F.C. Reis

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.

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%.

Absorption and translocation of sulfometuron-methyl in sugarcane (Saccharum officinarum L.) at different growth stages

ABSTRACT In Brazil, weed management in sugarcane fields is mainly done with the use of selective herbicide formulations. For many years, diuron+hexazinone was one of the main herbicide mixture formulations used in sugarcane. Later, sulfometuron-methyl was included in the same mixture, which was marketed as a new herbicide formulation for residual in-season weed control in sugarcane. The mixture diuron+hexazinone+sulfometuron-methyl has been widely used in commercial sugarcane fields in Brazil. However, recent field observations have shown that sugarcane plants at different growth stages varied in their phytotoxicity levels after treatment with diuron+hexazinone+sulfometuron-methyl. Greenhouse and laboratory studies were conducted to determine 14Csulfometuron-methyl absorption and translocation, as well as 14C distribution in sugarcane at two growth stages, 2 to 3 leaves and 5 to 6 leaves. 14Csulfometuron-methyl absorption by sugarcane did not differ between the two growth stages. Different patterns of 14C accumulation were observed, which may explain variations in sulfometuron-methyl phytotoxic responses observed in the field.