Northern Buenos Aires Province Research Articles

Diversity and phenology of epigeal Coleoptera assemblages in lettuce and tomato crops in Northern Buenos Aires province, Argentina.

Epigeic coleopteran species are linked by complex trophic webs and implicated in several ecosystem services for agriculture. Although there are reports of ground-dwelling Coleopterans inhabiting main extensive agroecosystems, their assemblages in horticultural crops in Argentina have been little explored. We examined the community structure of epigeal Coleoptera assemblages of Curculionidae, Carabidae, Staphylinidae and Coccinellidae species, in lettuce and tomato crops located in Northern Buenos Aires province, over a 3-year sampling period (2010 to 2013) by using pit-fall traps. Crop species and cycles, and phytosanitary measures (conventional and organic farming), were main factors considered as influencing the insect species composition, abundance and seasonal occurrence in the assemblages. Seventy coleopteran species were identified. The curculionids Ceutorhynchini sp. and Phyrdenus muriceus (Germar), the carabid Scarithes anthracinus Dejean, the coccinelid Eriopis connexa (Germar) and the staphylinids Aleochara sp. and Aleochara obscurus Bernhauer are the most common species in lettuce and tomato crops in the region studied. Especially the carabids, staphylinids and E. connexa are known act as natural enemies of several pests in the agroecosystems studied. Coleopteran assemblages found in lettuce differed from those associated to tomato crops, being the cropping season the main factor that influenced the community structure.

Relationship between MODIS-NDVI data and wheat yield: A case study in Northern Buenos Aires province, Argentina

In countries like Argentina, whose economy depends heavily on crop production, the estimation of harvests is an elementary requirement. Besides providing objectivity, the use of remote sensing allows estimating yield in advance. Since the time of maximum leaf area in wheat corresponds with the critical period of the crop, a good relationship is expected between the Normalized Difference Vegetation Index (NDVI) and yield. The present study was carried out in the North of Buenos Aires province, Argentina. Based on the type of soil, the study area can be divided into two homogeneous subzones: a subzone with lower clay content in the southwest and a subzone with higher clay content in the northeast. Nine growing seasons (2003–2011) were studied. In the first five years, an empirical model was calibrated and validated with field-observed wheat yields and MOD13q1 product-NDVI data, whereas in the other four years, the calibrated model was applied by means of yield maps and by comparing with official yields. The MOD13q1 image corresponding to Julian day 289 showed the best fit between NDVI and yield to estimate wheat yield early. Through yield maps, better weather conditions showed higher yields and higher soil productivity presented a greater proportion of the area occupied by higher yields. At department level, an R2 value of 0.75 was found after relating the estimation of the calibrated empirical model with official yields. The method used allows predicting wheat yield 30days before harvest. Through yield maps, the NDVI perceived the temporal and spatial variability in the study area.

Género y patrimonio: las ‘pro-mujeres’ de Capilla del Señor

Vastas publicaciones dan cuenta de la construcción de discursos en los que se coloca a la mujer en el ámbito de lo doméstico, invisibilizando su rol como productora cultural. Estas ideas, en mayor o menor medida, aún se encuentran instaladas en la sociedad y se recrean en los procesos de construcción y prácticas patrimoniales y turísticas. Por ello, este artículo busca reflexionar y discutir ciertas ideas en torno a la escasa representación de la mujer en el proceso de construcción patrimonial. Para analizar estos puntos se presenta un estudio de caso localizado en el municipio de Exaltación de la Cruz, noreste de la provincia de Buenos Aires, Argentina. De esta forma se espera generar un aporte a las recientes discusiones sobre género y patrimonio.

Magnetostratigraphy and environmental magnetism in a sedimentary sequence of Miramar, Buenos Aires, Argentina

A sedimentary sequence called “Fogones de la Costa” located at 38° 17′ 35″ S, 57° 50′ 50″ W, on the coastal cliffs, south of Miramar city, was studied from geological, paleomagnetic and rock magnetic viewpoints. The stratigraphic column shows normal and reverse polarity records associated with chrons and subchrons of magnetopolarity. The younger sediments were assigned to the Brunhes Polarity Chron (<0.78 Ma) and the older sediments of the middle and lower part of the profile were assigned to Upper Matuyama (0.99–0.78 Ma), Jaramillo (1.05–0.99 Ma) and Middle Matuyama (1.78–1.05 Ma). A very short normal polarity record between cycles V and VI, at the base of the cliff, suggests the presence of a condensed record of Cobb (or Olduvai?). The oldest reverse polarity layers at the base of the profile should be related to the lower Matuyama (>1.9 Ma). On the basis of these data, the sequence should span from the Lower Pleistocene to the Holocene, and may be correlated (although partially) with the geological formations of San Andrés, Miramar, and Arroyo Seco described in coastal cliffs north of Miramar. The model of behavior of concentration parameters (κ, χ, Ms and Mr) is in agreement with that determined in other loess sections studied in northern Buenos Aires province. The values of the concentration of magnetic parameters decrease with increasing pedogenesis and weathering of the original material (loess and loess-like). This is a behavioral feature, independent of the carrier agent (wind or water). The medium silt fraction is dominant over the other grain sizes. In that fraction, the amount of magnetic minerals increases significantly. Conversely, the layers corresponding to paleochannels and paleolagoons show a decrease of magnetic minerals, the medium silt fraction also decreases, and the very fine silts and clays increase.

Wind wave climate change: Impacts on the littoral processes at the Northern Buenos Aires Province Coast, Argentina

Several works reported wind-wave climate changes at Buenos Aires Province continental shelf. The aim of this work is to investigate the impact of these changes in the coastal processes of the region. This study is carried out by means of visual wave parameters gathered at the surf zone of Pinamar and by a conveniently implemented and validated numerical wave model (SWAN). Numerical results corresponding to a grid point located 30 km off Pinamar show a significant increase of wave heights from the S and SSE directions and in the frequency of occurrence of waves coming from the S, SSE and E. It is shown that these slight offshore appreciated trends would not have significant effects on the breaker heights observed at the surf zone at Pinamar. On the contrary, the slight positive trend observed offshore in the frequency of occurrence could be affecting the incidence of waves onshore, producing an increase in the number of cases of normal incidence at the surf zone and, consequently, a significant decrease in the alongshore wave energy flux assessed at Pinamar. This reduction in the alongshore wave energy flux could be responsible for some coastal changes detected in the region as, for instance, the remarkable shortening of Punta Rasa spit located 70 km northward Pinamar.

Phytophthora multivora causing leaf spot on rhododendrons in Argentina

Rhododendron is a genus belonging to the family Ericaceae and contains over 1000 species commonly known as rhododendrons and azaleas (Dimitri, 2). Phytophthora multivora is a species that was described in Western Australia in 2008 but before that it was misidentified as P. citricola (Scott et al., 4). During the early spring of 2011, leaf spot symptoms were observed on rhododendrons in two gardens in Tigre (northern Buenos Aires province) and in containers in a nursery near Buenos Aires city. Leaf spots were dark brown to almost black, visible on both sides near the leaf tips and margins, while tissue death continued down the leaf along the midrib (Fig. 1A). The veins under the diseased area of the leaves presented a reddish tint (Fig. 1B). Some leaves became brown and died, while in others the infection remained as spots on leaves. A Phytophthora species was consistently isolated from symptom-bearing leaf tissues on PARBH medium (Jeffers & Martin, 3). Hyphal tips reaching the surface of the medium were transferred onto potato dextrose agar (PDA) without inhibitors for purification and identification. Sporangia were produced abundantly in non-sterile soil extract. The majority of them were semi-papillate and ovoid, limoniform, ellipsoid or obpyriform (Fig. 2). Sporangia with two papillae were occasionally formed (Scott et al., 4). Chlamydospores were not observed. Isolates were homothallic with plerotic oospores, 22.9 ± 1.9 μm and paragynous antheridia (Fig. 3). The optimum growth temperature was 25 ± 1°C on V8A (Scott et al., 4) and the maximum growth temperature was 32 ± 1°C. The ITS was amplified and sequenced (GenBank Accession No. JQ812127) and showed that it was identical to P. multivora, ex-type CBS 124.094 (FJ237517) by BLAST analysis (Altschul et al., 1). The isolate (ARod 110) was deposited in the culture collection of the Phytopathology Chair of the Faculty of Agronomy of Buenos Aires (FAUBA). Due to the difficulty of performing pathogenicity tests in the field, detached leaves of Rhododendron spp., Camellia sp. Viburnum tinus and Photinia fraseri were inoculated in the laboratory with the ARod 110 isolate. The tests were performed by inoculating five detached leaves with a 5 mm mycelium plug taken from a seven-day-old PDA culture. Controls were inoculated with PDA discs. Leaves were incubated at 20-22°C under 12h light/12h dark cycle. All the inoculated leaves, except Camellia sp., developed necrotic lesions seven days after inoculation. P. multivora was re-isolated from infected tissue. Symptoms were not detected on the controls. These characteristics conformed to those of Phytophthora multivora Scott & Jung. To our knowledge, this is the first record of P. multivora causing leaf spot on Rhododendron in Argentina and in Latin America, and it may be a potential pathogen for Viburnum tinus and Photinia fraseri. The authors would like to thank Gloria Abad (USDA/ APHIS/ PPQ/ PHP/ RIPPS) for sharing her knowledge with us.

Neochrysocharis formosa (Westwood) (Hymenoptera: Eulophidae), a newly recorded parasitoid of the tomato moth, Tuta absoluta (Meyrick) (Lepidoptera: Gelechiidae), in Argentina

We report the first record of Neochrysocharis formosa (Westwood) parasitizing larvae of the tomato moth, Tuta absoluta (Meyrick), in tomato crops in Northern Buenos Aires Province, Argentina. Tomato moth larvae were sampled during four consecutive growing cycles, between 2003 and 2005, in 10 sites. Neochrysocharis formosa was present only in organic outdoor and protected crops, and predominantly during the late season. Parasitism rates varied from 1.5% to 5%. The finding of this species is a new record for Argentina and South America, and T. absoluta is a new host record.

Presencia del género Ctenomys (Rodentia, Ctenomyidae) en el noreste de la provincia de Buenos Aires, Argentina

Presence of the genus Ctenomys (Rodentia, Ctenomyidae) in northeastern Buenos Aires province, Argentina. The genus Ctenomys found at the locality of Lima, in the northeastern region of Buenos Aires province, is reported in this paper. The finding of specimens of this genus is located more than 150 kilometers to the North of previous mentions for the province, being possible its adcription to C. talarum or to any other species from the mesopotamian region of Argentina. Previous papers indicate the presence of fossil Ctenomys in several localities in northern Buenos Aires province, and suggest that the genus disappeared from this region before the XIXth century. Thus, the record of living Ctenomys in northeastern Buenos Aires province provide new interesting clues about the biogeography of this genus in the area.

Trichothecenes and Mycoflora in Wheat Harvested in Nine Locations in Buenos Aires Province, Argentina

A total of 120 freshly harvested wheat samples from the 2004 season in nine locations from Northern Buenos Aires Province, Argentina, were analysed for trichothecene natural occurrence and associated mycoflora, and for determining the influence of commonly used fungicide field treatment and the cultivar type on trichothecene contamination. The trichothecenes T-2 tetraol, T-2 triol, HT-2 and T-2 toxin (HT-2, T-2), diacetoxyscirpenol (DAS), nivalenol (NIV), deoxynivalenol (DON), 3-acetyldeoxynivalenol (3-ADON) and 15-acetyldeoxynivalenol (15-ADON) were analysed by gas chromatography and electron capture detection. Detection limits ranged from 4 to 20 microg/kg. The isolation frequencies of species were calculated. Alternaria alternata, Fusarium graminearum, Fusarium poae and Fusarium semitectum were the predominant fungal species identified as endogenous mycoflora. The type of cultivar and the fungicide field treatment did not affect significantly the trichothecene contamination. The trichothecenes type A detected were HT-2 and T-2 triol toxins and the type B were DON, NIV and 3-ADON. Based on 120 samples the incidences were 21.7% for 3-ADON, 22.5% for HT-2, 27.5% for T-2 triol and 85% for DON. NIV was confirmed in one sample. Mean levels of trichothecene positive samples were between 7 and 2788 microg/kg.

Occurrence of Stem Rot on Canola Caused by Sclerotinia sclerotiorum in Argentina

Canola (Brassica napus) was introduced as an alternative crop for wheat in Argentina. During 2003, typical symptoms of stem rot disease were observed on canola plants in two commercial fields located at Bragado, in northern Buenos Aires Province in Argentina. Average disease incidence across four canola cultivars was 21% (range = 13 to 29%). Symptoms included chlorosis and wilting of foliage and necrosis of basal stems. The disease appeared singly or in patches consisting of 4- to 5-month-old plants. The first visible symptom noticed was chlorosis and wilting of the foliage beginning from the basal leaves. Infection of the main stem at ground level typically was followed by a grayish white discoloration that progressed above the soil line to the apex. In advanced stages of the disease, stems and branches became bleached and eventually died. Black and irregularly shaped sclerotia (average size 5.5 × 2.8 mm) inside necrotic stem tissue were the typical signs of the pathogen. From September to October 2003, four samples consisting of six affected plants per sample were arbitrarily collected from two commercial fields located at Bragado. Sclerotia were taken from diseased stems, dipped in 70% ethanol, surface sterilized with 1% sodium hypochlorite for 1 min, and rinsed in sterile water. Each sclerotium was blotted dry on sterile Whatman's filter paper and placed on potato dextrose agar. Plates were incubated in the dark at 25°C for 2 to 3 days, followed by incubation under 12-h NUV light/12-h dark for 6 to 8 days. Six resulting colonies were identified as Sclerotinia sclerotiorum (Lib.) de Bary on the basis of taxonomic characteristics of the plant pathogenic species of Sclerotinia (3). Koch's postulates for three fungal isolates from infected plants were carried out on 6-week-old canola plants (cvs. Eclipse, Impulse, Master, and Mistral) by placing a colonized agar disk into wounds made in the basal stem region with a sterile scalpel. Pathogenicity tests, which included five inoculated and three control plants potted in a sterilized soil mix (soil/sand, 3:1), were conducted in a greenhouse at 23 to 26°C and 75% relative humidity with no supplemental light. Characteristic symptoms identical to the original observations developed within 12 days after inoculation on 100% of the inoculated plants for three isolates. Symptoms included wilted foliage, collapsed plants, and plant death. White mycelium and sclerotia developed on infected tissues, and the pathogen was successfully reisolated from symptomatic plants in all instances. Control plants, which were treated similarly except that the agar disk did not contain fungal growth, remained healthy. The experiment was repeated, and the results were identical to the first inoculations. Canola stem rot disease incited by S. sclerotiorum was first reported in Argentina during 1995 at experimental field plots in Buenos Aires. S. sclerotiorum, which has been reported to cause disease in canola in Canada (2) and the United States (1,4), currently represents a serious problem to the main canola cultivars grown in Argentina. To our knowledge, this is the first report of the occurrence of S. sclerotiorum causing a high incidence of stem rot in commercial crops of canola in Argentina.

First Outbreak of Blackleg Caused by Phoma lingam in Commercial Canola Fields in Argentina.

Canola (Brassica napus) was introduced as an alternative crop to wheat in Argentina. During 2004, typical symptoms of foliar blackleg disease were observed on canola plants in commercial and experimental fields in southern Buenos Aires Province. Average disease incidence was 32% on 2- to 4-month-old plants of canola cvs. Impulse, Master, Mistral, and Teddy. The range of incidence on these cultivars was 21 to 43%. Foliar symptoms were randomly distributed at seedling, rosette, and flowering stages. Symptoms included necrosis and chlorosis of the affected leaf tissue and defoliation. Foliar leaf spots were circular to irregularly oval, 5 to 12 mm in diameter, pale brown in the center, and grayish green at the margin. Small, black pycnidia formed in the center of the adaxial surface of diseased foliage. Under favorable temperature and moisture conditions, lesions enlarged and coalesced. Older lesions appeared chlorotic and desiccated with shredded tissue at the center. A severe defoliation of the lower leaves was observed. As the disease developed, basal stem cankers formed on these plants, although disease incidence in this phase was low. Pieces (0.5 cm long) were taken from leaves and stems of diseased plants, dipped in 70% ethanol, surface sterilized with NaOCl (1%) for 2 min, and rinsed in sterile water. Each segment was blotted dry and placed on potato dextrose agar (PDA). Plates were incubated in the dark at 26°C for 4 days, and then plates were incubated under 12 h of NUV light and 12-h dark for 7 days. Four fungal isolates were obtained. The fungi were examined microscopically and confirmed as Phoma lingam (Tode:Fr.) Desmaz. (Leptosphaeria maculans (Desmaz.) Ces. & De Not) (3,4). P. lingam was the only fungus isolated from the infected tissue. The teleomorph stage was not observed. Koch's postulates were completed for two isolates by spray-inoculating foliage of 3-week-old canola plants of cvs. Impulse, Master, Mistral, and Teddy with a conidial suspension (1 × 106 conidia per ml). The experiment, which included four inoculated plants per isolate and two noninoculated control plants for each cultivar, was performed in a greenhouse at 22 to 24°C and maintained at 75% relative humidity with no supplemental light. Inoculated and control plants were covered with polyethylene bags for 48 h after inoculation. Plants developed small, pale brown lesions on leaves within 11 days for both isolates, and the pathogen was reisolated. Control plants, inoculated only with sterile distilled water, remained symptomless. The experiment was repeated once with similar results. Blackleg is the most important fungal disease affecting canola with a worldwide distribution (1,2). In 1995, the disease was first observed on canola in Argentina in northern Buenos Aires Province, but only in experimental field plots with a low disease incidence. Since that time, it has not been found in other areas where canola is produced. The results emphasize the importance of this pathogen in Argentina, since at the current time most commercial cultivars were susceptible to P. lingam. To our knowledge, this is the first report of an outbreak of P. lingam infection in commercial crops in the main canola-production region in Argentina.

Contents and main fractions of trace elements in Typic Argiudolls of the Argentinean Pampas

The knowledge of the trace elements in soils of the Pampas remains fragmentary. Agriculture has been intensified in this region increasing the crop demand of micronutrients and increasing the use of fertilizers, which could add measurable quantities of trace elements to soils. We analysed the status of 12 trace elements in three soil fractions of different availability. Typic Argiudolls (soil taxonomy) from six locations of northern Buenos Aires province were sampled. Arsenic (As), cadmium (Cd), chromium (Cr), cobalt (Co), copper (Cu), iron (Fe), lead (Pb), manganese (Mn), molybdenum (Mo), nickel (Ni) and zinc (Zn) were extracted with DTPA, with 2N HNO3 and with HCl–HNO3–H2SO4 and HClO4. The exceptions were bioavailable boron (B), extracted with hot water, and total B and Cr, determined through instrumental neutron activation analysis. The analysis of the other elements were performed by inductively coupled plasma-atomic emission spectrometry. The total contents were similar or below values found in other soils of the region. Extractable DTPAZn, Cu and Fe were within the range of variation for the region but Mn data were lower than those found previously in the area. As, B, Co, Cr, Fe, Mo, Pb and Zn predominated in chemical forms which are almost insoluble for plants. Our results broaden the previous information for micronutrients in the Pampean region. For heavy metals, our results corroborate the lack of soil contamination in rural areas of the Pampas.

The Ensenada and Buenos Aires formations (Pleistocene) in a quarry near La Plata, Argentina

An interdisciplinary study of a section in a quarry near La Plata sheds new light on the geologic, climatic, and biologic evolution of the northeastern Pampean area of Argentina. The stratigraphic succession is composed of seven mainly eolian levels, each one including a soil and separated by a disconformity. Two geosols defined in northern Buenos Aires Province (Hisisa and El Tala) are identified in the Ensenada Formation. The boundary between the Ensenada and Buenos Aires formations is defined by a conspicuous disconformity which overlies the El Tala Geosol. In the section, the boundary between the Tolypeutes pampaeus (Ensenadan) and Megatherium americanum (lower Lujanian) biozones coincides with that of Ensenada and Buenos Aires formations. The boundary between the Matuyama and Brunhes zones of polarity occurs in the upper part of the Ensenada Formation above the Hisisa Geosol. According to geologic evidence, most of the succession was deposited under semiarid to arid climate.