Egg Paeasitoids ofDalbulus maidis(Hemiptera: Cicadellidae) in Jalisco State, Mexico

Abstract

The corn leafhopper, Dalbulus maidis (Delong & Wolcott) (Hemiptera: Cicadellidae) is broadly distributed throughout the American continent, from southeastern and southwestern USA to Argentina. It is the most important leafhopper pest of maize, Zea mays L., in Latin America (Nault 1990), and causes great losses to corn crops because of its capacity to transmit efficiently corn stunt spiroplasma (CSS), maize bushy stunt phytoplasma (MBSP), and maize rayado fino virus (MRFV) (Nault & Ammar 1989). Egg parasitoids are the most important natural enemies of leafhoppers (Freytag 1985). The known egg parasitoids of D. maidis comprise 4 taxa of Mymaridae, 4 of Trichogrammatidae, and 1 Eulophidae (Table 1), but none of these are known in Mexico, putative corn leafhopper origin center (Nault 1990). In the laboratory, 6-10 females of D. maidis, which were 2 weeks old and obtained from Zapopan site, were placed in polyethylen-terephtalathe (PET) cylindrical cages (35 cm high × 18 cm diam.) on maize leaves in order to obtain sentinel eggs. Potted maize plants (pot of ca. 10 dm) in the vegetative stage (3 to 5 leaves) were checked daily for eggs. Twice, on 17 Aug and 23 Aug, 10 plants containing less than 24-h-old eggs were exposed in each site during 72-96 h. Potted plants containing sentinel eggs were placed inside the cornfield at no more than 3 m from the edge of the field. Sentinel eggs of D. maidis were exposed to parasitization in 2 cornfields in Jalisco State from Aug to Sep, 2008 at Zapopan site (20°44’40.2”N, 103°30’48.3”W, elevation 1,662 m), and El Grullo site (19°47’50.4”N, 104°12’43”W, elevation 869 m). After 8 to 10 d, the leaves containing exposed eggs were cut from the plant in the laboratory and transferred to a petri dish with the bottom containing wet tissue paper and covered with clear plastic food wrapping to avoid desiccation, and to keep wasps from escaping. Parasitized eggs were checked daily to ensure leaf quality until the emergence of the adult wasps. The parasitization rates were not measured due to rotting or desiccation of some leaves containing exposed eggs.