A. Andres

Detecção da resistência de capim-arroz (Echinochloa sp.) ao herbicida quinclorac em regiões orizícolas do sul do Brasil

The monitoring of Echinochloa sp. plants resistant to quinclorac was conducted in Rio Grande do Sul and Santa Catarina, Brazil to determine the origin of resistance and its dissemination, as well as to detect practices or climatic conditions related to the selection and geographic distribution of the resistant biotype. The seeds were collected, purified and standardized, and trials conducted under growth chamber and greenhouse conditions. In the growth chamber, a standard germination test was conducted with the seeds being submitted to rates of 0x, 1x, 2x, 6x, 16x and 32x and to the recommended rate of quinclorac, followed by germination curve and seedlings survival evaluation 14 days after sowing (DAS); the same herbicide rates were evaluated under greenhouse conditions, applied over the plants 20 days after emergence (DAE). Dry weight and control were evaluated 35 DAE, and biotypes with RI above four were considered resistant. A map of both states was elaborated where distribution of resistance to quinclorac was showed graphically, followed by herbicide profoxydim test as an alternative for the resistant biotype control.

Desempenho do cultivar de arroz BRS pelota e controle de capim-arroz (Echinochloa spp.) submetidos a quatro épocas de entrada d'água após aplicação de doses reduzidas de herbicidas

The objectives of this work were to evaluate the possibility of reducing herbicide rates in flooded rice, using flooding as a tool to avoid weed emergence; to evaluate Echinochloa spp. control, culture establishment and growth and the effect of herbicides applied in pre-emergence on the physiological attributes of the rice culture. The experiment was conducted in a randomized block design with split-split plots, four floodings, two herbicides and three rates, with four replications. The plots were the floodings (A) 5, 10, 15 and 20 days after herbicide application and the split plots were the herbicides (H) bispyribac-sodium and bispyribac-sodium + clomazone, and the split-split plots the herbicide rates (D), 32, 40 and 48 g ha-1 of bispyribac-sodium alone and in mixture with 300 g ha-1 of clomazone. Bispyribac-sodium was efficient in controlling Echinochloa spp. plants up to the stage of three leaves, when flooding occurred in the field until 5 days after application, and/or until rice tillering started when mixed with clomazone. It is possible to work with rates of bispyribac-sodium alone below the recommended dosage if flooding starts immediately after application. When using the bispyribac-sodium and clomazone mixture, it is possible to start the flooding when the tillering process begins.

Avaliação de germinação e dormência de ecótipos de arroz-vermelho

The objective of this work was to evaluate aspects related to the phenotypic characterization of red rice ecotypes collected in the states of Rio Grande do Sul and Santa Catarina. The ecotypes were studied and compared to the commercial rice cultivars BR-IRGA 409, BR-IRGA 410, IRGA 417, and El Paso L 144. In the laboratory experiment, seed biometry, 1000 seed-weight and seed germination and dormancy 30, 60, 90, 120, and 150 days after harvesting were evaluated. The red rice ecotypes from the rice fields evaluated showed wide variability in seed characteristics and dormancy intensity and duration. Some ecotypes showed dormancy period above 150 days after harvesting. The results of this study confirm that red rice populations infesting rice fields are quite diverse, and appropriate control of red rice is only achieved when growers adopt not only isolated control measures, but also several management practices to reduce red rice yield losses.

Caracterização morfológica de ecótipos de arroz daninho (Oryza sativa) provenientes de áreas de arroz irrigado

Objetivou-se neste estudo a caracterizacao fenotipica de 16 ecotipos de arroz daninho provenientes de lavouras comerciais dos Estados do Rio Grande do Sul e Santa Catarina, quando comparados aos cultivares BR-IRGA 409, BR-IRGA 410, IRGA 417 e El Paso L 144, em casa de vegetacao. Foram semeados 16 ecotipos de arroz daninho e os quatro cultivares de arroz irrigado. O cultivo foi realizado em vasos plasticos com capacidade para 9 litros, contendo solo, utilizando-se cinco repeticoes por genotipo. Foram avaliadas as seguintes variaveis: coloracao das folhas, pilosidade, afilhamento efetivo, graus-dia biologico para completar o florescimento, degrane, numero de afilhos ferteis, area foliar da folha-bandeira, altura de planta, numero de sementes por panicula e producao por planta. Os resultados obtidos evidenciam grande variabilidade morfologica entre os ecotipos estudados.

Rice seedling and plant development as affected by increasing rates of penoxsulam under controlled environments

Rice is a major staple in many countries. Weed control is one of the factors limiting higher rice yield. ALS (acetolactate synthase)-inhibiting herbicides are desirable weed control herbicides because of their high efficacy, low toxicity to mammalians, and low rates used. An important herbicide characteristic is high selectivity to the crop, since it facilitates fast crop establishment and greater crop advantage over the weeds. The objectives of this work were to study the effects of increasing rates of the ALS-inhibiting herbicide penoxsulam on seed integrity and germination, and seedling and plant development of rice cv. BRS Pelota under controlled laboratory and greenhouse conditions. The results showed that penoxsulam affected rice germination and seedling and plant growth at rates above 54 g a.i. ha-1, and that penoxsulam is safe for rice seedling development at the currently recommended rates.