Master of Science / Department of Agronomy / Anita Dille / A better understanding of kochia (Kochia scoparia) seed characteristics is necessary for long term management of this increasingly troublesome weed. The objectives were to evaluate maternal environmental factors influencing kochia seed produced in the field and to document variability in dormancy and seed viability produced within a single kochia plant grown in the greenhouse or field. Field experiments were conducted in 2012 and 2013 at the Kansas State Agricultural Research Center in Hays. Two different kochia biotypes from Hays were planted with and without five canopy types, namely corn, soybean, grain sorghum, wheat stubble, and kochia plants. A greenhouse experiment with two generations (F1 and F2) of self-pollination was conducted with the same kochia biotypes. Date of initial flowering and final plant heights were recorded. Plants were harvested when seed was mature and divided into three equal parts (top, middle, and bottom). Seeds were cold treated or not, and approximately 50 seeds were placed in petri dishes with water for germination counts taken over six weeks. Viability of remaining seeds were then tested. For field-grown kochia, plants were taller in corn, sorghum and weedy canopies compared to the absence of a canopy. Seed germination from field grown kochia ranged between 77 and 100% for both treatments. There was reduced germination in the presence of a weedy canopy for both treatments and biotypes (77 to 82%) compared to the absence (93 to 99%), with an increase in hard viable seed in the presence of weedy canopy (5 to 14%). In the greenhouse, the F2 generation produced more immediately germinable seed compared to the F1 generation which had more seed with delayed germinability. Seed from bottom third of F1 and F2 plants had greater total germination (73 and 70%, respectively) compared to the middle (61 and 65%) and top (50 and 59%) thirds of the plant. There was a maternal environmental effect on kochia seed characteristics with implications on generating persistent seed for the future seedbank.

Fumaria officinalis es una maleza importante del cultivo de trigo en el sur y sudoeste de la provincia de Buenos Aires. Durante los últimos años ha incrementado su presencia en los partidos de Villarino y Patagones, tanto en sistemas de labranza convencional como conservacionista, aumentando su densidad poblacional y la superficie ocupada dentro de los cultivos de trigo. Fueron estudiados algunos aspectos sobre la bioecología y el manejo de F. officinalis en el cultivo de trigo dentro del agroecosistema regional. Se formula la hipótesis de que un mayor conocimiento de la dinámica de emergencia de la maleza en el campo, su competencia con el cultivo y del control con diferentes herbicidas ayudará a un manejo más eficiente y sustentable de la maleza en la región. Se estudió el patrón de emergencia de la maleza, así como la influencia que sobre el proceso tiene la remoción del suelo (labranzas otoñales), la profundidad de entierro y la compactación del suelo. Paralelamente fue estudiada la competencia cultivo-maleza, evaluando el efecto que tiene la fertilización nitrogenada, el momento de emergencia relativo y la densidad de la maleza. También se evaluaron herbicidas postemergentes selectivos de trigo en diferentes momentos fenológicos del cultivo y se estudió la respuesta de F. officinalis a diferentes dosis del herbicida glifosato en dos estadios fenológicos de la maleza. Los resultados en cuanto a la emergencia de la maleza en el campo, indican que se produce en el otoño e invierno, y se estimula principalmente por las precipitaciones y las labranzas del suelo. En la interferencia cultivo maleza, F. officinalis demostró ser un buen competidor por nitrógeno del suelo frente al trigo. La competencia que ejerce la maleza sobre el cultivo es baja y los mayores perjuicios se observan cuando la emergencia ocurre antes de las 2-3 hojas del cultivo y en altas densidades de la maleza. En cuanto al control químico en postemergencia de trigo, los herbicidas prosulfurón + triasulfurón e iodosulfurón + metsulfurón tienen muy buena efectividad sobre la maleza. El herbicida glifosato tiene muy buena acción de control inclusive en dosis bajas, dependiendo del estado fenológico de las plantas. Los resultados sugieren la realización de un manejo sustentable de F. officinalis, adelantando la fecha de siembra del cultivo, monitoreando las densidades de infestación y reduciendo las dosis de aplicación de herbicidas según el estado fenológico de la maleza. / Fumaria officinalis is an important weed of wheat crops in the south and southwest of Buenos Aires province. During the past few years its presence in conventional as well as in conservationist farming systems has increased in the area of Villarino and Patagones, increasing its population density and the surface occupied within wheat. Some aspects of the ecology and management of F. officinalis in wheat crops within agro-ecosystems of the south-southwest of Buenos Aires province were studied. The hypothesis formulated is that a greater knowledge of the emergence dynamics the weed in the field, of its competition with the culture, and of the degree of control by different herbicides will help to a more efficient and sustainable handling of this weed in the region. The pattern of emergence of the weeds was studied, as well as the influence that the following factors have on the process: 1) Soil disruption (autumn tillage), 2) Depth and 3) Compaction of the ground. Crop - weed competition was studied, evaluating the effect of nitrogen fertilization, the relative moment of emergence and the density of the weeds. Also, selective post-emergent herbicides applied at different phenological stages of the crop were evaluated, and the answer of F. officinalis to different doses of glyphosate herbicide at two phenological stages of the weed was studied. Results, indicate that the emergence of the weeds in the field, takes place in autumn and winter, and is mainly stimulated by precipitations and soil tillage. Regarding crop - weed interference, F. officinalis competed well against wheat for the nitrogen of the soil. The competition that exerts the weed on the culture is low and the greatest damages are observed when the emergence happens before the 2-3 leaves stage of the crop, and with high densities of the weed. Regarding chemical control at post-emergence of wheat, the herbicides prosulfurón + triasulfurón and iodosulfurón + metsulfurón have very good effectiveness against the weed. Depending on the phenological state of the plants, the herbicide glyphosate has very good effect on the weed, even at low doses. Considering all these results, a sustainable management of F. officinalis is proposed, advancing the date of sowing of the culture, monitoring weed densities and reducing the application doses of herbicides according to the phenological state of the weed.