Made available in DSpace on 2014-06-11T19:22:18Z (GMT). No. of bitstreams: 0 Previous issue date: 2012-02-17Bitstream added on 2014-06-13T20:48:39Z : No. of bitstreams: 1 leal_uas_me_sjrp.pdf: 567532 bytes, checksum: 52bca74b9f676be787c66a5f2d9bea27 (MD5) / Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq) / O propósito desta pesquisa é o estudo de dois modelos de otimização dinâmica para a aplicação seletiva de herbicida , sendo um modelo de otimização multi-objetivo , no qual maximiza o lucro e minimiza a resistência , e o utro mono-objetivo da otimização da concentração de mistura de herbicidas, no sistema anual de colheita da cultura do milho para o período de 5 e 10 anos. A densidade de sementes no solo no início do plantio e a frequência de alelos são tomados como variáveis de estado . A variável de controle é expressa na função de dose-resposta. Os modelos de otimização levam em consideração a diminuição da eficiência do herbicida ao longo do tempo , causada pela evolução da re-sistência da planta daninha . O objetivo é maximizar o lucro num período pré-determinado e minimizar a evolução da resistência. O problema de otimização dinâmica multi-objetivo foi resolvido via abordagem−restrito. O problema resultante e o problema de otimização da concentração de misturas de herbicidas foram resolvidos por programação não-linear via o método ASA_CG. Para os dois casos estudados, os resultados das simulações numéricas a presentam uma estratégia ótima da aplicação de herbicidas, para... / The purpose of this research is the study of two dynamic optimization models for the selective application/mixture of herbicide in the annual system of corn crop harvest for period of 5 and 10 years. The density o f seeds at the beginning of the planting and allele frequency are taken as state variables. The control variable is given by the dose-response function. The optimization models take into account the decreased efficiency of the herbicide overtime caused by the evolution of weed resistance. The goal is to maximize profit in a predetermined period and minimize the resistance evolution. The dynamic optimization problem of multi-objective approach was solved by the e-constraint method. The resulting problem and the problem of dynamic optimization of the concentration of the herbicide mixture were solved by non- linear programming with the conjugate gradient method combined with the method of projected gradient. Results of numerical simulations provide an optimal strategy of selective application of herbicides to control weed infestation by the Bidens subalternans. Two models studied, the first considers only... (Complete abstract click electronic access below)

Orientador: Geraldo Nunes Silva. / Banca: Weldon A. Lodwick. / Banca: Valeriano Antunes de Oliveira. / Resumo: O propósito desta pesquisa é o estudo de dois modelos de otimização dinâmica para a aplicação seletiva de herbicida , sendo um modelo de otimização multi-objetivo , no qual maximiza o lucro e minimiza a resistência , e o utro mono-objetivo da otimização da concentração de mistura de herbicidas, no sistema anual de colheita da cultura do milho para o período de 5 e 10 anos. A densidade de sementes no solo no início do plantio e a frequência de alelos são tomados como variáveis de estado . A variável de controle é expressa na função de dose-resposta. Os modelos de otimização levam em consideração a diminuição da eficiência do herbicida ao longo do tempo , causada pela evolução da re-sistência da planta daninha . O objetivo é maximizar o lucro num período pré-determinado e minimizar a evolução da resistência. O problema de otimização dinâmica multi-objetivo foi resolvido via abordagem−restrito. O problema resultante e o problema de otimização da concentração de misturas de herbicidas foram resolvidos por programação não-linear via o método ASA_CG. Para os dois casos estudados, os resultados das simulações numéricas a presentam uma estratégia ótima da aplicação de herbicidas, para... (Resumo completo, clicar acesso eletrônico abaixo) / Abstract: The purpose of this research is the study of two dynamic optimization models for the selective application/mixture of herbicide in the annual system of corn crop harvest for period of 5 and 10 years. The density o f seeds at the beginning of the planting and allele frequency are taken as state variables. The control variable is given by the dose-response function. The optimization models take into account the decreased efficiency of the herbicide overtime caused by the evolution of weed resistance. The goal is to maximize profit in a predetermined period and minimize the resistance evolution. The dynamic optimization problem of multi-objective approach was solved by the e-constraint method. The resulting problem and the problem of dynamic optimization of the concentration of the herbicide mixture were solved by non- linear programming with the conjugate gradient method combined with the method of projected gradient. Results of numerical simulations provide an optimal strategy of selective application of herbicides to control weed infestation by the Bidens subalternans. Two models studied, the first considers only... (Complete abstract click electronic access below) / Mestre

Herbicide resistance development among weed populations in cotton and peanut is becoming increasingly difficult to manage. If resistant populations continue to persist, weed control practices for producers will become less efficient and more costly. The objective of this research was to evaluate alternative weed control techniques designed to mitigate herbicide resistance development for their agronomic and economic impact on weed management systems. Studies were conducted in 2019, 2020, and 2021 at multiple locations in Mississippi and Arkansas investigating multiple techniques including the addition of soil surfactants in herbicide tank mixtures, increasing SOAs utilized in peanut herbicide programs, applying non-labeled herbicides to cotton with post-directed spray placement, and applying complete residual herbicide programs in cotton. Our results suggests that some novel strategies incorporated into existing weed management programs, can provide sufficient control of troublesome weed species and conserve crop yield and profit returns. For example, the use of post-directed application placement allowed for non-labeled herbicides to be applied to cotton without detrimental effects, thus increasing potential options for POST weed control within that crop. Additionally, weed control, seed cotton yield, and net returns were not affected when only residual herbicides were applied in season-long weed control programs as opposed to the standard of mixed, foliar and residual programs. This indicates that high selection pressure associated with foliar chemistries which leads to resistance development, can be alleviated through the adoption of alternative strategies.

Submitted by Débora de Oliveira Latorre (deboraolatorre@gmail.com) on 2018-09-18T18:32:45Z No. of bitstreams: 1 Debora de Oliveira Latorre_ Dissertation.pdf: 3050527 bytes, checksum: 150c83efeaa3123bb2b38f3187b2e760 (MD5) / Approved for entry into archive by Maria Lucia Martins Frederico null (mlucia@fca.unesp.br) on 2018-09-18T19:29:22Z (GMT) No. of bitstreams: 1 latorre_do_dr_botfca.pdf: 3050527 bytes, checksum: 150c83efeaa3123bb2b38f3187b2e760 (MD5) / Made available in DSpace on 2018-09-18T19:29:22Z (GMT). No. of bitstreams: 1 latorre_do_dr_botfca.pdf: 3050527 bytes, checksum: 150c83efeaa3123bb2b38f3187b2e760 (MD5) Previous issue date: 2017-09-15 / Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES) / Os herbicidas são um dos fatores mais importantes que vem consideravelmente contribuindo no aumento na proteção das culturas, devido sua inovação no controle de plantas daninhas ao longo dos últimos 70 anos. O uso continuo de um mesmo ingrediente ativo ou modo de ação impõe uma alta pressão de seleção em uma população de plantas daninhas e a seleção de indivíduos resistentes a herbicidas pode ocorrer. A intensidade da seleção imposta pelos herbicidas e a frequência inicial de indivíduos resistentes a herbicidas dentro de uma população de plantas daninhas são fatores chave importantes no processo de evolução da resistência. Fluxo gênico via pólen, sementes e propágulos vegetativos são uma potencial fonte de distribuição de resistência a herbicidas, como previamente reportado em Conyza canadensis e Amaranthus ssp. Conyza canadensis e Amaranthus ssp são potencialmente capazes de transferir genes que conferem resistência a herbicidas via pólen e/ou sementes, por produzirem pólen que pode ser disseminado a longas distancia e grande número de sementes. Os objetivos gerais dos estudos realizados foram caracterizar o nível de resistência de duas espécies de plantas daninhas de Nebraska, Estados Unidos da América. Um primeiro estudo em casa de vegetação foi conduzido para caracterizar o nível de resistência a glyphosate de populações de buva coletadas em áreas não cultivadas foi conduzido. Experimentos de dose-resposta com 9 doses de glyphosate e 28 populações de buva foram avaliados. Um segundo estudo em casa de vegetação foi conduzido para caracterizar o nível de uma população de caruru resistente a 2,4-D a diferentes formulações de herbicidas fenóxicos. De acordo com o primeiro estudo de dose-resposta, menos de sete por cento das populações de Conyza canadensis em áreas de pastagem próximas a áreas de cultivo expressaram “resistência prática” a glyphosate (plantas sobreviventes a dose de glyphosate mais usual em Nebraska – 1,260 g ae ha-1). Baseado em nossos resultados, foi detectado baixa frequência de resistência a glyphosate em populações de Conyza canadensis em áreas de pastagem de Nebraska, indicando que indivíduos resistentes a glyphosate dispersos das áreas de cultivo não são o biótipo predominante nessas áreas. Os resultados do segundo estudo mostraram que a população de Amarantus tuberculatus resistente a 2,4-D foi significativamente mais suscetíveis às formulações dos herbicidas Dicamba DGA, Dicamba DMA, Corasil, 2,4-DP, e 2,4-DP-p, enquanto sobreviveram a altas doses dos herbicidas 2,4-D 2EHE, 2,4-D EE, 2,4-DB, MCPB, MCPA, MCPA 2EHE, CMPP e CMPP-p. / Herbicides are one of the most important factors that have contributed to protect crop yields. This is due to innovative weed control over the last 70 years. The over-reliance on a single herbicide active ingredient or mode of action impose a high selection pressure on a weed population and the selection of herbicide-resistant individual plants may occur. The intensity of selection imposed by herbicides and the initial frequency of herbicide resistant in a weed population play a major role in the herbicide resistance evolution. Gene flow by pollen, seed, and vegetative propagules have the potential to move herbicide-resistant weed species, as reported previous reported in Conyza canadensis and Amaranthus genus. Conyza canadensis and Amaranthus tuberculatus are potentially able to proliferate herbicide resistance by pollen and/or seeds due to be prolific seed producer and its pollen are capable to be disseminated for long distances. The general objectives of these studies were to characterize the herbicide resistance level of two weed species in Nebraska, United States. A greenhouse study was performed to characterize the fold of glyphosate resistance in horseweed populations from non-crop areas. Dose-response experiments with 28 horseweed populations were evaluated across nine glyphosate rates. A second greenhouse study was performed to characterize the level of a 2,4-D-resistant waterhemp population resistance to various auxinic herbicides. According to the first dose-response study, less than seven percent of the rangeland Conyza canadensis populations screened expressed “practical” resistance to glyphosate (plants surviving to most common glyphosate rate used in Nebraska of 1,260g ae ha-1). Therefore, low frequency of GR in horseweed populations was detected in Nebraska rangeland indicating that GR individuals dispersed from row crops into rangeland are not the predominant biotype in these non-row crop areas. For the second study, the results showed that 2,4-D-WR population were significantly more sensitive to Dicamba DGA, Dicamba DMA, Corasil, 2,4-DP, and 2,4-DP-p herbicides formulations, whereas survived to the higher doses of 2,4-D 2EHE, 2,4-D EE, 2,4-DB, MCPB, MCPA, MCPA 2EHE, CMPP and CMPP-p. The founds on this studied showed the 2,4-D-WR population exhibits cross-resistance to 2,4-D 2EHE, 2,4-D EE, 2,4-DB, MCPB, MCPA, MCPA 2EHE, CMPP and CMPP-p herbicides. / 006860/2015-00

Using data envelopment analysis with principal components, we calculate an adoption-intensity index for herbicide-resistance best management practices (BMPs). Empirical results for over 1,100 farmers in twenty-two U.S. states suggest that many farmers could improve their herbicide resistance BMP adoption. Two-limit truncated regression results show that higher yields and a greater proportion of acres planted with Roundup Ready (R) seeds motivate weed BMP adoption. While soybean and corn farmers have lower adoption intensity than cotton farmers, farmer educational attainment and greater concern for herbicide effectiveness and for human and environmental safety are found to help increase the adoption of weed BMPs.

<p dir="ltr">Palmer amaranth (Amaranthus palmeri S. Watts) and waterhemp [Amaranthus tuberculatus (Moq.) J. D. Sauer] are two of the most troublesome weeds in U.S. soybean production and the auxin herbicides dicamba and 2,4-D, are currently used extensively for postemergence control of these species. In some cases, complete control of weeds at the time of auxin application is not achieved due to adverse environmental conditions, plant factors or misapplications. In these instances, a subsequent postemergence herbicide may be required to control any plant that survived the initial auxin herbicide application. This research was conducted to determine the efficacy and optimal successive time interval between applications of viable postemergence herbicides in soybean on Palmer amaranth and waterhemp plants surviving a previous application of 2,4-D or dicamba. Results from this research indicated that respraying a failed auxin herbicide application with a subsequent auxin herbicide, especially dicamba, was less effective than respraying with glufosinate or fomesafen to control waterhemp in addition to being a less desirable approach for resistance management. Additionally, respray herbicide applications should target 7 to 14 d after the initial failed herbicide application on waterhemp for optimal overall efficacy. When dicamba was the initial herbicide sprayed on Palmer amaranth, 94% or greater control was achieved with glufosinate in 2019 on a 7- and 14-d respray interval, which was greater than the efficacy observed with either dicamba or 2,4-D (< 82%). In 2020, these differences in herbicide efficacy were not evident within these time intervals. These general trends in treatment differences were also manifested in the data for plant height, biomass and viable apical meristems. When 2,4-D was the initial herbicide sprayed on Palmer amaranth, fomesafen and glufosinate applications on a 7-d respray interval and glufosinate on a 14-d respray interval resulted in greater control than 2,4-D in 2019. All other trends in herbicide treatments and time intervals were consistent with dicamba applied as the initial herbicide. Another part of his research was conducted with the objective of quantifying herbicide spray solution deposition and herbicide efficacy on waterhemp growing in different densities plant densities: low, high-thinned and high densities. In both field and greenhouse experiments, spray deposition (µl cm-2) on waterhemp leaves was up to 53% less on plants grown in high density compared to the other density treatments. Even though no differences in herbicide deposition between low and the high-thinned densities were observed, there were differences in herbicide efficacy. When applied to plants growing in low density, applications of glufosinate, fomesafen and topramezone reduced weed biomass to a greater extent than plants growing in the high-thinned density. Following herbicide damage to the apical meristem, plants growing in high-density produced new branches from axillary buds that were previously dormant, whereas plants growing in the low density already had axillary branches initiated from these buds and did not provide an opportunity for new shoot growth. In general, no differences in herbicide efficacy were observed across weed densities following dicamba applications. Source-to-sink translocation of dicamba to previously active meristems, or axillary buds that broke dormancy after the herbicide application, may have compensated for less spray solution interception on plants growing in high density. Lower levels of postemergence herbicide efficacy in high density weed populations are not only influenced by spray deposition differences, but also by changes in plant growth and apical dominance. This research provides further evidence that justifies the need for weed managers to reduce weed densities as much as possible, via non-chemical or soil residual herbicides (preemergence), as much as possible to optimize the efficacy of foliar herbicide applications.</p>