O cancro bacteriano, causado por Clavibacter michiganensis subsp. michiganensis (Cmm), é uma das doenças mais importantes da cultura do tomate (Lycopersicon esculentum Mill.), especialmente para tomateiros estaqueados. O controle está fundamentado na adoção de um conjunto de medidas preventivas, pois poucas são as informações sobre materiais resistentes à doença e não existe um produto químico que a controle eficientemente. Os objetivos desta tese foram determinar um método de inoculação adequado à seleção de genótipos de tomateiro resistentes ao cancro bacteriano; avaliar a reação de genótipos de tomateiro à inoculação com Cmm; e avaliar o efeito de acibenzolar-S-metil e outros produtos fitossanitários no controle da doença. Para o ensaio de metodologia, foram avaliados quatro métodos de inoculação (aspersão de suspensão bacteriana na face inferior das folhas; aspersão, sob pressão, de suspensão bacteriana na face inferior das folhas; corte do sistema radicular, com tesoura, seguido de imersão na suspensão bacteriana; e ferimento na haste com alfinete entomológico transpassando uma gota de suspensão de inóculo depositada na axila foliar) e três concentrações de inóculo (108 ufc/mL, 107 ufc/mL e 106 ufc/mL). Posteriormente, foi avaliado o efeito da inoculação em plantas com diferentes idades, aos 7, 14, 21 e 28 dias após a emergência. Foram utilizados os genótipos Kadá e Rotam-4 e um isolado bacteriano proveniente de Bragança Paulista, SP. A avaliação foi realizada através de uma escala descritiva, atribuindo-se notas que foram convertidas em índice de murcha bacteriana. A inoculação de Cmm, quatorze dias após a emergência das plantas, através da aspersão de suspensão bacteriana (108 ufc/mL) na face inferior das folhas, com avaliação aos 30 dias após inoculação, foi a metodologia mais apropriada para a avaliar a reação de genótipos de tomateiro. Estabelecida a metodologia, foram avaliados dez genótipos comerciais de tomateiro (Carmen, Débora max, IPA-6, Santa Clara, Alambra, Júpiter, Olimpo, Fanny, Jumbo e Densus) para identificação de materiais resistentes ao cancro bacteriano, tendo-se Kadá e Rotam-4 como controles suscetível e resistente, respectivamente. Alambra e Jumbo apresentaram comportamento semelhante a Rotam-4, sendo materiais promissores para o plantio em áreas com histórico de ocorrência da doença. Para a avaliação de controle do cancro bacteriano foram testados os seguintes produtos: acibenzolar-S-metil (ASM), ASM + mancozeb, ASM + oxicloreto de cobre, mancozeb + oxicloreto de cobre, e oxitetraciclina. Três esquemas de aplicação dos produtos foram adotados: (E1) 4 aplicações (a primeira e a segunda realizadas seis e três dias antes da inoculação; a terceira e a quarta, aos três e seis dias após a inoculação); (E2) apenas as duas aplicações préinoculação; (E3) apenas as duas aplicações pós-inoculação. Esses produtos foram incorporados a meio de cultura para avaliação in vitro de seus efeitos sobre Cmm. Independente da forma de aplicação, o ASM, isolado ou em mistura com fungicidas, proporcionou reduções significativas na severidade da doença e não inibiu o desenvolvimento da bactéria in vitro. / Bacterial canker, caused by Clavibacter michiganensis subsp. michiganensis (Cmm), is one of the most important diseases of tomato (Lycopersicon esculentum Mill.). Its control is based on a set of preventive measures, once there is a few information about resistant materials and the chemical control is not efficient. The objectives of this thesis were to determine a suitable inoculation methodology to bacterial canker resistance studies; to evaluate the reaction of commercial tomato genotypes to the inoculation with Cmm; and to evaluate the acibenzolar-S-methyl and other phytossanitary products effects on the control of that disease. To methodology trial, four inoculation methods were evaluated, including foliar pulverization with bacterial suspension; foliar pulverization under pressure with bacterial suspension; cutting of roots with scissor, followed by their immersion in bacterial suspension; and stem wounding with a pin passing over a drop of inoculum suspension deposited on the insertion point of leaf. Besides the inoculation methods, three inoculum concentrations were investigated: 108 cfu/mL; 107 cfu/mL and 106 cfu/mL. Later, it was evaluated the effect of inoculation on plants with different ages: 7, 14, 21 and 28 days after emergency. To those trials, genotypes Kadá and Rotam-4, and a bacterial isolate from Bragança Paulista, SP, were employed. The evaluation was accomplished through a descriptive scale, being attributed notes that were turned into bacterial wilt index. Inoculation of Cmm, fourteen days after emergency of plants, through aspersion with bacterial suspension (108 cfu/mL) over the inferior face of leaves, and evaluation 30 days after inoculation, was the most appropriated methodology to evaluate resistance to bacterial canker in tomato genotypes. After the establishment of the inoculation methodology, ten commercial tomato genotypes (Carmen, Débora max, IPA-6, Santa Clara, Alambra, Jupiter, Olimpo, Fanny, Jumbo and Densus) were investigated to identify resistant materials to the bacterial canker. Kadá and Rotam-4 were employed as susceptible and resistant controls, respectively. Alambra and Jumbo had a similar behavior to Rotam-4, being the most promising materials for the planting in areas with report of occurrence of bacterial canker. To evaluate the bacterial canker control following products were tested: acibenzolar-S-methyl (ASM), ASM + mancozeb, ASM + copper oxicloride, mancozeb + copper oxicloride, and oxytetracycline. Three schemes of application of the products were adopted: (E1) 4 applications (first and second ones were accomplished six and three days before inoculation; third and fourth ones, three and six days after inoculation); (E2) two applications before inoculation only; (E3) two applications after inoculation only. The effect in vitro of these products on Cmm was also evaluated. ASM, isolated or in mixture with fungicides, provided significant reductions in the disease severity independent of the scheme of application and had no effect on bacterial development in vitro.

Em áreas onde o herbicida glyphosate é utilizado freqüentemente, populações da planta daninha trapoeraba (Commelina benghalensis L.) têm sido selecionadas, devido à tolerância da espécie à ação deste herbicida. Neste sentido, há necessidade de utilização de alternativas de manejo, as quais, por sua vez, são dependentes de conhecimentos profundos sobre a biologia da espécie; e também do controle químico eficiente em condições de pós-emergência, cuja eficácia depende, sobretudo, do estádio de desenvolvimento da planta daninha no momento da aplicação. Desta forma, este trabalho foi desenvolvido com o objetivo de avaliar: a germinação e a emergência das plântulas de sementes aéreas pequenas de trapoeraba (Commelina benghalensis L.) quando submetidas a diferentes temperaturas, condições de luz, superação de dormência e profundidade de semeadura; a competitividade com a cultura da soja; e avaliar a resposta biológica da C. benghalensis e da B. plantaginea a aplicações de diferentes doses do herbicida glyphosate em seis estádios fenológicos, ajustando-as aos modelos tradicionais e a funções de duas variáveis. Com relação à germinação, avaliouse o efeito da luz, temperatura, escarificação química e profundidade de semeadura no substrato. A temperatura ótima para germinação da trapoeraba foi de 25°C. Não houve efeito da luz na germinação das sementes. Não houve interferência positiva na germinação por conseqüência do tratamento das sementes com ácido sulfúrico, em diferentes períodos de exposição, indicando que o lote de sementes de trapoeraba testado não possuía impermeabilidade do tegumento à água. A emergência das plântulas de trapoeraba é influenciada negativamente e de forma linear, pela profundidade de semeadura dos propágulos no substrato. Não houve emergência das plântulas quando as sementes foram depositadas a 80 mm de profundidade. O substrato areia favorece a emergência das plântulas. Com relação à competitividade, a habilidade competitiva da trapoeraba foi semelhante à das plantas de soja, com evidências que a competição intraespecífica teve maior importância para as espécies que a competição interespecífica. Com relação ao controle químico com glyphosate, observou-se que o desenvolvimento das plantas de trapoeraba comprometeu o controle, ou seja, melhores controles foram obtidos com a aplicação de glyphosate sobre plantas jovens. Quando em análise conjunta, a trapoeraba foi mais tolerante ao herbicida que o capim-marmelada. Houve ajuste dos dados a modelos tridimensionais, correlacionando estádio fenológico, dose e controle, contudo novas estimativas devem ser realizadas, sobretudo com a inclusão de doses mais elevadas de glyphosate / In areas where the herbicide glyphosate is used frequently, populations of the weed Bengal dayflower (Commelina benghalensis) have been selected, due to the species tolerance to the action of that herbicide. This way, the use of alternative management is necessary, which are dependent upon deep knowledge on species biology; as well as, the efficient chemical control in post emergence conditions, which efficacy depends on the growth development stage of the weed at the moment of herbicide application. Therefore, this work was carried out with the objective of evaluating: the germination and emergency of small aerial seeds of Bengal dayflower (Commelina benghalensis L.) when exposed to different temperatures, light conditions, dormancy overcoming and seeding depth; the competitive ability with the soybean crop; to evaluate the biological rates of the C. benghalensis and the B. plantaginea the applications of different rates of the herbicide glyphosate in six phenologic stages, adjusting them the traditional models and the functions of two variable. Related to germination, light, temperature, chemical scarification and depth of seeding effects were evaluated. The optimal temperature for Bengal dayflower germination was 25°C. Light effects were not observed on seed germination. Positive consequences of seed treatment with sulfuric acid were not identified, considering different periods of exposition; that indicates that the portion of Bengal dayflower seeds tested did not have tegument water impermeability. Seedling emergence is negative and linearly influenced by seeding depth in the substrate. Seedling emergence was not figured out when seeds were 80 mm depth placed. Sand substrate favored seedling emergence. Related to competitiveness, Bengal dayflower competitive ability revealed similar to soybean plants, with evidences that intraspecific competition was more important for species than interespecific competition. Studying chemical control with glyphosate, it was observed that the development of Bengal dayflower plants compromised the control, i.e., better results were obtained with glyphosate applications on young plants. When in joint analysis, Bengal dayflower was more tolerant than alexandergrass to the herbicide. Data were adjusted to tridimensional models, correlating phenologic stage, rate and control, although new estimative must be achieved, mainly including higher doses of glyphosate.

Foram realizados experimentos em laboratório, casa-de-vegetação e campo visando os seguintes objetivos: (i) avaliar a eficiência de diferentes métodos de detecção do fungo Fusarium graminearum em sementes de trigo (Triticum aestivum L.); (ii) estudar o efeito do patógeno na germinação das sementes, bem como na emergência de plântulas e verificar a sua transmissão da semente para a plântula; (iii) avaliar o efeito de diferentes doses de nitrogênio (0, 30, 60, 90, 120 e 180 kg.ha-1), cultivares (IAC – 24, IAC – 350 e IAC – 370), aplicação de mistura de fungicidas (triciclazole + tebuconazol: três aplicações de 0,75 L.ha-1) na parte aérea das plantas na incidência de F. graminearum; (iv) avaliar o efeito do tratamento de sementes de trigo na incidência do patógeno empregando, individualmente, os seguintes fungicidas com as respectivas dosagens (g i.a.100 kg–1 de sementes): captana (150,0), tiofanato metílico (75,0), triflumizole (45,0), triticonazole (45,0), triadimenol (13,5), tolyfluanida (75,0), tebuconazole (5,0), fludioxonil (5,0), difeconazole (30,0) e thiabendazole (30,0). Na detecção de F. graminearum em sementes de trigo da cultivar BR 23 foram utilizados os seguintes métodos: meio semi-seletivo (MSS); MSS + 2,4- D (0,02%); MSS + KCl (-0,8MPa); papel de filtro (PF) com e sem o congelamento das sementes; PF + 2,4 – D (0,02%); restritores hídricos (KCl, NaCl, manitol e sacarose) nos potenciais osmóticos de –0,4, -0,6, -0,8 e –1,0 MPa. A maior incidência do patógeno foi observada com a utilização de MSS + 2,4 – D e a menor percentagem de sementes germinadas foi observada com o uso de PF com congelamento. A germinação de 30 diferentes genótipos de trigo foi significativamente influenciada pela quantidade de sementes mortas com a presença de F. graminearum, contudo não foi encontrada correlação entre a incidência do patógeno e a germinação das sementes. Também foi constatado que o fungo não afeta a emergência das plântulas, contudo verificou-se que a sua taxa de transmissão para diferentes partes da plântula (raiz, colo e haste) é variável de acordo com a com o genótipo infectado. O inóculo da semente pode contribuir para o desenvolvimento de epidemias no campo. Verificou-se que maiores doses de N promovem o aumento da incidência do patógeno nas sementes, enquanto que a aplicação da mistura de fungicidas promove a redução. Não houve diferenças significativas entre as cultivares IAC – 250, IAC – 350 e IAC – 370 na incidência do patógeno. No tratamento químico de sementes de trigo da cultivar BR 18 Terena, as menores incidências do fungo foram observadas empregando-se os fungicidas tiofanato metílico e tebuconazole. Não houve influência dos fungicidas tanto na germinação quanto na emergência e velocidade de emergência de plântulas. Por outro lado, fungicidas como o captana, triticonazole, tebuconazole e triadimenol afetaram negativamente a altura de plântulas, interferindo no desempenho das mesmas. / Experiments were carried out in laboratory, green house and field aiming at the following objectives: (i) to evaluate the efficiency of different methods of detection of Fusarium graminearum; (ii) to study the effect of the pathogen in the germination of wheat seeds, as well as in the emergence of seedlings and to verify the transmission of the seed to the seedling; (iii) to evaluate the effect of different dosages of nitrogen (0, 30, 60, 90, 120 and 180 kg.ha-1), in the incidence of cultivars (IAC - 24, IAC - 350 and IAC - 370) and the application of a mixture of fungicides (triciclazole + tebuconazol: three applications of 0,75 L.ha-1) in the aerial part of the plants in the incidence of F. graminearum; (iv) to evaluate the effect of the treatment of wheat seeds in the incidence of the pathogen employed individually, the following fungicides, with the respective dosages (g i.a.100 kg-1 of seeds): captana (150,0), methylic tiophanate (75,0), triflumizole (45,0), triticonazole (45,0), triadimenol (13,5), tolyfluanida (75,0), tebuconazole (5,0), fludioxonil (5,0), difeconazole (30,0) and thiabendazole (30,0). In the detection of F. graminearum in wheat seeds of the cultivar BR 23 the following methods were used: semiselective media (MSS); MSS + 2,4-D (0,02%); MSS + KCl (-0,8MPa); blotter (PF) with and without the freezing of the seeds; 2,4 PF + - D (0,02%); hidric restrictors (KCl, NaCl, manitol and sacarose) in the osmotic potentials of -0,4, -0,6, -0,8 and -1,0 MPa. The highest incidence of the pathogen was observed with the use of MSS + 2,4 - D and the lowest percentage of germinated seeds was observed with the use deep freezing blotter method of PF with freezing. The germination of 30 different wheat genotypes was significantly influenced by the quantity of dead seeds with the presence of F. graminearum. However, correlation between the incidence of the pathogen and the germination of the seeds was not found. It was found that the fungus does not affect the emergence of seedlings, however it was verified that its rate of transmission for different parts of seedling is variable in accordance with the infected genotype. It was also verified that higher doses of N promote the increase of the incidence of the pathogen in the seeds, and that the application of the mixture of fungicides promotes the reduction. There was no effect of cultivars IAC – 250, IAC – 350 e IAC – 370 on the incidence of pathogen. Regarding the chemical treatment of wheat seeds of cultivar BR 18 Terena, the lowest incidences of the fungus were observed using the fungicides methylic tiophanate and tebuconazole. There was no effect of fungicides both on the germination and on the seedlings emergence and emergence velocity. On the other hand, fungicides such as the captan, triticonazole, tebuconazole and triadimenol affected the height of plântulas negatively, interfering with their performance.

A adoção da calda sulfocálcica como um produto alternativo para o controle de Brevipalpus phoenicis (Geijskes) tem sido intensificada pelos citricultores brasileiros. A calda sulfocálcica é o único produto eficiente no controle de B. phoenicis permitido pelas certificadoras de produtos orgânicos, sendo pulverizada em média 11 vezes por ano. Devido à intensificação no uso da calda sulfocálcica, os objetivos do presente trabalho foram avaliar a evolução da resistência de B. phoenicis e o impacto sobre Iphiseiodes zuluagai Denmark & Muma mediante condução de estudos de: (a) detecção e caracterização da resistência de B. phoenicis à calda sulfocálcica pelo monitoramento da suscetibilidade de populações originárias do sistema de manejo orgânico e convencional, e avaliação de resistência cruzada entre enxofre e calda sulfocálcica; (b) avaliação da toxicidade de calda sulfocálcica na evolução da resistência de B phoenicis mediante estimativa da demografia de linhagens suscetível (S), e resistentes à calda sulfocálcica (Calda-R) e enxofre (Enxofre-R); (c) avaliação da estabilidade da resistência de B. phoenicis à calda sulfocálcica em laboratório, pela estimativa da freqüência de resistência ao longo do tempo e da taxa instantânea de crescimento (ri) das linhagens S e Calda-R; e (d) avaliação do efeito letal e subletal de calda sulfocálcica sobre I. zuluagai. Para monitorar a suscetibilidade de B. phoenicis à calda sulfocálcica, concentração diagnóstica de 320 µg de enxofre/ml de água [(ppm) I.A.] foi definida pela caracterização da linhagem S com bioensaio de contato direto e residual. Diferenças significativas na suscetibilidade foram detectadas entre as populações, mas não entre os sistemas de manejo. A população com maior sobrevivência foi selecionada com concentração diagnóstica para a resistência à calda sulfocálcica (R). A CL50 estimada para as linhagens S e Calda-R à calda sulfocálcica foram 200,79 e 1.142,75 ppm respectivamente, e razão de resistência de 5,69 vezes. Foi detectada resistência cruzada positiva entre enxofre e calda sulfocálcica em B. phoenicis. A avaliação da toxicidade de calda sulfocálcica na evolução da resistência foi baseada na estimativa da ri. A ri diminuiu com o aumento das concentrações de calda sulfocálcica. As linhagens Calda-R e Enxofre-R apresentaram crescimento positivo mesmo nas concentrações de calda sulfocálcica de 3.000 e 6.000 ppm, enquanto a linhagem S foi extinta a partir de 3.000 ppm. Discriminação entre as linhagens S, e resistentes Calda-R e Enxofre-R foi verificada a partir das concentrações de 320 e 240 ppm, respectivamente. A resistência de B. phoenicis à calda sulfocálcica em laboratório foi estável. A toxicidade de calda sulfocálcica a I. zuluagai foi avaliada com bioensaio de contato direto e residual. A persistência da calda sulfocálcica a I. zuluagai foi avaliada em plantas de Canavalia ensiformis L. pulverizadas com concentração de 6.000 ppm. A calda sulfocálcica nas concentrações de 3.000 e 6.000 ppm afetou negativamente a demografia de I. zuluagai, levando a extinção. A persistência da calda sulfocálcica foi relativamente longa, resíduo com 41 dias de idade afetou significativamente a demografia de I. zuluagai. Baseado nos resultados, estratégias de manejo da resistência de B. phoenicis à calda sulfocálcica devem ser implementadas para preservar sua vida útil. / The use of the lime sulfur as an alternative product for controlling Brevipalpus phoenicis (Geijskes) has intensified in Brazilian citrus groves. The lime sulfur is the only efficient product used to control B. phoenicis and certified by organic producers with an average of 11 sprayings per year. Due to intense use of this product, the major objectives of this research were to understand the evolution of resistance of lime sulfur in B. phoenicis and the impact on Iphiseiodes zuluagai Denmark & Muma by conducting studies (a) to detect and characterize B. phoenicis resistance to lime sulfur by monitoring susceptibility in populations collected from citrus groves managed organically and conventionally, and by assessing the possible crossresistance between sulfur and lime sulfur; (b) to understand the impact of lime sulfur toxicity in B. phoenicis resistance evolution, by comparing the demography of susceptible (S), lime sulfurresistant (Lime-R) and sulfur-resistant (Sulfur-R) strains; (c) to evaluate the stability of B. phoenicis resistance to lime sulfur under laboratory conditions, by estimating temporal changes in the frequency of resistance and the instantaneous rate of increase (ri) in S and Lime-R strains; and (d) to evaluate the lethal and sublethal effect of lime sulfur on I. zuluagai. To monitor susceptibility of B. phoenicis to lime sulfur, a diagnostic concentration of 320 g of sulfur/ml of water [(ppm) AI] was defined, by characterization of S strain through direct and residual contact bioassays. Significant differences in susceptibility were detected among populations, but not between management systems. A population with the highest survivorship was identified for selecting a resistant strain to lime sulfur (R) with diagnostic concentration. The estimated LC50 of lime sulfur for S and R strains were 200.79 and 1,142.75 ppm respectively. Therefore, the resistance ratio was 5.69-fold. Cross-resistance between sulfur and lime sulfur was detected in B. phoenicis. The evaluation of the toxicity of lime sulfur on resistance evolution was based on estimation of ri. The ri decreased with the increase of lime sulfur concentrations to all strains. The Lime-R and Sulfur-R strains showed positive population growth, even at concentrations of 3,000 and 6,000 ppm, while the S strain was extinct from concentration of 3,000 ppm of lime sulfur. Discrimination between the S and the Lime-R and Sulfur-R was observed from concentrations of 320 and 240 ppm, respectively. The resistance of B. phoenicis to lime sulfur was stable under laboratory conditions. The toxicity of lime sulfur in I. zuluagai was evaluated with residual and direct contact bioassay. The persistence of lime sulfur to I. zuluagai was evaluated on plants of Canavalia ensiformis L. sprayed at concentrations up to 6,000 ppm. The lime sulfur at concentrations of 3,000 and 6,000 ppm had negative impact on population growth of I. zuluagai, by leading to extinction. The persistence of lime sulfur was relatively high because even 41-day old residues had also negative impact on I. zuluagai population growth. Based on results obtained herein, strategies for managing B. phoenicis resistance to lime sulfur should be implemented to preserve the lifetime of this product.

O Brasil é o maior produtor e exportador de suco de laranja do mundo e a produção é concentrada em pomares no Estado de São Paulo. Embora a cultura tenha se adaptado bem ao clima tropical predominante no país, essa cultura sofre perdas na produção ocasionadas por doenças, principalmente pelo Huanglongbing dos citros (HLB). O HLB dos citros é associado aos procariotos \'Candidatus Liberibacter africanus\', \'Candidatus Liberibacter asiaticus\' e \'Candidatus Liberibacter americanus\' restritos aos vasos do floema. No Brasil há predominância da bactéria \'Ca. Liberibacter asiaticus\' que é disseminada pelo inseto psilídeo vetor Diaphorina citri Kuwayama (Hemiptera: Liviidae). Não há controle curativo viável para essa doença, com isso o manejo é realizado de maneira preventiva com a utilização de mudas sadias, roguing de plantas sintomáticas e controle químico do vetor. O HLB é considerado uma doença policíclica, contudo, em pomares com manejo intensivo da doença e do vetor acredita-se que as disseminações secundárias praticamente não ocorrem, ou não são predominantes, e a epidemia seria governada pelas disseminações primárias contínuas como sugerido por Bergamin Filho et al. (2016). Com isso, esse estudo teve por objetivo demonstrar por meio de análises epidemiológicas o progresso temporal do HLB em quatro propriedades comerciais de citros as quais realizam o manejo da doença e do vetor. Além disso, outro objetivo foi demonstrar, com ajustes do modelo monomolecular, a importância da disseminação primária nessas propriedades. E ainda, verificar a influência de áreas vizinhas, comerciais e não comerciais, na distribuição espacial da doença e do vetor e assim estabelecer hipóteses acerca da localização das fontes de inóculo primário para as epidemias estudadas. O modelo monomolecular foi ajustado adequadamente aos dados de plantas erradicadas das propriedades A, B, C e D, com ajustes significativos (p<0,05) em 88,3%, 81,6%, 64,5% e 69,8% das tentativas (combinações de anos e talhões). A taxa média de progresso da doença pelo modelo monomolecular (rM) foi de 7,9; 6,9; 7,2 e 4,5 para as propriedades A, B, C e D, respectivamente. Contudo, de modo geral, as taxas (rM) não apresentaram-se correlacionadas com as incidências acumuladas da doença. Lotes de perímetro apresentaram incidências de HLB mais elevadas, assim como maior número de psilídeos, em relação aos lotes internos das propriedades, indicando maior influência de fontes de inóculo externas. Plantas não comerciais de citros sem o manejo da doença e do vetor foram as fontes de inóculo primário responsáveis pelas epidemias de HLB observadas nessas quatro propriedades. / Brazil is the world\'s largest orange juice producer and exporter, and São Paulo State is the major producing region. Although the citrus crop is well adapted to the tropical climate in Brazil, the crop has been suffering many losses due to diseases, mainly by citrus Huanglongbing (HLB). The disease is associated with prokaryots \'Candidatus Liberibacter africanus\', \'Candidatus Liberibacter americanus\' and \'Candidatus Liberibacter asiaticus\' which are spread by the psyllid vector Diaphorina citri Kuwayama (Hemiptera: Liviidae). There is no feasible curative control to this disease. Therefore, the management is carried out to prevent the disease based on eradication of symptomatic trees, chemical sprays against the psyllid, and using HLB-free nursery citrus plants. The HLB is considered a polycyclic disease, however, in orchards with rigorous disease and vector management it is suggested that secondary spread does not occur or are not prevalent, and the epidemic would be ruled by the continuous primary spread as suggested by Bergamin Filho et al. (2016). Therefore, the aim of this study was demonstrate by epidemiological analysis the HLB temporal progress in four commercial citrus areas with management of disease and vector. Furthermore, another aim was demonstrate the importance of primary spread in these areas by monomolecular model adjustment. In addition, verify the influence of neighbouring areas , commercial or non-commercial, in the spatial distribution of the disease and vector. Afterwards, generate hypotheses about the location of primary sources of inoculum to the studied epidemics. The monomolecular model was properly adjusted to data of plant eradication in the areas A, B, C and D, with significant adjustments (p<0,05) in 88.3%, 81.6%, 64.5% and 69.8% of the attempts (combining years and plots). The average rate of disease progress by monomolecular model (rM) was 7.9; 6.9; 7.2 and 4.5 to the areas A, B, C e D, respectively. However, in general, there is no correlation between the disease rates (rM) and HLB incidence. Plots located in the perimeter presented higher HLB incidences and higher number of psyllids than internal plots in the studied areas. This suggested the major influence of external sources of inoculum. Non-commercial citrus trees without disease and vector management were the primary sources of inoculum responsible for causing the HLB epidemics in the studied areas.

The blast rice, caused of fungus Pyricularia oryzae is the most important rice crop disease and can cause up to 100% crop damage. The cultural, varietal and chemical management at the field level and the monitoring and knowledge of in vitro blast isolates sensitivity are essential tools for better understanding and control of this disease. The objective of this project was to evaluate the effect of the fungicides most used in blast control in three cultivars of irrigated rice in two sowing seasons and to determine in vitro the sensitivity of the mycelial growth of two isolates of P. oryzae to the same fungicides: Triciclazole, Tebuconazole, Azoxystrobin, Trifloxystrobin + Tebuconazole and Casugamycin. For that, an experiment was carried at the field level in the 2015/2016 cropseason in Santa Maria-RS and another experiment in the laboratory. In the first experiment the cultivars used were Guri INTA CL, Puitá INTA CL and IRGA 424 RI sown in the beginning and end of the recommended period and submitted to the same fungicides. The second experiment tested the fungicides at concentrations of 0, 0.01, 0.1, 1, 10 and 100 ppm in two isolates of blast. It was concluded that the cultivar IRGA 424 IR showed to be resistant to blast and that for the maintenance of productive levels in the cultivars susceptible to P. oryzae, especially in the second sowing season, the adoption of more efficient fungicides is indispensable. In relation to mycelial growth in vitro, the first insensitivity of a P. oryzae isolate to the active ingredients Triciclazol and Azoxystrobin was verified at the national level. / A brusone, causada pelo fungo Pyricularia oryzae, é a doença mais importante da cultura do arroz, podendo causar até 100% de prejuízos à cultura. O manejo cultural, varietal e químico a nível de campo bem como o monitoramento e conhecimento da sensibilidade in vitro de isolados de brusone, são ferramentas imprescindíveis para o melhor entendimento e controle desta doença. O objetivo deste projeto, foi avaliar o efeito dos fungicidas mais utilizados no controle de brusone, em três cultivares de arroz irrigado, em duas épocas de semeadura e determinar in vitro a sensibilidade do crescimento micelial de dois isolados de P. oryzae aos mesmos fungicidas: Triciclazol, Tebuconazole, Azoxistrobina, Trifloxistrobina + Tebuconazole e Casugamicina. Para tal, foi realizado um experimento em nível de campo na safra 2015/2016 em Santa Maria-RS e outro experimento em laboratório. No primeiro experimento foram utilizadas as cultivares GURI INTA CL, PUITÁ INTA CL e IRGA 424 RI, semeadas no início e no final da época recomendada e essas submetidas aos mesmos fungicidas. O segundo experimento, testou os fungicidas anteriormente citados nas concentrações de 0, 0.01, 0.1, 1, 10 e 100 ppm em dois isolados de brusone. Concluiu-se que a cultivar IRGA 424 RI mostrou-se resistente à brusone e que para a manutenção dos patamares produtivos nas cultivares suscetíveis a P. oryzae, principalmente na segunda época de semeadura, torna-se necessário a adoção de fungicidas mais eficientes. Em relação ao crescimento micelial in vitro, constatou-se à nível nacional, a primeira insensibilidade de um isolado de P. oryzae aos ingredientes ativos Triciclazol e Azoxistrobina.

<p>Frogeye leaf spot (FLS) is a foliar disease in soybean (<i>Glycine max</i> (L.) Merr.) caused by the fungal pathogen <i>Cercospora sojina</i> Hara. FLS is commonly found in hot and humid regions of the southern United States but has become more common in the North Central states. Foliar application of quinone outside inhibitor (QoI) fungicides has been one of the major tools used in the management of this disease, but QoI-resistant <i>C. sojina</i> isolates have been already confirmed in 21 states, including Indiana. We hypothesized that resistant populations of <i>C. sojina</i> to QoIs fungicides are widespread in Indiana and that sexual reproduction is occurring within <i>C. sojina</i> populations, likely contributing to the dissemination of fungicide resistance. The main objectives of this research were to determine the distribution of QoI-resistant <i>C. sojina</i> isolates on soybean from Indiana and to evaluate <i>C. sojina </i>populations for potential sexual reproduction. In the summer of 2019 and 2020, 406 isolates of <i>C. sojina </i>were collected from 32 counties across Indiana and screened for QoI-fungicide resistance using a PCR-RFLP method. An i<i>n vitro </i>fungicide sensitivity test was performed on a subset of isolates to evaluate the sensitivity of <i>C. sojina</i> isolates to azoxystrobin, pyraclostrobin, picoxystrobin, and prothioconazole. A discriminatory dose of picoxystrobin (QoI) and prothioconazole (demethylation inhibitor- DMI) were established at 1 μg/ml and 10 μg/ml, respectively, to distinguish between QoI-resistant and sensitive isolates and to identify a reduction in sensitivity to DMI fungicides, respectively. Discriminatory doses were estimated by testing five concentrations (0.001, 0.01, 0.1, 1, and 10 µg/ml) of each fungicide. QoI-resistant isolates were found in 29 out of the 32 counties. Two hundred and fifty-one (251) out of the 406 isolates (61.8%) were confirmed as QoI-resistant. Partial nucleotide sequences of the cyt <i>b</i> gene from four resistant and four sensitive <i>C. sojina</i> isolates corroborated the presence and absence of the G143A mutation, respectively. Results from the sensitivity assays with azoxystrobin and pyraclostrobin discriminatory doses supported the findings from the PCR-RFLP assay as all QoI-resistant mutants were inhibited less than 50% when exposed to these doses. Results from this study indicated that QoI-resistant <i>C. sojina</i> isolates are spread throughout Indiana and that prothioconazole (DMI) could be a potential supplemental or alternative fungicide to control FLS. Additionally, mating type distribution was determined in 43 <i>C. sojina</i> populations for assessment of potential sexual reproduction. Fifteen (15) populations did not deviate significantly from the expected 1:1 ratio, suggesting potential for cryptic sexual reproduction in these populations, but further research on genetic diversity is required to verify these results. </p> <p> </p>

Mealybugs (Order Hemiptera: Superfamily Coccoidea) represent a persistent problem in grape-growing regions globally, with a notable increase in infestations in recent times. The current study investigates the species composition and seasonal dynamics of mealybugs in vineyards. Pseudococcus maritimus and Ferissia gilli remain the dominant species, while Pseudococcus viburni was also spotted during two separate instances and Planococcus ficus remained absent. Commercially available pheromone delta traps and adhesive bands were deployed to capture the male mealybugs, while numerically higher efficacy was observed in the adhesive band trap. Notably, the placement of adhesive band traps on the cordon and trunk revealed differential male mealybug captures, probably indicating their movement within the vines. The research also divulges into the life cycle of mealybugs and their population densities during the sampling season. The main highlight has been the lower population density of earlier nymphal stages of the first generation of mealybugs followed by the colonization of grapevines by the second-generation crawlers. Adults of second generations give rise to the overwintering stages of mealybugs. Traditionally the research also explores the species and seasonal population dynamics of ants along with mealybugs and their management in Virginia vineyards. The activity of fifteen genera of ants in the vineyard was recorded, with some of the dominant ant genera like Tetramorium, Crematogaster, and Lasius were recorded in the vineyard actively tending and defending the mealybugs and moving them around. Fruit cluster infestation was also higher in the control treatment in comparison to sugar dispenser and ant bait dispenser treatments. This comprehensive assessment of ant diversity further deepens our understanding of the intricate ecosystem within vineyards. A spray trial using three different insecticides with distinct modes of action (Buprofezin, Bifenthrin, and Spirotetramat) in two of the commercial vineyards. Preliminary results indicate that on some days after treatment, insecticides effectively controlled mealybug populations, offering a glimmer of hope to vineyard owners grappling with infestations. Mealybugs pose a significant threat to grape cultivation, and this research provides valuable insights that can help vineyard owners and grape growers develop more targeted and effective control strategies. Species identification, understanding their behavior, and exploring potential allies in the fight against mealybugs are all crucial steps toward maintaining the health and productivity of vineyards in Virginia. While challenges remain in the battle against mealybugs, this research marks a significant step forward in safeguarding grape cultivation in Virginia and potentially reshaping strategies for controlling these persistent pests in vineyards. Growers and researchers alike eagerly await further developments and the practical application of these findings to protect the flourishing vineyards of the region. / Doctor of Philosophy / Mealybugs are common grapevine pests, recently causing a nuisance in vineyards across the United States and Canada. Some of the previously documented species of mealybugs common in the eastern part of the States include grape mealybug, obscure mealybug, Gill's mealybug, and long-tailed mealybugs. The research has mainly addressed the mealybugs and their tending ant species and their management in vineyards in Virginia. The study identifies grape mealybug and Gill's mealybug as the dominant species with occasional sightings of obscure mealybug and a lack of vine mealybug throughout the sampled vineyard sites. The male mealybugs were monitored using commercially available pheromone delta traps and adhesive band traps. Placement of adhesive band traps in the cordon and trunk of grapevines revealed different male mealybug capture data suggesting their movement within the grapevines. Two generations of mealybugs including the first generation with lower population density emerging out from the overwintering life-stage and the subsequent second generation responsible for colonizing different parts of the grapevines and producing overwintering life-stages were observed. Fifteen genera of ants were sampled from the vineyard via pitfall trap with some ants like pavement ants, acrobat ants, and medium garden ants actively tending and protecting the mealybugs. The use of sugar dispensers in the vineyards also led to lower fruit cluster infestations with mealybugs in comparison to the area without dispensers. The insecticidal spray trial using three different insecticides was also effective in controlling populations of mealybugs on some of the dates after treatment. The research offers valuable insights for grape growers, aiding in the development of effective control strategies for mealybug control. It emphasizes the importance of identifying the species present, understanding their behavior, and exploring potential allies and insecticide options in pest management.

The loss of ecosystem resilience and rangeland (often referred to as veld in South Africa) productivity is a major problem in the semi-arid Savanna environments of southern Africa. The over-utilization of rangelands in the Molopo region of the North- West Province in South Africa has resulted in profound habitat transformations. A common regional indicator of rangeland degradation is the imbalance in the grasswoody ratio, characterized by a loss of grass cover and density with increased shrub or tree density. This can result in major reductions of rangeland productivity for the grazing animal, forcing land users to apply active or passive restoration actions to improve rangeland condition, control the thickening of woody species (bush thickening), mitigate economic losses and restoring the aesthetical value of the Savanna environment for ecotourism and game hunting aspects. This study formed part of the multinational EU-funded PRACTICE project (“Prevention and restoration actions to combat desertification: an integrated assessment”). The first aim of the study was to evaluate locally applied restoration actions using a participatory approach, followed by interviews with certain stakeholders that formed part of a multi-stakeholder platform (MSP) related to the livestock and game farming community in the Molopo. Participants of the MSP ranked indicators according to their relative importance regarding the restoration actions on an individual basis. The individual ranking results were combined with quantitative bio-physical and qualitative socio-economic measurements for each indicator in a multi-criteria decision analysis (MCDA), whereby the alternative actions were ranked according to their relevancy and performance. The results were then shared with members of the MSP in order to stimulate discussion among the members and contribute to the social learning of the project outcome. The overall positive response and acceptance of results by members of the MSP changed the perceptions and objectives of the land users regarding rangeland management. This type of participatory assessment was therefore found to be very promising in helping to identify more sustainable actions to mitigate rangeland degradation in the Molopo Savanna region. There is, however, still an urgent need to create legal policy frameworks and institution-building, to support local-level implementation in all socio-ecological and economic settings, particularly in communal areas. The second aim was to evaluate the effect of two chemical bush control actions (chemical hand- (HC) and aeroplane control (AC)) as well as rotational grazing (RGM) on the Molopo Savanna vegetation. Results show that rangeland productivity, i.e. forage production and grazing capacity, was found to be negatively related to the woody phytomass in the savanna system studied. Bush thickening influenced grass species composition which was commonly associated with a decline in the abundance of sub-climax to climax grasses, respectively. All three actions (HC, AC & RGM) significantly reduced the woody phytomass and increased forage production and grazing capacity. Although AC resulted in the highest reduction of woody phytomass, the highest forage production and grazing capacity was found under RGM. The second highest grazing capacity was found in HC sites, which was due to a high abundance of perennial, palatable climax grass species. Results from this study also show that the patterns and compositions of grass species, grass functional groups (GFGs) and woody densities indicated by RGM and chemical HC, best resemble a productive and stable savanna system that provides important key resources to support both grazing and browsing herbivores. / MSc (Environmental Sciences), North-West University, Potchefstroom Campus, 2014

Tradicionalmente o manejo das plantas daninhas é realizado levando-se em consideração a infestação média destas plantas nas áreas agrícolas; sendo então adotadas estratégias de manejo de forma homogênea em toda a área. Porém, as plantas daninhas não se distribuem uniformemente, sendo comum o comportamento contagioso, formando manchas ou "reboleiras". No entanto, a localização e mapeamento de diferentes infestações são tarefas difíceis de serem executadas em larga escala e requerem metodologias adequadas. Desta forma, métodos de determinação dessa variabilidade espacial necessitam de melhores esclarecimentos e estudos científicos. Com o objetivo de estudar o comportamento da variabilidade espacial das plantas daninhas e seu respectivo banco de sementes com a utilização de ferramentas da agricultura de precisão, foram realizados quatro experimentos para avaliar esta variabilidade espacial e temporal e analisar a potencialidade que a mesma pode proporcionar para o manejo racional das plantas daninhas, principalmente a possibilidade da aplicação localizada de herbicidas. O primeiro experimento consistiu do mapeamento do banco de sementes ao longo de dois anos consecutivos no intuito de comparar sua variabilidade espacial com a flora emergente. Concluiu-se que existe uma correlação entre o banco de sementes e a flora emergente e entre bancos de sementes de anos consecutivos, principalmente para as plantas daninhas Ageratum conyzoides L. e Commelina benghalensis L.. Analisando a dependência espacial, foi detectada uma dependência entre 7 e 15 m para o banco de sementes e a flora emergente. Os mapas gerados mostraram uma grande variabilidade espacial das plantas daninhas, sendo observadas algumas tendências de estabilidade ao longo do tempo. No segundo experimento foram feitos dois mapeamentos da infestação da planta Panicum maximum Jacq., um durante a colheita da cultura de milho e outro após a colheita, para fins de aferição do método de mapeamento realizado durante a colheita. Foi constatada uma subestimação de 6% da área infestada pelo método de mapeamento durante a colheita, quando este foi comparado com o caminhamento numa grade regular após a colheita. Os dois métodos foram coincidentes em 45% das áreas marcadas. O terceiro experimento consistiu de uma avaliação da eficácia da aplicação localizada de herbicidas pós-emergentes na cultura da soja, baseada em mapas de infestação das plantas daninhas. Para isto foi feito uma amostragem numa grade de 6 x 6 m e, baseado na infestação em cada célula, foi pulverizado duas doses de herbicidas pós-emergentes dependendo da infestação de cada local. Foi obtida uma economia de produto da ordem de 18 e 44%, sendo a eficácia similar à aplicação convencional utilizando dose única e pulverização uniforme em área total. No quarto experimento foi realizada uma pulverização localizada de herbicida pré-emergente baseada no mapeamento prévio do banco de sementes das plantas daninhas; sendo verificado uma eficácia igual à convencional e uma economia de 22% de produto herbicida. Portanto, técnicas de mapeamento da variabilidade espacial das plantas daninhas são importantes ferramentas para que melhores decisões sejam tomadas dentro dos sistemas de produção agrícola, sendo de extrema urgência um maior conhecimento e embasamento técnico-científico de técnicas agronômicas que considerem esta variabilidade espacial. / Traditionally the weed management has been done considering the overall weed infestation in the whole field and then herbicides are sprayed according to a single weed control recommendation for the field. But weeds are not uniformly distributed and normally have clumped populations showing weed patches presenting high spatial variability. This nature of the weed populations can be mapped, and so it can help the decisions associated with weed management on agricultural systems. However, localization and mapping of the weed clusters are very difficult tasks in large areas, and require adequate methodology. Therefore, determination method of this weed infestation variability in space must be scientifically studied. With the objective of studying the weed spatial variability and temporal behavior of weed seedlings infestations and their respective seed banks, four experiments were conducted to evaluate the spatial temporal behavior of the weeds and the potential of weed mapping technology could bring to the rational weed management. The aim of the first experiment was to evaluate the spatial temporal behavior of the weed seedlings and their respective seed banks using the mapping technology. A grid sampling was used to understand the seedling and seed bank behavior in the space and time. Correlations using "Spearman rank" test were observed, mainly in Ageratum conyzoides L. and Commelina benghalensis L. The spatial dependence was noted between 7 and 15 m for the weed seedlings and seed banks. The weed maps showed that the weeds have a high spatial variability making patches with some temporal stability. In the second experiment two weed surveys were done with the objective of mapping Panicum maximum Jacq. during and after corn harvest. The grid sampling method after harvest corn was used to evaluate the harvest mapping method. It was underestimated about 6% of the weed infestation using the harvest mapping method when it was compared with the grid sampling method after corn harvest. In this experiment the harvest mapping method had just 45% of efficiency in recording weed infestation areas. The third experiment was done in order to analyzed the post emergence herbicide efficacy in soybeans based on weed maps constructed with grid sampling mapping. The weed seedling was counted in a 6 by 6 m grid and, based on weed infestation of each grid, it was sprayed two post emergence herbicide rates according to the weed infestation. It was saved 18 to 44% of herbicides compared to broadcast application with the same herbicide efficacy. In the fourth experiment a pre emergence herbicide application was carried out in soybeans crop based on weed seed bank map and, it was observed that the site-specific application had similar efficacy saving 22% of herbicides. So, the weed mapping technology is an important tool to bear on decisions associated with crop production, and it is a priority for the implementation of this technology multiple sources of scientific knowledge in weed biology and management regarding to the weed spatial variability.