Spatial Distribution of Jacobiasca lybica (Bergenin & Zanon) (Homoptera: Cicadellidae) Egg Populations in an Irrigated Sherry Vineyard

摘要

Jacobiasca lybica (Berg. & Zanon) (Homoptera: Cicadellidae), the green leaf hopper, is the most serious phytosanitary problem in vineyards in the southern regions of the Iberian Peninsula, producing serious economic damage (Araujo 1988, Quartau et al.1989, Quartau & Rebelo 1992), Damage is usually very serious because it affects not only the quality and quantity of grapes but also because the plant nutrient reserves for the following season are severely curtailed. Adults and nymphs feed almost continuously, piercing and sucking the cell contents in all mesophyll cells. Attacked leaves eventually change color and become scorched from the lack of sap movement. The leaves frequently curl toward the undersides. After very severe attacks, leaves drop tothe ground, leaving the grapes exposed to the sun and thus causing "scalding" of the berries. Despite the high incidence of J. lybica infestations, at present little is known of its spatial distribution and biology because of its new pest status in Spanish vineyards (Toledo 1992, Ramirez-Davila 2003). Previous studies in Italy (Delrio et al. 2001) suggested that the nymphs of J. lybica follow an aggregated pattern in vineyard. However, they don't give any indication about the egg distributions.