5 research outputs found
Delimitacion del periodo critico de competencia de malezas en el cultivo de lino (Linum usitatissimum) Determination of the critical period of weed competition in linseed (Linum usitatissimum)
La planta de lino oleaginoso es especialmente sensible a la competencia con malezas, que limita el rendimiento potencial. El objetivo de este trabajo fue delimitar el perÃodo crÃtico de competencia del lino con una comunidad natural de malezas. Se realizó una experiencia de campo durante 1993, 1994 y 1995 en La Plata, Argentina. Los tratamientos consistieron en mantener el lino con y sin presencia de malezas en distintas etapas de su desarrollo. La comunidad de malezas fue evaluada en su composición y producción de materia seca y el cultivo en su rendimiento en semillas y componentes. El perÃodo crÃtico se delimitó entre los 30 y 80 dÃas después de la siembra. En este perÃodo, la disminución de rendimiento de lino respecto del testigo sin malezas fue superior al 10%. La disminución de rendimiento del cultivo totalmente enmalezado fue del 79% respecto del desmalezado todo el ciclo. Fue afectado el número de semillas por planta ya que su definición está incluida en el perÃodo delimitado. Los resultados obtenidos sugieren que las alternativas de control deben considerar el perÃodo crÃtico y también propiciar su utilización en modelos de predicción.<br>Linseed plant is especially sensitive to weed competition, which limits its potential yield. The aim of this work was to determine the critical period of linseed competition with a natural weed community. A field experiment was carried out in 1993, 1994 and 1995 in La Plata, Argentina. Treatments consisted of keeping linseed with and without weeds at different stages of development. Weed composition and dry biomass, and linseed yield and its components were evaluated. The critical period of competition was determined, starting at 30 days and ending 80 days after crop seeding. Linseed yield decrease was greater than 10% during the critical period of competition,when compared to the check plot kept without competition. The maximum yield decrease of the check plot kept totally weeded crop from seeding to harvest was 79%. The number of seeds per linseed plant was affected, since its definition was included in the delimited critical period. The results obtained suggest that alternative weed management must consider long critical periods and should be used in predictive models
Honeybee health in South America
Honeybees are essential components to modern agriculture and economy. However, a continuous increase in cases of colony losses and colony depopulation are being reported worldwide. This critical situation has put the fragile equilibrium between bees and plants on the edge. As a consequence, several scientists have begun to focus their lines of research on this issue. Most researchers agree that there is no single explanation for the observed colony losses. Instead, these losses result from a synergistic interaction between different stressors. South America is not the exception; several cases of colony losses and colony depopulation were reported by beekeepers throughout the continent, yet no accurate data has been published to date. Therefore, this article attempts to analyze the past and present situation of honeybee health in South America, specifically in Argentina, Chile, Uruguay, Brazil, and Venezuela. Furthermore, it is intended to serve as a comparison to future colony losses, as well as to provide guidance for future hypothesis-driven research on the causes of colony mortality. We evaluate the impact of the main parasites and pathogens affecting honeybee colonies and discuss the role of each with respect to reported honeybee losses. We also contemplate the main challenges that each nation must confront with regards to honeybee health.Fil: Maggi, MatÃas Daniel. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Antunez, Karina. Instituto de Investigaciones Biológicas "Clemente Estable"; UruguayFil: Invernizzi, Ciro. Universidad de la República; UruguayFil: Aldea, Patricia. Universidad Mayor. Facultad de SilvoagropecuarÃa. Centro de Emprendimiento ApÃcola; ChileFil: Vargas, Marisol. Universidad de Concepción; ChileFil: Negri, Pedro. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: Brasesco, Maria Constanza. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; ArgentinaFil: de Jong, David. Universidade de Sao Paulo; BrasilFil: Message, Dejair. Universidade Federal do Semiárido; BrasilFil: Texeira, Erica Weinstein. Agencia Paulista de Tecnologia dos Agronegocios; BrasilFil: Principal, Judith. Universidad Centroccidental Lisandro Alvarado. Decanato de Ciencias Veterinarias. Estación de Apicultura; VenezuelaFil: Barrios, Carlos. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Mar del Plata; Argentina. Universidad Centroccidental Lisandro Alvarado. Decanato de Ciencias Veterinarias. Estación de Apicultura; VenezuelaFil: Ruffinengo, Sergio Roberto. Universidad Nacional de Mar del Plata; ArgentinaFil: RodrÃguez Da Silva, Rafael. Universidad Mayor. Facultad de SilvoagropecuarÃa. Centro de Emprendimiento ApÃcola; ChileFil: Eguaras, Martin Javier. Universidad Nacional de Mar del Plata. Facultad de Ciencias Exactas y Naturales; Argentina. Consejo Nacional de Investigaciones CientÃficas y Técnicas. Centro CientÃfico Tecnológico Conicet - Mar del Plata; Argentin