Erivelton Scherer Roman

Interferência de populações de Euphorbia heterophylla e Ipomoea ramosissima isoladas ou em misturas sobre a cultura de soja

Euphorbia heterophylla (wild poinsettia), and, more recently, Ipomoea ramosissima (morningglory) are among the main weeds infesting soybean crop in southern Brazil. This work aimed to evaluate the effects of wild poinsettia and morningglory as single or mixed populations in coexistence with soybean. Two experimentswere conducted to compare associations of wild poinsettia or moningglory with soybean, using five ratios of wild poinsettia plants and soybean or morningglory (0:8, 2:6, 4:4, 6:2 and 8:0). In a third experiment, four soybean plants per pot were kept constant and five ratios of of wild poinsettia and moningglory plants were used (0:8, 2:6, 4:4, 6:2 and 8:0), established in two weed emergence periods related to the soybean. The results indicated that a higher reduction in soybean biomass was caused by morningglory than by wild poinsettia, when these species were established before the crop. In mixed communities, morningglory is more competitive than wild poinsettia.

Identificação de biótipos de azevém (Lolium multiflorum) resistentes ao herbicida glyphosate em pomares de maçã

Glyphosate is a wide spectrum herbicide used for over 15 years in apple orchards in Vacaria-RS for weed control in rows of trees. Usually, 3 to 4 applications per year are made at a rate of 720 to 1080 g a.e. glyphosate ha-1 (2 to 3 L ha-1 of commercial product). Ryegrass (Lolium multiflorum) is a common weed in orchards and traditionally sensitive to glyphosate. However, in the last years, some ryegrass plants have not been found to show significant toxicity symptoms after treatment with glyphosate, suggesting that they acquired resistance to this product. To evaluate the response of a ryegrass plant population to glyphosate, one field and two greenhouse experiments were carried out. The field experiment treatments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880; 5,760 and 11,520 g a.e. ha-1), in addition to the herbicides paraquat, glufosinate-ammonium, haloxyfop and diclofop-methyl as standards, sprayed at two different vegetative growth stages of ryegrass. The greenhouse experiments had increasing rates of glyphosate (0; 360; 720; 1,440; 2,880 and 5,760 g a.e. ha-1) plus the above listed check herbicides sprayed on biotypes considered resistant and on plants of one susceptible biotype. In the second greenhouse experiment, glyphosate rates (720; 1,440; 2,880; 720 + 720 and 720 + 1,440 g a.e. ha-1) were sprayed in single and sequential applications, in addition to the herbicides paraquat, glufosinate-ammonium, haloxyfop, clethodim, sethoxydim, diclofop-methyl, fenoxaprop, fluazifop, paraquat + diuron, atrazine + simazine, trifluralin, and metolachlor. Toxicicity to the herbicides was assessed at 15, 30 and 45 DAT (days after treatment). Overall, the field and greenhouse experiment results showed that the susceptible biotype is easily controlled by glyphosate and by the other postemergence herbicides tested, independent of the vegetative growth stage. In addition, the results showed that the resistant biotype, similarly to the susceptible biotype, is highly sensitive to herbicides with mode of action differing from that of glyphosate. However, the resistant biotype presents low response to glyphosate, even if used in high rates, showing that some biotypes acquired resistance to this product.

Effect of cardinal temperature and water potential on morning glory (Ipomoea triloba) seed germination.

This work aimed to assess the effect of temperature and moisture on the germination and emergence of morning glory (Ipomoea triloba) and to determine the effect of water potential and temperature on seed germination and hypocotyl and radicle elongation. Thermoperiods of 9.3 and 5 (7.5); 14.3 and 10 (12.5); 19.3 and 15 (17.5); 24.3 and 20 (22.5); 29.3 and 25 (27.5); 34.3 and 30 (32.5); 39.2 and 35 (37.5) and 44.2 and 40 (42.5) and 49.2 and 45 (47.5) oC, which alternated for 14 and 10 hours, and water potentials of 0, -0.03, -0.06, -0.1, -0.2, -0.4, -0.6 and -0.9 MPa were evaluated. The germination of morning glory seeds occurred through temperature and water potential interaction whereas radicle and hypocotyl elongation was triggered by temperature. With regard to germination, the parameters of the model used to estimate cardinal temperatures and the baseline water potential were determined by probit analysis. As to elongation processes, cardinal temperatures were calculated by linear regression and their responses to temperature were described by a second-order regression equation. The mathematical models described the processes of seed germination and of hypocotyl and radicle elongation of this species as a function of hydrothermal time and temperature, respectively.

Influência do orvalho e volume de calda de aplicação na eficácia do glyphosate na dessecação de Brachiaria plantaginea

A eficacia de herbicidas e influenciada por diversos fatores que afetam a absorcao e a translocacao desses compostos na planta. A absorcao de herbicidas pelas plantas, por exemplo, e influenciada, tanto fisica como biologicamente, pela temperatura e pela umidade relativa do ar dentro do dossel. Com a diminuicao da umidade relativa do ar e/ou com o aumento da temperatura, as gotas da pulverizacao secam mais rapidamente e a absorcao do produto diminui, ou ate mesmo cessa, afetando o desempenho biologico. Com base nessa premissa, o presente estudo teve como objetivo examinar a influencia do orvalho e do volume de calda de aplicacao na eficiencia de doses de glyphosate para o controle de Brachiaria plantaginea. Foram observadas interacoes significativas entre volume de calda, orvalho e dose de glyphosate. O volume mais baixo (100 L ha-1) resultou em melhor controle da especie, especialmente quando o herbicida foi usado na menor dose (90 g ha-1). A presenca de orvalho nas folhas causou reducoes na atividade do produto, especialmente quando aplicado na menor dose e combinado com maior volume de calda.