Fundação de Amparo a Pesquisa no Estado do Rio Grande do Sul / The species Eragrostis pilosa and Eragrostis plana has been found in lowland environment promoting interference by competing with the rice (Oryza sativa). Eragrostis are exotic plants to the floodplain environment and usually develops in deep soils and well drained as the highlands. The characterization of the species and the study of their biology in different environments is needed to understand the process of adaptation of these species in these poorly drained environments in order to develop an efficient management of these. In this sense the present study at Masters level, aims to assess the phenotypic behavior and the anatomical and morphological alterations of these plants when subjected to three soil moisture conditions (50% soil water capacity, 100% soil water capacity and Flooding). The study was conducted in 2014/2015 season in greenhouse using seeds of Eragrostis pilosa and Eragrostis plana access derived from rice producing areas of Itaqui/ Rio Grande do Sul Brazil.The results showed that each species showed different responses to treatments which have been submitted. For E. plana there was a reduction in tillering, less formation of panicles and reduction of aerenchymas of the plants when exposed to flooding. As for the plants E. pilosa, the responses to treatment flooding were observed with reduced tillering, with consequent reduction in the formation of panicles per plant, changes in the development of the flag leaf, reduction in dry weight root, and shoot and increasing the vegetative cycle of plants. The two species showed formation aerenchyma the roots and stems and adventitious roots on the soil surface when subjected to treatments of 100% of soil water capacity and flooding, in response to hypoxic stress. For chlorophyll parameters, the responses were similar in both species, by reducing the amount of chlorophyll, reflecting the low electron transport capability. The flooding affect the development of plants evaluated, which infers that the management of the rice crop water plays an important role in the management of invasive plants. / As espécies Eragrostis pilosa e Eragrostis plana tem sido encontradas em ambientes de terras baixas promovendo interferência por competição com a cultura do arroz (Oryza sativa). Eragrostis são plantas exóticas ao ambiente várzea e, normalmente, se desenvolvem em solos profundos e bem drenados como as terras altas. A caracterização das espécies e o estudo da sua biologia em diferentes ambientes é necessário para entender o processo de adaptação destas espécies nestes ambientes mal drenados como forma de desenvolver um manejo eficiente destas. Neste sentido o presente trabalho tem por objetivo avaliar o comportamento do crescimento e desenvolvimento destas plantas quando submetidas a três condições de umidade do solo, uma simulando ambiente natural dessas plantas com umidade reduzida de 50% da capacidade de retenção de água do solo (CRA) e outros dois tratamentos simulando ambiente de terras baixas com maior umidade do solo, um com 100% da CRA, simulando ambientes mal drenados de várzea, e outro com lâmina de água de 10 cm simulando a lavoura de arroz irrigado. Foram analisadas as alterações morfológicas-anatomicas dos acessos através com medições de parâmetros morfológicos, alterações anatômicas com a quantificação da formação de mecanismos adaptativos ao meio hipóxico, ainda foram quantificados os pigmentos fotossintéticos e realizada a avaliação da capacidade de transporte de elétrons pela cadeia transportadora da fotossíntese. O estudo foi desenvolvido no ano de 2014/2015 em ambiente controlado de casa de vegetação, utilizando-se sementes de acessos de Eragrostis pilosa e Eragrostis plana oriundos de áreas de produção de arroz de Itaqui/RS. Os resultados permitem concluir que cada espécie apresentou respostas diferentes para os tratamentos os quais foram submetidas. Para E. plana houve a redução no perfilhamento, menor formação de panículas e redução do volume da parte aérea das plantas quando submetidas a lâmina de água. Já para as plantas de E. pilosa, as respostas ao tratamento de lâmina de água foram evidenciadas com a redução do perfilhamento, com consequente redução na formação de panículas por planta, alterações no desenvolvimento da folha bandeira, na redução de massa seca de raiz e parte aérea e no aumento do ciclo vegetativo das plantas. As duas espécies estudadas apresentaram formação de aerênquimas nas raízes e colmos e raízes adventícias na superfície do solo quando submetidas aos tratamentos de 100% da CRA e lâmina de água, como resposta ao estresse hipóxico. Para os parâmetros de clorofila, as respostas foram semelhantes para as duas espécies, com a redução da quantidade de clorofila a e clorofila total, refletindo na baixa capacidade de transporte de elétrons. A lâmina de água interferiu negativamente o desenvolvimento das plantas avaliadas, o que infere que o manejo da água da lavoura de arroz cumpre importante papel no manejo das plantas invasoras.

The knowledge of spatial distribution in weed populations allows site specific management that can entail economic benefits of materials, and preservation of the environment. The objective of this study is to evaluate the emergence flow, spatial distribution with utilization of maps, and chemical and mechanical management on horseweed (Conyza bonariensis and Conyza Canadensis) resistant to herbicide glyphosate. The first analysis has samples from previously harvested soybean sites in the municipality of Cruz Alta and São Gabriel, Rio Grande do Sul, Brazil; with an area of 9.47 and of 4.98 ha, respectively. The samples were taken from each sample point of 0.50 x 0.50m by counting the number of horseweed presented. The analysis of the spatial distribution was done with semivariograms in different emergence flows of horseweed with a map generated by the software program ArcGis 9.3, and spatial dependence was estimated by classification of Cambardella et al. (1994). The second analysis consisted of six treatments: two mechanical managements (plowing followed by harrowing and harrowing one-way); three chemical managements (glyphosate + 2,4-D®, glyphosate + saflufenacil, and glyphosate alone), and a control without management. The weeds Conyza bonariensis and Conyza canadensis presented in the experimental area were in the reproductive phase with an average height of 75cm and 80% soil coverage. The evaluation of the experiment was performed in 7, 14 and 28 days after application of treatment (DAT). The treatment of glyphosate alone was unsuccessful, thus confirming that the weeds have developed a resistance to the chemical. The combinations between the herbicides of 2,4-D® and saflufenacil with glyphosate propitiated significant increases in the control of horseweed. The mechanical management (plowing followed by harrowing) obtained total control of horseweed. The chemical treatments, with exception to glyphosate, can be recommended for the management of horseweed in pre-sowed soybeans. / O conhecimento da distribuição espacial das populações daninhas permite ações de manejo localizado, que podem ocasionar o benefício da economia de insumos e da preservação da qualidade do ambiente. O objetivo do estudo foi avaliar o fluxo de emergência, a distribuição espacial com a utilização de mapas e o manejo químico e mecânico para o controle de buva (Conyza bonariensis e Conyza canadensis) resistente ao herbicida glifosato. O primeiro capítulo apresenta amostragens realizadas na entressafra da cultura da soja, nos municípios de Cruz Alta e São Gabriel, RS, Brasil, em área de 9,47 ha e de 4,98 ha, respectivamente. As amostragens de buva foram realizadas em cada ponto amostral através da contagem de plantas de buva no interior do quadro amostral com dimensões de 0,50 x 0,50m. A análise da variabilidade espacial foi feita com semivariogramas nos diferentes fluxos de emergência de buva, os mapas foram gerados com o programa computacional ArcGis 9.3, e a dependência espacial estimada pela classificação de Cambardella et al. (1994). A distribuição espacial de buva apresenta dependência espacial nas duas áreas analisadas em seus respectivos fluxos de emergência. Os grides amostrais utilizados foram apropriados para caracterizar a distribuição espacial de buva. No segundo capítulo, o ensaio foi constituído por seis tratamentos; dois manejos mecânicos (aração seguida de gradagem e gradagem em sentido único) e três manejos químicos (associações entre glifosato + 2,4 D, glifosato + saflufenacil e glifosato isolado), além de uma testemunha (sem controle). As plantas daninhas presentes na área de experimento foram Conyza bonariensis e Conyza canadensis em fase reprodutiva, com altura média de 75cm, e com 80% de cobertura do solo. As avaliações de controle foram realizadas aos 7, 14 e 28 dias após a aplicação dos tratamentos (DAT). O tratamento do herbicida glifosato isolado não obteve êxito, confirmando assim, a suspeita de resistência da planta daninha alvo. As combinações entre os herbicidas 2,4-D e saflufenacil associados ao glifosato propiciaram incremento significativo no controle de plantas de buva. O manejo mecânico (aração + gradagem) obteve controle total. Estes tratamentos, com excessão do glifosato aplicado isolado, podem ser recomendados para o manejo de buva em pré-semeadura da cultura da soja.

The alien invader plant Parthenium hysterophorus is a Category 1 weed in South Africa, where it poses a serious threat to indigenous vegetation in particular, and to biodiversity in general. In addition to its competitive ability, it is hypothesized that the successful invasiveness of P. hysterophorus is linked to the allelopathic potential of the plant. One compound in particular, parthenin, is alleged to play a major role in this allelopathic potential. Interference between P. hysterophorus and three indigenous grass species (Eragrostis curvula, Panicum maximum, Digitaria eriantha) was investigated on a site with a natural parthenium infestation at Skukuza, Kruger National Park. The trial was conducted over two growing seasons on exclosure plots which eliminated mammal herbivory. P. maximum displayed best overall performance and was eventually able to completely overwhelm P. hysterophorus. Eragrostis curvula and D. eriantha grew more favourably in the second season after becoming better established but were clearly not well adapted to the trial conditions. Although P. maximum was the supreme interferer, all grasses were able to significantly interfere with P. hysterophorus growth in the second season. The ability of P. maximum to interfere with P. hysterophorus growth so efficiently that it caused mortalities of the latter species, indicates that P. maximum exhibits high potential for use as an antagonistic species in an integrated control programme. An investigation on the production dynamics of parthenin in the leaves of P. hysterophorus indicated that high levels of this compound are produced and maintained in the plant up until senescence. The high resource allocation priority of the plant towards this secondary metabolite even in the final growth stages may indicate the use of residual allelopathy to inhibit or impede the recruitment of other species. Studies on the persistence of parthenin in soil revealed that parthenin is readily degraded in soil and that microbial degradation appears to play a predominant role. Significant differences between parthenin disappearance-time half-life (DT50) values were observed in soils incubated at different temperatures and in soils with different textures. Exposure of the three grass species to pure parthenin showed that, in terms of their early development, the order of sensitivity of the grasses was: Panicum maximum>Digitaria eriantha>Eragrostis curvula. It may therefore prove challenging to establish P. maximum from seed in P. hysterophorus stands during the execution of an integrated control programme due to the sensitivity of this grass species to parthenin. From the research findings it appears possible that P. hysterophorus can inhibit or impede the recruitment of indigenous vegetation under natural conditions. At least one mechanism through which this alien species can exert its negative influence on other plant species is the production and release of parthenin. / Dissertation (MSc (Agric) Agronomy)--University of Pretoria, 2007. / Plant Production and Soil Science / unrestricted

The successful biological control of the shrub-like prickly pear Opuntia stricta Haworth in Australia by cactoblastis cactorum (Berg) was not repeated when C. cactorum, derived from the Australian population, was released in South Africa in the 1930's against the tree prickly pear Opuntia ficus-indica (L.) Miller. Resistance of the woody portions of o. ficus-indica to attack by C. cactorum was regarded as the main reason for the poor performance of C. cactorum in South Africa. C. cactorum also oviposits and feeds on Opuntia aurantiaca Lindley, which is currently South Africa's most important weed and which is also considered to be partly resistant to attack by C. cactorum. This study had three main objectives: (i) to compare the ecology and effectiveness of C. cactorum as a biological control agent on O. ficusindica and O. aurantiaca; (ii) to reassess why C. cactorum has not been as effective a biological control agent in South Africa as it has been in Australia; and (iii) to evaluate whether inundative release or the importation of new biotypes of C. cactorum from South America (where it is indigenous) might be feasible methods of improving its effectiveness as a biological control agent of O. aurantiaca in South Africa. All field work was undertaken at a site near Grahamstown in South Africa. The ecology and effectiveness of C. cactorum on O. ficus-indica and O. aurantiaca was assessed in terms of its oviposition behaviour, survival and feeding on these host plants. The proportion of C. cactorum eggs laid on O. ficus-indica and O. aurantiaca was similar and was influenced by the size, conspicuousness and condition of the host plant as well as by the proximity of the host plant to moth emergence sites. Factors affecting oviposition site selection on the plant are also considered. Life tables, compiled for a summer and a winter generation, showed that the survival of C. cactorum was greater on O. ficus-indica than on O. aurantiaca, mainly because higher egg predation by ants occurred on the latter host plant species. During the period of study, the population size of C. cactorum was reduced by a number of mortality factors, of which egg predation and the effects of low temperatures on fecundity were the most important. Although there was evidence of a partial, positive response by predatory ants to C. cactorum egg densities on plants, the extent of egg predation was also affected by other factors, particularly seasonal effects. C. cactorum destroyed a greater percentage of cladodes on O. ficu-indica than on O. aurantiaca, but even on O. ficus-indica it was unable to contain the growth of plants within the study area. C. cactorum larvae rarely killed the woody rooted cladodes of O. ficus-indica and O. aurantiaca and consequently whole plants were not often destroyed. The detrimental effects of host plant resistance, natural enemies and climate on the effectiveness of C. cactorum as a biological control agent all appear to be greater in South Africa than in most of the regions occupied by C. cactorum in Australia. A field experiment conducted at the study site showed that inundative release methods for improving the effectiveness of C. cactorum on O. aurantiaca are not feasible. The importation of biotypes of C. cactorum from South America that might be better suited for destroying O. aurantiaca infestations in South Africa, is also not a viable option. Results of a survey of a 218 ha area that is regarded as being heavily infested with O. aurantiaca, illustrate how this cactus species has been overrated as a weed problem. It is argued that the present strategy for O. aurantiaca control in South Africa is not based on sound economic or ecological criteria.

In 1985 the Diama Dam was built near the mouth of the Senegal River to regulate flows during the rainy season and prevent the intrusion of seawater during the dry season. This created ideal conditions upstream of the dam wall for invasion by two highly invasive aquatic weeds, first by water lettuce Pistia stratiotes Linnaeus (Araceae) in 1993, and then by salvinia Salvinia molesta D.S. Mitchell (Salviniaceae) in 1999. This study was focused on the management of P. stratiotes and S. molesta. Following successes that were achieved elsewhere in the world, biological control programmes involving two weevil species were inaugurated against both weeds and research was focused on several aspects. These included pre-release studies to determine the weevils' host-specificity and impact on the plants in the laboratory, their subsequent mass-rearing and releases at selected sites and post-release evaluations on their impact on the weed populations in the field. Both programmes, which reprepresented the first biocontrol efforts against aquatic weeds in Senegal, proved highly successful with severe damage inflicted on the weed populations and complete control achieved within a relatively short time span. A laboratory exclusion experiment with N. affinis on P. stratiotes showed that in treated tubs, the weevil strongly depressed plant performance as measured by the plant growth parameters: mass, rosette diameter, root length, number of leaves and daughter plants whereas control plants were healthy. Field releases started in September 1994 and water coverage by P. stratiotes at Lake Guiers was reduced by 25% in January 1995 and 50% in April 1995. A general decline of 65% in water coverage by P. stratiotes was observed in June 1995 and by August 1995, eight months after releases P. stratiotes mats were destroyed. Further, although no releases were made there, good results were obtained within 18 months at Djoudj Park water bodies, located 150 km NW from Lake Guiers indicating the potential of the weevil to disperse long distances. In 2005, P. stratiotes reappeared and the weevil N. affinis has located and controlled all of these P. stratiotes recurrences after new releases. In 1999, S. molesta covered an estimated area of 18 000 ha on the Senegal River Left Bank and tributaries (Senegal) and 7 840 ha on the Senegal River Right Bank (Mauritania). Military and Civil Development Committee (CCMAD) and community volunteers made an effort to control S. molesta using physical removal, but this costly and labour-intensive approach was unsustainable. Hence, biological control was adopted by Senegal and Mauritania to manage the weed. Host range tests to assess feeding by C. salviniae on S. molesta and non-target plants and carried out on 13 crop species showed that no feeding damage was observed on the latter and weevils only fed on S. molesta. Field releases of some 48 953 weevils at 270 sites were made from early January 2002 to August 2002. Within one year, weevils were established and were being recovered up to 50 km from the release sites. In a case study conducted at one of the release sites, the S. molesta infestation was reduced from 100% to less than 3% 24 months after release. These results are discussed in the context of the weeds’ negative impact on aquatic systems and riverside communities, and in the involvement of these communities in the programmes.

The water hyacinth (Eichhornia crassipes (Mart.) Solms-Laub (Pontederiaceae)) biological control programme makes use of tight plant-insect interactions to control the weed, by reestablishing the interactions between the plant and its natural enemies. Since the beginning of the water hyacinth biological control initiative, the impact of biological control agent herbivory on water hyacinth’s population growth and fitness have been well documented; however, very few investigations have been conducted to determine whether herbivory elicits insect-induced responses by water hyacinth. Studies were conducted to determine the presence and function of water hyacinth insectinduced responses, using the plant activator, BION®, in attempt to determine the plant hormone-mediated pathways regulating the final expressions of insect-induced defences in response to herbivory by the phloem-feeder, Eccritotarsus catarinensis (Carvalho) (Hemiptera: Miridae) and the leaf chewer, Neochetina bruchi Hustache (Coleoptera: Curculionidae). BION® (Syngenta, acibensolar-S-methyl (benzothiadiazole)) is a dissolvable, granular formulation that contains a chemical analogue of the plant hormone, salicylic acid (SA), which typically regulates defences against pathogens. The application of BION® results in the induction of the SA-mediated defence pathways in plants (activation of defences against pathogens), and consequently the inhibition of the jasmonic acid (JA)- mediated defence pathways (de-activation of defences against insect herbivores). To test for induced defence responses in water hyacinth, plants treated with BION® and then subjected to herbivory, were compared to un-treated plants that were also subjected to herbivory, BION®-only treated plants and control plants. The application of BION® did not confer resistance against the two insect herbivores, as herbivory, reductions in chlorophyll content and plant growth (leaf production and second petiole lengths) significantly increased in comparison to non-BION® treated plants. Furthermore, palatability indices significantly increased (>1.00) in BION® treated plants, reflecting increased weevil preferences for SAinduced water hyacinth plants. This concluded that SA-mediated defences are not effective against insect herbivory in water hyacinth plants, but are in fact palatable to insect herbivores, which reflects ecological and physiological costs of SA-mediated defences (pathogen defences) in water hyacinth. Biochemical analyses of leaves exhibited increases in nitrogen content in BION® treated plants. These elevated levels of nitrogenous compounds account for the increases in mirid and weevil preferences for BION® treated plants. The increases in nitrogenous compounds are probably structural proteins (e.g. peroxidises), because leaves treated with BION® increased in toughness, but only when exposed to herbivory. Regardless, insect herbivory was elevated on these leaves, probably because the nitrogenous compounds were nutritionally viable for the insects.

Orientador: George John Shepherd / Dissertação (mestrado) - Universidade Estadual de Campinas, Instituto de Biologia / Made available in DSpace on 2018-08-07T20:50:25Z (GMT). No. of bitstreams: 1 Morbiolo_SergioRodrigues_M.pdf: 2368807 bytes, checksum: 47541963ceac1776da4ed3c27c6b3085 (MD5) Previous issue date: 2006 / Resumo: A taxonomia de Lantana camara tem sido alvo de discussão de estudiosos em todo o mundo. A variabilidade morfológica, ecológica e química da espécie é extremamente grande. Alguns autores consideram que L. camara seja um complexo de espécie ao invés de um táxon monotípico, algumas vezes descrito como composto por até 150 táxons diferentes. Neste trabalho, a variabilidade de L. camara é colocada a prova através de dois métodos: a morfometria geométrica e a modelagem matemática. Os métodos morfométricos são utilizados para analisar a variabilidade morfológica do corpo vegetativo dos indivíduos da espécie no Brasil, país que faz parte da região original de distribuição da espécie, a América tropical. A análise dos dados é feita por métodos multivariados a fim de verificar se existe uma unidade taxonômica nas amostras brasileiras da espécie ou não. É verificado que não existe qualquer ponto confiável em que se possa reconhecer táxons específicos ou subespecíficos em todo o território; apesar da grande discrepância entre os extremos, as medidas formam um contínuo. No segundo capítulo, um algoritmo genético (GARP) é utilizado para traçar um mapa de distribuição potencial da espécie sobre o mundo, baseado em pontos de ocorrência da espécie em áreas nativas da América tropical. Verifica-se uma grande área potencial de distribuição no Novo Mundo e em outros continentes; porém, não houve previsão de ocorrência potencial na Austrália e na África do Sul. Estes dois países estão entre os que mais investem em programas de erradicação da espécie, com populações muito bem estabelecidas em áreas naturais e cultivadas. Como o algoritmo não previu possibilidade de ocupação desses países por L. camara, infere-se, então, que as linhagens ocorrentes nesses países sejam relativamente distantes taxonomicamente da espécie típica, podendo ser oriundas de hibridização e manipulação horticultural. Aparentemente, é necessária uma revisão da espécie em nível mundial / Abstract: The taxonomy of Lantana camara has been the target of discussion by taxonomists all over the world. The morphological, ecological and chemical plasticity observed is very extensive. Some autors consider that L. camara is a species complex instead of a monotypic taxon, composed of up to 150 different taxa. In this sudy, the variability of L. camara is studied using two methods: geometric morphology and mathmatical modelling. Morphological methods are used to analyze the morphological variability of the vegetative parts of brazilian populations. Brazil is within the native distribution for the species, which occurs over a large part of the Neotropics. The data analysis is made using multivariate methods to verify if there is any obvious morphological discontinuity within brazilian samples which would allow specific or insfraspecific taxa to be recognized. It does not appear to be possible to define reliable subdivisions within this taxon; in spite of the huge discrepancy among the more extreme samples, the measures are continuous. In the second chapter, a genetic algorithm (GARP) is used to draw a potential distribution map of the species over the world, based on occurrence points of Lantana camara in areas of the Neotropics where it is native. In spite of having an extremely widespread distribution in the Americas and other continents, no potencial occurrence is predicted for Australia and South Africa, two of the countries with the most active erradication programs for this species. It is inferred that the variants found in these countries may be taxonomically distant from the typical species, possibly resulting from horticultural hybridization and manipulation. A comprehensive review of the species at world level is necessary / Mestrado / Biologia Vegetal / Mestre em Biologia Vegetal

O controle de plantas daninhas é uma importante preocupação para a agricultura tendo em vista as perdas de produtividade que estas causam ao competir com a cultura por água, luz e nutrientes. O uso de herbicida é a forma de manejo mais empregada em todo o mundo para o controle destas plantas. Entretanto, o uso frequente de um dado herbicida, além de causar diversos impactos ambientais, pode levar à diminuição da eficiência do próprio herbicida ao promover a seleção de plantas que são resistentes a este herbicida. Com o crescente número de novos casos de biótipos resistentes aos herbicidas, conter a evolução da resistência tornou-se uma necessidade para a agricultura convencional. Assim, grande esforço tem sido despendido para compreender este fenômeno e tentar contornar este problema. Neste sentido, os modelos computacionais se apresentam como importantes ferramentas para investigar os efeitos dos diversos fatores, em particular das estratégias de aplicação dos herbicidas, que influenciam na dinâmica da evolução da resistência. Com esta motivação, este trabalho tem como objetivo propor e estudar algumas estratégias de aplicação de herbicidas, ou ditos simplesmente controladores, que sejam implementáveis e que diminuam os impactos ambientais considerando a evolução da resistência. Para isto, assumimos que existe um herbicida, denominado neste trabalho por herbicida recomendado, que é o preferível dentre os disponíveis por produzir uma boa relação entre os benefícios produtivos e os malefícios aos ecossistemas. Para projetar os controladores, assumimos que é possível obter informações sobre a identificação visual da resistência em campo, feitas por um agente quando o número de indivíduos resistentes ultrapassa um certo limiar, assim como informações sobre a quantidade de plantas daninhas na área, feita possivelmente empregando técnicas de sensoriamento remoto. Então, para definir os controladores, empregamos diretamente a identificação visual da resistência e estimativas para o banco de sementes e para a fração dos genótipos do banco, geradas por um filtro de Kalman a partir de informações sobre a quantidade de plantas na área. Os controladores foram avaliados em relação à preservação da eficiência do herbicida recomendado, produtividade, impacto ambiental e propagação da resistência. Concluímos destes estudos que o controlador sugerido pode apresentar melhores resultados que os obtidos por controladores ditos convencionais, que se baseiam apenas na informação de identificação da resistência em campo. / Weed control is a major concern in agriculture as it causes significant loss of productivity by competition for water, sunlight and nutrients. The use of herbicides is the most common practice in the world to control them. However, the frequent use of a particular herbicide, besides causing many environmental impacts, may lead to loss of efficiency by promoting herbicide resistance via selection of resistant individuals. Considering the increasing number of herbicide resistant biotic, restraining resistance evolution is becoming a necessity for the conventional agriculture. This motivates a great deal of research effort to understand the involved phenomena and eventually to circumvent the problem. To this end, computational models are of great aid to understand the impact of many different aspects involved in this problem, in particular, to understand how different herbicide strategies usage lead to different resistance evolution dynamics. In this thesis we propose and study some strategies for herbicide application, which we refer to as controllers. We seek for controllers that can be implemented in real word crops growing, while decreasing environmental impacts and restrain resistance evolution. We assume that there exists one herbicide of choice for a given crop, meaning that it is preferred in terms of environmental impact and efficiency. To define the controllers, we assume that it is possible to obtain visual information on resistance, meaning that we observe when the proportion of resistant individuals is above a threshold. Also, we assume noisy observation of the number of adult weed individuals, possibly made by remote sensing. So, the controller directly employs the visual identification information and an estimate for the number of resistant seeds in the seed bank, generated by the Kalman filter using information on the number of adult weed. This strategy was evaluated in terms of herbicide efficiency preservation, crop production, environmental impact and resistance proliferation. We conclude that the proposed control strategies performed better than other strategies, called conventional strategies that are based only on the visual identification information.

<p>There is an existing conflict thrust upon U.S. food production systems; optimize crop yield to provide sustenance to a growing population while minimizing ecological impacts of high-intensity agriculture. This balancing act is experienced by Indiana’s watermelon growers who must maintain marketability of a crop that is reliant on insect pollinators. The dependence on pollinators to produce yield means that growers have to consider the negative impacts pesticide applications may have on both the desired pest and non-target pollinators. Navigating these trade-offs must be considered not just in the watermelon fields, but the surrounding agricultural landscape that has become increasingly reliant on prophylactic insecticides to control pests. This dissertation work results from an intensive set of experiments replicating grower practices in experimental fields throughout Indiana to assess the relationships of pests, pollinators, and crop yield.</p> Beginning with a priming year in 2017, watermelon plots were planted within larger corn fields to replicate the agriculture landscape and provide a “snapshot” of typical environment. These plots were paired at multiple locations and provided a contrast between a conventional management system that replicates grower insecticide programs with an IPM approach that removes insecticide applications outside of those based on scouting recommendations. I found that, while pest abundance and damage was higher in IPM fields, the increased pollinator visits in IPM fields led to higher yields in watermelons while corn yield was unaffected by an absence of insecticide use. Managed pollinator hives were placed in these fields and IPM resulted in the colonies exhibiting greater weight gain, lower mortality, increased reproductive growth, and higher insecticide residue accumulation. Insecticide residues were found more frequently at higher levels in the leaf tissue, crop pollen, field soil, and honey bee-collected pollen taken from CM fields. Despite these findings, there was a variable effect of the surrounding land use on the quality of collected pollen or the insecticides gathered by pollinators. These experiments demonstrate that IPM is a viable set of practices for specialty crop growers in the Midwest; successfully monitoring insect pests and conserving pollination services from both managed and wild pollinators. These findings provide a comprehensive look at the effect of IPM practices not just on the a specialty crop, but to the surrounding agricultural landscape as well. An IPM approach can be implemented by growers to decrease non-target effects from insecticides while maintaining or even improving productivity and profitability.

<p>The western corn rootworm (WCR) <i>Diabrotica virgifera virgifera</i> Leconte is a major pest of maize in the United States. Currently, it is principally managed using Bt maize hybrids and neonicotinoid seed treatments (NSTs), which were concurrently introduced in the early 2000s. This simultaneous release, and subsequent rapid adoption, created a situation in which Bt maize hybrids were never assessed in the absence of NSTs, and vice versa. Consequently, neonicotinoids’ influence on refuge function, primarily whether these insecticides aid or hinder the production of a sufficient population of susceptible beetles to delay resistance, has not been assessed. Moreover, a mounting suite of detrimental environmental effects of NSTs have been documented, lending some urgency to questions about their necessity.</p><p>To determine the influence of NSTs on refuge function, untreated and treated Bt maize fields were planted with 5% untreated refuge marked with ¹⁵N. Throughout the field seasons of 2019 and 2020, adults were collected from these fields and analyzed to determine their natal host plant. Results documented that the numbers of refuge beetles produced by the 5% seed blend are likely insufficient to result in rates of mating to delay resistance development.</p><p>To determine if the effect of using NSTs in combination with Bt maize hybrids is additive, synergistic, or neutral at managing secondary soil pests in the Midwest, four 16 block fields were planted in 2018, 2019 and 2020 comparing four treatments (1. Untreated, Bt seed; 2. NST, Bt seed; 3. Untreated, non-Bt seed; 4. NST, non-Bt seed). Compact method sampling, root rating, and yield were used to document the presence of secondary soil pests. All three sampling years documented low abundance of white grubs and wireworms. There was minimal influence of NSTs on maize yield (2018: p = 0.07; 2019: p = 0.62; 2020: p = 0.056) and root damage (0-3 scale) (2018: M = 0.0092; 2019: M = 0.0091; 2020: M = 0.0361). These same fields were used to document the presence of NSTs in soil, as well as residues in nearby waterways. Results documented greatest soil and water clothianidin levels earlier in the season and declined as the season progressed.</p><p><br></p>