Influenza dei fattori ambientali e agronomici sulle popopolazioni di Empoasca Vitis (GOETHE)

In this work the effects of a number of agronomic and environmental factors on populations of the green grape leafhopper Empoasca vitis (Gothe) (Homoptera: Cicadellidae) have been studied in north-eastern Italy. The life cycle of E. vitis has been studied in vineyards of the Veneto region from 2006 to 2008. Grape phenology showed significant changes in spring of 2007 when temperatures were higher than in 2006 and 2008. In this season the first and the second generations of E. vitis developed in advance and a fourth generation was recorded in a hilly vineyard (new record for Italy). The spatial and temporal distribution of E. vitis and its major parasitoid (Anagrus atomus group) has been studied in an agroecosystem including a large vineyard and a natural stand. The distribution of the two species showed be aggregated in spring, sometimes in summer. A positive association betwene the two species was observed in spring. In this period Empoasca vitis adult catches were higher near the stand while in summer adults dispersed in the whole vineyard area. Anagrus populations resulted higher in the area nearby the stand. Implications for natural control of E. vitis are suggested. Grape training systems can exert pronounced effects on E. vitis abundance. Higher E. vitis densities have been found in two training systems, i.e. Guyot and “pergola”. This trend occurred probably because of the homogeneous canopy structure of these systems compared to Sylvoz or GDC systems. The irrigation affects positively E. vitis numbers in vineyards. The effects of different irrigation systems on grape leafhoppers were compared in an experimental vineyard. Highest E. vitis densities were detected in drop irrigation plots as compared with not irrigated plots where water stress was remarkable. A moderate water stress (sub-irrigation and partial root-zone drying plots) was associated with intermediate leafhopper densities. Ad hoc studies conducted on potted vines showed that a moderate water stress reduces significantly the reproductive potential and the egg survival of E. vitis. A remarkable stress reduces dramatically the survival of eggs and the density of offspring. A survey was conducted on a cultivar collection in order to evaluate their susceptibility to E. vitis. Carmenere and Sauvignon Blanc showed to be very susceptible in contrast with Cabernet Sauvignon and Incrocio Manzoni 6.0. 13. Some cultivars showed a low incidence of symptoms despite relatively high leafhopper densities. These results may be useful for monitoring leafhoppers in vineyards. The impact of E. vitis infestations on yield parameters was studied on some cultivars (i.i. Prosecco, Merlot, Cabernet Franc). Similar population sizes were associated with a different impact on yield parameters (especially solid soluble contents and acidity) depending on the cultivar. Control trials showed the high effectiveness of flufenoxuron and thiamethoxam on E. vitis populations resistant to chlorpyriphos-ethyl. A number of fungicides showed an impact on E. vitis numbers, a finding potentially useful in managing the pest in vineyards.