Elemar Voll

Resistência de amendoim - bravo aos herbicidas inibidores da enzima ALS

One of the most efficient methods of weed control in agriculture is the use of selective herbicides. However, repetitive use of the same herbicide or herbicides having the same mechanism of action, has led to the appearance of weed biotypes which have developed resistance. Thus, an experiment was carried out at Embrapa Soja, in Londrina, Parana State, Brazil, in order to confirm whether or not there has been resistance of the weed E. heterophylla to the ALS inhibitor herbicides which had been sprayed for several years in a soybean field where the grower has observed failure of the weed control by the ALS inhibitor herbicides. The suspected resistant plants (E-298) from Cafelândia county, Parana, Brazil, were treated with various doses of several herbicides, compared to a known susceptible biotype. The herbicides and its doses were cloransulan 0,0; 0,015; 0,03; 0,06; 0,12; 0,24 kg a.i./ha, plus Agral 0,2% v/v, imazetaphapyr 0,0; 0,05; 0,1; 0,2; 0,4 e 0,8 kg a.i./ha, imazaquin 0,0; 0,075; 0,15; 0,3; 0,6; 1,2 kg a.i./ha, plus Assist 0,3% v/v, sulfentrazone 0,0; 0,3; 0,6; 1,2; 2,4; 4,8 kg a.i./ha, plus Assist 0,3% v/v and lactofen 0,0; 0,082; 0,165; 0,33; 0,664; 1,329 kg a.i./ha.The results indicated different patterns of cross resistance to cloransulan, imazethapyr and imazaquin; and the GR50 ratios were 97.74; 11.90 and 10.86, respectively. The dose response curves of the resistant biotype presented lower values than the susceptible biotype in all the studied rates for the herbicides cloransulan, imazethapyr and imazaquin. On the other hand, there was no difference in the control between the resistant and susceptible biotypes when sulfentrazone and lactofen were sprayed. It was observed efficient control, mainly with the highest rates of both herbicides, proving that there is no multiple herbicide resistance of the wild poinsettia studied.

Chemical Interactions of Brachiaria plantaginea with Commelina bengalensis and Acanthospermum hispidum in Soybean Cropping Systems

Previous results obtained in soybean–wheat rotations under no-tillage conditions showed reductions in the seedbank of the weed species Commelina benghalensis, but no alteration in the seedbank of Acanthospermum hispidum in areas infested with Brachiaria plantaginea. Analyses of the soluble fraction of B. plantaginea indicated the predominance of aconitic acid (AA) among the aliphatic acids and ferulic acid (FA) among the phenolic acids. Laboratory bioassays using C. benghalensis and A. hispidum were carried out to evaluate phytotoxic effects of pure organic acid solutions and dilute extracts of B. plantaginea on seed germination, root development, and fungal germination. Solutions of AA and FA were prepared at 0.25, 0.50, and 1.0 mM. Extracts of B. plantaginea were diluted to obtain concentrations of AA similar to those in the prepared solutions. Seeds were sown on 0.5% agar (containing AA, FA, or diluted extract) in plastic-covered receptacles and maintained in a germination chamber for 10 days. AA and FA solutions and the B. plantaginea extract reduced germination and root length, mainly of C. benghalensis. AA also stimulated the development of endophytic fungi (Fusarium solani), which had complementary adverse effects on C. benghalensis germination. FA and AA may play important roles in reducing the seedbank of some weed species, acting directly on germination and development and, indirectly, by stimulating endophytic fungi that alter germination.

Allelopathic effects of aconitic acid on wild poinsettia (Euphorbia heterophylla) and morningglory (Ipomoea grandifolia).

High infestations of alexandergrass (Brachiaria plantaginea) in experimental area have reduced seedbank of some weed species in soil at a greater degree compared to those obtained with the use of an efficient herbicide. Aconitic acid (AA) has been identified in those plants in high concentration. Thus, two experiments were carried out in the laboratory to determine the effects of pure AA on weed seed germination and on endophytic fungi in wild poinsettia (Euphorbia heterophylla) and morningglory (Ipomoea grandifolia) weed species. Doses of AA (0, 0.5, 1.0, and 2.0 mM) were introduced in agar-water 0.5% medium and weed seeds treated with and without external sterilization by sodium hypochloride. Four replications of fifty seeds of each species by treatment were sown in plastic boxes with cover and maintained in germination chamber for 12 days. Reduction in germination rate, root and stem growth were observed in both species, as well as reduction in root number in morningglory were also observed at 2.0 mM concentration of AA. An increase in number of seeds with presence of endophytic fungi was also observed in both species, independently of seed sterilization, mainly of a green type fungi coloration in wild poinsettia. Aconitic acid presents allelopathic activity and can stimulate endophytic fungi species growth in weed seeds.Abstract High infestations of alexandergrass (Brachiaria plantaginea) in experimental area have reduced seedbank of some weed species in soil at a greater degree compared to those obtained with the use of an efficient herbicide. Aconitic acid (AA) has been identified in those plants in high concentration. Thus, two experiments were carried out in the laboratory to determine the effects of pure AA on weed seed germination and on endophytic fungi in wild poinsettia (Euphorbia heterophylla) and morningglory (Ipomoea grandifolia) weed species. Doses of AA (0, 0.5, 1.0, and 2.0 mM) were introduced in agar-water 0.5% medium and weed seeds treated with and without external sterilization by sodium hypochloride. Four replications of fifty seeds of each species by treatment were sown in plastic boxes with cover and maintained in germination chamber for 12 days. Reduction in germination rate, root and stem growth were observed in both species, as well as reduction in root number in morningglory were also observed at 2.0 mM concentration of AA. An increase in number of seeds with presence of endophytic fungi was also observed in both species, independently of seed sterilization, mainly of a green type fungi coloration in wild poinsettia. Aconitic acid presents allelopathic activity and can stimulate endophytic fungi species growth in weed seeds.

Persistência dos herbicidas imazaquin e imazethapyr no solo e os efeitos sobre plantas de milho e pepino

Dois experimentos foram instalados em Londrina, PR, com o objetivo de avaliar a persistencia dos herbicidas imazaquin e imazethapyr no solo, aplicados em pre emergencia e pre e pos emergencia. respectivamente. Nas subparcelas foram usados imazaquin nas doses de 0,12: 0,15 (normal) e 0,30 kg/ha e imazethapyr nas doses de 0,1 (normal) e 0,2 kg/ha. Nos blocos foram distribuidos seis epocas de semeadura: 0, 30, 60, 90, 120 e 150 dias apos a aplicacao (DAA). A atividade residual foi avaliada com a semeadura do milho Pioneer 3072, no campo, e do pepino em casa de vegetacao. Os resultados foram descritos com base nas avaliacoes visuais de fitotoxicidade e hiomassa seca das plantas de milho e da hiomassa seca e altura das plantas de pepino. A fitotoxicidade de imazaquin e de imazethapyr nao foi considerada prejudicial as plantas de milho. quando a semeadura ocorreu 90 dias apos as suas aplicacoes, respectivamente em pre e pos-emergencia. As plantas de pepino mostraramse mais sensiveis aos herbicidas do que as plantas de milho, especialmente ao imazaquin. Para imazaquin, nas doses normais, os sintomas desapareceram aos 120 dias apos aplicacao. No mesmo periodo, para imazethapyr, na menor dose, ocorreu recuperacao da altura das plantas de pepino, mas nao do seu peso.

Amostragem do banco de semente e flora emergente de plantas daninhas

O objetivo desta pesquisa foi determinar o numero de amostras necessarias para estimar com precisao aceitavel a quantidade de sementes no solo e a flora de plantas daninhas emergentes, em areas experimentais e de lavoura, para auxiliar na tomada de decisao das estrategias de manejo das plantas daninhas. A amostragem do solo para quantificacao do banco de sementes foi feita com trado tubular de 5,0 cm de diâmetro, na profundidade de 0 a 10 cm. A flora emergente foi contada por meio de um gabarito de ferro nas dimensoes de 0,5x0,5 m, de forma aleatoria na area. O numero de amostras necessario foi estimado em razao da media de sementes da amostra, para uma determinada precisao (CV = 20% ou 40%). Foi estimado que, nas areas experimentais, para medias de 10 a 20 sementes/amostra de solo (500 a 1.000 sementes/m2) e coeficiente de variacao de 20%, sao necessarias entre 40 e 90 amostras, respectivamente; com 40% (menor precisao), entre 10 e 20 amostras. Considerando o mesmo intervalo em areas de lavoura, representativas de glebas homogeneas, o tamanho de amostragem necessaria e cerca de tres vezes maior. Levantamentos da flora daninha emergente apresentam menor associacao dos dados (media e variância) entre si, portanto, sao menos apropriados para decisoes de manejo.

Manejo de plantas daninhas em milho safrinha em cultivo solteiro ou consorciado à braquiária ruziziensis

The objective of this work was to evaluate the efficiency of post-emergence herbicides for weed control, and its selectivity to Congo signal grass (Urochloa ruziziensis) and to off-season corn cropped alone or intercropped. The trial was carried out in randomized blocks with four replicates in a 2x14 factorial design: off-season corn intercropped or not to U. ruziziensis, and 14 different treatments with herbicides, besides two tests with or without weed control. Weed control, herbicide phytotoxicity to U. ruziziensis, and corn yield were evaluated. All herbicide treatments provided weed control over 80% at 14 days after the application. The treatments with atrazine+oil, at 800 and 1,200 g ha-1, formed the most selective group to U. ruziziensis; the group with the lowest selectivity consisted of the application of tembotrione alone and in associations with atrazine. The competition between U. ruziziensis and corn reduced corn yield up to 45.3%. However, there were no differences between treatments in the plots treated with herbicides.

Dinâmica da população de Cardiospermum halicacabum e competição com a cultura da soja

Abstract€–€Balloonvine Cardiospermum halicacabum( ) was recently introduced in Parana State, and it€hascaused economical damages in soybean crop in the Southern region of Brazil. In€order to determine time andemergence rate, the competition and the survival of balloonvine with soybeans cultivar Embrapa€62, grownunder two management systems, an€experiment was carried out at Londrina, PR, from 1997 to 2000. Five populationdensities of ballonvine (zero, 60, 120, 240 and 480€seeds/m 2 ) were established by sowing seeds in till and no-tillmanagements for soybeans. A€split-plot completely randomized block, with four replications, was used. An€annualseedbank decrease rate of 61.6% and 56.4% was observed for till and no-till, respectively, related to six and sevenyears survival. A nnual rates of emergence, in the absence of reinfestations, were higher in no-till (42.6%, 32.0%and 5.0%) than€till (29.9%, 10.9% and 0.7%), in those three years. Losses of soybeans were estimated at an€averageof 8,1% in the presence of 10€plants/m

Cobertura de aveia e calagem sobre amendoim-bravo em semeadura direta de soja

The objective of this study was to evaluate the behavior of wild poinsetia (Euphorbia heterophylla L.), and its control by soil liming and black oat cover crop management in no-till soybeans. One experiment was conducted on Latossolo Roxo dystrophic soil, at Embrapa Soja Experiment Station, at Warta, Londrina, PR, in 1997/98. The experimental design was a randomized complete block design, in a factorial 2x2x2, with four replications. The treatments consisted of: 1. Liming (with and without), 2. Oat cover crop (with and without) and, 3. herbicide control (with and without). Assessment of the weed seedbank evolution in time and of the emerging flora were made at preand post-emergence of soybean sowing. From the time oat was chopped until soybean pod filling stage (R5), there was a mean decrease of the seedbank by 83,2%, under liming or oat cover management, and 91,9% where there was a no liming or oat cover. Emergence rate at pre-sowing soybean were of 4,7%, as a mean, equal for liming or not, but higher for oat absence, as to presence; at post-sowing, mean emergence rate was of 12,6%, with no differences between managements. A major weed infestation in the oat management treatment, without control, reduced s oybean yield. The infestation was supressed by liming, producing significatively more.

Efeitos da interação de ácido ferúlico e glifosate em soja

An experiment was carried out for soybeans [Glycine max (L.) Merr.] cv. Ramson, under greenhouse conditions, to evaluate its growing responses to glyphosate [N-(phosphonomethyl) glycine] (GLY), a herbicide with hormonal action, in interaction with ferulic acid (4-hydroxy-3-methoxy-t-cinnamic acid) (FA), an allelopathic substance found in wheat straw under no-till plantings, which in combination could favour competition against weeds Doses of 0.00, 0.75, 1.50, 2.25 and 3.00 kg/ha of glyphosate and 0,75, 150, 225 and 300 ppm pf ferulic acid were used. A randomized block design in factorial 5x5, with four replications was used. Paper pots were filled with 1,0 kg of mixed soil (3:2 clay/sand), with two plants/pot. The duration of experiment was 22 days. Applications of FA and GLY caused etiolation of soybean shoots and decrease of root biomass. Increases of soybean shoot biomass observed for FA were red

Efeitos de ácido ferúlico em interações com densidades de soja e caruru

A replacement series experiment under greenhouse conditions was carried out to evaluate the effects of ferulic acid (4-hydroxy-3-methoxy-t-cinnamic acid) on soybean [Glicine max (L.) Merr. cv. Bragg] and redroot pigweed (Amaranthus retroflexus L.) plant density combinations. Soybeans and redroot pigweed were combined at 4:0, 3:2, 2:4, 1:6 and 0:8 plants per pot. Ferulic acid dosages used were zero, 500 and 1000 ppm. A randomized block design with four replications was used. The duration of the experiment was 33 days. For ferulic acid dosages of 500 and 1000 ppm, delays in soybean emergence of 2 and 3 days respectively were observed. Soybean plant height was increased at lower soybean: pigweed rates and at higher ferulic acid dosages; the opposite was observed in pigweed. Soybean shoot and root dry weights decreased as the number of soybeans plants increased, in contrast to pigweed. Higher doses of ferulic acid reduced shoot dry weight and relative total yield of pigweed. Intraspecific competition in pure stands was higher for soybeans than pigweed. Soybeans were more competitive than pigweed up to the harvest time at 33 days. Ferulic acid affected redroot pigweed competitiveness to a much higher degree than that of soybeans.