This study aimed to assess, in a microcosm condition, the efficacy of electrostatic spraying of herbicide imazamox in the control of Salvinia molesta and the effects of decomposition of plant ...material on water quality. The herbicide rates used were 600, 700, 800, and 900 g ai ha
−1
and spray volume of 50 L ha
−1
in electrostatic application. Control effectiveness was assessed at 7, 15, 30, 45, and 60 days after application (DAA), expressed in percentage (0-100%) of visible injury symptoms in the plants, biochemical oxygen demand (BOD
5
), chemical oxygen demand (COD), chlorophyll a and pheophytin a contents at 0, 7, 15, 30, 45, and 60 DAA, and fresh and dry biomass at 60 DAA. Imazamox was effective in controlling 63% of S. molesta with 900 g ai ha
−1
in 45 DAA and 30% with 800 g ai ha
−1
in 30 DAA, and reduced 82.3% and 17.5% of fresh weight and 62.6% and 9.3% of dry weight of plant at 60 DAA, respectively. The imazamox spray reduced chlorophyll a with all doses applied and increased BOD
5
in 45 DAA with 900 g ai ha
−1
and COD in all assessment periods, but for temperature, dissolved oxygen, electrical conductivity, and pH, there was no significant effect after spraying. The herbicide imazamox reduced S. molesta plants with 900 g ai ha
−1
, without causing significant effects on environmental indicators of water quality. Electrostatic spraying of herbicide can be used in management strategies of aquatic plants to reduce plant density in water bodies and maintain the colonization of plants at a level not harmful to the aquatic biota.
The aim of this study was to assess the efficacy of imazamox for control of S. molesta and to assess the effects of plant decomposition on environmental indicators after application of this herbicide ...in microcosm conditions. The following rates were used: 600, 700, 800 and 900 g ai ha
−1
and spray volume 50 L ha
−1
. Control efficacy was determined as the percentage (from 0 to 100%) of visible injury symptoms in the plants, biochemical and chemical oxygen demand (BOD
5
and COD), water quality variables, chlorophyll a and pheophytin a at 0, 7, 15, 30, 45 and 60 days after application (DAA) and fresh and dry biomass at 60 DAA. Imazamox was effective in controlling 94% of S. molesta with 900 g ai ha
−1
; it reduced 95% of fresh weight and 92% of dry weight of plant at 60 DAA, and reduced chlorophyll a of the plants for all rates. For BOD
5
, there was an increase for all rates at 15, 30 and 45 DAA with restoration of the parameters at 60 DAA, and for COD, there was an increase at 60 DAA with 700 and 900 g ai ha
−1
. For temperature, pH, dissolved oxygen and electrical conductivity, there was no significant effect after spraying. Imazamox was effective in controlling S. molesta with 900 g ai ha
−1
without causing significant effects on the physical-chemical parameters of water quality.
Apesar de ser considerado um potencial bioagente de controle do amendoim-bravo (Euphorbia heterophylla L.) em cultivos de soja no Brasil, pouco se conhece sobre as características nutricionais do ...fungo Muchovej & Carvalho Bipolaris euphorbiae. O objetivo deste trabalho foi avaliar diferentes fontes de carbono (glicose, amido, sacarose, lactose e maltose), de nitrogênio (nitrato de sódio, nitrato de amônio, sulfato de amônio, fosfato de amônio dibásico, cloreto de amônio), de fósforo (fosfato de potássio monobásico, fosfato de potássio bibásico, fosfato de cálcio, fosfato de sódio, ácido fosfórico, fosfato de amônio) e a suplementação do meio de cultivo com fontes orgânicas de macro e micronutrientes, para o crescimento e a esporulação de B. euphorbiae. O amido proporcionou o maior crescimento, sendo também considerada a fonte de carbono mais favorável para a esporulação. O melhor crescimento e esporulação de B. euphorbiae foram obtidos usando o nitrato de sódio como fonte de nitrogênio e fosfato de potássio monobásico e fosfato de cálcio como fonte de fósforo, embora as demais fontes de fósforo analisadas, exceto o ácido fosfórico, tenham igualmente favorecido a esporulação. A suplementação do meio de cultivo com peptona e extrato de levedura resultou em melhor crescimento e esporulação do fungo e a adição de vitaminas favoreceu a produção de conídios
The objective was to evaluate the effects of initial weedy periods on the weed community and on the productivity of direct seeded and transplanted table beet cropping systems. A field trial was ...conducted at Sao Paulo State University, Brazil, in a randomized complete block design using a 2 x 13 factorial scheme. Direct seeding and seedling transplanting methods were evaluated within thirteen increasing weekly weedy periods. Weed relative importance was calculated and weed density and weed dry matter accumulation data were analyzed by nonlinear regression as well as beet yield and stand, which were submitted to analysis of variance. Amaranthus viridis, Coronopus didymus, Cyperus rotundus, Digitaria nuda, Galinsoga parviflora and Nicandra physaloides were the most important weeds found, with special reference to C. didymus. Weed dry matter accumulation was greater in the direct seeded crop, although weed density was higher in the transplanted crop. Transplanted beet yield was greater than of direct seeded beet in the weed-free treatment during the whole crop cycle. Crop-weed coexistence could remain for four and seven weeks after seeding/transplanting in direct seeded and in transplanted beet, respectively, before reducing yield economically. Thus, direct seeded crop was more susceptible to weed interference than the transplanted one. Key words: Beta vulgaris, weeds, interference, direct seeding, seedling transplanting. Objetivando avaliar efeitos de periodos de infestacao inicial na comunidade infestante e na produtividade da beterraba em sistema de semeadura direta e transplantio, conduziu-se um experimento em delineamento de blocos casualizados, esquema fatorial 2 x 13. Metodos de semeadura direta e transplante de mudas foram avaliados dentro de 13 periodos semanais crescentes de infestacao. Importancia relativa, densidade e materia seca acumulada pelas plantas daninhas foram analisadas por regressao nao-linear, assim como produtividade e estande da cultura de beterraba, que foram submetidos a analise de variancia. Amaranthus viridis, Coronopus didymus, Cyperus rotundus, Digitaria nuda, Galinsoga parviflora e Nicandra physaloides foram as plantas daninhas mais importantes, destacando-se C. didymus. O acumulo de materia seca das plantas daninhas foi maior na cultura em semeadura direta, embora a densidade de plantas daninhas tenha sido mais alta em sistema de transplantio. A produtividade da beterraba transplantada foi maior que a da semeadura direta no tratamento livre de plantas daninhas. A convivencia das plantas daninhas com a cultura pode permanecer por quatro e sete semanas depois da semeadura/transplantio, respectivamente, antes de reduzir a produtividade. A cultura em sistema de semeadura direta foi mais susceptivel a interferencia das plantas daninhas que a cultura sob sistema de transplantio. Palavras-chave: Beta vulgaris, plantas daninhas, interferencia, semeadura direta, transplante de mudas.
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