Surveys of the presence of Hyalesthes obsoletus Signoret (Rhynchota: Cixiidae) and other hoppers in Lombardy (Northern Italy)

A monitoring programme was carried out in Lombardy from 2000 to study the presence and biology of the leafhoppers involved in phytoplasma transmission to grape. From 2003 also biomolecular analyses were performed to assess the frequency of “positive” insects using PCR. Special attention was given to Hyalesthes obsoletus Signoret (Rhynchota: Cixiidae), a leafhopper whose presence in vineyards is worrying because it is well known from literature that this insect can transmit to the grape the “bois noir”, a phytoplasma disease whose symptoms are very similar to those produced by the “golden flavescence”. During the surveys this species was only occasionally collected directly from grape, but it was quite abundant on weeds, mainly Urtica sp. and in a lesser extent, Convolvulus arvensis and Calystegia sp.. The percentage of “positive” specimens was quite different in the various localities but on the average the percentage of positive ones was rather low. According to these results, H. obsoletus does not seem to play a major role in transmitting the “bois noir” in Lombardy, as the insect can be found only occasionally on grape, and moreover because the percentage of “positive” specimens, at least in some areas, is very low.