin and Rhumbler 1927, Mikloš 1954, Schwerdtfeger 1957, Scherff 1964, Lemperiere and Malphettes 1983, Tsankov et al. 1990, Pojras 1993, Blando and Mineo 2004), and they differ in the number of generations, and the time of the occurrence of various developmental stages. Data on fertility and female fecundity, number of larval stages, quantity of food consumed by larvae and adults of ash weevil are insufficient in the available literature data.
Research is undertaken aimed at studying those parts of insect biology that are unknown, or various data referring to those parts are found in the literature. Good knowledge of the insect biology is the basis for exploration and application of efficient protection measures.
Materijal i metode
Biology of ash weevil was studied in the period 2007–2009 in the narrow – leaved ash stands in the Branjevina forest near Odžaci in Serbia (N 45° 27´ 15´´, E 19° 12´ 11´´) in the laboratory and in building with walls covered with mesh (outdoor conditions) in Novi Sad.
Overwintered adults activation time, their number, number of larvae, cocoons, and adults of new generation was observed and registered in Branjevina forest on 15 permanently marked lower branches on 15 trees, approx. 1 m in length. For every 6–9 days from February to July in 2008 and 2009 branches are thoroughly inspected and recorded present number of adults, adults in copulation, larvae and cocoons of ash weevil on branches.
By growing insects in the building with the outdoor conditions we studied fertility and fecundity, the duration of the embryonic, larval and pupal stage of development, the amount of food consumed by larvae and adults, as well as the number of generations.
In order to determine the time of laying eggs, fertility and fecundity of the ash weevil females, moss was collected in the forest Branjevina from twelve narrow – leaved ash trees in January 2008. The moss was inhabited by overwintering adults of ash weevil. The moss was placed in two cages lined with mesh size 50 ´ 50 ´ 70 cm, which were kept in the building with outdoor conditions. From the moss were extracted three females to review reproductive organs and determining the presence of eggs in the ovaries on 1st, 11th, 18th and 28th February and 10th March 2008. After activation of adults from moss on March 15th adults were put into a plastic box with a diameter of 15 cm and a height of 8 cm covered with mesh and fed by narrow – leaved ash buds and grown in outdoor conditions. The dissection of three females was carried out every three days until the end of March. Also, immediately after overwintered adults activation, from the moss in cages, based on morphological difference was allocated 20 pairs of males and females from March 15th to March 21st and they were separately grown in 20 plastic boxes with a diameter of 12 cm and a height of 6 cm covered by the net. Branches of narrow – leafed ash with 5–10 undamaged buds, and undamaged shoots were placed into the cages. Buds and shoots were taken from undamaged and for that purpose cultivated plants. Cages were cleaned periodically every 1–2 days, the new feed added, and eggs oviposited in all previously placed buds, shoots and stronger leaf stems were observed with examination under stereo microscope and counted. In this way the period of egg laying and female fertility was determined. After death, females were dissected in order to determine the number of eggs remained in the ovary and the total fecundity. Experiment was established under outdoor conditions.