Ricardo Victoria Filho

Resistência de plantas daninhas aos herbicidas

Weed herbicide resistance has evolved from weed evolution. The modern agriculture is responsible for this evolution because of the intensive use of herbicides. The knowledge of mechanisms and factors that influence the weed herbicide resistance play an important role in the weed manegement techniques used to avoid or delay herbicide resistance appearence. There are not many report or scientific papers about herbi cide resistance in Brasil. Therefore, this literature review aims to provide information about the main advances and discoveries in the field of weed herbicide resistance.A resistencia de plantas daninhas aos herbicidas ocorre em funcao de um processo evolutivo. O desenvolvimento de biotipos de plantas daninhas resistentes e imposto pela agricultura moderna, atraves da pressao de selecao causada pelo uso intensivo dos herbicidas. O conhecimento dos mecanismos e fatores que favorecem o aparecimento de biotipos de plantas daninhas resistentes e fundamental para que tecnicas de manejo sejam utilizadas no sentido de evitar ou retardar o aparecimento de plantas resistentes em uma area. Sao poucos os relatos ou citacoes de literatura no Brasil. Sendo assim, este trabalho de revisao procura relatar os principais avancos e descobertas na area de plantas daninhas resistentes aos herbicidas.

Efeitos da densidade e proporção de plantas de milho (Zea mays L.) e caruru (Amaranhus retroflexus L.) em competição

A maioria dos estudos de competicao, entre plantas daninhas e cultivadas, conduzidos nos ultimos anos, procuram quantificar a interferencia que as plantas daninhas causam sobre as culturas; no entanto, poucos destes trabalhos estudam mecanisticamente os efeitos da densidade e da proporcao de plantas em uma mistura de especies, a importância da competicao intra e interespecifica e a diferenciacao de nicho ecologico. Desta forma, foi desenvolvida a presente pesquisa com o objetivo principal de descrever as interacoes competitivas e os indices de competitividade entre plantas de milho (Zea mays L.) e caruru (Amarathus retroflexus L.). A metodologia utilizada foi a de um experimento substitutivo com densidade total de 400 plantas/m2 e 5 proporcoes, alem da monocultura que variou de 50 a 800 plantas/m2, sendo conduzido no delineamento experimental de blocos casualizados, com quatro repeticoes. Os resultados obtidos foram analisados pelo metodo convencional de analise de experimentos substitutivos e pelo metodo da producao reciproca total e por planta. O milho foi um competidor muito mais agressivo que o caruru, sendo que para a planta cultivada a competicao intraespecifica e mais importante que a competicao interespecifica. O contrario e verdadeiro para o caruru, ou seja, a competicao interespecifica e mais importante que a intraespecifica. Ambas especies de plantas estao competindo pelos mesmos fatores de crescimento, pois o indice que mede a diferenciacao de nicho ecologico e menor que 1,0. A determinacao da influencia da densidade e proporcao de especies em estudos de competicao entre plantas e muito importante para a compreensao das interacoes competitivas.

Curvas dose-resposta em espécies de plantas daninhas com o uso do herbicida glyphosate(1)

With the objective of veryfing the response of different doses in species of weeds by herbicide glyphosate, an experiment was conducted in growth chamber in a completetly randomized design with three repetitions, in the Department of Vegetable Production at ESALQ/USP. For that, were chosen six species of weeds: Bidens pilosa L., Tridax procumbens L., Digitaria insularis (L.) Feed, Spermacoce latifolia Aubl., Ipomoea grandifolia L. and Commelina benghalensis L. The herbicide glyphosate, inhibitor of the enzyme EPSPs, was used at rate 0.0; 11.3; 22.5; 45; 90; 180; 360; 720 and 1440 g.ha-1 a.i. Curves of dose-response were made by the adjustment of the equation of the collected data of green biomass using the log-logistic model: Y = C+D-C / 1 + Exp{b[log(x)-log(RC50)]}, calculated by the no linear statistical model through the SAS statistical program. After the determination of the dose-response curves for the species mentioned above the Bidens pilosa was considered the most susceptible weed to glyphosate, showing the houvest RC50 (31.86 g.ha-1 a.i.). The species Tridax procumbens, Digitaria insularis, Spermacoce latifolia, Ipomoea grandifolia and Commelina benghalensis obtained RC50 equal to 58.40; 128.50; 250.44; 615.49 and > 1440.00 g.ha-1 a.i., respectively, what means that the necessary amount of herbicide to reduce in 50% the green biomass was 1.83; 4.03; 7.86; 19.31 and >359.56 times higher in relation the Bidens pilosa.

Efeito da palha de cana-de-açúcar e do tamanho do tubérculo na brotação e no desenvolvimento da parte aérea de tiririca

The Sao Paulo State Legislation established a gradual increase in the use of mechanical sugar cane harvest, which leaves a thick layer of straw, possibly affecting the development of purple nutsedge. Purple nutsedge (Cyperus rotundus L.) is one of the most crop-damaging weeds, infesting wide areas mainly in tropical and sub-tropical regions, causing substantial yield losses. It is considered one of most important weeds in sugar cane crop, by interfering directly on plant development, competing for essential growth factors (such as water, light, and nutrients) and by releasing allelopathic substances. There are few works about the effect of tuber size of weed species on the germination and development of plants. This experiment aimed to verify if the addition of sugar cane straw could affect the development of the aboveground part of purple nutsedge derived from tubers of small (0,2 to 0,3 g) and large (1,0 to 1,1 g) sizes, planted at three different times of the year. The experiment was set up in a greenhouse in Campinas, State of Sao Paulo, arranged in a randomized block design with four replicates. Dormant purple nutsedge tubers of small and large sizes were planted in May, July and September, and RB 855156 sugar cane straw was added in quantities corresponding to 0,0, 5,0, 10,0 and 15,0 ton/ha. Every 28 days until 84 days after each planting, the number of emerged sprouts, average plant height, foliar area and fresh and dry leaf and total aboveground part (leaves + inflorescences) weights were evaluated. The tubers planted in May emerged sooner and more uniformly than those planted in July and September. The number of emerged sprouts was not affected by tuber size. On the other hand, plant height, leaf area, and fresh and dry leaf and aboveground part weights were larger when originated from large-sized tubers. The addition of sugar cane straw to the soil affected more the plants derived from small than from large tubers. It was verified that, with the exception of average height, the September planting originated plants with larger number of sprouts, leaf area, fresh and dry leaf and total aboveground part weights. Larger average plant height values were observed in the May planting. For all analyzed variables, the July planting presented always the smallest values. The application of increasing quantities of sugar cane straw caused a decrease in the number of sprouts, foliar area, and fresh and dry leaf and total aerial aboveground weights. The number, leaf area, and average plant height of the sprouts, and the fresh and dry leaf and total aboveground part weights increased linearly as function of time.EFFECT OF SUGAR CANE HARVEST STRAW AND TUBER SIZE ON SPROUTING AND SHOOT GROWTH OF PURPLE NUTSEDGE (CYPERUS ROTUNDUS L.) The Sao Paulo State Legislation established a gradual increase in the use of mechanical sugar cane harvest, which leaves a thick layer of straw, possibly affecting the development of purple nutsedge. Purple nutsedge (Cyperus rotundus L.) is one of the most crop-damaging weeds, infesting wide areas mainly in tropical and sub-tropical regions, causing substantial yield losses. It is considered one of most important weeds in sugar cane crop, by interfering directly on plant development, competing for essential growth factors (such as water, light, and nutrients) and by releasing allelopathic substances. There are few works about the effect of tuber size of weed species on the germination and development of plants. This experiment (1) Recebido para publicacao em 13 de dezembro de 2004 e aceito em 3 de janeiro de 2006 (2) Instituto Agronomico (IAC), Caixa Postal 28, 13001-970 Campinas (SP). E-mail mcdesalvo@hotmail.com; (3) ESALQ-USP, Caixa Postal 9, 13418-900 Piracicaba (SP). E-mail rvictori@esalq.usp.br (4) Faculdade de Ciencias Biologicas, PUCCampinas, Av. John Boyd Dunlop, sn, 13059-900, Campinas (SP). M.C. S. S. Novo et al. Bragantia, Campinas, v.65, n.1, p.97-107, 2006 98 aimed to verify if the addition of sugar cane straw could affect the development of the aboveground part of purple nutsedge derived from tubers of small (0,2 to 0,3 g) and large (1,0 to 1,1 g) sizes, planted at three different times of the year. The experiment was set up in a greenhouse in Campinas, State of Sao Paulo, arranged in a randomized block design with four replicates. Dormant purple nutsedge tubers of small and large sizes were planted in May, July and September, and RB 855156 sugar cane straw was added in quantities corresponding to 0,0, 5,0, 10,0 and 15,0 ton/ha. Every 28 days until 84 days after each planting, the number of emerged sprouts, average plant height, foliar area and fresh and dry leaf and total aboveground part (leaves + inflorescences) weights were evaluated. The tubers planted in May emerged sooner and more uniformly than those planted in July and September. The number of emerged sprouts was not affected by tuber size. On the other hand, plant height, leaf area, and fresh and dry leaf and aboveground part weights were larger when originated from large-sized tubers. The addition of sugar cane straw to the soil affected more the plants derived from small than from large tubers. It was verified that, with the exception of average height, the September planting originated plants with larger number of sprouts, leaf area, fresh and dry leaf and total aboveground part weights. Larger average plant height values were observed in the May planting. For all analyzed variables, the July planting presented always the smallest values. The application of increasing quantities of sugar cane straw caused a decrease in the number of sprouts, foliar area, and fresh and dry leaf and total aerial aboveground weights. The number, leaf area, and average plant height of the sprouts, and the fresh and dry leaf and total aboveground part weights increased linearly as function of time.

Uptake, translocation, and control of trumpet flower (Tecoma stans) with aminocyclopyrachlor.

To gain a better understanding of the physiology of the herbicide aminocyclopyrachlor in young plants of trumpet flower, the uptake and translocation were evaluated after the application of herbicide. This was determined by treating individual leaves with formulated herbicides plus 14C-aminocyclopyrachlor after the application of the formulated herbicide. This experiment used a randomized experimental design with three replications. In addition, field studies were conducted to assess the effectiveness of foliar applications of aminocyclopyrachlor in association with metsulfuton-methyl. The plant absorbed 20% of the herbicide applied. The translocation percentage did not surpass 5% of the total amount applied. Only 1% of the herbicide applied was translocated to the roots. Rate of 40 + 13 g a.i. 100 L−1 of aminocyclopyrachlor+metsulfuron-methyl was effective to control T. stans.

Different Glyphosate Susceptibility in Chloris polydactyla Accessions

Abstract Glyphosate is now the most widely used herbicide; after years of frequent utilization, resistant weeds were selected, mainly due to widespread adoption of glyphosate-resistant crops and no-tillage sowing system. Increasing difficulty in controlling Chloris polydactyla with glyphosate has been noticed in agricultural areas. Here, the susceptibility level of various C. polydactyla accessions from Brazil is examined. Two whole-plant studies were conducted to confirm the presence and extent of glyphosate susceptibility among accessions, which involved the application of seven glyphosate doses on four accessions. The four accessions showed different glyphosate susceptibilities. The “Matão” accession presented major tolerance for glyphosate compared to “Palotina” accessions. “Jaboticabal” plants showed an intermediary susceptibility. The resistance factor (RF) was 3.76 between the “Matão” and “Palotina” accessions. All biotypes died at 2,880 g ae ha−1 glyphosate. Nomenclature: Glyphosate; Chloris polydactyla (L.) Sw. Resumen Glyphosate es actualmente el herbicida más ampliamente usado. Después de años de uso frecuente, malezas resistentes fueron seleccionadas, principalmente debido a la amplia adopción de cultivos resistentes a glyphosate y de sistemas de siembra con labranza cero. En áreas agrícolas, se ha notado el incremento en la dificultad para controlar Chloris polydactyla con glyphosate. Aquí, se examinó el nivel de susceptibilidad de varias accesiones de C. polydactyla de Brasil. Dos estudios de plantas enteras fueron realizados para confirmar la presencia y la magnitud de la susceptibilidad a glyphosate entre accesiones, los cuales involucraron la aplicación de siete dosis de glyphosate sobre cuatro accesiones. Las cuatro accesiones mostraron diferentes susceptibilidades a glyphosate. La accesión “Matão” presentó una tolerancia mayor al compararse con la accesión “Palotina”. Las plantas de “Jaboticabal” mostraron una susceptibilidad intermedia. El factor de resistencia (RF) fue 3.76 entre las accesiones “Matão” y “Palotina”. Todos los biotipos murieron al ser expuestos a 2,880 g ae ha−1 de glyphosate.

Resistence of Euphorbia Heterophylla L. to ALS-inhibiting herbicides in soybean

Herbicides are widely used in soybean for weed control, and the selection pressure attributed to the repeated use of herbicides with similar modes of action on the same site has caused selection for resistant biotypes within and among previously susceptible species, such as Euphorbia heterophylla L., in relation to ALS enzyme inhibitors, in the states of Parana, Rio Grande do Sul, and Sao Paulo, Brazil. Seeds of E. heterophylla were collected to examine possible new cases of resistant populations and to test alternative herbicide treatments to manage these populations, in the Caarapo region, State of Mato Grosso do Sul, Brazil, in areas where plants of this species have survived continuous herbicide applications. The experiment was carried out under greenhouse conditions, where biotypes with a history of suspected resistance were compared with a known susceptible biotype. Several post-emergence herbicides were sprayed at zero, one, two, four, and eight times the recommended field application rates. Twenty days after application, plants were harvested, and control percentage and fresh weight were determined to establish dose-response curves, in the aim to obtain the resistance factor using CD50 and RD50 data. The chlorimuron-ethyl resistance factor values for the control percentage and fresh weight parameters were higher than 16.5 and 16.9, respectively, while imazethapyr showed resistance factors higher than 25.0 and 23.5, respectively. The resistant biotype showed different resistance levels to chlorimuron-ethyl and imazethapyr, showing cross-resistance to the sulfonylurea and imidazolinone groups. Nevertheless, this biotype was effectively controlled by fomesafen (250 g ha-1), lactofen (120 g ha-1), flumiclorac-pentyl (40 g ha-1), glufosinate-ammonium (150 g ha-1), and glyphosate (360 g ha-1).

Glyphosate has low toxicity to citrus plants growing in the field

Gravena, R., Filho, R. V., Alves, P. L. C. A., Mazzafera, P. and Gravena, A. R. 2012. Glyphosate has low toxicity to citrus plants growing in the field. Can. J. Plant Sci. 92: 119–127. There has been controversy over whether glyphosate used for weed management in citrus fields causes significant toxicity to citrus plants. Glyphosate may be toxic to non-target plants exposed to accidental application or drift. This work evaluated glyphosate toxicity in plants of Valencia citrus (Citrus sinensis L. Osbeck) grafted onto ‘Rangpur lime’ (Citrus limonia L. Osbeck) and citrumelo ‘Swingle’ (Poncirus trifoliata (L.) Raf×Citrus paradisi Macf) by trunk- or foliar-directed herbicide applications under field conditions. In the first experiment, glyphosate was sprayed at rates of 0, 90, 180, 260, 540, 1080 and 2160 g a.e. ha−1 directly on the trunk to a height of 5 cm above the grafting region. In the second experiment, glyphosate was sprayed on the plant canopies at rates of 0, 0.036, 0.36, 3.6, 36, 360 and 720 g a.e....

Leaching of Diuron, Hexazinone, and Sulfometuron-methyl Applied Alone and in Mixture in Soils with Contrasting Textures

When herbicides are applied in mixture, interactions among them could potentially promote changes in herbicide behavior in the soil. Thus, application mode (isolated or in mixture) and soil texture (sandy or clayey) were investigated in the total leaching of the commercial mixture diuron + hexazinone + sulfometuron-methyl, and of each isolated compound. Experiments in soil columns also evaluated the movement of each herbicide and mixtures across soil layers. In the sandy soil, the greatest total leaching was observed with hexazinone compared to diuron and sulfometuron. Most of the applied diuron remained at the top layer of the soil, indicating that this herbicide has low soil mobility. Overall, our results show that hexazinone has greater leaching potential and mobility along the soil profile compared to diuron and sulfometuron. Our data can be used in assessing the fate of diuron, hexazinone, and sulfometuron alone or in mixture on natural ecosystems, under different soil types and application modes.

Germination and emergence of trumpet flower (tecoma stans) under different environmental conditions

The aim of this work was to analyze the effect of temperature and light intensity on trumpet flower seed germination, as well as the effect of seeding depth on its emergence. To study the influence of temperature, nine temperature intervals were evaluated, ranging from 15.0 to 40.0 oC. A randomized block design experiment was used with five replications and 20 seeds per replication, and performed twice. To evaluate light intensity on seed germination, a randomized experimental design was used with eight replications and 25 seeds per replication. The treatments applied were: photoperiod with temperature alternation; photoperiod with constant temperature; darkness with temperature alternation; and darkness with constant temperature. The photoperiod consisted of 8 hours of light and 16 hours of darkness, and the constant temperature was 25 oC. The treatments with temperature alternations were established with 8 hours at 30 oC, and 16 hours at 20 oC. Germination was assessed daily to calculate the total percentage of germination as well as the Germination Velocity Index (GVI). To study the influence of seeding depth on plant emergence, 25 seeds were seeded at 0, 20, 40, and 80 mm in pots with sieved soil. The experiment was arranged in a randomized block design with four replications. Seedling emergence was monitored daily until the 15th day after seeding. After that period, the total percentage of emergence was calculated for each experimental unit, as well as the Emergence Velocity Index (EVI). Formation of normal seedlings and the Germination Velocity Index were different among temperatures and higher germination percentages were observed between 20.3 oC and 37.5 oC. Tecoma stans seedlings did not germinate when planted at 40 and 80 mm depth. However, the seedlings placed on the soil surface had an emergence percentage of 72. At 20 mm depth, the emergence rate was 31%.