Luca Picciau

Parasitoid recruitment to the globally invasive chestnut gall wasp Dryocosmus kuriphilus

The chestnut gall wasp Dryocosmus kuriphilus is a global pest of chestnut (Castanea). Established as a pest in the mid 20th century in Japan, Korea and the USA, this species has now reached Europe. Successful deployment of a biocontrol agent, Torymus sinensis, in Japan has led to its early release in Italy. Here we provide the first overview of the natural enemies associated with D. kuriphilus in its native and invaded ranges, and discuss general patterns in community development. We then use what is known about European oak gall wasp communities to predict possible future developments for D. kuriphilus, and possible interactions between parasitoid communities attacking hosts on chestnut and oaks.

Molecular differentiation of four Reptalus species (Hemiptera: Cixiidae).

The cixiid species Reptalus quinquecostatus, R. cuspidatus, R. panzeri and R. melanochaetus are widely distributed in Europe and are receiving growing attention because of their potential role as phytoplasma vectors. Identifying the Reptalus species is restricted to a few specialist entomologists and relies on the morphology of the male genitalia, hampering the identification of juveniles and females. This study provides the tools for species discrimination by integrating the morphological description, which is primarily for the genus identification, with new molecular assays, based on both ribosomal and mitochondrial DNA. PCR-RFLP assays carried out on the mitochondrial cytochrome oxidase I gene (COI) with AluI provided species-specific profiles for the four Reptalus species. Amplification of a ribosomal internal transcribed spacer (ITS2) region produced species-specific fragments of different sizes for R. quinquecostatus, R. melanochaetus, R. cuspidatus and R. panzeri. The digestion of the ITS2 PCR product with TaqI allowed the discrimination of these latter two species. This molecular identification key ensures reliable results and can be successfully applied not only to adults, but also to the nymphs feeding on the roots. The identification of the nymphs (i) extends the collection period of these monovoltine species to the whole year (adults are present for a short summer period) and (ii) allows the unambiguous identification of their actual host plants because nymphs are steady on the root system while adults tend to disperse onto other plants. Fast and reliable identification of the Reptalus species provides useful help in monitoring activities and, therefore, in designing rational control strategies to protect crops from phytoplasma infection.

Leafhoppers and Cixiids in Phytoplasma-infected Carrot Fields: Species Composition and Potential Phytoplasma Vectors

SUMMARY The first molecular analysis of samples collected in southern Backa (Serbia) confirmed the presence of aster yellows (16SrI) and stolbur phytoplasmas (16SrXII) in insects belonging to the family Cicadellidae, as well as in carrot plants where the insects were collected. A correct identification of the phytoplasmas and their vectors is essential to arrange effective control strategies to prevent diseases associated with phytoplasmas from spreading to carrots and other vegetable crops. In order to enhance knowledge about insect vectors of aster yellows and stolbur phytoplasmas in Serbia, Cicadellidae and Cixiidae (Homoptera Auchenorrhyncha), the most common vectors of these phytoplasmas, were monitored in southern Backa during 2008. Adults leaf- and planthoppers were collected and identified at species level using standard entomological methods, and tested for phytoplasma presence by means of PCR/RFLP. A total of 13 insect species of Cicadellidae were identified, as follows: a) three species of the subfamily Agallinae: Anaceratagallia ribauti (Ossiannilsson), Anaceratagallia venosa (Fourcroy), and Anaceratagallia laevis (Ribaut); b) seven species of the subfamily Deltocephalinae: Psammotettix confinis (Dahlbom), Psammotettix striatus (Linnaues) Psammottettix alienus (Dahlbom), Macrosteles sexnotatus (Fallen), Ophiola decumana (Kontkanen), Errastunus ocellaris Fallen, and Scaphoideus titanus Ball; c) three species of the subfamily Typhlocibinae: Eupteryx atropunctata (Goeze), Eupteryx mellissae Curtis, Zyginidia pullula (Boheman). Female specimens of the genus Euscelis (Deltocephalinae) were also collected,

Wild plants could play a role in the spread of diseases associated with phytoplasmas of pigeon pea witches'-broom group (16SrIX)

Phytoplasmas are cell wall-less prokaryotic parasites associated with diseases affecting hundreds of plant species. In the Middle East, phytoplasmas of taxonomic subgroups 16SrIX-B and -C are the etiological agents of important diseases of almond and sesame, and are transmitted from plant-to-plant by leafhoppers and planthoppers. In the present study, surveys on wild plants as reservoirs of 16SrIX phytoplasmas have been carried out in North and South Lebanon. During field surveys, leaf samples were collected from 261 wild plants belonging to 41 species within 25 families. PCR-based analyses allowed the detection of 16SrIX phytoplasmas in the leaf samples of 24 plants belonging to 12 species. Eight of such species have been reported as phytoplasma hosts for the first time. Molecular characterization by nucleotide sequence analysis of 16S rRNA and rplV-rpsC genes revealed that the infected wild plant species harbored 16SrIX-C phytoplasma strains genetically undistinguishable. In silico enzymatic digestion of 16S rDNA sequences of phytoplasma strains, described in previous works, allowed the recognition of two new tentative subgroups (16SrIX-G and -H) within group 16SrIX. Results of the present study highlighted the wide host range of 16SrIX-C phytoplasma, associated with almond broomings, an almond witches’- broom-like disease in Iran, and with sesame phyllody in Iran and Turkey. The potential adaptation of 16SrIX-C phytoplasma to numerous wild plants highlights the elevated risk of its spread throughout the Middle East and neighbouring geographic regions.

Insect vectors of plant pathogenic Mollicutes in the Euro-Mediterranean region

This paper embeds a review of insect vectors of Mollicutes plant pathogens in Europe and Middle East. A dissertation on systematic and phylogeny introduces the two groups of vectors: Auchenorrhyncha and Sternorrhyncha (Psyllidae). Aspects involving the differences in the transmission process of pathogens and the relationships of insect vectors and host plants have been considered. From an environmental point of view, flight activity, dispersal and spatial distribution have been dealt with in relationship with plant disease epidemiology. Finally, the main control and monitoring strategies have been discussed, along with the problem concerning alien species and quarantine regulations.

Transmission of 16SrIII-J phytoplasma by Paratanus exitiosus (Beamer) leafhopper in grapevine

The most common insect in Chilean phytoplasma-infected vineyards, belonging to the family Cicadellidae, is Paratanus exitiosus (Beamer). This leafhopper was proved to be able to transmit the 16SrIII-J phytoplasma to periwinkle plants. In the present work we demonstrate that P. exitiosus transmits the same phytoplasma to grapevine plants too.

Transmission of 16SrIII-J phytoplasma by Bergallia valdiviana Berg 1881 leafhopper

One of the most common insects in vineyards infected with phytoplasmas belonging to the family Cicadellidae, is Bergallia valdiviana Berg 1881 This leafhopper has not yet been described as a phytoplasma vector. The present work demonstrates that B. valdiviana is able to transmit phytoplasmas to periwinkle plants.

New insights in phytoplasma-vector interaction: acquisition and inoculation of flavescence dorée phytoplasma by Scaphoideus titanus adults in a short window of time: Phytoplasma acquisition and transmission by Scaphoideus titanus adults

The leafhopper Scaphoideus titanus is able to transmit 16SrV phytoplasmas agents of grapevine’s flavescence dorée (FD) within 30–45 days, following an acquisition access period (AAP) of a few days feeding on infected plants as a nymph, a latency period (LP) of 3–5 weeks becoming meanwhile an adult, and an inoculation access period (IAP) of a few days on healthy plants. However, several aspects of FD epidemiology suggest how the whole transmission process may take less time, and may start directly with adults of the insect vector. Transmission experiments have been set up under lab condition. Phytoplasma-free S. titanus adults were placed on broad bean (BB) plants (Vicia faba) infected by FD-C (16SrV-C) phytoplasmas for an AAP=7 days. Afterwards, they were immediately moved onto healthy BB for IAP, which were changed every 7 days, obtaining three timings of inoculation: IAP 1, IAP 2 and IAP 3, lasting 7, 14 and 21 days from the end of AAP, respectively. DNA was extracted from plants and insects, and PCR tests were performed to identify FD phytoplasmas. Insects were dissected and fluorescence in situ hybridisation was made to detect the presence of phytoplasmas in midguts and salivary glands. The rate of infection in insects ranged 46–68% without significant differences among IAPs. Inoculation in plants succeeded in all IAPs, at a rate of 16–23% (no significant differences). Phytoplasma load was significantly higher in IAP 3 than IAP 1–2 for both plants and insects. Phytoplasmas were identified both in midgut and salivary glands of S. titanus at all IAP times. The possible implications of these results in the epidemiology of flavescence dorée are discussed.

The genus Cixius Latreille, 1804 (Hemiptera, Fulgoromorpha, Cixiidae) in Lebanon with the description of two new species

A first list of Cixius fauna of Lebanon is here provided with the description of two new species: one within the subgenus Acanthocixius, Cixius bifidispinus sp. nov. and one within the subgenus Ceratocixius Cixius superremotus sp. nov. The standard morphological description is supplemented by sequence data of the mitochondrial cytochrome c oxidase subunit I (COI) gene fragment. Some notes on their distribution and economic importance are also reported.