Susana L. Paradell

Exitianus obscurinervis (Hemiptera: Cicadellidae), a New Experimental Vector of Spiroplasma kunkelii

ABSTRACT “Corn stunt” caused by the mollicute Spiroplasma kunkelii (Whitcomb) is potentially one of the most severe diseases affecting the corn (Zea mays L.) crop in the Americas, and the leafhopper Dalbulus maidis (DeLong & Wolcott) is considered its most important vector. However, other insects seen quite frequently in corn crops might well be its vectors in Argentina. To identify any leafhoppers species other than D. maidis that can transmit S. kunkelii, transmission assays were conducted, using individuals of Exitianus obscurinervis (Stål) collected in field and reared under controlled conditions. S. kunkelii was transmitted to corn plants by E. obscurinervis. The pathogen was transmitted to seven of the 11 plants, which showed characteristic corn stunt symptoms, and the presence of the pathogen was confirmed by DAS-ELISA. The presence of S. kunkelii in the E. obscurinervis individuals used in transmission experiments was confirmed by polymerase chain reaction and electron microscopy. The current study shows the existence of a new experimental vector of S. kunkelii, the leafhopper E. obscurinervis, which acquired spiroplasmas from infected plants and inoculated it to healthy plants.

Proconiini Sharpshooters of Argentina, with notes on its distribution, host plants, and natural enemies

Abstract The American tribe Proconiini (Hemiptera: Cicadellidae: Cicadellinae) is one of the largest groups of xylem-feeding insects and includes the majority of the known vectors of xylem-born phytopathogenic organisms. The significance of the pathogens that this group transmits gives them an important role as pests, mostly for citrus fruit, grapes, and almonds. Knowledge of these Hemiptera in Argentina is insufficient and fragmentary. Thus one of the aims of this paper is to summarize the available information of the Proconiini sharpshooters in Argentina. In addition, 14 species are mentioned for the first time in the country, and new distributional data are given for 18 species. Thirty-four new associations between sharpshooters and host plants are recorded. New records of egg parasitoids are given for Dechacona missionum, Molomea consolida, M. lineiceps, and Tapajosa similis.

Presence of Dalbulus maidis (Hemiptera: Cicadellidae) and of Spiroplasma kunkelii in the Temperate Region of Argentina

ABSTRACT “Corn stunt” is one of the main corn (Zea mays L.) diseases in the Americas and Dalbulus maidis (DeLong & Wolcott) is the key vector of the pathogen Spiroplasma kunkelii Whitcomb. In Argentina, the corn-producing area is in the temperate region, where vector and pathogen prevalence levels are unknown. In this study, the prevalence and distribution of D. maidis and S. kunkelii in the temperate region of Argentina and D. maidis overwintering ability in this region were determined. Surveys were conducted in 2005–2006 and 2006–2007 seasons to determine D. maidis and S. kunkelii presence, and in winter 2006 to determine the vector overwintering ability. The highest S. kunkelii prevalence and incidence levels were found in the transition area from the temperate to the subtropical region, related to the highest D. maidis prevalence and insects sampled per location. D. maidis adults were found in volunteer corn plants and spontaneous vegetation in autumn and winter months, which were inoculative for the pathogen S. kunkelii. This overwintering ability was related to detection of D. maidis insects in corn crops at early growth stages in the following growing season. This work emphasizes that corn stunt disease is present in the temperate region of Argentina, and this highlights the need to develop proper agronomic practices like monitoring insect vector populations and controlling voluntary plants. This study also indicates that further research is needed to understand the potential yield reduction caused by this pathogen on symptomless plants and population dynamics of the insect vector.

New Records on the Geographical Distribution of South American Sharpshooters (Cicadellidae: Cicadellinae: Proconiini) and their Potential as Vectors of Xylella fastidiosa

Wells et al. 1978, which occurs only in the xylemof plants (Marucci et al. 2002).Strains of X. fastidiosa cause diseases such as“Pierce’ s Disease” (PD) in grape ( Vitis vinifera L.),“Phony Peach Disease” (PPD), “Coffee LeafScorch” (CLS), “Oleander Leaf Scorch” (OLS), and“Citrus Variegated Chlorosis” (CVC) among oth-ers. These incurable maladies produce substan-tial economic losses in a diverse variety of crops(Hernandez-Martinez et al. 2006).In South America the major threat is CVCwhich has spread rapidly throughout Brazil(Lopes 1996). X. fastidiosa is also present inUnited States, Mexico, Venezuela, Brazil, Para-guay, Uruguay, Argentina (Redak et al. 2004), andCosta Rica (Aguilar et al. 2005). However, CVC isnot yet reported from the USA although it has thepotential to threaten orange (

Diversity of Auchenorrhyncha (Hemiptera: Cicadellidae: Delphacidae) Associated with Vicia villosa in Southern Buenos Aires Province, Argentina

Abstract Among the Hemiptera, the Auchenorrhyncha are well known owing to their phytosanitary relevance since the group includes pathogen vector species able to damage commercial crops. Vicia villosa Roth (Fabaceae) is a fodder plant species, mainly distributed in central Argentina. Previous contributions have shown that V. villosa is colonized by diverse species of Auchenorrhyncha, either naturalized or native to valley of Colorado River area, in southern Buenos Aires province. To date, the only information about the species of hoppers associated with Vicia has come from preliminary field observations. The dearth of demographic knowledge about these phytophagous insects associated with this crop in Argentina motivates the study. The aims of this work were: 1) to characterize the diversity of the species of Auchenorrhyncha associated with V. villosa and 2) to determine the seasonal fluctuation of the most abundant species in relation to local weather variables and crop phonological phases. The study was conducted in Vicia plots located at EEA INTA Hilario Ascasubi (S 39° 23′ 36″ -W 62° 37′ 59″, 15 m.a.s.l.) southern Buenos Aires province. The specimens were collected with a sweep net during 2 yr (2009 and 2011). Weather variables were recorded using a meteorological station located at the sampling site. To measure species richness and community diversity we calculated both Margalef (DMg) and the Simpson (D) indexes, and also, the Relative Importance Index (RII). The relationships between population densities of the leafhoppers, Paratanus exitiosus (Beamer) and Agalliana ensigera Oman (Cicadellidae), with weather variables were analyzed through simple and multiple linear regression. A total of 17 species were associated with V. villosa crops in Argentina, of which 15 belong to the Cicadellidae and 2 to the Delphacidae. Abundance and species richness were higher in 2009 than in 2011. In general, the results of the Margalef index showed that species richness was higher in 2009, while Simpson Index (D) indicated a higher dominance in 2011 than in 2009. The species, P. exitiosus and A. ensigera, stood out for their abundance, frequency and phytosanitary relevance during the sampling period. Both species presented population increases since Nov coinciding with different phenological phases of the crop and the maximum density of the canopy. Additionally, the population density of P. exitiosus showed strong dependence on the hydric balance and photoperiod, while A. ensigera was influenced by Degree-days10 and hydric balance. Vicia villlosa was a new host-plant record for 15 species. Buenos Aires province was cited as a new distribution record for 2 species.

Epidemiological aspects of garlic decline disease caused by a phytoplasma in Asiatic and Argentinean garlic cultivars

Garlic decline is a disease that has been detected in most of the garlic-growing areas of Argentina. The associated pathogen has been identified as a 16SrIII-group phytoplasma. Little is known, however, about epidemiological aspects of the disease. Incidence and prevalence of the disease were analysed during 3 consecutive years infields of an Asiatic garlic cultivar (Chino) and two Argentinean cultivars (Blanco and Colorado) from the principal garlic-growing areas of Argentina. Although low incidence was registered (0.03-0.78%), disease prevalence was high in both sampled regions (23-100% fields had at least one diseased plant). Cultivars Chino and Blanco were more susceptible to the disease since incidence and prevalence were significantly higher than in cv. Colorado. The pathogen was detected by polymerase chain reaction (PCR) in a high proportion of cloves from infected plants and in plants derived from potentially infected cloves, showing that the phytoplasma can be transmitted from a crop cycle to the following by planting infected cloves. The phytoplasma was detected by transmission electronic microscopy,PCRand dot blot immunoassay in all parts of the symptomatic plants, and the highest pathogen concentration was found in root tissues. Although 22 leafhopper species were found associated with the garlic crop, insect populations were low during the whole crop cycle.

Bionomics of Oncometopia tucumana (Hemiptera: Cicadellidae), a Sharpshooter from Argentina, With Notes on its Distribution, Host Plants, and Egg Parasitoids

Abstract Bionomics of the proconiine sharpshooter Oncometopia tucumana Schröder (Hemiptera: Cicadellidae) from northern Argentina is reported. Leafhoppers were monitored during the entire season in a citrus orchard in Horco Molle, Tucumán Province, and also sampled in Jujuy and Salta Provinces. The sharpshooters were found from spring to late fall; they overwinter as adults and females do not lay eggs from Apr to Oct. Oncometopia tucumana is polyphagous, 12 plants in 11 families were recorded as its hosts for the first time. Egg masses of O. tucumana were attacked by 3 parasitoid species, Gonatocerus annulicornis (Ogloblin), G. metanotalis (Ogloblin), and G. tuberculifemur (Ogloblin) (Hymenoptera: Mymaridae), that collectively produced egg mortality close to 60%. Gonatocerus annulicornis was the main egg parasitoid, emerging from nearly 80% of the parasitized eggs.

ABUNDANCE AND SPECIES RICHNESS OF LEAFHOPPERS AND PLANTHOPPERS (HEMIPTERA: CICADELLIDAE AND DELPHACIDAE) IN BRAZILIAN MAIZE CROPS

Abstract Insects in the Cicadellidae and Delphacidae families, common in grasses, are an important group of vectors of viruses and mollicutes, which cause diseases in several plant species. The goal of this study was to evaluate the abundance and species richness of Cicadellidae and Delphacidae and the presence of potential vectors of viruses and mollicutes in maize crops in Brazil. Insects were collected using sweep nets in maize crops in 48 counties of 8 states, distributed in 4 regions of Brazil in the yr 2005, 2006 and 2007, with a total of 198 samples. The collected material was screened, and the leafhoppers and planthoppers were identified at the species level. A total of 4233 Cicadellidae specimens, including 30 species, and 205 Delphacidae specimens, including 9 species, were collected. The most abundant species was Dalbulus maidis (Delong & Wolcott) representing 90.1% of leafhoppers and planthoppers. Abundance and species richness differences were observed between the northeast and center-south regions of Brazil. Eight species of leafhoppers and planthoppers were identified as vectors or potential vectors of viruses and mollicutes in maize, although some of these viruses are not reported in Brazil. Among these species, we identified the planthoppers, Caenodelphax teapae (Fowler), Peregrinus maidis Ashmed, Pyrophagus tigrinus Remes Lenicov & Varela and Toya propinqua (Fieber) are experimental vectors of Mal de Río Cuarto virus, which is a quarantine virus in Brazil. Two Cicadellidae species and 3 Delphacidae species were reported for the first time in Brazil.

Diversity of Cicadomorpha (Hemiptera: Auchenorrhyncha) in Citrus Orchards in Northeastern Argentina

ABSTRACT Among phytophagous insects, the Cicadomorpha are important economically because they damage crops by sucking plant sap and by transmitting plant pathogens, such as Spiroplasma citri and Xylella fastidiosa to citrus. In Argentina little knowledge exists about this subject. The aim of this work was to study the diversity of Cicadomorpha associated with citrus orchards in Entre Ríos province, and their seasonal fluctuation in relation with climatic and phenological conditions. A total of 1,554 specimens belonging to 28 species of Cicadomorpha were collected with yellow sticky traps in sweet orange (Citrus × sinensis (L.) Osbeck) and tangerine (Citrus unshiu Marc) orchards. The Shannon index and the Simpson index suggested a similar trend in the distribution of the dominant species in both crops. In the orange orchard, Cicadomorpha populations increased in the summer coincidently with temperature increases. On the other hand, a significant increase in abundance during the winter months was coincident with increase of early sprouts of the citrus plants. Entre Ríos province represents a new distribution record for 13 species. Tangerine is a newly recorded host-plant for 16 species studied, and eight species are reported for the first time on ‘Valencia Late’ orange.

Occurrence of the Tamarix Leafhopper, Opsius stactogalus Fieber (Hemiptera: Cicadellidae), in Argentina

Abstract The paleartic tamarix leafhopper, Opsius stactogalus Fieber (Hemiptera: Cicadellidae), can reduce the growth of tamarisk due to the aggregate feeding imposed by their populations. The species was mentioned for Argentina in Metcalfs catalogue (1967) without locality or region reference, and the contributions on Cicadellidae published by many authors after Metcalf omitted this distributional data. Populations of O. stactogalus on Tamarix sp. were found in 12 sites between 28° 48′ to 39° 17′ S and 64° 06′ to 70° 04′ W, located in both the Neotropical and Andean biogeographic regions.