Thirty-two species of Cicadellidae, including the Macropsinae, Agalliinae, Penthimiinae, Aphrodinae, Cicadellinae, Typhlocybinae and Deltocephalinae, 10 of which were already known as phytoplasma vectors, were captured in vineyards using yellow sticky traps. Adult population dynamics of the most abundant species of Penthimiinae and Deltocephalinae were studied over the whole growing season. Penthimia nigra was captured in May and June, Anoplotettix fuscovenosus in June-August, Fieberiella jlorii in August-October, Macrosteles sexnotatus in May and October, Scaphoideus titanus in July-September, Thamnotettix spp. (Th. confinis, Th. dilutior, Th. exemtus, Th. zelEeri) in April-June, while Euscelidius variegatus, Neoaliturus fenestratus, Platymetopius major and Psammotettix spp. (P. alienus, P. confinis) were trapped throughout the growing season. The aggregation level of the above species was investigated by means of Taylor's power law. A. fuscovenosus showed a nearly random distribution in vineyards (0.95 < b < 1.11), while N. fenestratus, P. major and S. titanus were strongly aggregated (1.32 < b < 1.81). The other species showed intermediate levels of aggregation (1.12 > b < 1.32). The results indicate that at least six Deltocephalinae species, A.fuscovenosus, E. variegatus, F. jlorii, M. sexnotatus, N. fenestratus and S. titanus, known as phytoplasma vectors and commonly found in vineyards, could play a role in Grapevine Yellows (GY) epidemiology. GY transmission trials with these species are needed.

A survey for the presence of aster yellows-related phytoplasmas in the different life stages of Scaphoideus titanus was carried out by means of PCR and nested-PCR assays. Using a phytoplasma 16Srl group-specific primer pair followed by RFLP analysis of amplified products, we were able to detect and identify phytoplasmas from eggs, newly hatched nymphs, fourth and fifth instar nymphs and adults reared on ten phytoplasma-free Vicia faba seedlings. Two of these broad beans became infected, whereas PCR failed to detect phytoplasmas in the same ten plants before leafhopper rearing. These results suggest the possibility of transovarial transmission of aster yellows-related phytoplasmas in S. titanus.

Chrysanthemum yellows (CY) phytoplasma is a plant‐pathogenic mollicutes belonging to the 16Sr‐IB genetic group which infects a variety of dicotyledonous plants and is transmitted in nature by some species of Cicadellidae Deltocephalinae. The transmission characteristics of CY and the factors influencing the vector efficiencies of the leafhoppers Macrosteles quadripunctulatus Kirschbaum and Euscelidius variegatus Kirschbaum are described in the present study using transmission experiments and phytoplasma‐specific polymerase chain reaction (PCR) assays. Vector insects were allowed to acquire CY under different experimental conditions and then transferred to healthy test plants for inoculation and/or sampled for DNA extraction and amplification. The transmission efficiency of CY was very high and almost all the leafhoppers became infective following acquisition on CY‐infected daisies. The latent period in the vector ranged from 16 to 20 days after the start of the acquisition and infectivity lasted, in general, for life. The PCR assay was successful in detecting CY phytoplasmas in the insects well before they became infective (5 versus 16–18 days) and was used to estimate the proportion of infective insects. When analysed for CY presence by PCR, all the leafhoppers fed for 7–18 days on source daisy reacted positively while, following one day of acquisition, some insects failed to provide amplification. Host‐plant species influenced CY acquisition, and daisy appeared a more efficient source for both leafhoppers compared to periwinkle. Life stage did not appear to be critical for CY acquisition, although newly‐hatched nymphs of E. variegatus acquired CY less efficiently than fifth instar nymphs.

No abstract

Homoptera Auchenorrhyncha are phytomyzous species having typical piercing-sucking mouth parts. These were carefully described for Deltocephalinae Macrosteles fascifrons (Forbes & Raine, 1973), Idiocerinae Idiocerus atkiasoni (Arora & Singh, 1962), Typhlocybinae Ribautiana ulmi (Willis, 1949), and Eupteryx melissae (Pollard, 1968). On the grounds of the vegetable tissue they involve, Auchenorrhyncha are divided into mesophyllomyzous, phloemomyzous, and xylemomyzous species when feeding concerns, respectively, parenchymatic cells, sieve-tubes or xylem-vessels. Considering their different trophic specialization, a comparative investigation of mouth parts of Cicadellidae with dissimilar feeding behaviour seemed to be interesting. Thus the mesophyllomyzous Zyginidia pullula (Boheman) (Typhlocybinae), the phloemomyzous Empoasca vitis (Goethe) (Typhlocybinae), and the xylemomyzous Graphocephala fennahi Young (Cicadellinae) were studied. In the present work, mouth parts of both adults and nymphs of 1st and 5th instars have been examined. MATERIALS AND METHODS ABSTRACT Head and mouth structures of the mesophyllomyzous species Zyginidia pullula (Typhlocybinae), the phloemomyzous Empoasca vitis (Typhlocybinae), and the xylemomyzous Graphocephala fennahi (Cicadellinae) were examined and shown to be very similar. On the other hand, the ratios between the lengths of mandibular and maxillary stylets were closely comparable in the two typhlocybines, but lower than that of the cicadelline, and apparently correlated with the systematic group rather than with the trophic behaviour.