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Weeds represent one of the main problems in agriculture today. One of the control methods is herbicides that inhibit acetolactate synthase (ALS), but the resistance of some populations makes control difficult. Herbicide resistance in plants is assumed to have an associated cost, but this is not always easy to detect through biological fitness studies. The aim of the study was to compare fitness in populations of Digitaria sanguinalis resistant and susceptible to acetolactate synthase (ALS) inhibitor herbicides, in different aspects such as germination, emergence and the interaction of the two populations with two different phenotypes of the parasitic fungus Ustilago syntherismae, which has a drastic effect on the reproduction of D. sanguinalis, as it reduces seed production by replacing spikelets with a mass of spores. The tests found significant differences between the two populations of D. sanguinalis in terms of germination (the resistant spikelets germinated faster than the susceptible ones), emergence (the resistant spikelets presented a greater percentage of seedlings that emerged at a shallow depth of burial), and in the interaction with the fungus (the proportion of charred plants was significantly higher in the resistant than in the susceptible ones, and on the other hand, in terms of individual reproductive capacity, the susceptible ones were significantly higher). These data provide a snapshot of the costs associated with the fitness of resistant versus susceptible populations, as well as providing valuable information for predicting evolutionary dynamics and designing resistance management strategies., Les males herbes representen un dels principals problemes de l'agricultura actual. Un dels mètodes de control son els herbicides inhibidors de l'acetolactat sintasa (ALS) però la resistència de algunes poblacions dificulta el control. Es suposa que la resistència als herbicides, en les plantes, té un cost associat, però aquest no sempre és fàcil de detectar a través d'estudis sobre l'aptitud biològica. L'objectiu de l'estudi va ser comparar la fitness en poblacions de Digitaria sanguinalis resistents i susceptibles als herbicides inhibidors de l'acetolactat sintasa (ALS), en diferents aspectes com la germinació, l'emergència i en la interacció de les dues poblacions amb dos fenotips diferents del fong paràsit Ustilago syntherismae, que té un efecte dràstic en la reproducció de D. sanguinalis, ja que redueix la producció de llavors al substituir les espiguetes per una massa d'espores. Els assajos van constatar diferències significatives entre les dues poblacions de D. sanguinalis en quant a la germinació ( les espiguetes resistents van germinar més ràpidament que les susceptibles), l'emergència (les espiguetes resistents van presentar un percentatge major de plàntules emergides a poca profunditat d'enterrament), i en la interacció amb el fong ( la proporció de plantes encarbonades va ser significativament superior en les resistents que en les susceptibles, i en canvi quant a la capacitat reproductiva individual van ser significadament superior les susceptibles). Aquestes dades ofereixen una compressió dels costos associats a la fitness de les poblacions resistents en comparació a les susceptibles, a més de proporcionar informació valuosa per a predir la dinàmica evolutiva i dissenyar estratègies de maneig de resistències., Las malas hierbas representan uno de los principales problemas de la agricultura actual. Uno de los métodos de control son los herbicidas inhibidores del acetolactato sintasa (ALS) pero la resistencia de algunas poblaciones dificulta el control. Se supone que la resistencia a los herbicidas, en las plantas, tiene un coste asociado, pero éste no siempre es fácil de detectar a través de estudios sobre la aptitud biológica. El objetivo del estudio fue comparar la fitness en poblaciones de Digitaria sanguinalis resistentes y susceptibles a los herbicidas inhibidores del acetolactato sintasa (ALS), en diferentes aspectos como la germinación, la emergencia y en la interacción de las dos poblaciones con dos fenotipos distintos del hongo parásito Ustilago syntherismae, que tiene un efecto drástico en la reproducción de D. sanguinalis, ya que reduce la producción de semillas al sustituir las espiguillas por una masa de esporas. Los ensayos constataron diferencias significativas entre las dos poblaciones de D. sanguinalis en cuanto a la germinación (las espiguillas resistentes germinaron más rápidamente que las susceptibles), la emergencia (las espiguillas resistentes presentaron un porcentaje mayor de plántulas emergidas a poca profundidad de entierro), y en la interacción con el hongo (la proporción de plantas tiznadas fue significativamente superior en las resistentes que en las susceptibles, y en cambio en cuanto a la capacidad reproductiva individual fueron significativamente superior las susceptibles). Estos datos ofrecen una compresión de los costes asociados a la fitness de las poblaciones resistentes en comparación con las susceptibles, además de proporcionar información valiosa para predecir la dinámica evolutiva y diseñar estrategias de manejo de resistencias.

This essay studies the possibility of substituting the use of herbicides and mechanical ground work in the earliest years of apple trees plantation, as they spoil the environment and the initial tree growth, respectively. The essay consists of 12 different treatments in which different thesis are compared; use of herbicide, mechanical work of the soil, combinations of those two and cover crops composed by several species. The next parameters are evaluated; vegetative tree growth, cover crops implantation, soil nutrients, attraction of pollinating insects, damage by the Mediterranean pine vole and production. From the obtained data a statistical analysis is made, discarding the species Agrostis stolonifera and Dichondra repens for injuring the main crop. The mechanical work of the soil and its combinations with herbicide have given good results regarding vegetative tree growth and the inexistent competence for water, whereas they don¿t stand out in other aspects, in which Trifolium repens shows to be useful by providing absorbable nitrogen to the soil. It also attracts pollinating insects and is capable to generate a uniform grassy layer, within all its perks, but in the other hand with its high water consumption necessities. There exist alternatives to the use of herbicide whom moreover promote biodiversity in our crops, it is then necessary to keep studying them., Se estudia la posibilidad de substituir el uso de herbicidas i trabajo mecánico del suelo los primeros años de la plantación de árboles de manzano, ya que afectan negativamente al medio ambiente y a la formación inicial de los árboles, respectivamente. El ensayo cuenta con 12 tratamientos en el cual se comparan las tesis de herbicida, trabajo mecánico, combinaciones de estos y siembras de diferentes especies. Se valoran parámetros de los siguientes ámbitos; crecimiento vegetativo del árbol, implantación de las especies sembradas, nutrientes en el suelo, atracción de insectos polinizadores, afectaciones por acción del topillo mediterráneo y producción. De los datos obtenidos se hace un análisis estadístico, y se descartan las especies de Agrostis stolonifera y Dichondra repens por dañar el cultivo. El trabajo mecánico del suelo y sus combinaciones con herbicida dan buenos resultados en cuanto al crecimiento vegetativo del árbol y la inexistente competencia por el agua, pero no destacan en otros ámbitos. En estos, el Trifolium repens muestra ser útil en aportar nitrógeno absorbible al suelo y atraer insectos polinizadores, generando una capa herbosa uniforme con todos les beneficios que conlleva, y con el inconveniente de tener elevadas necesidades de agua. Existen alternativas al uso de herbicida que además promueven la biodiversidad en nuestros cultivos, es necesario seguir estudiándolas., S’estudia la possibilitat de substituir l’ús dels herbicides i del treball mecànic els primers anys de plantació de pomera, ja que malmeten el medi ambient i la formació inicial dels arbres, respectivament. L’assaig consta de 12 tractaments en el qual es comparen les tesis d’herbicida, treball mecànic del sòl, combinacions d’aquests i sembres de diferents espècies. Es valoren paràmetres dels següents àmbits; creixement vegetatiu de l’arbre, implantació de les espècies sembrades, presència de nutrients al sòl, atracció d’insectes pol·linitzadors, afectacions per acció de talpons i producció. De les dades obtingudes se’n fa un anàlisi estadístic, i es descarten les espècies d’Agrostis stolonifera i Dichondra repens per malmetre el cultiu. El treball mecànic del sòl i les seves combinacions amb herbicida donen bons resultats en quant al creixement vegetatiu de l’arbre i la inexistent competència per l’aigua, però no destaquen en els altres àmbits. En aquests, el Trifolium repens demostra ser útil en aportar nitrogen absorbible al sòl i atraure insectes pol·linitzadors tot generant una capa herbosa uniforme amb tots els beneficis que comporta, amb l’inconvenient de tenir necessitats d’aigua elevades. Existeixen alternatives a l’herbicida que a més promouen la biodiversitat en els nostres cultius, cal seguir estudiant-les, Objectius de Desenvolupament Sostenible::13 - Acció per al Clima, Objectius de Desenvolupament Sostenible::15 - Vida d'Ecosistemes Terrestres

This work aims to extend our knowledge about the pathosystem Digitaria sanguinalis - Ustilago syntherismae. Nowadays D. sanguinalis is described as one of the worst weeds in the world due to its abundance and economic losses. On the other hand, U. syntherismae could be the alternative that is needed for its biological control, as it replaces its spikelets with a mass of spores and this causes a significant reduction in seed production. This study has focused on the spore germination phase and the infection phase. In the first experiment, the differences in germination and the development of U. syntherismae spores in relation to their method of washing were studied. Three different methods compared: copper sulphate, ethanol and sodium hypochlorite (at different concentrations and different contact times). In the second one, the differences on the spore growth depending on the culture medium were studied. Five different types of culture medium were compared: ING, YMA, YEA, ASC and PDA. The third experiment aimed to verify the existence of differences in the probability of D. sanguinalis seedling infection depending on the distance between the spikelet and the spore mass of U. syntherismae. The inoculated seedlings were dyed and observed under an optical microscope to verify the presence of fungus in their tissues. It can be stated that there are significant differences (P<0.05) in the average of germination percentage of spores washed with copper sulphate regarding the other types of washing, but it cannot be stated that there are significant differences in the average of the germination percentage if the spores have been washed with ethanol or sodium hypochlorite. It can be stated that the mean of germinated spores, the average length of the hyphae that are formed during germination, and the average number of bifurcations that this hyphae present in the ASC medium are significantly different (P<0.05) than the other medium, and that the averages of the proportion of g, Este trabajo pretende ampliar conocimientos sobre el patosistemas Digitaria sanguinalis - Ustilago syntherismae. Actualmente D. sanguinalis es descrita como una de las peores malezas del mundo por su abundancia y las pérdidas económicas que causa. Por otro lado, U. syntherismae podría ser la alternativa que se necesita para su control biológico, ya que sustituye sus espiguillas por una masa de esporas y, por tanto, causa una importante reducción en la producción de semillas. Concretamente se ha centrado el estudio en la fase de germinación de esporas y en la fase de infección. En el primer experimento se quiso conocer las diferencias en la germinación y el desarrollo de esporas de U. syntherismae en relación con su método de lavado. Se trabajó con 3 métodos diferentes: sulfato de cobre, etanol e hipoclorito sódico (a diferentes concentraciones y diferentes tiempos de contacto). En el segundo ensayo se quisieron estudiar las diferencias que conlleva la utilización de diferentes medios de cultivo para el crecimiento de las esporas. Se trabajó con 5 tipos de medio de cultivo diferentes: ING, YMA, YEA, ASC y PDA. En el tercer experimento se quiso verificar la existencia de diferencias en la probabilidad de infección de plántulas de D. sanguinalis en función de la distancia entre la espiguilla y la masa de esporas de U. syntherismae. Las plántulas inoculadas se tiñeron y se observaron al microscopio óptico para comprobar la existencia de hongo en sus tejidos. Se puede afirmar que hay diferencias significativas (P<0,05) en la media del porcentaje de germinación de lavadas con sulfato de cobre respecto a los otros tipos de lavado, pero no se puede afirmar que existan diferencias significativas en la media del porcentaje de germinación si las esporas han sido lavadas con etanol o hipoclorito sódico. Se puede afirmar que la media de esporas germinadas, la media de longitudes de las hifas que se forman en germinar y la media del número de bifurcaciones que presentan estas hif, Aquest treball pretén ampliar coneixements sobre el patosistema Digitaria sanguinalis - Ustilago syntherismae. Actualment D. sanguinalis és descrita com una de les pitjors males herbes del món per la seva abundància i les pèrdues econòmiques que causa. Per altra banda, U. syntherismae podria ser l’alternativa que es necessita per al seu control biològic, ja que substitueix les seves espiguetes per una massa d’espores i, per tant, causa una important reducció en la producció de llavors. Concretament s’ha centrat l’estudi en la fase de germinació d’espores i en la fase d’infecció. En el primer experiment es va voler determinar l’existència de diferències en la germinació i el desenvolupament d’espores d’U. syntherismae en relació amb el seu mètode de rentat. Es va treballar amb 3 mètodes diferents: sulfat de coure, etanol i hipoclorit sòdic (a diferents concentracions i diferents temps de contacte). En el segon assaig es van voler estudiar les diferències que comporta la utilització de diferents medis de cultiu per al creixement de les espores. Es va treballar amb 5 tipus de medi de cultiu diferents: ING, YMA, YEA, ASC i PDA. En el tercer experiment es va voler verificar l’existència de diferències en la probabilitat d’infecció de plàntules de D. sanguinalis en funció de la distància entre l'espigueta i la massa d'espores d’U. syntherismae. Les plàntules inoculades es tenyiren i s’observaren al microscopi òptic per comprovar l’existència de fong en els seus teixits. Es pot afirmar que hi ha diferències significatives (P<0,05) en la mitjana del percentatge de germinació d’espores rentades amb sulfat de coure respecte els altres tipus de rentat, però no es pot afirmar que existeixin diferències significatives en la mitjana del percentatge de germinació si les espores han estat rentades amb etanol o hipoclorit sòdic. Es pot afirmar que la mitjana d’espores germinades, la mitjana de longituds de les hifes que es formen en germinar i la mitjana del nombre de bifurcacions q

Discusses the two basic variable-rate application technologies, map-based and sensor-based, for fertilizer, lime, weed control, and seed.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Selective application of herbicide in agricultural cropping systems provides both economic and environmental benefits. Implementation of this technology requires knowledge of the location and density of weed species within a crop. In this study, two image classification techniques (Artificial Neural Networks (ANNs) and Maximum Likelihood Classification (MLC)) are compared for accuracy in weed/crop species discrimination. In the summer of 2005, high spatial resolution (1.25mm) ground-based hyperspectral image data were acquired over field plots of three crop species seeded with two weed species. Image data were segmented using a threshold technique to identify vegetation for classification. The ANNs consistently outperformed MLC in single-date and multitemporal classification accuracy. With advancements in imaging technology and computer processing speed, these network models would constitute an option for real-time detection and mapping of weeds for the implementation of site-specific herbicide management.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

Biocontrol has been critized because the target effects of biocontrol introductions have not been studied rigorously. The objectives of this thesis were 1)to assess quantitatively the efficacy of a classical biocontrol agent after its release and 2)to suggest factors that affect the density and distribution of the biocontrol agent. In 1997, Aphthona lacertosa, a root-feeding flea beetle that is native to Europe, was released for the biological control of leafy spurge in Alberta. The beetles had established at more than 75% of the release sites that were monitored in 1999. In 2000, the peak abundance of A.lacertosa across release sites ranged from low (<10 beetles m-2) to high (>70 beetles m-2). Sites with high beetle densities had a significantly greater local (ie. within 5m of release point) reduction of leafy spurge than sites with low beetle densities. The density and distribution of A. lacertosa are affected by cumulative degree-days (CDD) at the release site and plant lacertosa are affected by cumulative degree-days (CDD) at the release site and plant morphology, respectively. Beetle population growth may be enhanced by releasing A. lacertosa at sites where there are more CDD. It is expected that high densities of A. lacertosa will effectively control leafy spurge populations.

The biology of an adventive weed, Ehrharta villosa (F. Schult) was investigated at Turakina beach, Rangitikei, in order to understand its means of spread and to discover a way of controlling the plant. Two populations have been found at Turakina, the smaller being on the dune system and the other in a nearby pine plantation. Studies of the seed biology showed that although viability was high (ca. 80%), the numbers of seed produced per m2 was low (8 to 102 seeds/m2). Dispersal of these seeds was limited to within 5m of the source population and no seeds were discovered in the soil seed bank. Circumstantial evidence suggests seed predation to be a contributing factor to this. Germination tests in sand showed seeds were capable of emerging from depths of up to 6cm. Stages in seedling development were described. Pypgrass displays a tall habit with internodes which elongate soon after germination, but its seedlings are less vigorous than most other grasses and weeds. The morphology and growth pattern of pypgrass allows it to have a smothering effect on other vegetation. The potential for vegetative spread by rhizome fragments was investigated by burial and reexcavation of fragments. Pypgrass is capable of reproduction from rhizome fragments of varying lengths. Mapping a 400m2 area of the advancing front of one population showed that over one year pypgrass had spread between 4.1 and 9.0m. Species associated with pypgrass were recorded at the beginning and the end of the study to give some indication of the effect of pypgrass density on those associated species. In quadrats where pypgrass was most dense, fewer species overall were found. Dune species including pypgrass were tested for the presence of mycorrhizal fungi. Pypgrass proved to have the greatest percentage mycorrhizal infection (88.9%) with the other species having significantly lower percent infection. Mycorrhizal association may give an advantage to pypgrass by allowinq greater uptake of water and minerals comp

Experiments were conducted at two sites in Blacksburg, Virginia to study the effects of tillage (conventional plow-disk and no-tillage) and overseeding (underseeding) of legume cover crops (red clover, Trifolium pratense L.; white clover, Trifolium repens L.; and hairy vetch, Vicia villosa Roth.) at transplanting on weed suppression and yield of ’Big Sur’ broccoli (Brassica oleracea var. italica Plenck). In both sites, weed suppression from overseeded red clover, white clover, and hairy vetch equalled or surpassed that of the preemergent herbicide (oxyfluorfen) control. The legumes did not affect broccoli yield components in site 1 nor head number in site 2. However, hairy vetch reduced broccoli yield and head size in site 2. These reductions were attributed to competition with the broccoli. Overseeding tended to delay broccoli yield and head number in the two sites, but this trend was not significant. Tillage system did not affect weed suppression or broccoli yield components, and there were no tillage x overseeding effects. Based on this data, overseeded legumes can provide residual weed control in no-till broccoli, thus allowing a more sustainable production method.

The study was initiated to determine the effects of RGP and three levels on weed control: no weed control (control), herbaceous weed control (Oust), and woody and herbaceous weed control (Oust-Garlon) on three pine seedlots: pitch x loblolly pine hybrid (pxL-F2), Virginia Department of Forestry loblolly pine (VDF-Iob), and westvaco loblolly pine (WCO-Iob). Lateral roots had the greatest response to the Oust treatment compared to all other seedling parts. All seedlot and treatment interactions were associated with lateral roots. After one growing season the Oust treatment resulted in a 148% increase in lateral root biomass compared to the control treatment. Shoot biomass in the Oust treatment increased by 70% compared to the control. The ability to respond to weed control was related to RGP. Compared the loblolly pine seedlots the PxL-F2 had both significant higher RGP at planting and biomass accumulation in response to the Oust treatment. Compared to the loblolly pine seedlots the PxL-F2 lateral root biomass and total tree biomass increased by 44% and 30%, respectively. The addition of woody weed control to herbaceous weed control in the Oust-Garlon treatment did not result in significant increasings in loblolly pine seedling biomass compared to herbaceous weed control. Because of a to sensitivity to Garlon 4™ the (PxL-F2) had 22% reduction in total tree biomass in the Oust-Garlon treatment compared to the Oust treatment. Therefore, the control of woody weeds in pitch x loblolly pine plantations will need to be accomplished using another herbicide.

L. scoparium is one of New Zealand's most important weeds of unploughable infertile hill country. The plant is an indigenous shrub, characteristic of the early stages of succession to forest in a wide range of habitats (Cockayne, 1928). In the eight years prior to 1959/60 nearly 40,000 acres of unimproved grassland reverted to scrub, fern and second growth each year. L. scoparium is one of the most important components of the scrub, fern and second growth category. By 1959/60 the total area of reverted land in New Zealand was 5.7 million acres of which 3.65 million were in the North Island. (Rigg, 1962). Control of L. scoparium on unploughable hill country has been limited to pulling, cutting, or cutting and burning, depending on stage of growth. Chemical methods and standing burns have generally proved unsuccessful. Most methods are expensive. Levy (1932, 1940, 1946) postulated that establishment of L. scoparium in pasture could be prevented by good farming techniques. Today there is a growing body of practical evidence to support this hypothesis (Suckling, 1959; New Zealand Farmer 83 (42, 43, 45)). This study was carried out to determine what intrinsic factors favour the establishment of L. scoparium, and the quantitative effect of farm management techniques on this process.

Item donated by the Upper Mississippi River Conservation Committee (UMRCC) to Murphy Library in 2018. Part of the UMRCC Collection housed at Murphy Library, University of Wisconsin-La Crosse., Field and laboratory studies of the movement of herbicides were conducted to determine their potential as contaminants in irrigation return flow. Special emphasis was given to the use of herbicides for vegetation control along ditches, canals and watersheds where high dosages are required to control the excessive growth of grasses and broadleaved weeds. The following herbicides have been studies: substituted urea (diuron), triazines (summitol and atrazine), phenoxyacetic acid (2, 4-D and 2, 4, 5-T) and a substituted pyridine (picloram). The greatest tendency for transport of herbicides in water coming in contact with soils occurs during the initial storms following spray application. If the intensity of the initial precipitation is not sufficient to cause movement across the soil, the danger of herbicide movement is essentially eliminated. The highest concentratoins (ppm) of herbicide observed in surface waters were 1.8, 0.5, 4.2 and 2.7 for diuron, summitol, 2, 4-D, 2, 4, 5-T and picloram, respectively. These levels were observed immediately below treated areas receiving the higher recommended dosages of the herbicides. All herbicide concentrations dropped below the limit of detection within a few hundred meters below the sprayed areas. Presumably, soil filtration, adsorption and dilution are primarily responsible for the loss of herbicides from water., Table of contents: Conclusions -- Recommendations -- Introduction -- Literature review -- Materials and methods -- Results and discussion -- Summary -- Acknowledgments -- References -- Publications resulting from project -- Appendices.

Boy Scouts of troop No. 157 of St. Paul's Lutheran church help pull ragweed on behalf of hay fever sufferers. L to R: Harold Dahlgren, Virgil Dahlgren, and Jack Murray. See P74400 to P74403.

Boy Scouts of troop No. 157 of St. Paul's Lutheran church help pull ragweed on behalf of hay fever sufferers. L to R: Bob Johnson, Ed Couture, scoutmaster, and Jack Murray. See P74400 to P74403.

Boy Scouts of troop No. 157 of St. Paul's Lutheran church help pull ragweed on behalf of hay fever sufferers. L to R: Virgil Dahlgren, Lindy Saline, and Bob Johnson. See P74400 to P74403.

Professor Immer, professor of plant genetics at the University of Minnesota, inspects a pit dug 4 feet deep to determine if bindweed propagated below subsoil. The pit was dug a year ago and the professor has determined that the bindweed did indeed propagate. See P87006-P87010.

Stahler, federal inspector of the bureau of plants, stands by a display showing how the roots of bindweed can grow up to 20 feet deep. See P87006-P87010.

Inspector Stahler (left), federal inspector of the bureau of plants, and Superintendent Eidem spray sodium chlorate in hopes of eradicating the bind weed. See P87006-P87010.

The university sets up grow houses with varying degrees of light to determine how much light is needed for creeping jennie to grow. See P87006-P87010.

L to R: Smith, Lindell (on truck) and Bryant of the Minneapolis engineering department are pictured killing weeds by spraying with butyl-ester 2,4-dichlorophenoxyacetic acid.

Baker (left) and Carlson spray herbicide on trees near Cedar Lake Boulevard.

Dr. Ausemus (left) of the United States Department of Agriculture and Professor Arny, university farm agronomist, examine how bindweed or creeping jennie can destroy plants in a cornfield. See P87006-P87010.

Hanson, seed analyst at the University of Minnesota Farm School, inspects a typical growth of marsh elder. This image is part of a photo series that illustrates how Hennepin county plans to educate Minnesota farmers on weed eradication. See P85903-P95905.

Larson (left), seed analyst in charge of the weed and seed division of the state department of agriculture, aided by Thornes classifies seeds according to species. This image is part of a photo series that illustrates how Hennepin county plans to educate Minnesota farmers on weed eradication. See P85903-P95905.

Colored plates of weed types hang on the wall of the barber shop of Charles A. Shonka (center). Olson (left), former mayor of Hopkins, and DeVall inspect the exhibit of state furnished weed pictures. This image is part of a photo series that illustrates how Hennepin county plans to educate Minnesota farmers on weed eradication. See P85903-P95905.

H. B. Martin, designer and builder, stands in his weedcutter craft the 'Winsome Willy' before its maiden voyage in Lake Harriet. Miss Carlson smashes an empty pop bottle on the prow on the vessel.

H. B. Martin, designer and builder, pilots his weedcutter craft the 'Winsome Willy' on its maiden voyage in Lake Harriet.

Martin Larkin, Hennepin County Weed Inspector, carries a pump sprayer with a tank of war-developed weed killer, which only requires 10 gallons of water per acre.

Martin Larkin, Hennepin County Weed Inspector, carries a pump sprayer with a tank of war-developed weed killer, which only requires 10 gallons of water per acre. Here, he sprays some Leafy Spurge in a field at 60th Street and France Avenue. Other weeds marked for destruction are: Canadian Thistle, Wild Sumac, and Marijuana.

Martin Larkin, Hennepin County Weed Inspector, travels the county with a mobile instruction unit, which teaches residents how to kill weeds. He has recently purchased a jeep with tanks, pumps, and extension sprayers to be used along the roads and in fields.

L to R: George G. Fleetham of Minneapolis and an unidentified assistant set up his new invention, a weed control machine, for a demonstration on the University of Minnesota campus. Powered by a gasoline engine, the machine forces a weed-killing mixture in a pressurized tank through atomizing jets that are pulled across the lawn. Fleetham hopes to manufacture the machine in Minneapolis.

Man illustrates high weeds along shoreline; 2-year-old had recently drown there, unseen because of the weeds

Weeds are cut down after drowning of 2-year-old Fitzgerald, who was unseen in the tall weeds

Gordon Dhein uses an air compressor to attach rubber handles to his weed cutters. The tools of his own invention re-use old shaving razor blades that are replaceable and cost effective.