Pteromalid fauna (Hymenoptera, Pteromalidae) in oilseed rape (Brassica napus L.) fields in Bulgaria – species composition and perspectives for biological control

Parasitoid wasps belonging to the family Pteromalidae are widespread and abundant members of the insect communities in the temperate regions of the world. As many other chalcids do, pteromalids serve as natural enemies of the pests in various crops and play an important role in the biological control of these harmful insects. Here we present the results of a field study in Bulgaria which was focused on the diversity of family Pteromalidae in ten oilseed rape fields. All samples were collected by sweep netting on the border line or inside the crop field. A total of 93 pteromalid specimens belonging to 26 taxa were gathered. The most abundant genus was Mesopolobus – 67% of the sampled pteromalids. The most numerous species in the samples was Mesopolobus morys – a well-known key parasitoid of the cabbage seed weevil, Ceutorhynchus obstrictus, in Europe. One species – Halticoptera patellana, is recorded for the first time in Bulgarian fauna. Clearfield oilseed rape fields had relatively higher parasitoid abundance and richness than the fields treated by conventional technology. In the present work we discuss the overall species composition of Pteromalidae obtained from the studied areas and present our point of view on the perspectives for biological control of oilseed rape pests

Morphological and molecular characterisation, and phylogenetic position of X. browni sp. n., X. penevi sp. n. and two known species of Xiphinema americanum-group (Nematoda, Longidoridae)

Using ribosomal (18S, ITS1, ITS2, D2-D3 expansion segments of 28S rDNA) and mitochondrial (partial cox1 and nad4) DNA markers in a study of several populations of Xiphinema americanum-group from Europe and Morocco, two cryptic species X. browni sp. n. (formerly reported as X. pachtaicum) and X. penevi sp. n. were revealed. The species are described, illustrated and their phylogenetic relationships discussed. The first species is most similar to X. parasimile and is a member of X. simile species complex. The phylogenetic reconstructions inferred from three molecular markers (18S, D2-D3 28S rDNA and cox1) showed that X. penevi sp. n. is part of X. pachtaicum-subgroup and is closely related to X. incertum, X. pachtaicum, X. parapachydermum, X. plesiopachtaicum, X. astaregiense and X. pachydermum. Also, a separate “X. simile-subgroup”, outside the X. pachtaicum-subgroup and so far consisting only of the parthenogenetic species X. simile, X. parasimile, X. browni sp. n. and probably X. vallense was formed. New primers for amplification and sequencing of part of the nad4 mitochondrial gene were designed and used

Studies of the genus Enchodelus Thorne, 1939 (Nematoda, Nordiidae) from Arctic polar deserts. 1. Species with long odontostyle: E. makarovae sp. n. and E. groenlandicus (Ditlevsen, 1927) Thorne, 1939, with an identification key to the species of the E. macrodorus group

Two nematode species of the genus Enchodelus Thorne, 1939, one new and one known from Arctic polar deserts were studied. Enchodelus makarovae sp. n. is an amphimictic species, characterised by females with body length of 1.57–2.00 mm, lip region 15–17.5 µm wide, amphid duplex, odontostyle 38–43 µm long or 2.3–2.8 times lip region diam. Odontophore with flanges, 1.2–1.4 times as long as odontostyle; pharynx length 320–377 µm, pharyngeal expansion 113–130 µm long or 32–37% of total pharynx length; female genital system amphidelphic, uterus tripartite, pars refringens vaginae with two trapezoid sclerotisations, vulva a transverse slit (V=45–51%); tail bluntly conoid (25–35 µm, c=45.8–70.3, c’=0.6–0.9 in females, and 29–33 µm, c=46.4–58.9, c’=0.7–0.8 in males). Males with 65–74 µm long spicules and 10–12 spaced ventromedian supplements. Additional information for Enchodelus groenlandicus is provided, this being a new geographic record for the Putorana Plateau, Russian Arctic

On two closely related species of Xiphinema americanum-group: X. simile Lamberti, Choleva & Agostinelli, 1983 and X. parasimile Barsi & Lamberti, 2004 (Longidoridae), with a description of the male of X. parasimile

Several populations of Xiphinema simile Lamberti, Choleva & Agostinelli, 1983 and two of X. parasimile Barsi & Lamberti, 2004, originating from various habitats – natural and man-made, have been studied. Xiphinema simile was associated both with cultivated and naturally growing plants, while X. parasimile was recovered from soil around grapevine. Data on the morphological and biometrical characteristics (including juvenile stages) are presented and variations discussed. Pharyngeal bulbus and glandularium length, vaginal and uterine characteristics were shown to be good differentiating characters. Present report of X. parasimile is a new record for Bulgaria as well as a new plant association for the species. The description of its male is provided for the first time. The Bulgarian population of X. parasimile showed the same pattern as the Serbian population revealed by the RFLP analyses of D1-D2 region

Ground beetles (Coleoptera: Carabidae) diversity from pastures in Southern Bulgaria

This study aimed at clarifying the species composition and ecological structure of carabids, associated with active pastures. Field work was carried out in 2017 and 2018. Pitfall traps (5 in each site) were set in 10 sampling sites in Thracean Lowland and Sarnena Sredna Gora Mts. Captured beetles belonged to 90 species and 33 genera, representing 12% of the species and 26% of the ground beetle genera occurring in Bulgaria. The most diverse was genus Harpalus (22 species), followed by the genera Amara (7 species), Microlestes (6 species), Ophonus (6 species) and Parophonus (5 species). Twenty species were new for the region of the Thracean Lowland: Amara fulvipes (Audinet-Serville, 1821), Anisodactylus binotatus (Fabricius, 1787), A. intermedius Dejean, 1829, Apotomus clypeonitens Müller, 1943, Calathus cinctus Motschulsky, 1850, Carterus gilvipes (Piochard de la Brûlerie, 1873), Gynandromorphus etruscus (Quensel en Schönherr, 1806), Harpalus fuscicornis Ménétriés, 1832, H. subcylindricus Dejean, 1829, Microlestes apterus Holdhaus, 1904, M. corticalis (L. Dufour, 1820), M. fulvibasis (Reitter, 1901), M. maurus (Sturm, 1827), M. minutulus (Goeze, 1777), Notiophilus laticollis Chaudoir, 1850, Pangus scaritides (Sturm, 1818), Parophonus laeviceps (Ménétriés, 1832), P. planicollis (Dejean, 1829), Polystichus connexus (Geoffroy in Fourcroy, 1785) and Pterostichus strenuus (Panzer, 1796). Twenty species were new for the whole Sredna Gora Mts.: Acinopus picipes (Olivier, 1795), A. megacephalus (P. Rossi, 1794), Amara anthobia A. Villa et G. B. Villa, 1833, Ditomus calydonius (P. Rossi, 1790), Harpalus albanicus Reitter, 1900, H. angulatus Putzeys, 1878, H. attenuatus Stephens, 1828, H. dimidiatus (P. Rossi, 1790), H. flavicornis Dejean, 1829, H. pumilus Sturm, 1818, H. pygmaeus Dejean, 1829, H. subcylindricus Dejean, 1829, H. tardus (Panzer, 1796), H. signaticornis (Duftschmid, 1812), Lebia scapularis (Geoffroy, 1785), Microlestes fissuralis (Reitter, 1901), M. fulvibasis (Reitter, 1901), M. maurus (Sturm, 1827), M. minutulus (Goeze, 1777) and Ophonus sabulicola (Panzer, 1796). Fourty-one species were new for the region of the Sarnena Sredna Gora. Genus Apotomus, Gynandromorphus, Pangus and Polystichus were new geographic records for Thracean Lowland. Genera Acinopus and Ditomus were new for the Sredna Gora Mts. Fourteen life form categories were established (9 zoophagous and 5 mixophytophagous). The analysis of the life forms showed a slight predominance of the mixophytophages (53 species; 59%) over the zoophages (37 species; 41%). Microlestes minutulus was a constant species occurring in all sampling sites

Nematode diversity in four crop types (pea, apple, lavender and rose) in southern Bulgaria

Nematodes represent one of the largest phyla in the animal kingdom and are a key component of the soil microfauna (organisms with body width <0.2 mm). Being a widespread and diverse group, they display a wide range of adaptations and lifestyle traits. Their functional role in soil food-webs is mostly related to their feeding type. The majority of terrestrial nematodes feed on plant roots, bacteria and fungi, while a small group of plant associated species spend part or their whole life cycle in roots. Some plant-feeding species are known as important pests that can parasitize various crops causing adverse effects on yield and production quality. Their effective management requires accurate detection and identification. In the frame of the National Research Program "Healthy Foods for a Strong Bio-Economy and Quality of Life", selected groups of soil nematodes are used as bioindicators for assessing soil and plant health, and ecosystem services in several agricultural ecosystems. Nematode communities from four crop types (pea, apple, lavender and rose) in southern Bulgaria managed by conventional and organic farming were sampled and investigated. Here we present some preliminary results on pea, lavender and rose associated nematode diversity. Multiple core samples from 18 sampling plots were collected in June 2019. Nematodes were isolated from 200 g of soil by decanting and sieving method, fixed, dehydrated and mounted on permanent slides. Overall, over 60 genera belonging to five trophic groups were identified. Approximately half of the nematode genera found are obligatory plant- and plant/fungus feeders. Parasitic nematodes were represented by 12 genera, some of which include important pests known to cause severe damages on crops e.g. Meloidogyne Goeldi, 1889, Pratylenchus Filipjev, 1934, Pratylenchoides Winslow, 1958 and Tylenchorhynchus Cobb, 1913

Predatory nematodes of the order Mononchida from riparian habitats in Bulgaria

The riparian zones represent habitats of high and specific biodiversity; however, historically they have been subject to intensive exploitation and most of them are drastically changed. Predatory nematodes are widespread terrestrial organisms and play an important role in biological regulation of litter/soil communities. Some preliminary results on the mononchid fauna in riparian habitats in South Bulgaria are presented. Thirty-four samples were collected from 29 localities with various vegetation types in three districts: Sofia, Smolyan and Burgas. Multiple core soil samples (3 per site) were collected from each habitat (15×15 m sampling site or along the river bank) around the roots of the dominant tree at a depth of 40–60 cm and from litter. The most intensively sampled plant tree was Salix spp. (11 samples) followed by Fraxinus spp. (8), Alnus glutinosa (L.) Gaertn. (6) and Ulmus spp. (3). Nematodes were isolated from 200 g of soil (by decanting and sieving method) and 10 g of litter (Baerman funnel method), fixed, dehydrated and mounted on permanent slides. More than 90% of all soil and litter samples contained at least one mononchid genus. Six genera: Prionchulus (Cobb, 1916) Wu and Hoeppli, 1929, Clarkus Jairajpuri, 1970, Mononchus Bastian, 1865  (fam. Mononchidae), Mylonchulus Cobb, 1916 (fam. Mylonchulidae), Miconchus Andrassy, 1958 and Anatonchus Cobb, 1916 (fam. Anatonchidae) were recovered. Prionchulus spp. prevailed in litter, occurring in half of the collected samples, while Mylonchulus spp. were most common in soil samples (35%). Representatives of Clarkus and rarely Mylonchulus occurred in both litter and soil. The highest diversity of mononchids (4 genera) was detected in the rhizosphere of Ulmus laevis Pall. along a small river in Strandzha Mt. Further morphological and molecular studies on populations and species identification are envisaged