We have identified the following three taxa related to the Aphidius colemani species group, which are important biological control agents: Aphidius colemani, Aphidius transcaspicus and Aphidius platensis. Using partial sequences of the mitochondrial cytochrome oxidase subunit I (mtCOI) gene and geometric morphometric analysis of the forewing shape, we have explored the genetic structure and morphological variability of the A. colemani group from different aphid host/plant associations covering a wide distribution area. The topology of the maximum parsimony and maximum likelihood trees were identical with 98-100% bootstrap support, clustering A. colemani, A. platensis and A. transcaspicus into separate species. The distances among the taxa ranged from 2.2 to 4.7%, which is a common rate for the between-species divergence within the subfamily Aphidiinae. Differences in the shape of the forewing investigated within the biotypes of A. colemani group are congruent with their genetic diversification. Both A. platensis and A. colemani share a common host range pattern, and it would be interesting to estimate and compare the role of these two species in future biological control strategies against aphids of economic importance. Our results indicate that 'genetic screening' is a reliable approach for identification within the A. colemani group. The high variation in the wing shape among species, including a significant divergence in the wing shape among specimens that emerged from different hosts, makes the forewing shape and wing venation less reliable for species determination. Aphidius platensis is diagnostified and redescribed, and the key for the A. colemani group is presented.

Maize redness (MR), induced by stolbur phytoplasma ('Candidatus Phytoplasma solani', subgroup 16SrXII-A), is characterized by midrib, leaf, and stalk reddening and abnormal ear development. MR has been reported from Serbia, Romania, and Bulgaria for 50 years, and recent epiphytotics reduced yields by 40 to 90% in South Banat District, Serbia. Potential vectors including leafhoppers and planthoppers in the order Hemiptera, suborder Auchenorrhyncha, were surveyed in MR-affected and low-MR-incidence fields, and 33 different species were identified. Only Reptalus panzeri populations displayed characteristics of a major MR vector. More R. panzeri individuals were present in MR-affected versus low-MR fields, higher populations were observed in maize plots than in field border areas, and peak population levels preceded the appearance of MR in late July. Stolbur phytoplasma was detected in 17% of R. panzeri adults using nested polymerase chain reaction but not in any other insects tested. Higher populations of R. panzeri nymphs were found on maize, Johnsongrass (Sorghum halepense), and wheat (Triticum aestivum) roots. Stolbur phytoplasma was detected in roots of these three plant species, as well as in R. panzeri L(3) and L(5) nymphs. When stolbur phytoplasma-infected R. panzeri L(3) nymphs were introduced into insect-free mesh cages containing healthy maize and wheat plants, 89 and 7%, respectively, became infected. These results suggest that the MR disease cycle in South Banat involves mid-July transmission of stolbur phytoplasma to maize by infected adult R. panzeri. The adult R. panzeri lay eggs on infected maize roots, and nymphs living on these roots acquire the phytoplasma from infected maize. The nymphs overwinter on the roots of wheat planted into maize fields in the autumn, allowing emergence of phytoplasma-infected vectors the following July.

Elm yellows phytoplasmas (EY) belonging to the 16SrV-A subgroup were recently proposed as a new candidate species 'Candidatus Phytoplasma ulmi'. These pathogens infect elm trees, causing leaf yellowing and premature drying. In this study, 25 isolates originating from localities in northeast, east and southwest Serbia were characterized by means of RFLP analysis and DNA sequencing of four genomic loci: 16S rRNA, ribosomal protein rpl22-rps3, secY and map. In total, five different genotypes were identified based on collective sequencing of all four genes. Four of these genotypes showed significant nucleotide changes compared with the EY1 T reference strain. Phylogeny based on parsimony analyses of ribosomal protein, secY and map genetic loci indicated a single monophyletic origin of EY1 T and the new 'Ca. Phytoplasma ulmi' strains. Unlike phylogenetic clustering, DNA sequence comparison of EY1 T and the novel strains revealed mutations in oligonucleotide signature sequences for all three genes (16S, rpl22-rps3 and secY) used for the characterization and assignment of 16SrV-A phytoplasmas to the 'Ca. Phytoplasma ulmi' species in the original description. Based on their high degree of genetic variability, the Serbian strains were assigned to four different subtypes of 'Ca. Phytoplasma ulmi' (EY-S1, EY-S2, EY-S3 and EY-S4). New diagnostic enzymes for practical use in 'Ca. Phytoplasma ulmi' identification are proposed for the 16S rRNA, ribosomal protein and secY genes. The implications of genetic variability within signature sequences for taxonomy and identification of 'Ca. Phytoplasma' species, as well as the importance of geographic variability and number of strains characterized for species description, are discussed.

In this study, the relationships among and the taxonomic status of three closely related parasitic wasps that are widely used as biological control agents of cereal aphids, Aphidius uzbekistanicus Luzhetzki, Aphidius rhopalosiphi De Stefani Perez, and Aphidius avenaphis (Fitch), were examined. Genetic divergence at an average of 6% was recorded between A. uzbekistanicus and A. rhopalosiphi by using the mitochondrial (mt) gene cytochrome oxidase I (COI) barcoding region. Identical mtCOI gene sequences were observed in A. uzbekistanicus specimens that originated from Eurasia and in the North American species A. avenaphis. The haplotype fluctuation in A. rhopalosiphi specimens that originated from the west Palaearctic was an average of 1.5% (maximum, 2.4%). In contrast, specimens of A. uzbekistanicus from central and western parts of Eurasia were largely homogenous, with only a single mutation recorded in a specimen from eastern Europe (Serbia). The morphological and genetic diversity found in A. rhopalosiphi may suggest the existence of cryptic species, especially for lineages that have a large degree of mtCOI diversity and sympatric occurrence. The geometric morphometric analysis of stigma shape presented in this study demonstrated that members of A. uzbekistanicus have a shorter forewing r vein and a more elongated stigma, relative to those of A. avenaphis. Our research validates the use of stigma shape and flagellomere 1 color for morphological discrimination between wasp species.

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Original information on aphidiines parasitizing aphids on herbaceous and shrubby ornamental plants in southeastern Europe is presented. In total, 22 species are keyed and illustrated with scanning electron micrographs, stereomicroscope micrographs, and line drawings. The aphidiines presented in this work have been identified from 40 aphid taxa. Two hundred sixty-six aphidiine— aphid—plant associations are presented, out of which 126 are new. The results are discussed in relation to the overall parasitoid—aphid-plant associations in the area.

We report the occurrence of Lysiphlebus orientalis in Serbia, an aphid parasitoid from the Far East that is new to Europe and has the potential to become invasive. Our finding based on morphological characters is confirmed by analyses of mitochondrial cytochrome oxidase subunit I sequences. An increase in number and an expansion of the host range were observed during field studies over the past two years, and it is determined that the current host range encompasses nine aphid hosts on 12 different host plants, forming 13 tri-trophic associations. A host range determined for European populations of L. orientalis appears wider compared with that in its Far Eastern native habitats where Aphis glycines Mats. is the sole known host. Moreover, it overlaps considerably with the host ranges of European parasitoids that play an important role in the natural control of pest aphids.

The genus Praon represents a large group of aphid endoparasitoids and is exemplary for the problems encountered in their taxonomy because of a great variability of morphological characters. To investigate the intraspecific variability and to ascertain cryptic speciation within the Praon abjectum Haliday group, biotypes in association with the aphid hosts Aphis sambuci L., Longicaudus trirhodus Walker, and Rhopabsiphum spp. were examined. We combined molecular and geometric morphometric analyses, that is, partial sequences of the mitochondrial cytochrome oxidase subunit I and nuclear 28SD2 genes and the shape of the forewing. Low variation of 28SD2 sequences confirmed the close relatedness of species from the genus Praon. Analysis of the cytochrome oxidase subunit I sequences however identified three separate taxa within the P. abjectum group with substantial genetic divergence. The biotype of P. abjectum associated with L. trirhodus differed from those associated with Rhopabsiphum sp. and A. sambuci by 5.4–6.5% and 7.7% sequence divergence, respectively, while the genetic distance between the latter two biotypes ranged from 9.5 to 10%. The main changes in the forewing shape that discriminate these three biotypes as revealed by geometric morphometrics are related to the stigma shape and the position of the radial nerve. Based on the differences determined in mitochondrial sequences and in the shape of the wing, we describe two new cryptic species within the P. abjectum group as follows: P. sambuci sp. n. in association with A. sambuci/S. nigra and P. longicaudus sp. n. in association with L. trirhodus/T. aquilegifolium.