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Herbicide resistant is associated with morphological, physiological and metabolic alterations in weeds. These alterations may reflect changes in the nutritional status of resistant plants and their growth it can be inferred in greater adaptability and competitive ability of the resistant biotypes. Thus, the objective of this research was to determine the dry matter and macronutrient accumulation and distribution by glyphosate-resistant and susceptible plants of Digitaria insularis (sourgrass), growing under mineral nutrition standard conditions. The experimental design was completely randomized, with eleven treatments and four replicates. The treatments consisted of evaluation periods at 15, 30, 45, 60, 75, 90, 105, 120, 135, 150 and 165 days after emergence (DAE). The average time for maximum theoretical accumulation (PtMax) and for inflection points of dry mass and macronutrient were lower for susceptible (133 DAE; 99 DAE) than for resistant biotype (141 DAE; 105 DAE). However, considering the average time obtained by susceptible, dry mass (g) and macronutrients (mg) accumulation was always higher for resistant biotype. The decreasing sequence of nutrient accumulation was similar for both sourgrass biotypes: K, N, Ca, Mg, P and S.

Weed interference is one of the main factors responsible for reducing the productivity of the peanut crop. Among weed control methods, the chemical is considered one of the main tools, however, the herbicides registered for this crop are scarce. The objective of this study was to evaluate the selectivity of herbicides applied in post-emergence in Runner peanut cultivars. For this, an experiment was performed in an 11x5 factorial scheme, meaning 10 herbicides plus one control (without herbicide) and five peanut cultivars, with four replicates. Visual evaluations of phytointoxication were carried out at 7, 14 and 21 days after application of the herbicides. At the end of the experiment, was determined the dry mass of aboveground and root parts. Based on the results obtained, it is concluded that the herbicides 2,4-D (1.50 L ha-1), mesotrione (0.3 L ha-1), saflufenacil (0.75 L ha-1), imazapic (175 g ha-1) and S-metolachlor (1.75 L ha-1) have potential to be used for all the peanut cultivars studied. Herbicides hexazinone (2.50 kg ha-1), amicarbazone (2.00 kg ha-1), tebuthiuron (2.00 L ha-1), clomazone (2.00 L ha-1) and sulfentrazone (1.20 L ha-1) must not be indicated, at these doses, for post-emergence spraying in the evaluated cultivars. The genotypes do not react equally to certain products, therefore, there is a need for further studies the at field conditions to attest the responses obtained in the present study and verify that the yield potential is not affected.

Eucalyptus plants are sensitive to stress factors in the initial growth phase. The plant growth regulator trinexapac-ethyl can provide gains to eucalyptus plants, a phenomenon known as hormesis. Thus, the aim of this work was to evaluate the effect of trinexapac-ethyl on the initial growth of two Eucalyptus urograndis clones (Clone 1 = I-144 and Clone 2 = 1407). The experiment was performed during 90 days after planting (DAP) of eucalyptus, in 100 L pots, with a randomized complete block design. The treatments were arranged in a 2 × 3 factorial scheme, with two eucalyptus clones and three trinexapac-ethyl doses (0, 30 and 60 g i.a. ha-1), with four replications. Fortnightly, plants height and stem diameter were evaluated. At 90 DAP, the leaf area and plants dry matter (DM) were evaluated. Clone 1 obtained leaf area and total DM 53% and 58% larger than Clone 2, respectively. The higher dose of trinexapac-ethyl provided mean gains of 30% in stem DM and total DM in Clone 1. For Clone 2, both doses of the product caused mean gains of 70% in stem DM, leaf DM and total DM. In conclusion, trinexapac-ethyl has a positive effect on the initial growth of E. urograndis, Clones I-144 and 1407. Clone I-144 showed higher growth than Clone 1407, regardless trinexapac-ethyl application. However, the Clone 1407 obtained more expressive gains with the application of trinexapac-ethyl, compared to Clone I-144.

The objective of this study was to evaluate the selectivity of fluazifop-p-butyl and haloxyfop-R methyl ester on Eucalyptus urograndis (clone GG100), as well as the use of fluazifop-p-butyl for control of Panicum maximum and Urochloa brizantha. Two experiments were conducted in 15-liter capacity pots, in a completely randomized design with four replications. The first experiment consisted of seven treatments, in which fluazifop-p-butyl and haloxyfop-R methyl ester were sprayed at 15, 30 and 37 days after planting (DAP) and a control plot without application. In the second experiment, the treatments consisted of a factorial 4 × 2 (four application periods and two weed species), in which three seedlings of P. maximum or U. brizantha were transplanted per pot. In both experiments, at 90 DAP, plant height, stem diameter, leaf area and total dry matter of eucalyptus were evaluated. In the second experiment, besides the morphological parameters, the percentage of weed control was evaluated. The data was submitted to analysis of variance by F test, and the means compared by Tukey test at the level of 5% of probability. Both herbicides did not cause visual effects of phytointoxication in eucalyptus, but haloxyfop-R methyl ester was not selective to clone GG100 (E. urograndis). Fluazifop-p-butyl was selective to clone GG100, providing better control in the first application period (15 DAP) but only for P. maximum, which negatively affected the initial development of eucalyptus, while U. brizantha was not efficiently controlled with the usage of fluazifop-p-butyl.