Management of commelina benghalensis with saflufenacil in shaded environments

Abstract

The repetitive use of glyphosate in the control of weeds in eucalyptus plantations has selected tolerant species such as Commelina benghalensis. Therefore, the use of herbicides of other mechanisms of action, such as saflufenacil, in rotation or combination with glyphosate, is necessary to reduce damages caused by C. benghalensis, whose sensitivity to herbicides can be influenced by the shading caused by the eucalyptus crop. This study aimed to assess the efficiency of saflufenacil in the management of C. benghalensis at different shading levels. Three experiments were carried out regarding a certain shading level (cultivation environment with 0, 40, and 55% shade). The experimental design was a randomized block design with five herbicide doses (0, 24.5, 49, 73.5, and 98 g ha-1 of saflufenacil) and four replications. At 28 days after herbicide application, the percentage of control and shoot dry matter were assessed, as well as the biomass allocation to leaves, stems, and roots of C. benghalensis. Plants cultivated at 0% shade presented a higher dry matter accumulation and a better distribution of biomass in leaves, stem, and roots, contributing with the increased tolerance to saflufenacil and not being controlled with effectiveness under the assessed doses. As shading was increased, plants of C. benghalensis allocated most of their biomass to the shoot, especially leaves, reducing their reserve structures and increasing the contact area with the herbicide, making them more susceptible to saflufenacil.