Important weed plants in transgenic cotton: management of Eleusine indica (L) Gaertn and Spermacoce latifolia Aubl

Abstract

Eleusine indica and Spermacocea latifolia have become difficult to control in cotton and soybean areas due to herbicide resistance and tolerance, respectively. Because of this, this work aims to verify the efficiency of different vegetation coverings on the soil and herbicides in the management of these weeds. The first experiment will be carried out in beds of 20 m2 for each treatment (previously solarized) in a randomized block design with four replications. The treatments will consist of different cover species: millet (Pennisetum glaucum), Brachiaria ruziziensis, Crotalaria juncea, Crotalaria spectabilis, P. glaucum + C. juncea, P. glaucum + C. spectabilis, B. ruziziensis + C. juncea, B ruziziensis + C. spectabilis. In the beds, on the same day of the sowing of the cover plants, the weeds S. latifolia and E. indica will be sown. They will be sown in order to obtain 20 plants / m2. The seed bank will be monitored at different times: before solarization, after solarization and at the end of the experiment. When at least 50% of cover crops are in pre-flowering, an assessment of green and dry mass and the mechanical management of straw-forming plants will be made. One day before and at 15, 30 and 45 days after straw management, weeds will be sampled in each plot. The second experiment will be developed in a greenhouse and seeds of the weeds S. latifolia and E. indica will be collected from areas with cotton production in MT. The history of herbicide use will be observed. The seeds of each weed will be sown separately, in order to obtain 5 plants per pot. The pots will be kept in a greenhouse with automatic irrigation to maintain the necessary humidity for germination and plant growth. Two days after sowing 6 herbicide treatments will be applied in pre-emergence of weeds - diclosulan, s-metolachlor, pyrosasulfone, diuron, clomazone and trifluralin, plus the control. At 15 days after the first application, we will have the sequential application with diquat or ammonium glufosinate and without sequential with four repetitions each. Therefore, a completely randomized design in a double factorial scheme (6x3), + control without herbicide will be used. The percentage of control and weed mass will be evaluated.