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ŠUMARSKI LIST 3-4/2021 str. 46     <-- 46 -->        PDF

(Wanat and Gosik 2003, Gosik 2006), could also explain its absence in the part of analysed seeds, as one of two sampling locations was a floodplain forest stand (Sunja).
The other pest found on both ash species in this research was P. conwagana, a phytophagous moth from Lepidoptera family widespread through the Eurasia region on the plants belonging to genera Ligustrum, Fraxinus, Syringa and Berberis (Tapper 1992). In Europe large numbers of its caterpillars were reported in seeds of common ash in England, causing 15-36% seed loss (Gardner 1977), and also in Sweden (Tapper 1992, Hayatgheibi 2013), Slovakia (Kollar 2007), Lithuania (Ostrauskas 2004) and Poland (Kubasik 2011). There are no reports of this pest in narrow-leaved ash and green ash seeds generally, nor was it found in Croatia before. Currently, P. conwagana is not a threat to the examined ash species in Croatia, since it was found in only two narrow-leaved ash seeds from Županja and in one green ash seed from Sunja (both in woodland areas). Regarding narrow-leaved ash, the low infestation rate could be the consequence of a decrease in seed production (Vincenc 2015, 2016, 2017, 2018, 2019), as Janzen (1971) reports that natural fluctuations of ash species in seed production lead to lower rates of moth infestation. However, this explanation is not applicable to green ash, and it might be that in Croatia ash species are not the primary source of food for this seed-feeding tortricid, but rather some other plant species.
In the seeds of both species of ash, parasitoid wasps were detected in the larval, pupal, and adult stages. The only determined species was E. urozonus collected from the green ash seeds from both sampling locations. This wasp is considered to be exceptionally polyphagous, as it occurs on hosts belonging to Lepidoptera (Gelechiidae, Oecophoridae, Tortricidae), Coleoptera (Bruchidae, Curculionidae, Scolytidae), Diptera (Agromyzidae, Cecidomyiidae, Tephritidae), Neuroptera (Chrysopidae) and Hymenoptera (Cynipidae, Braconidae, Tenthredinindae, Ichneumonidae) (Gibson and Fusu 2016). Although E. urozonus is reported to be established throughout Europe (Gibson and Fusu 2016), this is the first official report of its presence in Croatia. Comparing found specimens of adult wasps with the descriptions in the literature (Al khatib et al. 2014), there is a possibility that some of the acquired adults could also be E. urozonus, but this requires further investigation. Larval stages of parasitoid wasps found in green ash where determined to belong to Pteromalidae family, which is the largest family within superfamily Chalcidoidea with over 3.500 mostly parasitic species, often difficult to determine (Burks 2009). Wasp larvae in narrow-leaved ash and adults found in both species of ash could not be identified by molecular genetic analysis due to their small numbers and size, but were identified by their morphological characteristics as parasitoid wasps. For further determination they require a more detailed examination.
Comparing the health status of the seeds of the native narrow-leaved ash and the introduced green ash, the native seeds were generally in a better state. As for green ash seeds, those collected from a forest stand (Sunja) were less damaged by insects than the ones collected from the urban park in Zagreb, which is in accordance with the claim that L. bischoffi most often occurs in the urban areas (Wanat and Gosik 2003, Gosik 2006). Considering that two most numerous pests found in this study, L. enucleator and L. bischoffi prefer urban areas, that relatively large number of parasitoids was found in the seeds and on their larvae, and that other pests were present in a very small number of seeds, it can be concluded that insects currently do not have a significant negative impact on the reproduction of narrow-leaved ash and green ash in forest stands.
We thank Croatian Forests Ltd. for providing samples for this research and Mirjana Grahovac-Tremski for kindly providing all the necessary information regarding seed origin, collection and storage.
Al khatib, F., L. Fusu, A., Cruaud, G., Gibson, N., Borowiec, J.-Y., Rasplus, N., Ris, G., Delvare, 2014: An integrative approach to species discrimination in the Eupelmus urozonus complex (Hymenoptera, Eupelmidae), with the description of 11 new species from the Western Palaearctic, Systematic Entomology, 39: 806–862.
Arndt, E., S., Hielscher, 2007: Ground beetles (Coleoptera: Carabidae) in the forest canopy: species composition, seasonality, and year-to-year fluctuation. In: M. Unterseher, W. Morawetz, S. Klotz, E. Arndt (eds.), The canopy of a temperate floodplain forest. Results from five years of research at the Leipzig Canopy Crane, Universitätsverlag, 106–110, Leipzig.
Arzanov, Y. G., 2013: Lignyodes bischoffi Blatchley, 1916 (Curculionidae) - A New Species of Invasive Weevils for Russia, Russian Journal of Biological Invasion, 4 (4): 209–211.
Bacal, S., N., Munteanu, I., Toderaș, 2013: Checklist of beetles (Insecta: Coleoptera) of the Republic of Moldova, Acta Musei, 8 (3): 415–450.
Battisti, A., A., Roques, F., Colombari, G., Frigimelica, M., Guido, 1999: Efficient transmission of an introduced pathogen via an ancient insect-fungus association, Naturwissenschaften, 86 (10): 479–483.
Benson, D. A., M., Cavanaugh, K., Clark, I., Karsch-Mizrachi, D. J., Lipman, J., Ostell, E. W., Sayers, 2017: GenBank, Nucleic Acids Research, 45 (1): 37–42.
Boivin, T., M.-A., Auger-Rozenberg, 2016: Native Fruit, Cone and Seed Insects in the Mediterranean Basin, In: T. Paine, F. Lieutier (eds.), Insects and Diseases of Mediterranean Forest Systems, Springer, 47–88, Cham.