Resumo -A ferrugem asiática é a principal doença na cultura da soja. O objetivo do trabalho foi avaliar o efeito de fungicidas à base de estrobilurina + triazol aplicados em diferentes momentos, na detecção e após a detecção da ferrugem asiática na área experimental. A segunda aplicação três semanas após a primeira. Os experimentos foram conduzidos nas safras 2006/07, 2008/09, 2009/10 e 2010/11, em Dourados -MS. A doença foi quantificada, avaliando a área foliar lesionada, o número de lesões e urédias por folíolo de cada terço da planta foram avaliados. A partir destes dados calculou-se a área abaixo da curva de progresso de lesões e urédias (AACPD). Foram avaliados também produtividade, massa de mil grãos e desfolha. Todos os ensaios foram conduzidos no delineamento de blocos ao acaso, com cinco repetições, exceto o realizado na safra 2006/07 com seis repetições. Nas quatro safras, aplicações de fungicidas, independente da época resultou em menores quantidades de doença em relação a testemunha, nos terços médio e inferior. Na safra 2008/09 não foi detectado efeito do fungicida sobre a produtividade. Em 2006Em /2007Em , 2008/09 e 2009/10, parcelas que receberam fungicida apresentaram menor porcentagem de desfolha. Na safra 2010/11, a aplicação na detecção da doença apresentou incremento na produtividade. O controle mais eficaz da doença ocorreu quando a primeira aplicação de fungicidas foi realizada mais próxima da detecção do patógeno na área. Palavras-chave: Glycine max, Phakopsora pachyrhizi, doenças da sojaAbstract: Asian soybean rust is the main disease of soybeans in Brazil. Our objective was to evaluate the effect of the strobilurin + triazole fungicides applied at and after pathogen detection in the experimental area. A second fungicide spray was done three weeks later. The experiments were carried out in, 2008/09, 2009/10 and 2010/11 crop seasons. The experiments were carried out in a randomized block design, with five replications. In the four crop seasons, disease levels were negatively affected by fungicide sprays, regardless of the application time. In 2009/10 crop season fungicide did not affect crop yield. The efficacy of chemical control was greater as the first fungicide was sprayed closer to the pathogen detection. Key-words: Glycine max, Phakopsora pachyrhizi, soybean diseases IntroduçãoA principal doença da soja é a ferrugem asiática da soja (FAS), causada por Phakopsora pachyrhizi. No campo, o fungo infecta o tecido foliar de uma ampla gama de hospedeiros, alem disto,seus uredinosporos são liberados por um ostíolo na urédia (Goellner et al. 2010). No início da doença são observadas pequenas lesões de coloração castanho. Entre 5 a 8 dias após infecção inicial, pústulas de ferrugem tornam-se visíveis, e desenvolvem-se na parte inferior do limbo foliar.A ferrugem asiática é a mais destrutiva doença foliar da soja, e perdas de rendimento superiores a 50% são comuns sob condições ambientais favoráveis para o desenvolvimento da doença. Temperaturas de 15ºC a 25ºC e o mínimo de seis horas de molh...
Halo blight caused by Pseudomonas syringae pv. garcae is a limiting disease in coffee production. There are few efficient commercial products on the market to control this disease, and therefore, the prospection of different biocontrol agents is a promising alternative. The objectives in this study were (i) to select saprobic fungi with the potential to control halo blight in coffee clones, and (ii) to evaluate the contributions of induced resistance as control mechanisms. Plants were sprayed with Gonytrichum chlamydosporium, Phialomyces macrosporus, and Moorella speciosa 7 d before inoculation with Pseudomonas. syringae pv. garcae. The area under the halo blight progress curve (AUDPC) and plant growth parameters were evaluated. M. speciose and G. clamydosporium did not reduce the AUDPC and even reduced plant growth in none of the trails compared to the water control. P. macrosporus consistently reduced AUDPC by 42-72% and increased plant height by 40%. Thereafter, the contributions of induced resistance was evaluated for the P. macrosporus, selected as the most promising biocontrol agent.. In order to determine induced resistance, phenylalanine ammonia lyase (PAL), peroxidase (POX), and ascorbate peroxidase (APX) activity of plant leaves were measured at two time points after stress challenge. Enzyme activity evaluation demonstrated high activity of POX and PAL at seven days after treatment with the saprobe, and high APX activity after 14 days. The results of this study indicate that P. macrosporus has the potential to be used in the management of coffee halo blight in seedling production, and one mechanism likely involved is induced resistance.
<p>Saprobe fungi and necrotrophic pathogens share the same niche within crop stubble and the search for fungi non-pathogenic to plants that are able to displace the plant pathogens from its overwintering substrate contributes to the disease management. Brown eye spot (<em>Cercospora coffeicola</em>) is among the most important coffee diseases, it is caused by a necrotrophic pathogen that has decaying leaves as its major source of inoculum. We have screened saprobe fungi for the ability to reduce <em>C. coffeicola</em> sporulation and viability and determined the possible mechanisms involved in the observed biocontrol. A selected saprobe fungus, <em>Phialomyces macrosporus</em>, reduced the pathogen’s viability by 40% both <em>in vitro</em> and <em>in vivo</em>. The fungus acts through antibiosis and competition for nutrients. It produced both volatile and non-volatile compounds that inhibited <em>C. coffeicola</em> growth, sporulation, and viability. It also produced the tissue maceration enzyme (polygalacturonase), which reduces the pathogen both in detached leaves or in planta. The reduction in the fungal viability either by the saprobe fungus or its polygalacturonase-fraction supernatant resulted in the reduction of the disease rate. Therefore, <em>P. macrosporus </em>is a potential microbial agent that can be used in an integrated management of brown eye spot through the reduction of the initial inoculum of the pathogen that survives and builds up in infected leaves.</p><p> </p>
Fungicides are one possible way to manage fungal and oomycete plant pathogens in order to safeguard yield and quality of crops and to improve shelf‐life of produce in agriculture and horticulture. However, global warming and the resulting temperature increase may affect the effectiveness of some important fungicides, including efficacy and duration of plant disease control. Nevertheless, according to our literature survey, there is little specific information available on whether and how temperature influences the effectiveness of fungicides. The very few publications that show specific data are summarized herein. Specific data are mainly gained under controlled conditions, both based on in vitro and in planta experiments. Field data are more or less missing. Most researchers assume that indirect effects of temperature on fungicide efficacy are particularly important. For example, temperature effects on pathogen spore germination and hyphal growth (optimal versus sub‐ and supra‐optimal), whereby optimal temperature conditions can improve pathogen fitness, thereby increasing the tolerance of pathogens to fungicides. Presumably, these indirect effects are often more important than the direct effects of temperature on fungicide performance. However, the data needed to prove this assumption are lacking. Therefore, it would be beneficial to conduct more in‐depth laboratory, greenhouse and field experiments in order to investigate the potential direct and indirect influence of temperature on the effectiveness of important fungicides. This would enable the establishment of appropriate recommendations for fungicide use in an increasingly warmer world and would assist the development of future fungicide solutions, based on improved knowledge.
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