Oviposition of Delphacodes kuscheli on barley plants under laboratoey conditions (Homoptera - Delphacidae).

Delphacodes kuscheli Fennah is at present the only species with demostrated ability as a vector of "Mal de Río Cuarto del maíz" in Argentina, the main virus disease nowadays affecting this crop. This insect develops on different gramineae. Under laboratory conditions, the barley is one of its preferred hosts. The main subject of this paper was to study the site preferences for oviposition. Egg characteristics and their localization in the plant tissues were also analyzed. The number of eggs in stem, leaf sheath, ligulae and leaf blade (lower, medium and upper third) were recorded. Leaf sheath and basal portion of leaf blade were significantly preferred for oviposition (ANOVA: F=18,6; gl 3/92; p< 0,001); the eggs being placed most frequently at 1cm over the ligule and 1,5 cm below it. They were attached predominantly to the midle vein (91,44%) and occasionally (8,55 %) to secondary veins. The more "exploited" leaf for oviposition was the number four, on which the greatest number of eggs was also recorded. The more frequent egg number by incision was two. In the leaf sheaths, they were located inside air spaces, or in the parenchymatic tissue, if they were absent. In the leaf blades, eggs were placed in the mesophyll, usually beside mid-vein. Egg features resemble those of other delphacids.

Key words: oviposition sites, Mal de Río Cuarto del maíz; Hordeum vulgare L; Argentina