Sistema Regional de Información
en línea para Revistas Científicas de América Latina,
el Caribe, España y Portugal

Diatraea saccharalis is a key pest of corn cultivation in the Pampas region of Argentina. The economic thresholds used are nominal and are not based on the current calculation of the economic injury level. The goals of this work were: to characterize the relationship between the infestation pressure of D. saccharalis and the yield of the corn crop and to calculate economic injury levels in different situations of crop development.A test was carried out with the hybrid DK696 with natural irrigation and infestation, following a split plot experimental design with five sowing dates and different crop protection windows.The yield showed a linear relationship with the intensity of injury caused by D. saccharalis and this response was independent of the sowing date. Injury caused to the middle third of the plants showed the greatest influence in the determination of yield, followed by the lower stratum, while damage to the upper stratum did not show a relationship with yield. Economic injury levels are proposed for different price scenarios.

Setaria sphacelata is a tropical forage grass, cultivated in diverse regionsdue to its plasticity. Like other summer perennial forages, it has a slow establishment. Hydration-dehydration (HD) pregerminative treatments improve the germination and establishment of many species. The objective of this work was to evaluate the effect of HD with water and potassium nitrate on Setariasphacelata seeds. A factorial treatment design of 2 x 3 x 2 was applied. The first factor was the imbibitory agent: water (A) and potassium nitrate at 2 % (N); the second the imbibition time: 24, 48 and 72 hours; and the third the lot evaluated (two). Four repetitions of 50 seeds per treatment and one control (T) were sown. Germinative energy, germination percentage, fresh and dead seeds (SM) were recorded. Between lots, only significant differences were found in SM. The treatments A24, A48, A72 and N24 were better than T in speed and  percentage of germination, while N48 and N72 were similar or inferior. It is concluded that HD treatment with water for 72 hours proved to be the best treatment. Immersion for more than 24 hours in potassium nitrate at 2 % impaired seed viability.

Conyza sumatrensis is one of the most problematic weeds in Argentina, withfrequent control failures after glyphosate application. The objective of this research was to evaluate sensitivity of C. sumatrensis biotypes, at two growth stages (rosette and vegetative), to glyphosate and acetolactate synthase(ALS)-inhibiting herbicides. Dose-response experiments were performed using 0, 1/16, 1/8, 1/4, 1/2, 1, 2, 4, 8, and 16-fold of the recommended dose for each herbicide. At rosette stage, the resistance level for glyphosate was 9.8, while at the vegetative stage neither biotype was controlled with the recommended dose, with lower sensitivity of biotype R (RI = 2.3). Control of both biotypes using ALS-inhibiting herbicides was excellent at rosette stage, with lower doses than the recommended. At vegetative stage controls were good (80 %) with lowerdoses than recommended (0.16 X to 0.97 X), except for metsulfuron-methyl +chlorsulfuron in biotype S (1.75 X). These results may confirm the existence of abiotype resistant to glyphosate in Argentina and that ALS-inhibiting herbicides could control resistant biotypes and more developed individuals.

Increasing the number of pregnant heifers per time unit improves reproductive efficiency in dairy herds. The objective of this work was to analyze the effect of management factors on conception. Reproductive events of 2532 heifers throughout 37 years were analyzed adjusting proportional risk models. Days to conception (DC) were measured as the interval in days from the start of the service period (IPS) to conception. The observation period per animal was 90 days. Models adjusted for DC include effects of age at IPS, year, number and season of services, conception rate of bulls, and year-to-season interaction with services. The Weibull model adjusts the DC variation pattern. Conception was lower in heifers under 18 months, in the 2nd and 3rd service, and when bulls with less conception rate were used. Conception was higher in fall services by 1.17 times compared to spring services. Identifying management factors affecting days to conception in heifers allows developing strategies to improve reproductive efficiency in dairy herds.

The present investigation carried out a survey of soft scales belonging to thegenus Ceroplastes Gray associated with Duranta erecta var. lemon L. for ornamental use in Paraná city (Entre Ríos, Argentina). These insects damagethe growth of plants, can cause their decay and affect their ornamental value.Through the analysis of microscope slides, the species Ceroplastes grandisHempel (Hemiptera: Coccomorpha: Coccidae) was identified in all the plantssurveyed. The slides were storedin the Coccomorpha Collection InstitutoFundación Miguel Lillo –IFML- (Tucumán, Argentina). The association betweenC. grandis and plants of D. erecta var. lemon is reported for the first time inArgentina.

Azospirillum spp. and Pseudomonas spp. are plant growth promoting rizobacteria that enhance crop growth and productivity. The aim of this article was to compare the effects of Azospirillum brasilense and Pseudomonas psychrophila over early wheat growth in contrasted fertility conditions. This research was carried out under controlled growth conditions combining inoculation and fertility with P and K in sterile substrate. Root length 10 days after sowing (DAS) and above ground and root biomass accumulation after 10 and 40 DAS were evaluated. 10 DAS, when inoculated, radicle length increased on average 8 %, while total biomass increased 6.3 % when inoculated with A. brasilense and 4.9 % when inoculated with P. psychrophila. 40 DAS, both rizobacteria increased root growthin 21 %. 10 DAS and 40 DAS, biomass accumulation was independent from substrate fertility, suggesting that the presence of A. brasilense and P. psychrophila are relevant during implantation and early crop growth.

We compared the balance of greenhouse gasses (GHG) of two contrasting livestock production models of the Salado river basin, Buenos Aires province. One model was characterized by the predominance of native grassland in good condition because of the application of controlled grazing (MP 1) and the other model by a larger surface of cultivated pastures and annual forage crops, higher stocking rate and beef production (MP 2). We applied the IPCC (Intergovernmental Panel on Climate Change) methodology for estimating primary emissions. We incorporated the estimation of secondary emissions and the gain or loss of soil carbon of to the GHG balance. Total emissions were higher in MP 2 than MP 1 (4500 vs. 2273 kg CO2 eq. ha-1 year-1 respectively, p<0,01). MP 1 sequestered carbon at a rate of 1851 kg CO2 eq. ha-1 year-1, while MP 2 emitted carbon at a rate of 601 kg CO2 eq. ha-1 year-1. GHF balance was ten times more negative for MP 2 than MP 1, whose balance resulted neutral. Livestock systems of Salado river basin with predominance of native grassland in good condition are able to mitigate the effect of global warming.

Diverse agronomic and environmental data are collected with geographical position systems enabling the construction of maps that describe the variation of the studied properties over the space. Uni and multivariate spatial variability has been used to understand observation variation within crop fields and between sites in a large territory, allowing the delimitation of homogeneous areas at different scales. The use of spatial statistics methods, both regionally and on a small scale, demands specialized software programs. FastMapping is an interactive web application developed to process spatial data. It allows users to preprocess georeferenced data (clean, standardize and re-scale), it facilitates spatial interpolation and the generation of spatial variability maps quasi-automatically. This work compares the multivariate zoning of agricultural fields according to soil properties produced by FastMapping and that obtained from commercial software used for precision agriculture. FastMapping allows to import, clean, analyze and visualize spatial data, in a single environment, provide an easy-to-use framework for the effective implementation of spatial statistics methods.

Quality and performance in potato production systems is seriously affected by fungi diseases such as R. solani, whose chemical control is inefficient. Theobjective of the present work was to select isolates of Trichoderma spp. in vitro as potential biofungicides for the control of Rhizoctonia solani on potato.From soil samples from Calamuchita, Río Primero, Punilla and San Javier departments in the Province of Córdoba (Argentina), 18 native Trichodermastrains were isolated and genetically identified. They were evaluated in vitro by the dual culture method on their competence for the substrate, mycoparasitism and antibiosis capacity. It was possible to identify a group of five promising strains: T. atroviride ACp8 y CBa3, T. konigiopsis CBk2 y CBk4 y T. harzianum CBh2. These strains had more than 85 % overgrowth over the pathogen, were very competitive for the substrate (Grade 1) and had an antibiosis capacity higher than 35 % which inhibited radial growth through at least four mechanisms of hyphal interaction against R. solani. The  selected strains that specifically recognize the phytopathogen and due to their native condition present highedaphoclimatic adaptation, may be incorporated into crop managementimproving the system sustainability.

Orchids (family Orchidaceae) are susceptible to several biotic and abiotic factors that affect their development and quality. Among them, Cymbidium mosaic virus (CymMV) and Odontoglossum  ingspot virus (ORSV) are the most frequent pathogens, with the greatest economic impact worldwide. The mechanical transmission of these viruses in addition to the predominantly agamic multiplication of orchids, make it necessary to work with virus-free plant material. The objective of this work was  to develop diagnostic reagents for the detection of CymMV and ORSV. A polyclonal antiserum against CymMV + ORSV was made with a titer of 1:10000 determined by NC-ELISA. The antiserum was processed generating IgG and IgG-conjugated” anti CymMV+ORSV were obtained for use in DAS-ELISA in a dilution of 1:500. The immunodiagnosticcapacity of this technique was evaluated by analyzing samples from orchids with characteristic viral symptoms, collected  from commercial nurseries in the city of Córdoba, Argentina. Viral infections were detected in 22 % of the samples analyzed and in 75 % of the nurseries surveyed.  The ability of these reagents to identify CymMV, ORSV and mixed infections in orchids, will speed up analyzes and reduce their costs. This would represent an advantage for large-scale detections.