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 dm3) 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).
SUMMARIZED INFORMATION ABOUT THE KNOWN EGG PARASITOIDS OF DALBULUS MAIDIS (HEMIPTERA: CICADELLIDAE).
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.
NUMBER OF SPECIMENS AND PERCENT OF TOTAL EGG PARASITOIDS OF DALBULUS MAIDIS, OBTAINED FROM SENTINEL EGGS DURING SUMMER 2008 IN 2 SITES OF JALISCO, MEXICO.
From the approximately 1600 exposed eggs, 923 wasps emerged. The specimens belonged to 5 species: 2 Mymaridae (Anagrus breviphragma Soyka and Polynema sp.), and 3 Trichogrammatidae (Paracentrobia nr subflava, Aphelinoidea sp., and Pseudoligosita sp.). Anagrus breviphragma and P. nr subflava were the most abundant taxa in the Zapopan site and El Grullo site, respectively, (Table 2).
Anagrus breviphragma belongs to the incarnatus species group, subgenus Anagrus s. str. It has a very broad distribution that includes Japan, England, France, Italy, Germany, Austria, Greece, Guadeloupe, Guyana, Colombia, Brazil, and Argentina (Chiappini 1989; Triapitsyn 1997). The known hosts for A. breviphragma are Cicadella viridis (L.), Dalbulus maidis (Cicadellidae), Conomelus anceps (Germar), Delphacodes kuscheli Fennah, Dicranotropis hamata (Boheman), Muellerianella fairmairei (Perris), Peregrinus maidis (Ashmead) (Delphacidae), and Orthotylus virescens (Douglas & Scott) (Miridae) (Triapitsyn 1997; Virla 2001).
The species of Paracentrobia is very close to P. subflava (Girault), but it has dense discal cilation in the forewings, between the areas delimited by the rows of the microtrichias, whereas in P. subflava, these areas are mostly bare, as reported by Girault in the original description, and in voucher specimens deposited in the entomological collection of La Plata Museum, Buenos Aires, Argentina (MLPA). We cannot yet determine the species of Polynema, Aphelinoidea, and Pseudoligosita because of the lack of specific keys to these genera.
Taking into account the importance of the corn leafhopper in Mexico and the lack of information about the egg parasitoid complex, we point out the need for a proper evaluation of this parasitoid guild and its influence on this leafhopper pest.
Slide-mounted and dried card-mounted voucher specimens resulting from this study were deposited in the collection of the Fundación e Instituto Miguel Lillo at San Miguel de Tucumán, Argentina (IMLA).
A survey of eggs parasitoids of the corn leafhopper, Dalbulus maidis (DeLong & Wolcott) was conducted in Jalisco State, Mexico. Samples were collected during the summer of 2008 with sentinel eggs. Five taxa, Anagrus breviphragma Soyka and Polynema sp. (Mymaridae), Paracentrobia nr subflava, Aphelinoidea sp., and Pseudoligosita sp. (Trichogrammatidae) were reared. This is the first reference to an egg parasitoid complex of the corn leafhopper in Mexico, and A breviphragma is recorded for the first time occurring in Mexico.
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