Fernando Storniolo Adegas

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.

Competição relativa de espécies de plantas daninhas com dois cultivares de soja.

An experiment was carried out to evaluate the relative weed species competition with two soybean cultivars of different maturation times, Embrapa-48 (precocious) and Embrapa-62 (median cycle), in Londrina, Parana, Brazil in 1998/99. Four weed species were compared: wild poinsettia (Euphorbia heterophylla), alexander grass (Brachiaria plantaginea), morning glory (Ipomoea grandifolia) and sicklepod (Senna obtusifolia), adjusted to the weed densities of zero, 15, and 30 plants m-2. The experiment was a randomized block design, in sub plots in a 4x3x2 factorial, with four replications. Soybeans and weeds emerged almost simultaneously. Both cultivars responded similarly to competition regarding yield. Productivity of Embrapa-48 was 2,819 kg ha-1 and of Embrapa-62 was 2,565 kg ha-1, with no weed competition. Relative intensity of competition between weed species and soybeans were: B. plantaginea (0.35) < I. grandifolia (0.59) < E. heterophylla (0.61) < S. obtusifolia (1.00). The estimated soybean yield losses (Y%) were accomplished by linear regression/cultivar per plant m-2: B. plantaginea (YE48 = -1,47; YE62 = -1,58; I. grandifolia (YE48 = -2,51; YE62 = -2,67), E. heterophylla (YE48= 2,47; YE62 = -2,83) and S. obtusifolia (YE48 = -4,52; YE62 = -4,21). Soybean yield loss equation adjustments to weeds are discussed.

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.

Relações entre germinação de sementes de espécies de plantas daninhas e uso da condutividade elétrica

Experiments were carried out under laboratory conditions to determine relationships between weed seed germination and electrical conductivity (EC). Recently-picked seeds of Euphorbia heterophylla, Acanthospermum hispidum, Ipomoea grandifolia, Sida rhombifolia, Bidens pilosa and Commelina benghalensis were used. The seeds were soaked in water for periods of six up to 48 hours, at 20 oC, to determine EC and water absorption levels and placed to germinate. The highest germination levels, for seeds soaked in water for 24 h, were obtained for B. pilosa(88%), E. heterophylla and S. rhombifolia (30%) and the lowest levels were obtained for I. grandifolia (5%), A. hispidum (4%) and C. benghalensis (3%). The weeds tested tend to germinate totally with a soaking periods > six hours, while water absorption tends to increase with CE tending not to accompany absorption levels at the end of longer periods. Further studies must be conducted on the use of electrical conductivity, what may provide an effective and faster evaluation of the dynamics of weed seed banks under a farming system.

Análise de crescimento de biótipos de amendoim-bravo (Euphorbia heterophylla) resistente e suscetível aos herbicidas inibidores da ALS

A aplicacao continua de herbicidas do grupo quimico das imidazolinonas, nas mesmas areas de producao de soja, durante anos seguidos, no municipio de Cafelândia, PR, favoreceu a selecao de um biotipo resistente de amendoim-bravo (Euphorbia heterophylla) aos herbicidas inibidores da acetolactato sintase (ALS). Um estudo comparativo das caracteristicas do crescimento do biotipo resistente e do suscetivel foi realizado em casa de vegetacao da Embrapa Soja, Londrina-PR, a fim de identificar diferencas no crescimento e no desenvolvimento das plantas e de seus orgaos. A producao de materia seca total, a area foliar, a materia seca dos caule, das raizes e das folhas, bem como a altura por planta, foram avaliadas em 13 vezes a intervalos regulares, iniciando aos 14 dias apos a semeadura. A partir desses parâmetros, foram calculadas a taxa de crescimento relativo, a taxa assimilatoria liquida, a razao de area foliar, a razao de peso foliar e a area foliar especifica, que decrescem com a ontogenia das plantas de amendoim-bravo, sendo similares para ambos os biotipos. A materia seca total acumulada pelas plantas e seus orgaos, a area foliar e a altura apresentaram comportamentos semelhantes para os biotipos resistente e suscetivel. O ciclo vegetativo dos dois biotipos estudados nao mostrou diferenca significativa quanto ao crescimento e ao desenvolvimento.

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

Tolerância de genótipos de soja aos herbicidas trifluralin e imazaquin

Two experiments were carried out under field conditions at Embrapa Soja, Londrina, Parana to evaluate the response of soybean genotypes to trifluralin and imazaquin, during the agricultural season of 2000/2001. The treatments were arranged in a split-plot design in a randomized complete block experiment with four replicates. Genotypes (BR 16, BRS 183, BRS 184, BRS 155, BRS 156, BRS 132, BRS 133, BRS 136, BRS 134, BRS 135, Embrapa 58, Embrapa 59, Embrapa 48, BRS 212, BR96-25619, BR96-12086 and BR95-8400) were sowed in the whole plots. In the subplots, trifluralin rates of 0.0 (check), 1.8 kg a.i. ha-1 (recommended rate) and 3.6 kg a.i. ha-1 (double rate - experiment 1) and imazaquin rates of 0.0 (check), 0.14 kg a.i. ha1 (recommended rate) and 0.28 kg a.i. ha-1 (double rate - experiment 2) were applied. All genotypes were tolerant to the recommended rates of both herbicides, with light symptoms of phytotoxicity without yield losses. However, cultivars BRS 183, BRS 156, Embrapa 59 and Embrapa 58 showed lower yields when submitted to double the recommended rate of trifluralin. Only BR9625619 showed significant yield reduction due to the double rate of imazaquin.

Periodic inspection of sprayers: diagnostic to the northern of Paraná

To optimize the use of pesticides, several countries have carried out periodic inspections in agricultural sprayers. In Brazil, knowing the conditions of this machinery canguide researches and investments in guidelines for its use and maintenance. The objective of this study was to verify the state of sprayer maintenance used in the North of the state of Parana, in Brazil. Several sprayer items were evaluated, such as: presence, status and scale of the manometer, status of the hose, status of the anti-drip component, presence of leaks, status of the bar, status of the filters, state of the spraying nozzles and errors in the targeted flow rate. Machines were named as approved when there was no failure in any item evaluated. The factor that caused the biggest level of reprove among the machines was incorrect scale of manometers, which reproved 84.55% of the machines evaluated. Other outstanding factor was the incorrect flow rate in 75.5% of the tested machines. Only one unit was approved from the total of 110 evaluated sprayers.