RESUMO A cada ano são descobertos e utilizados novos produtos para o tratamento de sementesna cultura da soja (Glycine max L. Merril), visando aumentos de produção. Há a necessidade de conhecer a influência desses produtos sobre o desenvolvimento das plantas, a fim de obter sucesso na atividade. O objetivo do
Germination, viability and longevity of horseweed (Conyza spp.) seeds as a function of temperature and evaluation periods.Ciência Rural, v.48, n.9, 2018. 1 Germination, viability and longevity of horseweed (Conyza spp.) seeds as a function of temperature and evaluation periods Germinação, viabilidade e longevidade de sementes de buva (Conyza spp.) em função da temperatura e períodos de avaliação ABSTRACT: In Brazil, horseweed is one of the most important weeds because of the resistance to herbicides and high competitive for the crops. A large of losses were reported in major crops such as soybeans, wheat and corn, where the use a no-tillage system and the herbicide resistance promote better establishment. A correct understanding of the way temperature influences germination enables the prediction of the regions with the highest potential for colonization by this weed and thus facilitates its control. The objective of this study; therefore, was to discern the ways temperature affected the germination, viability and longevity of horseweed seeds. Testing was done at 10, 20 and 30°C, while evaluation occurred on days 0, 15, 30, 45 and 60. Seeds were packed in a nylon mesh bag (5x5cm), with 10g of upland soil (Yellow Red Argissolo, sandy loam texture), placed in transparent plastic boxes at 0 to 0.5cm soil depth, at the temperatures specified. Percentage of remaining seeds, first and second germination counts, abnormal seedlings, and dead, dormant, viable and non-viable seeds, were assessed. Horseweed seeds achieve secondary dormancy at 10, 20 and 30°C, while their quality and the longevity showed damage at 20 and 30°C temperatures. RESUMO:No Brasil, a buva (Conyza spp.) é uma das principais plantas daninhas devido à resistência a herbicidas e alta competividade com as culturas. Esta é responsável por perdas de produtividade em culturas como soja, milho, algodão e trigo cuja implementação da semeadura direta e a resistência aos herbicidas favorecem seu estabelecimento. O conhecimento do efeito da temperatura na germinação permite prever as regiões com maior potencial de colonização e auxiliar no manejo. Assim, objetivou-se com este trabalho determinar o efeito da temperatura na germinação, viabilidade e longevidade de sementes de buva em solo de terras altas. As temperaturas testadas foram 10, 20 e 30ºC e os períodos de avaliação 0, 15, 30, 45 e 60 dias. As sementes foram acondicionadas em saco de malha de nylon (5 x 5cm), distribuídas em 10g de solo de terras altas (Argissolo Vermelho Amarelo, de textura franco-arenosa), e, alocadas em caixas gerbox com solo a profundidade de 0 a 0,5 cm, nas temperaturas descritas. Avaliou-se em percentagem de sementes remanescentes, primeira e segunda contagem de germinação, plântulas anormais, sementes mortas, dormentes, viáveis e não viáveis. A semente de buva atinge dormência secundária, nas temperaturas de 10, 20 e 30ºC e sua qualidade e longevidade são prejudicadas nas temperaturas de 20 e 30ºC. Palavras-chave: dormência secundária, profundidade, manejo, qualidade de sementes. ...
The awareness of agronomic practices that affect the resistance selection of weeds to a particular herbicide is of utmost importance in order to advocate management practices that aim to avoid or prolong the resistance. The objectives of this study were to identify and map the occurrence of the wild poinsettia's low-level resistance to glyphosate in Rio Grande do Sul State (RS), Brazil, and to define the main agronomic factors associated with the selection of these biotypes. Seed and / or soil samples in areas with suspected resistance were collected in Roundup Ready ® (RR) soybean crops in different counties in the RS region during the 2010/11 and 2011/12 seasons. A questionnaire on the operations history in the area was applied at each site in order to establish relationships between the distribution of wild poinsettia with cases of suspected resistance to glyphosate and the likely agronomic factors involved in this occurrence. The study included the response of wild poinsettia biotypes with suspected resistance to glyphosate and an analysis of the questionnaires carried out with producers. The main agronomic practices used by producers that favor the emergence of resistant biotypes were the continued cultivation of the RR ® soybean; an overdependence on the use of glyphosate; a low rate of crop rotation and efficient chemical alternatives for wild poinsettia control and management.Key words: crop rotation; 5-enolpiruvil chiquimato 3-fosfato sintase; Euphorbia heterophylla; selection pressure Fatores agronômicos envolvidos na resistência de nível baixo de leiteira a glyphosate RESUMOO conhecimento das práticas agronômicas que interferem na seleção de plantas resistentes a determinado herbicida é de extrema importância para preconizar práticas de manejo que visem evitar ou retardar a resistência. Os objetivos do trabalho foram identificar e mapear a ocorrência da resistência de nível baixo de leiteira ao glyphosate no Rio Grande do Sul (RS), e definir os pricipais fatores agronômicos associados na seleção desses biótipos. Amostras de sementes e/ou solo em áreas com a suspeita de resistência foram coletadas em lavouras de soja Roundup Ready ® em diferentes Municípios do RS nas safras 2010/11 e 2011/12. Em cada local, foi aplicado questionário sobre o histórico de manejo da área, visando estabelecer relações entre a distribuição de casos de leiteira com suspeita de resistência ao glyphosate e os prováveis fatores agronômicos envolvidos nessa característica. O estudo constou da resposta dos biótipos de leiteira com suspeita de resistência ao glyphosate e análise dos questionários realizados com os produtores. As principais práticas agronômicas utilizadas pelos produtores que favorece o surgimento de biótipos resistentes foi o cultivo continuado de soja RR ® , excessiva dependência do uso de glyphosate, baixo índice de rotação de culturas e de alternativas químicas eficientes para o controle de leiteira.
This study aims to verify, accurate and precisely, the responses of Italian ryegrass 'BRS
Ryegrass management has been difficult by the occurrence of resistant biotypes to several herbicides with different action mechanisms. Since herbicides mixes and rotations are an important alternative for resistant weed management, the objective of this work was to evaluate the interaction of the dose of the herbicides glufosinate and atrazine on ryegrass control and its seeds’ quality exposed to their association. For this study, three experiments were carried out using factorial design in field, laboratory, and greenhouse conditions. Two factors (A and B) were evaluated in each experiment, where factor A and B represented the doses of glufosinate and atrazine, respectively. Ryegrass control was evaluated in field experiment, while germination percentage and Emergence Speed Index (ESI), were obtained in laboratory and greenhouse analyses, respectively. The data were submitted to variance analysis (P≤0.05) and the significant results were analyzed through response surface graphs. For ryegrass control data, the effect of the interaction was analyzed by the Colby method; glufosinate provides efficient ryegrass control, but its association with atrazine reduces the efficiency, being characterized as an antagonism between molecules. Glufosinate herbicide application, independent of atrazine presence, reduced the ryegrass seeds quality at the post-flowering stage.
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