Poblaciones infestantes de Oxalis latifolia en tres cultivos de Guipúzcoa

Se estudia la distribución de tres poblaciones de Oxalis latifolia, una de huerta, otra de maizal y la tercera de vivero, en cuanto al origen apical o lateral- y al peso de los bulbos; así mismo, se analiza la forma taxonómica common o cornwall- a que pertenecen los bulbos hijos apicales

Identificación de bulbos de las formas Common y Cornwall y de sus bulbos apicales y laterales de Oxalis latifolia kunth.

Se describen los caracteres morfológicos y cromáticos que permiten distinguir las dos formas de Oxalis latifolia, common y cornwall, así como los tipos de bulbos que aparecen en las poblaciones naturales de los campos de cultivo

Modelling leaf development in Oxalis latifolia

This study was carried to develop functions that could explain the growth of Oxalis latifolia, in both early stages and throughout the season, contributing to the improvement of its cultural control. Bulbs of the Cornwall form of O. latifolia were buried at 1 and 8 cm in March 1999 and 2000. Samples were destructive at fixed times, and at each time the corresponding BBCH scale codes as well as the absolute number of growing and adult leaves were noted. Using the absolute number of adult leaves (transformed to percentages), a Gaussian curve of three parameters that explains the growth during the season (R2 = 0.9355) was developed. The BBCH scale permitted the fit of two regression lines that were accurately adjusted for each burial depth (R2 = 0.9969 and R2 = 0.9930 respectively for 1 and 8 cm). The best moment for an early defoliation in Northern Spain could be calculated with these regression lines, and was found to be the second week of May. In addition, it was observed that a burial depth of 8 cm does not affect the growing pattern of the weed, but it affects the number of leaves they produce, which decreases to less than a half of those produced at 1 cm

Effect of burial on productivity and extinction of Oxalis latifolia Kunth

The effect of burial on productivity and extinction of Oxalis latifolia bulbs has been studied. Linear regression formula showed that complete extinction of bulbs would be possible only at a burial depth of 32 cm. O. latifolia also sacrificed a number of its descendents in order to maintain its mean weight at increasing depth, mainly at depths greater than 28 cm, where a change in productivity distribution was observed. A comparison of these results with field population weights showed that a combination of agro-ecosystem conditions and deep burial would improve control of the weed

Biología de Oxalis latifolia: revisión acerca de su origen, ciclo anual, características biológicas más notables y formas taxonómicas

Biología de Oxalis latifolia: revisión acerca de su origen, ciclo anual, características biológicas más notables y formas taxonómicas. En el presente trabajo se describe el origen, ciclo anual de la planta de Oxalis latifolia, comúnmente conocida como trebolillo de huerta o aleluya. Las razones para abordar esta investigación han sido principalmente dos: por un lado, el avance en el conocimiento de esta mala hierba hace necesaria una actualización de toda la información sobre su biología y ecología que, a su vez, abre nuevas posibilidades de control de la misma; y por el otro, su rápida y preocupante dispersión. También se comentan las características más notables de O. latifolia: su pecíolo, carácter superficial, capacidad de rebrote, gran productividad y multiplicación y rejuvenecimiento anual. Estas características convierten a esta planta en una mala hierba difícil de erradicar en huertas, maizales y jardines, por lo que su presencia no es deseada. Finalmente, el presente estudio recopila las diferencias que se han encontrado entre las formas common y cornwall de la mala hierba

Germination differences between seeds from apical and basal fruits of "Camelina microcarpa" Andrz. ex DC. produced in two different climates

En el presente trabajo se han estudiado las diferencias de germinación entre semillas de una población de “Camelina microcarpa” Andrz. ex DC. producidas en los frutos apicales y basales de las mismas infrutescencias, y producidas en dos condiciones climáticas diferentes (Lleida y Minnesota). Las semillas apicales germinaron más y antes que las basales, principalmente cuando fueron producidas en Lleida, mientras que estas diferencias se difuminaron en las semillas procedentes de Minnesota; estas últimas semillas también germinaron en mayor medida que las de Lleida. A pesar de las diferencias, los ritmos de germinación fueron similares en casi todos los casos. Los resultados ponen de manifiesto la importancia del lugar de producción de las semillas de cara a su posible comercialización como cultivo oleaginoso.Germination characteristics of seeds collected from apical and basal fruits of the infrutescences, and produced in two different climatic conditions (Lleida and Minnesota) were studied. Apical seeds germinated more and earlier than basal seeds, mainly when they were produced in Lleida, while these differences blur between seeds produced in Minnesota, which germinated in a greater amount than those of Lleida. Despite these differences, germination rates were similar in all cases. The results show the importance of the seed production site if these species was considered as a potential commercial oilseed crop

Management options for "Papaver rhoeas" with multiple herbicide resistance

Se han estudiado diferentes sistemas de GIMh en una población de "Papaver rhoeas" con resistencia múltiple a tribenurón-metil y 2,4-D. Se establecieron cuatro sistemas de GIMh, con dos tipos de labores del suelo (siembra directa o mínimo laboreo), que incluyen rotación con girasol, retraso de la fecha de siembra, o aplicaciones herbicidas en diferentes momentos. Las densidades de amapola fueron mayores en siembra directa que en mínimo laboreo. Los sistemas de GIMh más eficaces en el manejo de “P. rhoeas” fueron aquéllos con una rotación con girasol y aplicaciones tempranas de herbicidas (pre-emergencia y/o post-emergencia precoz). La eficacia del retraso de la fecha de siembra difirió entre campañas. En cereales de invierno, es posible el desarrollo de sistemas de GIMh para el control de poblaciones resistentes de “P. rhoeas” integrando herramientas químicas y culturales.Different integrated weed management (IWM) systems have been studied in a multiple herbicide resistant “P. rhoeas” population to tribenuron-methyl and 2,4-D. Four systems were established with two types of soil management (direct drilling and minimum tillage), which included rotation with sunflower, sowing delay or different herbicide application timings. Corn poppy densities were higher during the experiment in direct drilling compared to minimum tillage. Most efficient IWM systems for “P. rhoeas” were those that included rotation with sunflower and early herbicide application timings (pre-emergence and/or early post-emergence). Sowing delay effectiveness depended on the growing season conditions. In winter cereals, the development of IWM systems to manage herbicide resistant P. rhoeas populations is possible integrating chemical and cultural tools

Effect of patch size on seed removal by harvester ants

The harvester ant Messor barbarus can be responsible for high weed seed losses in dry land cereals in Spain. Because weeds occur in patches, harvester ants have to be able to find and exploit patches. However, seed patches can differ in size and may, therefore, differ in the probability of being discovered and exploited. Here, 90 patches varying in size from 0.25 to 9 m2 were created in three 50 × 50 m subareas in a cereal field. Oat seeds were sown as weed seed surrogates in the patches at 2000 seeds m−2. After 24 h, those remaining were collected and the exploitation rate (the percentage of seeds removed per patch discovered by ants) was estimated. Harvester ant nests and the location of the seed patches were georeferenced and used to estimate distances between them. The patch encounter rate (the proportion of patches discovered by the ants) decreased slightly, but significantly, with decreasing patch size, though not the exploitation rate, which was lowest in the smallest patches (78-94%) and highest in the largest (99-100%). Seed patches that were not found or partially exploited were mostly located in subareas with a lower ant nest density or a longer distance away from the nearest nest than seed patches that were fully exploited. The results of this study indicate that the interaction between the spatial distribution of ant nests and the patchy distribution of seeds can create opportunities for seeds to be subjected to lower levels of predation